Uma História: a Palavra do Ano do Dicionário.
Palavra do ano.
Nossa escolha de Palavra do Ano serve como um símbolo dos eventos mais significativos de cada ano e das tendências de pesquisa. É uma oportunidade para refletirmos sobre a linguagem e as ideias que representam a cada ano. Então, dê uma volta pela pista da memória para lembrar todas as nossas últimas seleções do Word of the Year.
Não foi moda, engraçado, nem foi cunhado no Twitter, mas achamos que a mudança contou uma história real sobre como nossos usuários definiram 2010. Ao contrário de 2008, a mudança não era mais um slogan de campanha. Mas o termo ainda tinha muito peso. Aqui está um trecho do nosso anúncio da Palavra do Ano em 2010:
O debate nacional pode ser resumido pela pergunta: Nos últimos dois anos, houve mudanças suficientes? Tem havido muito? Enquanto isso, muitos americanos continuam enfrentando mudanças em suas casas, contas bancárias e empregos. Só o tempo dirá se a última onda de mudanças pela qual os americanos votaram nas eleições intermediárias resultará em um resultado negativo ou positivo.
Tergiversar.
Esta palavra rara foi escolhida para representar 2011 porque descreveu muito do mundo ao nosso redor. Tergiversar significa "mudar repetidamente a atitude ou opiniões de uma pessoa em relação a uma causa, assunto, etc." Os editores do dicionário viram o mercado de ações, os grupos políticos e a opinião pública passarem por uma montanha-russa de mudanças ao longo de 2011. E assim, nomeamos tergiversar a Palavra do Ano de 2011.
Em um ano conhecido pelo movimento Occupy e o que ficou conhecido como a Primavera Árabe, nossos lexicógrafos escolheram a tag como sua Palavra do Ano de 2012. Aqui está um trecho do nosso lançamento que dá uma boa explicação para a nossa escolha:
2012 viu as campanhas políticas mais caras e alguns dos eventos climáticos mais extremos da história da humanidade, desde enchentes na Austrália a ciclones na China, ao furacão Sandy e muitos outros.
Ficamos sérios em 2013. A privacidade de todos estava naquele ano, desde a revelação de Edward Snowden do Project PRISM até a chegada do Google Glass. Aqui está um trecho do nosso anúncio em 2013:
Muitos de nós abraçamos as mídias sociais, optando por oferecer informações íntimas e fotografias pessoais no Facebook, Twitter e Instagram; Essa participação robusta ecoa uma observação de Mark Zuckerberg em 2010 de que o nível de conforto do público em compartilhar informações pessoais on-line é uma “norma social” que “evoluiu com o tempo”. Mesmo assim, uma pesquisa recente da Harris Poll mostra que os jovens estão agora monitorando e alterando suas configurações de privacidade mais do que nunca, um desenvolvimento que o USA Today apelidou de "efeito de Edward Snowden".
Alerta de spoiler: As coisas não ficaram menos sérias em 2014. Nossa Palavra do Ano foi a exposição, que destacou o surto do vírus Ebola no ano, chocantes atos de violência tanto no exterior quanto nos EUA e o roubo generalizado de informações pessoais. Aqui está o que nós tivemos a dizer sobre a exposição em 2014:
Do senso de vulnerabilidade que permeia o Ebola à visibilidade de atos de crime ou má conduta que provocaram conversas críticas sobre raça, gênero e violência, vários sentidos de exposição foram expostos ao público este ano.
A fluidez da identidade foi um grande tema em 2015. A linguagem em torno do gênero e da identidade sexual se ampliou, tornando-se mais inclusiva, com acréscimos ao dicionário, como gênero fluido, bem como o prefixo neutro de gênero Mx. A identidade racial também teve muito debate em 2015, após Rachel Dolezal, uma mulher branca se apresentar como uma mulher negra, disse que ela se identificou como biracial ou transracial. Nossa Palavra do Ano em 2015 refletiu as muitas facetas da identidade que surgiram naquele ano.
Xenofobia.
Em 2016, selecionamos a xenofobia como nossa Palavra do Ano. O medo do "outro" foi um grande tema em 2016, do Brexit à retórica de campanha do presidente Donald Trump. Em nosso anúncio, pedimos aos nossos leitores que refletissem sobre este termo em vez de celebrá-lo:
Apesar de ser escolhida como a Palavra do Ano de 2016, a xenofobia não deve ser celebrada. Pelo contrário, é uma palavra para refletir profundamente à luz dos acontecimentos do passado recente.
A palavra cúmplice surgiu em conversas em 2017 sobre aqueles que se manifestaram contra figuras e instituições poderosas e sobre aqueles que permaneceram em silêncio. Foi um ano de despertar real para a cumplicidade em vários setores da sociedade, da política à cultura pop. De nosso anúncio de Palavra do Ano de 2017:
Nossa escolha para Palavra do Ano é tanto sobre o que é visível quanto sobre o que não é. É uma palavra que nos lembra que até a inação é um tipo de ação. A aceitação silenciosa do erro é como chegamos a esse ponto. Não devemos deixar que isso continue a ser a norma. Se fizermos isso, então somos todos cúmplices.
REVISÕES DE NEGOCIAÇÃO.
Comentários de negociação.
Comentários de negociação.
Estoque, Forex e Credenciamento de Opções.
Eles dizem que a idade média de um gestor de fundos é de 27 anos. Os mercados se movem em ciclos geralmente em torno de 8 anos. Isso significa que no início de cada ciclo global de mercado de baixa, a maioria dos gerentes de fundos não tem ideia do que esperar, como reagir e como proteger seu dinheiro. Eles caem nos mesmos truques que o resto do dinheiro idiota, não importa quantas telas eles estejam manipulando.
Não acredita nisto? Basta olhar para o valor do seu portfólio. Nosso palpite é que você não estaria aqui agora, se você não achava que havia uma maneira melhor de administrar seu dinheiro arduamente ganho.
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A idade média de um gestor de fundos é 27.
Dê uma boa olhada, lá está algo que combina perfeitamente com o seu estilo.
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& # 8211; O produto funciona?
& # 8211; O produto é uma farsa?
& # 8211; Revisão e conclusão do produto.
Nem todas as avaliações premium são positivas. As avaliações premium lhe darão todas as informações necessárias para tomar uma decisão informada.
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Esperamos que nossos comentários o ajudem a chegar a uma decisão informada sobre qualquer produto que você deseja comprar. Estamos aqui para ajudar. Se você tiver alguma dúvida, não hesite em nos contatar. Obrigado.
Termos de pesquisa relacionados:
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Estratégia de opção binária sinhala
Dois grandes anúncios hoje!
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Inspeção de embuste 2018 | O IQ Option Scam Broker?
RESUMO: Sendo uma das maiores corretoras de opções binárias do mundo, a IQ Option é uma corretora de escolha para muitos traders satisfeitos. Graças a um depósito mínimo de apenas US $ 10 e um investimento mínimo de US $ 1, é também o corretor mais acessível. Todas as operações de negociação e transações conduzidas pela IQ Option são reguladas por várias instituições responsáveis, incluindo o regulamento CySEC com o número de licença 247/14, assegurando um ambiente seguro e justo para todos os comerciantes. A IQ Option é uma corretora perfeitamente segura e segura para negociar, e você pode até mesmo testar a plataforma com uma conta demo sem fornecer as informações do seu cartão de crédito.
IQ Option Binary Options Broker tornou-se uma plataforma bem conhecida em todo o mundo hoje em dia. Cada vez mais os traders preferem essa plataforma específica para negociar não apenas opções binárias, mas também moedas estrangeiras e até moedas criptográficas. Mas há um risco de que a IQ Option pareça ser uma fraude? É muito fácil revelar isso, mas hoje em dia também é fácil enganar, pois há muitos corretores diferentes e muitos comerciantes inexperientes. Scammers estão, infelizmente, presentes no mercado e cada corretor deve ser verificado cuidadosamente antes de qualquer passo para o depósito é tomado. Por isso, é vital realizar uma inspeção de esquema IQ Option.
IQ Option Inspeção Scam | História e Plataforma de Negociação.
Primeiro de tudo, os corretores de fraudes podem ser facilmente detectados por fatos de sua história. De fato, às vezes não há história alguma. IQ Option foi apresentado ao mercado em 2013, a Rússia foi a primeira a ver e usar a plataforma, e entre os comerciantes russos rapidamente ganhou uma forte reputação e também se tornou popular em um curto período de tempo. Isso permitiu que a IQ Option se desenvolvesse e se espalhasse ainda mais, logo se tornou conhecida em países europeus, China, América e assim por diante. Também há uma coisa importante neste tópico da inspeção de esquema IQ Option: logo após a revelação da plataforma, os desenvolvedores forneceram aplicativos para iOS e Android. Tal esforço para tornar a plataforma mais acessível a todos sugere que os desenvolvedores se importem com cada cliente que decide confiar na IQ Option. Mas não aceite apenas nossa palavra, visite o website deles e veja você mesmo.
Teste seu suporte ao cliente, converse com eles via chat ao vivo, pergunte qualquer coisa que lhe interesse por e-mail ou formulários da web e veja o quão rápido e bom as respostas serão. Você pode até mesmo abrir uma conta demo com eles, que é, até onde sabemos, um dos melhores do ramo - pode ser usado indefinidamente e nem requer um depósito! Um clique é tudo que você precisa. Estes são provavelmente alguns dos métodos mais importantes de pesquisar um corretor e estamos muito satisfeitos com os resultados que eles produziram. No mínimo, podemos dizer que a inspeção histórica do IQ Option foi muito bem.
IQ Option Awards.
IQ Option Inspeção Scam | Reputação internacional.
Especialistas internacionais já valorizaram altamente a IQ Option. Em 2013, a plataforma foi nomeada como a corretora de opções binárias mais inovadora, pois fornece maneiras fáceis de negociar, que foram até mesmo chamadas de revolucionárias pelo Relatório Forex. O ano de 2014 trouxe à plataforma o nome do corretor de opções binárias mais confiável, os especialistas são altamente confiáveis - os da academia MasterForex-V. Com seu design colorido e muitos acessórios úteis, a plataforma é igualmente bem aceita tanto por iniciantes como por traders especializados, porque oferece uma maneira clara e rápida de negociação e praticamente qualquer um pode aprender a usá-la. Deve-se dizer que a plataforma é proprietária, o que não é comum neste negócio, mas isso não faz mais complicado. Pelo contrário, todos os ativos oferecidos são conhecidos mundialmente, por isso ninguém terá que perder tempo pesquisando novos mercados e se familiarizando com novas empresas. Aqui, obviamente, o nosso detector de golpes IQ Option diz que ele também passa como um corretor seguro e você pode aprender mais se for à nossa análise da IQ Option Trading Platform 4.0.
Plataforma de Negociação IQ Option 4.0.
IQ Option Inspeção Scam | Forma de pagamento.
Embora o depósito mínimo e o comércio mínimo sejam excepcionalmente baixos, o que é uma das características mais importantes do corretor, a IQ Option pratica uma política de pagamento bastante rígida, que inclui seguro obrigatório da conta de cada cliente em um banco europeu. Isto é devido à sua licença CySeC. Abordam todas as transações com grande cuidado, têm regras que explicam todas as situações até ao mais ínfimo pormenor e são geralmente muito sérias e profissionais. Os clientes perceberam isso e você pode encontrar vários comentários positivos e comentários sobre esse corretor. Afinal, eles receberam muitos prêmios nos últimos anos, o que realmente diz muito. Obviamente, também existem alguns comentários negativos, mas você verá que eles vêm de pessoas que perderam dinheiro com seus próprios erros e estão apenas procurando alguém para culpar. Tudo isso nos garante que esta inspeção do IQ Option está indo muito bem. E, como dissemos anteriormente, você sempre tem a opção de testar tudo por si mesmo se abrir sua conta de demonstração do IQ Option. É totalmente gratuito e você não terá que deixar nenhuma informação financeira!
IQ Option Inspeção Scam | Retirada.
Um momento muito sensível e significativo na inspeção do golpe IQ Option é a questão da retirada de fundos, pois mostra a facilidade com que você pode - ou não pode - receber seu próprio dinheiro. A retirada pode ser realizada de diferentes maneiras, dependendo das preferências do cliente. WebMoney, QIWI, Skrill, Neteller estão disponíveis, bem como Visa e Mastercard. O trader precisa preencher e enviar uma solicitação, mas isso geralmente leva alguns minutos, o que é importante para os operadores ocupados e ocupados. Todas as retiradas serão processadas dentro de um dia útil. A facilidade com que qualquer pessoa pode retirar seu dinheiro mostra a confiabilidade da plataforma. Além disso, se um profissional tiver algum problema, ele poderá sempre consultar a equipe de suporte da IQ Option e receber uma consulta completa. Analisamos o processo de retirada com grande detalhe em nossa Revisão de Retirada da IQ Option, que pode ser mais útil se você quiser pesquisar mais este tópico.
IQ Option Inspeção Scam | Conclusão.
Por tudo isso, podemos dizer que o exame de fraude da IQ Option correu bem e que a plataforma pode ser recomendada aos operadores que apreciam a segurança e a honestidade. Este é um corretor que valoriza muito os seus clientes e fornecerá um excelente serviço para eles. Eles são absolutamente confiáveis e seguros, têm muita experiência e oferecem algumas características únicas. Você é capaz de testá-los completamente graças à sua conta demo sem limitações e a equipe de suporte é rápida em responder através de todos os meios habituais de comunicação. Tanto os comerciantes novatos como os mais experientes têm a certeza de encontrar algo que lhes convém e se procura um novo corretor, a IQ Option é certamente uma excelente escolha.
Opção IQ | Visualização do site ao vivo.
Ei Max, eu só quero esclarecer como foi a retirada.
& # 8211; Por que eu deveria retirar todo o montante dos meus ganhos assumidos e meu depósito?
& # 8211; Gostaria de saber se posso continuar sendo meu depósito e retirar apenas meus ganhos. isso é possível?
& # 8211; o lock-in, digamos que os cartões bancários são 90 dias, certo? se eu ganhar $ 50 e depositar $ 50, esperarei pelo prazo de 90 dias? é que a opção iq governa?
por favor, deixe-me esclarecer em sua opinião como o que eu li.
Apenas para esclarecer uma coisa, você tem total controle sobre quanto você retira (contanto que você tenha esse dinheiro em sua conta de negociação, é claro). Então você não precisa retirar nada, retirar o quanto quiser.
Quanto aos 90 dias, isso significa que você poderá retirar a quantia de seus depósitos nos últimos 90 dias para o seu cartão. Tudo o que excede esse montante (lucro) deve ser retirado para uma carteira eletrônica (Skrill, Neteller, Webmoney) ou via transferência bancária.
Oi. Eu gostaria de dar aos meus filhos um presente Bitcoin. Como eu tenho uma conta aqui, posso usar essa para fazer três depósitos separados que eles poderiam usar de forma independente. Ou precisarei iniciar três contas separadas?
Olá Pete. Você pode esclarecer um pouco? Você quer saber se você pode fazer três depósitos separados no mesmo saldo de conta para que eles possam ser usados separadamente? Eu receio que isso não funcione dessa maneira. Se eu entendi corretamente, abrir três contas diferentes parece muito mais fácil.
Basta clicar no botão na parte inferior do artigo e se inscrever.
Eu abri uma conta com a opção de QI, mas lê-se que eu deveria verificar minha conta e eu não sei como posso fazê-lo, por favor, ajuda, o que posso fazer ?. Se minha conta não for confirmada, não poderei negociar com este corretor ?.
Desde que eu abri uma conta com este corretor eu nunca recebi qualquer chamada deles, isso significa que eu fiz um erro enquanto eu abri a conta que os impediu de me ligar de volta e confirmar que eu fiz isso ?.
Por favor responda minha pergunta. Obrigado!
Olá John, obrigado pelas perguntas 🙂
A confirmação da conta é um processo que você precisa concluir para poder fazer um saque. Para fazer isso, você precisa enviar uma cópia de algum tipo de identificação com foto emitida pelo governo, uma prova do seu endereço (uma conta de luz ou um extrato bancário) e uma cópia do cartão que você usou, se você método para depositar.
Quanto à ligação, eu não sei sobre isso, mas você pode entrar em contato com a empresa e agendar uma ligação, eu acho. Espero que tudo isso ajude 🙂 Você tem alguma outra pergunta?
Oi, Muito interessante revisão sobre IQ Option. Eu tenho alguma experiência em negociação forex e interessado em iniciar a IQ Option para viver. você pode me responder o seguinte ou qual é o melhor caminho para mim:
1. Quero começar a depositar com meu cartão Visa de débito (que aceitou on-line internacional).
2. Retirarei para o meu cartão de débito o mesmo valor que foi depositado via cartão Visa de débito.
3. Se eu usar o Skrill para uma nova retirada de despesas. Está tudo bem?
4. Você tem alguma outra sugestão, por favor?
Tudo isso soa muito bom para mim, mas eu recomendo que você use o Skrill (ou qualquer outro e-wallet) tanto quanto você pode aqui, porque as taxas são muito menores dessa maneira. É claro que o seu cartão de débito Visa deve ser bom, mas como você disse, você precisará retirar a quantia que depositou antes de poder retirar o lucro através de outro método.
Eu também posso direcionar você para nossa página de estratégia (binaryoptionstrading-review / binary-options-strategy /) se você precisar de alguns materiais educacionais.
Se não, basta clicar no botão no final do artigo aqui e você será levado para a tela de criação da conta.
Você tem mais perguntas? Por favor, não hesite em perguntar.
Eu sou Hong Kong, é legal?
Sim, claro. A IQ Option trabalha com traders de Hong Kong e todos os métodos de pagamento, incluindo o Skrill, devem estar disponíveis para você. Outras opções de carteira eletrônica incluem Neteller e Webmoney.
Se eu investir por 1 dólar, então, como obterá lucro ou quanta perda.
Depende do ativo. Seu lucro pode subir para cerca de 90%, então quanto mais você investe, mais você pode ganhar. Então, é tudo sobre encontrar o equilíbrio que combina com você. Você já fez um depósito?
A opção iq é legel na Índia?
Sim absolutamente! Basta abrir uma conta através do link na parte inferior deste artigo e você estará pronto!
é possível usar a opção iq na áfrica do sul.
sim, claro. basta usar o link na parte inferior do nosso artigo para se inscrever e você estará pronto em pouco tempo!
Você precisará adicionar uma carteira eletrônica para poder retirar os lucros. Você só poderá retirar o valor de vencimento do depósito que fez na sua conta de cartão de crédito.
Exemplo: Deposite US $ 100 & # 8211; faça lucro US $ 50 = saldo da conta US $ 150. Primeiro você precisa retirar seu depósito.
Então, se você quiser retirar seu lucro de US $ 50, você precisa fazer um saque na sua conta de cartão de crédito! Somente depois de ter feito a retirada do total de vencimento de US $ 100 para sua conta de cartão de crédito, você poderá (e só poderá usá-lo) em sua carteira eletrônica.
Depois de retirar seu capital de maturidade de US $ 100, só há uma transferência para a carteira eletrônica possível. Depois disso, todos os levantamentos posteriores para a sua conta do cartão de crédito não serão executados.
Como carteira eletrônica eu recomendo o uso de SKRILL porque eles também estão oferecendo uma opção de bitcoin para transferências de dinheiro.
O SKRILL é usado para lidar melhor com o problema filipino de não ter uma identidade nacional oficial. Minha namorada abriu uma conta SKRILL e usou o ID do eleitor para o processo de verificação. Tudo correu bem.
A NETELLER fez muitos problemas com a verificação da conta, embora a SKRILL pertença à empresa NETELLER.
A NETELLER tem um problema com os vários IDs filipinos. Eles geralmente não estão preparados para resolver esse problema.
Por favor, verifique primeiro todos os métodos de transferência de dinheiro. Uma vez verificado pela IQ Option, não haverá mais problemas com as retiradas. Primeiro o KYC & # 8211; verificação.
É o mesmo procedimento, como nas Filipinas & # 8211; Primeiro você precisa prosseguir com a verificação do KYC para abrir uma conta bancária & # 8211; Conta PayMaya & # 8211; Conta do GCash. & # 8211; conta coins. ph. Depois disso tudo está funcionando bem.
Ao enviar philipé PESO php pelo seu cartão de crédito você sempre deve se lembrar que a taxa de câmbio para a transferência de dinheiro de PhP para USD é de cerca de 4%.
Portanto, para fazer um depósito de US $ 100 na sua conta PayMaya PESO usando a opção Cartão de Crédito, você terá um custo de US $ 104. Se a taxa de câmbio for PhP50 / 1 USD, significa que você precisará de um saldo de valor de cerca de 5.200 PhP.
Para abrir uma conta coins. ph, você pode transferir o dinheiro do SKRILL para o coins. ph usando o BITCOIN. Todo o processamento custará cerca de 10% do valor original transferido. Então, se você estava procedendo a retirada de US $ 50 para sua conta coins. ph, haverá cerca de US $ 45.
Mas assim a negociação é possível sem o uso de qualquer conta bancária (para somas menores & # 8211; coins. ph permite apenas um saldo máximo de 400.000 / ano).
Oi eu só quero perguntar .. Eu sou das Filipinas e eu tenho um cartão de débito / mastercard .. eu poderia usar esse cartão para financiar minha conta e começar a negociar?
Olá john! Sim, a MasterCard deve estar bem. Só não se esqueça de que precisa de uma cópia do cartão para concluir o processo de verificação 🙂
Im De Filipinas, eu tenho uma moeda de cartão de débito (VISA) é PESO. será que vai dar certo? para depósito e retirada ou eu preciso abrir uma conta em dólar.
Olá! Eu acho que você deveria estar bem porque a moeda deve ser trocada automaticamente. Você tem tudo o que precisa para verificar sua conta?
Sim eu quero. Obrigado! com relação à taxa de câmbio? Devo seguir a taxa de câmbio aqui em nosso país, depositando dinheiro?
Como eu disse, acho que o dinheiro será trocado automaticamente de acordo com a taxa internacional atual. Mas ter informações extras nunca é demais, então fique de olho na situação 🙂
Você deve ler também meu comentário acima sobre a abertura de uma carteira eletrônica.
Sobre o cartão Visa. Você deve verificar quanto o emissor do seu cartão Visa está cobrando pelas trocas de moeda.
Meu cartão Visa é da Alemanha e cobra 1,75% pelo câmbio de EUR para qualquer outra moeda.
A taxa de câmbio que o cartão Visa está usando é menor do que a taxa de câmbio oficial. Então você só é capaz de calcular um valor estimado.
Exemplo: eu quero depositar USD100 & # 8211; inclusive a taxa de câmbio custa-me USD101.75. Se a taxa de câmbio for 1,195USD / 1 EUR, estou usando 1,185 para ter certeza de que o valor da minha conta do cartão Visa é suficiente. USD101,75 / 1,185 USD / EUR significa que eu preciso de um montante em torno de EUR85.87 = EUR86 na minha conta.
Conta de cartão Visa PhP: Por exemplo, a taxa de câmbio do seu provedor de cartão Visa pode ser de 2,5%. Você precisa de um montante de USD102,5. A taxa de câmbio de pode ser PhP50.5 / 1 USD. Para estar seguro com o valor em sua conta, eu usaria 49PhP / 1 USD. O valor a ser depositado na conta do cartão Visa PhP deve ser em torno de PHP5.023 significa que você precisará de = PHP 5.050 em sua conta do cartão Visa.
Fui contatado pelo Instagram com uma oportunidade de alguém e eles usam sua plataforma .. $ 500 é o pedido e 6000 é o retorno com 10%. isso parece legítimo de seus corretores?
Olá Dre. Por favor, note que esta não é a nossa plataforma. Nós simplesmente revisamos e não fazemos parte da IQ Option.
Essa pessoa que contatou você se apresentou? Eles são um representante oficial da IQ Option?
Talvez você possa me dizer como fazer uma transferência bancária ou Skrill para que eu possa depositar o mais rápido possível.
Basta ir ao seu banco e fazer um depósito na conta que o corretor fornece. Acho que está na seção de depósito da sua conta quando você faz login na sua conta da IQ Option. Você já criou um?
Oi, eu sou do Reino Unido e gostaria de participar, mas eu não sei muito sobre negociação. Você orienta e apoia para ganhar experiência?
Além disso, eu só tenho PayPal. Para o Reino Unido, que outras opções de contas eu poderia ter?
Olá Abby! Se você quiser aprender sobre negociação, você pode conferir nossa seção Estratégia (binaryoptionstrading-review / binary-options-strategy /). Nós temos muitos artigos educativos lá.
Você pode, por favor, explicar o que você quer dizer com as opções de conta & # 8221 ;?
oi eu frm paquistão eu tenho pouco medo de depositar dinheiro como eu não tenho muito então apenas me dê uma pequena ajuda para se sentar e eu não entendo as contas para abrir como eu vou fazer essa ajuda plz.
Bem, com a IQ Option, você não precisa investir muito. Você pode começar a negociar com apenas 10 dólares. Quais métodos de depósito você tem acesso?
Eu não sei qual método você prefere? e gentilmente semid me link para vedios para iniciantes & # 8230 ;.
Bem, talvez um cartão de crédito ou de débito seja o caminho mais rápido. Mas você também pode usar uma transferência bancária ou Skrill & # 8230; Qual desses métodos você tem?
Eu sou de Dubai, graças à opção de QI, realmente foi bom. Eu depositei $ 400 de desejo que eu quisesse mudar meus móveis em casa. Acabei de receber meu pagamento de $ 1000. agradeço muito, vou investir mais até o final do mês.
Oi eu sou Leah de filipinas e eu comecei hoje! Eu me registrei no IQ Options e preciso ter uma conta real e isso é dólar. Eu tenho conta bancária, mas eu não sei como abrir uma conta no QI. E mais uma coisa se eu investir um mínimo de 10 $ como posso ganhar e como posso widraw-lo! Eu aprecio se você pudesse me ajudar com este assunto.
Muito obrigado.
Olá Leah! Para começar a negociar com este corretor, basta clicar no botão laranja na parte inferior deste artigo e você será levado para a página onde você pode criar sua conta de negociação.
Se você investir US $ 10, você ganha dinheiro fazendo negócios bem sucedidos, porque toda previsão correta traz lucro. Quando você quiser sacar dinheiro, tudo o que você precisa fazer é preencher um formulário de solicitação de retirada no site do corretor e submetê-lo e o processo de retirada será iniciado.
Posso te ajudar com mais alguma coisa?
E se eu não tiver cartão de crédito? sou das Filipinas.
Você tem Skrill ou talvez uma conta bancária para realizar uma transferência bancária?
Nestas conta online POLI, WebMoney, Skrill e Neteller qual é o melhor e mais fácil de abrir como im do Paquistão. Muito obrigado.
Basicamente, é tudo a mesma coisa, muitos comerciantes do Paquistão preferem o Skrill ou o Neteller, mas é sempre da sua preferência qual você prefere.
Há mais alguma coisa que eu possa ajudá-lo?
im do Paquistão, gostaria de saber que o procedimento para obter dinheiro do lucro de IQ opção de negociação para a minha mão tão gentilmente me ajudar em detalhes completos, incluindo as partes que envolvem isso. Muito obrigado.
se eu abrir minha conta no skrill ou em qualquer outra conta, então como eu posso sacar dinheiro do skrill?
Para retirar, tudo o que você precisa fazer é clicar em Retirar Fundos. Uma lista de ícones grandes de métodos de retirada disponíveis aparecerá. Basta escolher o que melhor lhe convier, insira o valor e outras informações e clique em "Levantar fundos". Sua solicitação será tratada em 24 horas.
Eu estou prestes a começar a negociar com você sou da Tanzânia é este país permitido? se não o que vai acontecer com o meu dinheiro em que vou investir?
Olá Tony! Sim, a IQ Option aceita comerciantes da Tanzânia. Basta clicar no botão laranja na parte inferior do artigo (o que diz OPEN FREE TRADING ACCOUNT NOW!) E você poderá começar a negociar imediatamente!
Isso funcionará no Nepal?
deve, tanto quanto eu sei. você já trocou opções binárias antes?
Olá. É válido se eu usei cartão de débito de visto do nosso país (filipinas) para depositar e retirar? Levará quantos dias para ser processado. Eu também tenho skrill. O que eu vou usar em vez disso? Obrigado.
Sim, claro, você pode usar este cartão se for internacional e válido para compras pela Internet. Além disso, o Skrill também deve ser bom. Você tem outros métodos em mente?
Geralmente, leva alguns dias para que as transferências bancárias fiquem visíveis no saldo da sua conta.
Eu tenho uma conta .. com 50 $ depósito .. eu ganho lucro de 300 $ depois de uma hora .. agora posso retirar 350 $ da minha conta? se sim quantos dias demora para processar.
você poderá retirar os 50 $ da mesma maneira que você os depositou, mas precisará escolher outro método para retirar o lucro. Sua solicitação deve ser processada em alguns dias.
você tem uma conta Skrill ou algo assim?
Ei .. eu depósito 1000 dólares e recebo 5000 dólares .. Posso retirar apenas 4000 dólares (lucro) no mesmo dia eu obter esse lucro?
E quais são os requisitos para retirada (lucro)?
não há requisitos mínimos de retirada, se é isso que você quer dizer. A retirada máxima é de 1.000.000 dólares por dia.
você deve poder retirar, mas pode demorar um dia ou dois para que sua solicitação seja processada. Qual método você está usando?
O método de retirada e depósito é o mesmo.
sim, você deve ter as mesmas escolhas. É isso que você quer dizer?
Desde então, eu sou do Sri Lanka, a prova que tenho de apresentar em levantamentos é apenas o meu cartão de identidade nacional e está impressa na língua nacional do nosso país, o cingalês. Será um problema retirar meus fundos no final? Porque eu ainda não tenho meu passaporte ou carteira de motorista.
Além disso, preciso saber se posso usar meu cartão de débito para receber fundos em saques, em vez de usar um cartão de crédito?
você tem / consegue um extrato bancário? isso deveria ser suficiente.
Oi, posso usar o visto de cartão de débito atm para depositar?
Claro, você pode usar este cartão se for internacional e válido para as compras pela Internet.
Quanto você estava pensando em depositar?
Por favor, como posso fazer meu depósito na minha conta Naira na Nigéria? Parece que os cartões de débito de visto não estão passando.
uma carteira eletrônica pode ser a solução certa. você tem um?
Eu quero saber se pagando porque eu Info que não paga?
você pode esclarecer? você não tem que pagar por uma conta de demonstração, se é isso que você quer dizer. caso contrário, 10 $ é o depósito mínimo para esta empresa.
você tem um código sem bonas?
Não, eu não acho que os corretores de opções binárias os deem. No entanto, podemos fornecer sinais gratuitos se você se juntar ao nosso Clube de Vencedores Binários (binaryoptionstrading-review / binary-winners-club-registration /)
Ansioso para ver você lá!
Como base da Nigéria, posso negociar com a opção IQ e posso fazer depósito com o meu banco A / C e retirar com ele ou eu preciso de uma conta especial para isso.
Eu não acho que você precise de uma conta especial para retirar dinheiro.
Posso ir ao site do corretor aqui nas Filipinas?
Existe um seminário no site?
Sim, acho que você deve poder acessar o site sem problemas. Quanto aos materiais educativos, há tutoriais em vídeo disponíveis. Não tenho certeza sobre seminários, mas é possível que eles os montem de vez em quando.
Isso requer cartão de crédito?
você pode depositar com cartão de crédito, sim, ou através de algum sistema de transferência on-line que essa empresa suporta. Naturalmente, os fios bancários também são uma opção.
ou você está perguntando sobre como acessar os materiais educacionais pagando?
posso negociar com a IQ Option na Tanzânia?
Eu acho que você pode, mas verifique com o corretor para ter certeza.
Em Bangladesh, eu começo a negociar? Eu tenho o cartão mestre payoneer. Posso i withdrow lucro com isso?
Eu acho que deve estar bem, mas verifique primeiro com o corretor.
Isso funcionará nas filipinas?
sim, eu acredito que deveria. Se você precisar de mais informações, entre em contato com o suporte do corretor em seu site.
para que este aplicativo é usado.
o pedido de retirada? isso é usado quando você quer fazer uma retirada. você fornece ao corretor os dados necessários para o processo passar sem problemas.
Oi .. eu tenho um problema em pagar a conta de 10 dólares. Os botões do teclado não aparecem quando clico no método de pagamento, portanto não consigo inserir o número do meu cartão.
você entrou em contato com a equipe de suporte sobre isso?
Posso começar a negociar nos Emirados Árabes Unidos?
Eu acho que você não deve ter problemas com a negociação lá.
Esta plataforma também funciona na Índia?
Eu acho que sim. Mas verifique com o suporte ao cliente do corretor, só para ter certeza.
Posso trocar o QI da vida real na Nigéria e, se sim, quais são os requisitos?
Eu acho que os requisitos são praticamente os mesmos em todos os lugares & # 8211; depósito mínimo de $ 10. Quanto ao seu país, você deve ir ao site do corretor e verificar, mas eu acho que você deve ser capaz de negociar.
Quanto pode um retirar de cada vez? Ou em um mês por favor?
Você pode retirar até US $ 1.000.000 por dia e não há restrições quanto ao número de retiradas. Qual método você estava planejando usar?
Os cidadãos indonésios podem participar no comércio de iqoption?
Onde fica o centro de corretagem de iqoption?
sim, os comerciantes da Indonésia devem poder negociar.
sua sede é em Limassol, Chipre. por que você pergunta? você precisa contatá-los?
é possível ganhar dinheiro negociando online?
claro que é. No entanto, você não pode simplesmente entrar cegamente. Uma estratégia sólida é necessária primeiro e você pode se instruir sobre o assunto na nossa guia Estratégia (binaryoptionstrading-review / binary-options-strategy /).
Além disso, você pode receber gratuitamente nossos sinais se você se inscrever no nosso Binary Winners Club (binaryoptionstrading-review / binary-winners-club-registration /), o que significa que você recebe algumas dicas muito úteis de nossos especialistas em negociação. Com isso, você deve estar no seu caminho para lucrar.
Oi, posso usar um cartão de débito para depositar na África do Sul.
claro. qual cartão de débito você planeja usar?
OHHH e eu esqueci de dizer, a opção iq é regulada pelo CYSEC então normalmente não deveria haver problemas. é difícil escolher o bom corretor de opções binárias sem ter medo de nunca mais ver nosso dinheiro sem perdê-lo em uma negociação. A última coisa, pessoas que perdem dinheiro em negócios, não se queixam porque o risco não é forçado a ser os corretores cita o problema, mas talvez suas estratégias e a segurança que você não tem por trás de sua estratégia.
concordou 🙂 você soa como um profissional experiente. você tem negociado com o QI por muito tempo?
Qualquer um sabe o produto da opção iq em que eles trabalham.
você pode esclarecer sua pergunta um pouco por favor?
A IQ Option é uma corretora de opções binárias, uma das melhores do mundo. Qual produto você quer dizer?
Como eu disse em outro lugar, nós não representamos a IQ Option de nenhuma maneira. Nós somos apenas revisores. Mas eu acho que os comerciantes sul-africanos são aceitos pela IQ Option. Verifique no site deles para ter certeza.
As Nigérians podem ser oportunas para negociar nesta Plataforma?
Não tenho certeza, mas acho que eles podem. Tente verificar o site deles.
sim. Eu sou um camaronês e estou negociando na plataforma.
obrigado pela informação. Tudo corre bem para você? 🙂
Posso ter seu contato pls & # 8230; am. em Camarões.
Esta Plataforma para Nigérians toi?
Sim. Apenas certifique-se de ter o método de depósito correto à sua disposição. Como você quer começar a negociar aqui?
Você tem permissão para aceitar clientes dos EUA? E você tem um escritório satélite nos EUA?
Nós não representamos a IQ Option de forma alguma, então você deve procurar por essa informação no site do corretor.
Pls pode u comércio na África Nigéria para b precisa? Pls me responde.
Sim, Moisés, você deveria poder negociar na Nigéria. Quanto você está querendo investir?
im na Tanzânia África Oriental, eu quero fazer um depósito e começar a negociar. é possível no meu país?
Você deve tentar encontrar essa informação no site do corretor. talvez pergunte a sua equipe de suporte sobre isso.
Se você puder depositar através de um dos métodos que eles aceitam, então eu não vejo um problema, mas verifique com a empresa para ter certeza.
está disponível nas Filipinas?
como eu disse a Steffan, logo acima de você, verifique no site do corretor 🙂
Eu sou um novato aqui e um filipino. Depois que visitei o site e vi as Filipinas, ele foi incluído na negociação. Há 120 países ativos participando.
Obrigado por essa informação. Do you have an account with IQ Option, too?
Will the ‘IQ option’ work with Nigerians?
Sim & # 8230; I am in Nigeria.. It works.. I’m using a real account.
Thanks for confirming that. How are things working out for you?
Please how did you make your deposit from Nigeria. It seems the debit cards are not working?
Im from the Philippines im interested to open an account do IQ Option allow traders as well?
I recommend you check that with the broker directly, via their customer support on their website.
I’m a student and I’m away from home I wanna know if I can use my bank statement to serve as proof of address?
do you have an ID to go along with it?
IQ option trading is scam site? resposta pls.
No, IQ Option is one of the very best companies when it comes to binary options trading. They also have a CySEC license, which proves they are reliable. Why do you ask about IQ Option being a scam?
I have noticed that IQOption does not make top ten. I hear that many people have complained about the platform.
Usually you need a government-issued ID, a proof of address and a copy of the credit card you used to make a deposit.
i live in india , is it legal to do binary option trading in india??
IQ Option should accept you, if that’s what you mean 🙂
there are no problems with that, as far as I’m aware of.
How much do i have to invest to start trading? or how much do I need to start trading.
Can I really earn money using iq option?
The minimum deposit you need to make is only 10$, one of the lowest in the whole binary options industry. Furthermore, you only need $1 to open a trade. So it’s really easy to start trading here 🙂
Do you need any more assistance?
please i would like to start……how do i start….i want to but afraid…
help….explain in detail pls.
I suggest you read our strategy section a bit and familiarize yourself with the basics. that should help you get rid of your fear.
Hi Iam from South Africa can I trade with real money and what is my minimum deposit required. I will be checking my email.
minimum deposit with this broker is $10.
Im so intrigued by this platform i have been using it for weeks now with a demo account and has not found any descripencies with it. My opinion i researched about this broker looked for everybit of prons and cons on them they are legit yes its a new organisation that was inteoduced 2008 and widespread on 2012 . Most people might not have faith on new invented company more eapecially dealing with money however i say trust your instincts read around hear what other researches have to say about iq options and make you decisions or other thing open a demo account utilise it see the educational facilities do trades and even call the customer support services and test them yourself. Im not dissapointed m soo sure you will never be aswell.
thank you for that thorough review 🙂
have you opened a real trading account with them after using the demo?
I need to know how the Call and Put buttons works, and generally how to operate the IQ app on mobile device?
You see I will the answer for you if you choose call button and you win the aamount of the losers will be credited to you I you losee you ammount will go to winners.
Call button means you expect the price to be higher at your expiry time than it was when you opened trade, while the Put button means you expect the price to go down.
The app can be downloaded from the broker’s website or the app stores. As for using it, it’s pretty much the same like the regular platform.
I this user friendly for south africans? And will I be paid in dollars or Rands ? Which documents do I need for withdrawals ?
You will need a copy of your ID, a proof of your address and a copy of your credit card if that’s what you decide to use.
Yes, South Africans can trade here and I think you will be paid in dollars, but that can be automatically converted to rands in your bank account, I think.
Which money transfer method are you using?
Does it option accept traders from the Caribbean Jamaica.
honestly, I don’t know. I recommend you check with their customer support.
Is iq option supported in the u. s?
Unfortunately, this s not the case at the moment.
I would recommend this broker if you’re from the US:
have you ever traded binary options before?
I just wanted to know..me who lives in the Bahamas can use this platform n how do I go throught the paces.
yes, just click on the button at the bottom of this article and you will be taken to the screen where you can create your trading profile. you are familiar with the financial requirements?
Can I use IQ options from Uganda, East Africa?
yes, I think IQ accepts all African countries. can I help you with anything else?
jebale sebbo. yes u can trade sebbo.
Im from india..can i trade with iq options??
As they demand investments only in USD, EUR AND GBP..
sim você pode. the amounts will simply be converted automatically. How much were you thinking of investing?
Is this broker is scam or real. any one help me.
This is a completely reliable broker. They even have a license fro CySEC, EU’s regulatory body. When it comes to safety, this broker is one of the best 🙂
Do you need help with anything else?
I’d like to know if they allow visa card for deposit and withdrawal of funds?
yes, yes they do 🙂
Love the website – very user friendly and whole lots to see!
Thank you very much! What do you like the most?
Can New Zealand Use This IQ Options?
yes, yes they can 🙂
as a matter of fact, it’s probably the best choice you have. Have you opened an account yet?
Hi, I’d like to know Can this platform is used in INDIANA trader also.
If you mean India, then yes. If you mean the state of Indiana, then I’m afraid not because US traders are not accepted at the moment. Can you clarify?
do they accept traders from philippines? obrigado.
yes they do. do you know how to get started?
I would like to know if traders from Indonesia is allow to join.
Thanks in advance for your response.
yes, Indonesian traders are accepted. Do you have any more questions? 🙂
How do I get hold of the support team?
go to the company’s website. there you will find addresses and phone numbers of all their offices around the world, as well as their e-mail address.
Are the demo results a real reflection of what i would achieve on a real live trading account? Been winning so much to a point where i felt like nah man it can’t be this easy…
What is the possible average profits can one get a day?
depends on how much you invest. profits can go up to 90% per trade. How much were you thinking of depositing?
What are the chances of winning?
That’s great. because I am nt needy but I wanna start trading,$10 is avodable even $1.um soo happy. i wanna start trading with u.
the chances of winning are pretty good if you have a decent strategy. if you need help with that, head on over to our strategy tab (binaryoptionstrading-review/binary-options-strategy/)
have you already opened an account?
I see they have the Bancontact/MrCash option enabled for deposit, pretty simple. So my question is , as a Maestro card holder, this option is enabling me to deposit with no problems, but can I get withdrawals (in case of) on the same Maestro debit card directly or do I need to select one of the options above and link that card to some other system … ?
you should be able to withdraw directly to your debit card, but be aware that you can withdraw only as much as you had deposited. All profits will be sent to you by another method (like bank wire or some online payment system)
hi do we have members from Saudi Arabia? do they not facing problems in withdrawing their money?
hello 🙂 I haven’t noticed any complaints from those traders or from traders in general about the withdrawal here. Are you from Saudi Arabia? Have you experienced any problems?
DO they charge for withdrawals?
it is how to start and how to sell and purchase.
i want to chatting with u i want to some inquirey about iq option.
depends on the method you’re using. Which method do you prefer?
Hi, can this be used in the Philippines?
yes, no problem 🙂 do you need help in getting started?
Do they accept traders from Nigeria?
Yes 🙂 How much are you looking to invest?
I really wanted to try IQ Option has it was highly recommended. I’m new to the game and am disappointed that the rules recently changed. What is my best option (as a Canadian) in the mobile trading world?
I’m from India and will it be safe for me to trade in this platform?
Yes, IQ Option applies the same high security standards to all clients, no matter where they come from. Which transfer method will you use?
NOT FOR CANADIANS. I loved this platform. Very user friendly and strait forward. And I was doing well at first with the 60 second options. Suddenly my 60seconds started turning into 90-120secs. This was irritating and I was starting to loose money because my strategy relies on the 60seconds options. I contacted support and was told Canada is no longer supported and to withdraw my available funds so that they can block my account. 5 mins prior to that message I had just completed a deposit that they allowed with no notification. Now they are refusing and explanation and I have to wait up to 3 days before my withdrawl is processed. Very disappointing, no explanation, no notification or alert, I feel like I’ve been robbed. If you live in Canada DO NOT use IQ Option.
Canadian regulation regarding trading has recently experienced major changes and dozens of brokers got banned almost overnight. That’s why they don’t accept traders from there anymore. However, mobile trading is still an option for Canadian traders.
So your saying mobile trading with iq option will still be available in canada?
I think it should, I think they found a loophole regarding mobile trading. However, I’m not 100% on that, so I recommend you contact the broker’s support.
Hi please explain ? Mobile trading with I Q options even from Canada ?
Eu acho que sim. I think that the app should be available in Canada. I’m not certain, though. Maybe it would be best if you talked to the broker’s support.
Hello am from swaziland can i use IQ option for trading?
Yes, I believe you should be able to trade. Have you traded anywhere else before?
Hi, I’d like to know if they allow paypal for deposit and withdrawal of funds.. anyone..
don’t think so. POLI, WebMoney, Skrill and Neteller are your options here.
How much do i have to invest to start trading? or how much do I need to start trading.
Can I really earn money using iq option?
minimum deposit is $10 and that’s one of this broker’s main strengths. on top of that, you can also open trades for one dollar, so I think you really don’t need much to start trading with IQ 🙂
based on this, one really doesn’t need much to achieve profit.
why do I have some difficulties in entering login to start trading . When I have filled e’mail and password , it is will stated ” you have already registered” and then I can not log in again. Give explaination. Obrigado.
have you opened an account with them before? maybe you’re confusing registering and logging in 🙂 happens all the time. have you contacted the customer support about this?
On entering their tournaments and receiving a virtual trading account of $100 I have logged in several minutes after the tournament has started and found the tournament leaders to have accounts in the four figure mark. This is not possible to do and I would have to question if these are made up accounts by IQ option to scam people out of their entry fees. In the period of the tournament the leaders grow that $100 into unbelievable amounts. I would appreciate other traders views on this.
there are some very short expiration times over there, plus you can pay extra to start with a bigger amount which gives you an edge in the tournament. have you completed the tournament? what’s your experience with that particular type of trading and with IQ Option in general?
Binary option strategy sinhala
This module contains regular expression matching functions for strings and binaries.
The regular expression syntax and semantics resemble that of Perl.
The matching algorithms of the library are based on the PCRE library, but not all of the PCRE library is interfaced and some parts of the library go beyond what PCRE offers. Currently PCRE version 8.40 (release date 2017-01-11) is used. The sections of the PCRE documentation that are relevant to this module are included here.
The Erlang literal syntax for strings uses the "\" (backslash) character as an escape code. You need to escape backslashes in literal strings, both in your code and in the shell, with an extra backslash, that is, "\\".
Data Types.
Opaque data type containing a compiled regular expression. mp() is guaranteed to be a tuple() having the atom re_pattern as its first element, to allow for matching in guards. The arity of the tuple or the content of the other fields can change in future Erlang/OTP releases.
В В В В unicode |
В В В В anchored |
В В В В caseless |
В В В В dollar_endonly |
В В В В extended |
В В В В firstline |
В В В В multiline |
В В В В no_auto_capture |
В В В В dupnames |
В В В В ungreedy |
В В В В bsr_anycrlf |
В В В В bsr_unicode |
В В В В no_start_optimize |
В В В В never_utf.
The return of this function is a string with the PCRE version of the system that was used in the Erlang/OTP compilation.
The same as compile(Regexp,[])
Compiles a regular expression, with the syntax described below, into an internal format to be used later as a parameter to run/2 and run/3 .
Compiling the regular expression before matching is useful if the same expression is to be used in matching against multiple subjects during the lifetime of the program. Compiling once and executing many times is far more efficient than compiling each time one wants to match.
When option unicode is specified, the regular expression is to be specified as a valid Unicode charlist() , otherwise as any valid iodata() .
The regular expression is specified as a Unicode charlist() and the resulting regular expression code is to be run against a valid Unicode charlist() subject. Also consider option ucp when using Unicode characters.
The pattern is forced to be "anchored", that is, it is constrained to match only at the first matching point in the string that is searched (the "subject string"). This effect can also be achieved by appropriate constructs in the pattern itself.
Letters in the pattern match both uppercase and lowercase letters. It is equivalent to Perl option /i and can be changed within a pattern by a (?i) option setting. Uppercase and lowercase letters are defined as in the ISO 8859-1 character set.
A dollar metacharacter in the pattern matches only at the end of the subject string. Without this option, a dollar also matches immediately before a newline at the end of the string (but not before any other newlines). This option is ignored if option multiline is specified. There is no equivalent option in Perl, and it cannot be set within a pattern.
A dot in the pattern matches all characters, including those indicating newline. Without it, a dot does not match when the current position is at a newline. This option is equivalent to Perl option /s and it can be changed within a pattern by a (?s) option setting. A negative class, such as [^a] , always matches newline characters, independent of the setting of this option.
If this option is set, most white space characters in the pattern are totally ignored except when escaped or inside a character class. However, white space is not allowed within sequences such as (?> that introduce various parenthesized subpatterns, nor within a numerical quantifier such as . However, ignorable white space is permitted between an item and a following quantifier and between a quantifier and a following + that indicates possessiveness.
White space did not used to include the VT character (code 11), because Perl did not treat this character as white space. However, Perl changed at release 5.18, so PCRE followed at release 8.34, and VT is now treated as white space.
This also causes characters between an unescaped # outside a character class and the next newline, inclusive, to be ignored. This is equivalent to Perl's /x option, and it can be changed within a pattern by a (?x) option setting.
With this option, comments inside complicated patterns can be included. However, notice that this applies only to data characters. Whitespace characters can never appear within special character sequences in a pattern, for example within sequence (?( that introduces a conditional subpattern.
An unanchored pattern is required to match before or at the first newline in the subject string, although the matched text can continue over the newline.
By default, PCRE treats the subject string as consisting of a single line of characters (even if it contains newlines). The "start of line" metacharacter ( ^ ) matches only at the start of the string, while the "end of line" metacharacter ( $ ) matches only at the end of the string, or before a terminating newline (unless option dollar_endonly is specified). This is the same as in Perl.
When this option is specified, the "start of line" and "end of line" constructs match immediately following or immediately before internal newlines in the subject string, respectively, as well as at the very start and end. This is equivalent to Perl option /m and can be changed within a pattern by a (?m) option setting. If there are no newlines in a subject string, or no occurrences of ^ or $ in a pattern, setting multiline has no effect.
Disables the use of numbered capturing parentheses in the pattern. Any opening parenthesis that is not followed by ? behaves as if it is followed by ?: . Named parentheses can still be used for capturing (and they acquire numbers in the usual way). There is no equivalent option in Perl.
Names used to identify capturing subpatterns need not be unique. This can be helpful for certain types of pattern when it is known that only one instance of the named subpattern can ever be matched. More details of named subpatterns are provided below.
Inverts the "greediness" of the quantifiers so that they are not greedy by default, but become greedy if followed by "?". It is not compatible with Perl. It can also be set by a (?U) option setting within the pattern.
Overrides the default definition of a newline in the subject string, which is LF (ASCII 10) in Erlang.
Newline is indicated by a single character cr (ASCII 13).
Newline is indicated by a single character LF (ASCII 10), the default.
Newline is indicated by the two-character CRLF (ASCII 13 followed by ASCII 10) sequence.
Any of the three preceding sequences is to be recognized.
Any of the newline sequences above, and the Unicode sequences VT (vertical tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS (paragraph separator, U+2029).
Specifies specifically that \R is to match only the CR, LF, or CRLF sequences, not the Unicode-specific newline characters.
Specifies specifically that \R is to match all the Unicode newline characters (including CRLF, and so on, the default).
Disables optimization that can malfunction if "Special start-of-pattern items" are present in the regular expression. A typical example would be when matching "DEFABC" against "(*COMMIT)ABC", where the start optimization of PCRE would skip the subject up to "A" and never realize that the (*COMMIT) instruction is to have made the matching fail. This option is only relevant if you use "start-of-pattern items", as discussed in section PCRE Regular Expression Details .
Specifies that Unicode character properties are to be used when resolving \B, \b, \D, \d, \S, \s, \W and \w. Without this flag, only ISO Latin-1 properties are used. Using Unicode properties hurts performance, but is semantically correct when working with Unicode characters beyond the ISO Latin-1 range.
Specifies that the (*UTF) and/or (*UTF8) "start-of-pattern items" are forbidden. This flag cannot be combined with option unicode . Useful if ISO Latin-1 patterns from an external source are to be compiled.
Takes a compiled regular expression and an item, and returns the relevant data from the regular expression. The only supported item is namelist , which returns the tuple , containing the names of all (unique) named subpatterns in the regular expression. Por exemplo:
Notice in the second example that the duplicate name only occurs once in the returned list, and that the list is in alphabetical order regardless of where the names are positioned in the regular expression. The order of the names is the same as the order of captured subexpressions if is specified as an option to run/3 . You can therefore create a name-to-value mapping from the result of run/3 like this:
Same as replace(Subject, RE, Replacement, []) .
В В В В anchored |
В В В В notempty |
В В В В notempty_atstart |
В В В В bsr_anycrlf |
В В В В bsr_unicode |
В В В В CompileOpt.
Replaces the matched part of the Subject string with the contents of Replacement .
The permissible options are the same as for run/3 , except that option capture is not allowed. Instead a is present. The default return type is iodata , constructed in a way to minimize copying. The iodata result can be used directly in many I/O operations. If a flat list() is desired, specify . If a binary is desired, specify .
As in function run/3 , an mp() compiled with option unicode requires Subject to be a Unicode charlist() . If compilation is done implicitly and the unicode compilation option is specified to this function, both the regular expression and Subject are to specified as valid Unicode charlist() s.
The replacement string can contain the special character & , which inserts the whole matching expression in the result, and the special sequence \ N (where N is an integer > 0), \g N, or \g , resulting in the subexpression number N, is inserted in the result. If no subexpression with that number is generated by the regular expression, nothing is inserted.
To insert an & or a \ in the result, precede it with a \. Notice that Erlang already gives a special meaning to \ in literal strings, so a single \ must be written as "\\" and therefore a double \ as "\\\\" .
As with run/3 , compilation errors raise the badarg exception. compile/2 can be used to get more information about the error.
Same as run(Subject, RE,[]) .
В В В В В В В | match | nomatch |
В В В В anchored |
В В В В notempty |
В В В В notempty_atstart |
В В В В report_errors |
В В В В bsr_anycrlf |
В В В В bsr_unicode |
В В В В CompileOpt.
В В В В all | all_but_first | all_names | first | none | ValueList.
В В В В | ListConversionData | binary()
В В В В match_limit | match_limit_recursion |
Executes a regular expression matching, and returns match/ or nomatch . The regular expression can be specified either as iodata() in which case it is automatically compiled (as by compile/2 ) and executed, or as a precompiled mp() in which case it is executed against the subject directly.
When compilation is involved, exception badarg is thrown if a compilation error occurs. Call compile/2 to get information about the location of the error in the regular expression.
If the regular expression is previously compiled, the option list can only contain the following options:
Otherwise all options valid for function compile/2 are also allowed. Options allowed both for compilation and execution of a match, namely anchored and , affect both the compilation and execution if present together with a non-precompiled regular expression.
If the regular expression was previously compiled with option unicode , Subject is to be provided as a valid Unicode charlist() , otherwise any iodata() will do. If compilation is involved and option unicode is specified, both Subject and the regular expression are to be specified as valid Unicode charlists() .
/ defines what to return from the function upon successful matching. The capture tuple can contain both a value specification, telling which of the captured substrings are to be returned, and a type specification, telling how captured substrings are to be returned (as index tuples, lists, or binaries). The options are described in detail below.
If the capture options describe that no substring capturing is to be done ( ), the function returns the single atom match upon successful matching, otherwise the tuple . Disabling capturing can be done either by specifying none or an empty list as ValueSpec .
Option report_errors adds the possibility that an error tuple is returned. The tuple either indicates a matching error ( match_limit or match_limit_recursion ), or a compilation error, where the error tuple has the format > . Notice that if option report_errors is not specified, the function never returns error tuples, but reports compilation errors as a badarg exception and failed matches because of exceeded match limits simply as nomatch .
The following options are relevant for execution:
Limits run/3 to matching at the first matching position. If a pattern was compiled with anchored , or turned out to be anchored by virtue of its contents, it cannot be made unanchored at matching time, hence there is no unanchored option.
Implements global (repetitive) search (flag g in Perl). Each match is returned as a separate list() containing the specific match and any matching subexpressions (or as specified by option capture . The Captured part of the return value is hence a list() of list() s when this option is specified.
The interaction of option global with a regular expression that matches an empty string surprises some users. When option global is specified, run/3 handles empty matches in the same way as Perl: a zero-length match at any point is also retried with options [anchored, notempty_atstart] . If that search gives a result of length > 0, the result is included. Example:
The following matchings are performed:
The regular expression (|at) first match at the initial position of string cat , giving the result set [ , ] (the second is because of the subexpression marked by the parentheses). As the length of the match is 0, we do not advance to the next position yet.
At offset 0 with [anchored, notempty_atstart]
The search is retried with options [anchored, notempty_atstart] at the same position, which does not give any interesting result of longer length, so the search position is advanced to the next character ( a ).
The search results in [ , ] , so this search is also repeated with the extra options.
At offset 1 with [anchored, notempty_atstart]
Alternative ab is found and the result is [ , ]. The result is added to the list of results and the position in the search string is advanced two steps.
The search once again matches the empty string, giving [ , ] .
At offset 1 with [anchored, notempty_atstart]
This gives no result of length > 0 and we are at the last position, so the global search is complete.
The result of the call is:
An empty string is not considered to be a valid match if this option is specified. If alternatives in the pattern exist, they are tried. If all the alternatives match the empty string, the entire match fails.
If the following pattern is applied to a string not beginning with "a" or "b", it would normally match the empty string at the start of the subject:
With option notempty , this match is invalid, so run/3 searches further into the string for occurrences of "a" or "b".
Like notempty , except that an empty string match that is not at the start of the subject is permitted. If the pattern is anchored, such a match can occur only if the pattern contains \K.
Perl has no direct equivalent of notempty or notempty_atstart , but it does make a special case of a pattern match of the empty string within its split() function, and when using modifier /g . The Perl behavior can be emulated after matching a null string by first trying the match again at the same offset with notempty_atstart and anchored , and then, if that fails, by advancing the starting offset (see below) and trying an ordinary match again.
Specifies that the first character of the subject string is not the beginning of a line, so the circumflex metacharacter is not to match before it. Setting this without multiline (at compile time) causes circumflex never to match. This option only affects the behavior of the circumflex metacharacter. It does not affect \A.
Specifies that the end of the subject string is not the end of a line, so the dollar metacharacter is not to match it nor (except in multiline mode) a newline immediately before it. Setting this without multiline (at compile time) causes dollar never to match. This option affects only the behavior of the dollar metacharacter. It does not affect \Z or \z.
Gives better control of the error handling in run/3 . When specified, compilation errors (if the regular expression is not already compiled) and runtime errors are explicitly returned as an error tuple.
The following are the possible runtime errors:
The PCRE library sets a limit on how many times the internal match function can be called. Defaults to 10,000,000 in the library compiled for Erlang. If is returned, the execution of the regular expression has reached this limit. This is normally to be regarded as a nomatch , which is the default return value when this occurs, but by specifying report_errors , you are informed when the match fails because of too many internal calls.
This error is very similar to match_limit , but occurs when the internal match function of PCRE is "recursively" called more times than the match_limit_recursion limit, which defaults to 10,000,000 as well. Notice that as long as the match_limit and match_limit_default values are kept at the default values, the match_limit_recursion error cannot occur, as the match_limit error occurs before that (each recursive call is also a call, but not conversely). Both limits can however be changed, either by setting limits directly in the regular expression string (see section PCRE Regular Eexpression Details ) or by specifying options to run/3 .
It is important to understand that what is referred to as "recursion" when limiting matches is not recursion on the C stack of the Erlang machine or on the Erlang process stack. The PCRE version compiled into the Erlang VM uses machine "heap" memory to store values that must be kept over recursion in regular expression matches.
Limits the execution time of a match in an implementation-specific way. It is described as follows by the PCRE documentation:
This means that runaway regular expression matches can fail faster if the limit is lowered using this option. The default value 10,000,000 is compiled into the Erlang VM.
This option does in no way affect the execution of the Erlang VM in terms of "long running BIFs". run/3 always gives control back to the scheduler of Erlang processes at intervals that ensures the real-time properties of the Erlang system.
Limits the execution time and memory consumption of a match in an implementation-specific way, very similar to match_limit . It is described as follows by the PCRE documentation:
The Erlang VM uses a PCRE library where heap memory is used when regular expression match recursion occurs. This therefore limits the use of machine heap, not C stack.
Specifying a lower value can result in matches with deep recursion failing, when they should have matched:
This option and option match_limit are only to be used in rare cases. Understanding of the PCRE library internals is recommended before tampering with these limits.
Start matching at the offset (position) specified in the subject string. The offset is zero-based, so that the default is (all of the subject string).
Overrides the default definition of a newline in the subject string, which is LF (ASCII 10) in Erlang.
Newline is indicated by a single character CR (ASCII 13).
Newline is indicated by a single character LF (ASCII 10), the default.
Newline is indicated by the two-character CRLF (ASCII 13 followed by ASCII 10) sequence.
Any of the three preceding sequences is be recognized.
Any of the newline sequences above, and the Unicode sequences VT (vertical tab, U+000B), FF (formfeed, U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS (paragraph separator, U+2029).
Specifies specifically that \R is to match only the CR LF, or CRLF sequences, not the Unicode-specific newline characters. (Overrides the compilation option.)
Specifies specifically that \R is to match all the Unicode newline characters (including CRLF, and so on, the default). (Overrides the compilation option.)
Specifies which captured substrings are returned and in what format. By default, run/3 captures all of the matching part of the substring and all capturing subpatterns (all of the pattern is automatically captured). The default return type is (zero-based) indexes of the captured parts of the string, specified as pairs (the index Type of capturing).
As an example of the default behavior, the following call returns, as first and only captured string, the matching part of the subject ("abcd" in the middle) as an index pair , where character positions are zero-based, just as in offsets:
The return value of this call is:
Another (and quite common) case is where the regular expression matches all of the subject:
Here the return value correspondingly points out all of the string, beginning at index 0, and it is 10 characters long:
If the regular expression contains capturing subpatterns, like in:
all of the matched subject is captured, as well as the captured substrings:
The complete matching pattern always gives the first return value in the list and the remaining subpatterns are added in the order they occurred in the regular expression.
The capture tuple is built up as follows:
Specifies which captured (sub)patterns are to be returned. ValueSpec can either be an atom describing a predefined set of return values, or a list containing the indexes or the names of specific subpatterns to return.
The following are the predefined sets of subpatterns:
All captured subpatterns including the complete matching string. Este é o padrão.
All named subpatterns in the regular expression, as if a list() of all the names in alphabetical order was specified. The list of all names can also be retrieved with inspect/2 .
Only the first captured subpattern, which is always the complete matching part of the subject. All explicitly captured subpatterns are discarded.
All but the first matching subpattern, that is, all explicitly captured subpatterns, but not the complete matching part of the subject string. This is useful if the regular expression as a whole matches a large part of the subject, but the part you are interested in is in an explicitly captured subpattern. If the return type is list or binary , not returning subpatterns you are not interested in is a good way to optimize.
Returns no matching subpatterns, gives the single atom match as the return value of the function when matching successfully instead of the return. Specifying an empty list gives the same behavior.
The value list is a list of indexes for the subpatterns to return, where index 0 is for all of the pattern, and 1 is for the first explicit capturing subpattern in the regular expression, and so on. When using named captured subpatterns (see below) in the regular expression, one can use atom() s or string() s to specify the subpatterns to be returned. For example, consider the regular expression:
matched against string "ABCabcdABC", capturing only the "abcd" part (the first explicit subpattern):
The call gives the following result, as the first explicitly captured subpattern is "(abcd)", matching "abcd" in the subject, at (zero-based) position 3, of length 4:
Consider the same regular expression, but with the subpattern explicitly named 'FOO':
With this expression, we could still give the index of the subpattern with the following call:
giving the same result as before. But, as the subpattern is named, we can also specify its name in the value list:
This would give the same result as the earlier examples, namely:
The values list can specify indexes or names not present in the regular expression, in which case the return values vary depending on the type. If the type is index , the tuple is returned for values with no corresponding subpattern in the regular expression, but for the other types ( binary and list ), the values are the empty binary or list, respectively.
Optionally specifies how captured substrings are to be returned. If omitted, the default of index is used.
Type can be one of the following:
Returns captured substrings as pairs of byte indexes into the subject string and length of the matching string in the subject (as if the subject string was flattened with erlang:iolist_to_binary/1 or unicode:characters_to_binary/2 before matching). Notice that option unicode results in byte-oriented indexes in a (possibly virtual) UTF-8 encoded binary. A byte index tuple can therefore represent one or two characters when unicode is in effect. This can seem counter-intuitive, but has been deemed the most effective and useful way to do it. To return lists instead can result in simpler code if that is desired. This return type is the default.
Returns matching substrings as lists of characters (Erlang string() s). It option unicode is used in combination with the \C sequence in the regular expression, a captured subpattern can contain bytes that are not valid UTF-8 (\C matches bytes regardless of character encoding). In that case the list capturing can result in the same types of tuples that unicode:characters_to_list/2 can return, namely three-tuples with tag incomplete or error , the successfully converted characters and the invalid UTF-8 tail of the conversion as a binary. The best strategy is to avoid using the \C sequence when capturing lists.
Returns matching substrings as binaries. If option unicode is used, these binaries are in UTF-8. If the \C sequence is used together with unicode , the binaries can be invalid UTF-8.
In general, subpatterns that were not assigned a value in the match are returned as the tuple when type is index . Unassigned subpatterns are returned as the empty binary or list, respectively, for other return types. Consider the following regular expression:
There are three explicitly capturing subpatterns, where the opening parenthesis position determines the order in the result, hence ((?<FOO>abdd)|a(..d)) is subpattern index 1, (?<FOO>abdd) is subpattern index 2, and (..d) is subpattern index 3. When matched against the following string:
the subpattern at index 2 does not match, as "abdd" is not present in the string, but the complete pattern matches (because of the alternative a(..d) ). The subpattern at index 2 is therefore unassigned and the default return value is:
Setting the capture Type to binary gives:
Here the empty binary ( <<>> ) represents the unassigned subpattern. In the binary case, some information about the matching is therefore lost, as <<>> can also be an empty string captured.
If differentiation between empty matches and non-existing subpatterns is necessary, use the type index and do the conversion to the final type in Erlang code.
When option global is speciified, the capture specification affects each match separately, so that:
For a descriptions of options only affecting the compilation step, see compile/2 .
Same as split(Subject, RE, []) .
В В В В anchored |
В В В В notempty |
В В В В notempty_atstart |
В В В В bsr_anycrlf |
В В В В bsr_unicode |
В В В В CompileOpt.
Splits the input into parts by finding tokens according to the regular expression supplied. The splitting is basically done by running a global regular expression match and dividing the initial string wherever a match occurs. The matching part of the string is removed from the output.
As in run/3 , an mp() compiled with option unicode requires Subject to be a Unicode charlist() . If compilation is done implicitly and the unicode compilation option is specified to this function, both the regular expression and Subject are to be specified as valid Unicode charlist() s.
The result is given as a list of "strings", the preferred data type specified in option return (default iodata ).
If subexpressions are specified in the regular expression, the matching subexpressions are returned in the resulting list as well. Por exemplo:
The text matching the subexpression (marked by the parentheses in the regular expression) is inserted in the result list where it was found. This means that concatenating the result of a split where the whole regular expression is a single subexpression (as in the last example) always results in the original string.
As there is no matching subexpression for the last part in the example (the "g"), nothing is inserted after that. To make the group of strings and the parts matching the subexpressions more obvious, one can use option group , which groups together the part of the subject string with the parts matching the subexpressions when the string was split:
Here the regular expression first matched the "l", causing "Er" to be the first part in the result. When the regular expression matched, the (only) subexpression was bound to the "l", so the "l" is inserted in the group together with "Er". The next match is of the "n", making "a" the next part to be returned. As the subexpression is bound to substring "n" in this case, the "n" is inserted into this group. The last group consists of the remaining string, as no more matches are found.
By default, all parts of the string, including the empty strings, are returned from the function, for example:
as the matching of the "g" in the end of the string leaves an empty rest, which is also returned. This behavior differs from the default behavior of the split function in Perl, where empty strings at the end are by default removed. To get the "trimming" default behavior of Perl, specify trim as an option:
The "trim" option says; "give me as many parts as possible except the empty ones", which sometimes can be useful. You can also specify how many parts you want, by specifying :
Notice that the last part is "ang", not "an", as splitting was specified into two parts, and the splitting stops when enough parts are given, which is why the result differs from that of trim .
More than three parts are not possible with this indata, so.
gives the same result as the default, which is to be viewed as "an infinite number of parts".
Specifying 0 as the number of parts gives the same effect as option trim . If subexpressions are captured, empty subexpressions matched at the end are also stripped from the result if trim or is specified.
The trim behavior corresponds exactly to the Perl default. , where N is a positive integer, corresponds exactly to the Perl behavior with a positive numerical third parameter. The default behavior of split/3 corresponds to the Perl behavior when a negative integer is specified as the third parameter for the Perl routine.
Summary of options not previously described for function run/3 :
Specifies how the parts of the original string are presented in the result list. Valid types:
The variant of iodata() that gives the least copying of data with the current implementation (often a binary, but do not depend on it).
All parts returned as binaries.
All parts returned as lists of characters ("strings").
Groups together the part of the string with the parts of the string matching the subexpressions of the regular expression.
The return value from the function is in this case a list() of list() s. Each sublist begins with the string picked out of the subject string, followed by the parts matching each of the subexpressions in order of occurrence in the regular expression.
Specifies the number of parts the subject string is to be split into.
The number of parts is to be a positive integer for a specific maximum number of parts, and infinity for the maximum number of parts possible (the default). Specifying gives as many parts as possible disregarding empty parts at the end, the same as specifying trim .
Specifies that empty parts at the end of the result list are to be disregarded. The same as specifying . This corresponds to the default behavior of the split built-in function in Perl.
Perl-Like Regular Expression Syntax.
The following sections contain reference material for the regular expressions used by this module. The information is based on the PCRE documentation, with changes where this module behaves differently to the PCRE library.
PCRE Regular Expression Details.
The syntax and semantics of the regular expressions supported by PCRE are described in detail in the following sections. Perl's regular expressions are described in its own documentation, and regular expressions in general are covered in many books, some with copious examples. Jeffrey Friedl's "Mastering Regular Expressions", published by O'Reilly, covers regular expressions in great detail. This description of the PCRE regular expressions is intended as reference material.
The reference material is divided into the following sections:
Special Start-of-Pattern Items.
Some options that can be passed to compile/2 can also be set by special items at the start of a pattern. These are not Perl-compatible, but are provided to make these options accessible to pattern writers who are not able to change the program that processes the pattern. Any number of these items can appear, but they must all be together right at the start of the pattern string, and the letters must be in upper case.
Unicode support is basically UTF-8 based. To use Unicode characters, you either call compile/2 or run/3 with option unicode , or the pattern must start with one of these special sequences:
Both options give the same effect, the input string is interpreted as UTF-8. Notice that with these instructions, the automatic conversion of lists to UTF-8 is not performed by the re functions. Therefore, using these sequences is not recommended. Add option unicode when running compile/2 instead.
Some applications that allow their users to supply patterns can wish to restrict them to non-UTF data for security reasons. If option never_utf is set at compile time, (*UTF), and so on, are not allowed, and their appearance causes an error.
Unicode Property Support.
The following is another special sequence that can appear at the start of a pattern:
This has the same effect as setting option ucp : it causes sequences such as \d and \w to use Unicode properties to determine character types, instead of recognizing only characters with codes < 256 through a lookup table.
Disabling Startup Optimizations.
If a pattern starts with (*NO_START_OPT) , it has the same effect as setting option no_start_optimize at compile time.
PCRE supports five conventions for indicating line breaks in strings: a single CR (carriage return) character, a single LF (line feed) character, the two-character sequence CRLF, any of the three preceding, and any Unicode newline sequence.
A newline convention can also be specified by starting a pattern string with one of the following five sequences:
(*CR) Carriage return (*LF) Line feed (*CRLF) >Carriage return followed by line feed (*ANYCRLF) Any of the three above (*ANY) All Unicode newline sequences.
These override the default and the options specified to compile/2 . For example, the following pattern changes the convention to CR:
This pattern matches a\nb , as LF is no longer a newline. If more than one of them is present, the last one is used.
The newline convention affects where the circumflex and dollar assertions are true. It also affects the interpretation of the dot metacharacter when dotall is not set, and the behavior of \N. However, it does not affect what the \R escape sequence matches. By default, this is any Unicode newline sequence, for Perl compatibility. However, this can be changed; see the description of \R in section Newline Sequences . A change of the \R setting can be combined with a change of the newline convention.
Setting Match and Recursion Limits.
The caller of run/3 can set a limit on the number of times the internal match() function is called and on the maximum depth of recursive calls. These facilities are provided to catch runaway matches that are provoked by patterns with huge matching trees (a typical example is a pattern with nested unlimited repeats) and to avoid running out of system stack by too much recursion. When one of these limits is reached, pcre_exec() gives an error return. The limits can also be set by items at the start of the pattern of the following forms:
Here d is any number of decimal digits. However, the value of the setting must be less than the value set by the caller of run/3 for it to have any effect. That is, the pattern writer can lower the limit set by the programmer, but not raise it. If there is more than one setting of one of these limits, the lower value is used.
The default value for both the limits is 10,000,000 in the Erlang VM. Notice that the recursion limit does not affect the stack depth of the VM, as PCRE for Erlang is compiled in such a way that the match function never does recursion on the C stack.
Note that LIMIT_MATCH and LIMIT_RECURSION can only reduce the value of the limits set by the caller, not increase them.
Characters and Metacharacters.
A regular expression is a pattern that is matched against a subject string from left to right. Most characters stand for themselves in a pattern and match the corresponding characters in the subject. As a trivial example, the following pattern matches a portion of a subject string that is identical to itself:
When caseless matching is specified (option caseless ), letters are matched independently of case.
The power of regular expressions comes from the ability to include alternatives and repetitions in the pattern. These are encoded in the pattern by the use of metacharacters , which do not stand for themselves but instead are interpreted in some special way.
Two sets of metacharacters exist: those that are recognized anywhere in the pattern except within square brackets, and those that are recognized within square brackets. Outside square brackets, the metacharacters are as follows:
\ General escape character with many uses ^ Assert start of string (or line, in multiline mode) $ Assert end of string (or line, in multiline mode) . Match any character except newline (by default) [ Start character class definition | Start of alternative branch ( Start subpattern ) End subpattern ? Extends the meaning of (, also 0 or 1 quantifier, also quantifier minimizer * 0 or more quantifiers + 1 or more quantifier, also "possessive quantifier" Start min/max quantifier.
Part of a pattern within square brackets is called a "character class". The following are the only metacharacters in a character class:
\ General escape character ^ Negate the class, but only if the first character - Indicates character range [ Posix character class (only if followed by Posix syntax) ] Terminates the character class.
The following sections describe the use of each metacharacter.
The backslash character has many uses. First, if it is followed by a character that is not a number or a letter, it takes away any special meaning that a character can have. This use of backslash as an escape character applies both inside and outside character classes.
For example, if you want to match a * character, you write \* in the pattern. This escaping action applies if the following character would otherwise be interpreted as a metacharacter, so it is always safe to precede a non-alphanumeric with backslash to specify that it stands for itself. In particular, if you want to match a backslash, write \\.
In unicode mode, only ASCII numbers and letters have any special meaning after a backslash. All other characters (in particular, those whose code points are > 127) are treated as literals.
If a pattern is compiled with option extended , whitespace in the pattern (other than in a character class) and characters between a # outside a character class and the next newline are ignored. An escaping backslash can be used to include a whitespace or # character as part of the pattern.
To remove the special meaning from a sequence of characters, put them between \Q and \E. This is different from Perl in that $ and @ are handled as literals in \Q. \E sequences in PCRE, while $ and @ cause variable interpolation in Perl. Notice the following examples:
The \Q. \E sequence is recognized both inside and outside character classes. An isolated \E that is not preceded by \Q is ignored. If \Q is not followed by \E later in the pattern, the literal interpretation continues to the end of the pattern (that is, \E is assumed at the end). If the isolated \Q is inside a character class, this causes an error, as the character class is not terminated.
A second use of backslash provides a way of encoding non-printing characters in patterns in a visible manner. There is no restriction on the appearance of non-printing characters, apart from the binary zero that terminates a pattern. When a pattern is prepared by text editing, it is often easier to use one of the following escape sequences than the binary character it represents:
\a Alarm, that is, the BEL character (hex 07) \cx "Control-x", where x is any ASCII character \e Escape (hex 1B) \f Form feed (hex 0C) \n Line feed (hex 0A) \r Carriage return (hex 0D) \t Tab (hex 09) \0dd Character with octal code 0dd \ddd Character with octal code ddd, or back reference \o character with octal code ddd.. \xhh Character with hex code hh \x Character with hex code hhh..
Note that \0dd is always an octal code, and that \8 and \9 are the literal characters "8" and "9".
The \c facility was designed for use with ASCII characters, but with the extension to Unicode it is even less useful than it once was.
After \0 up to two further octal digits are read. If there are fewer than two digits, just those that are present are used. Thus the sequence \0\x\015 specifies two binary zeros followed by a CR character (code value 13). Make sure you supply two digits after the initial zero if the pattern character that follows is itself an octal digit.
The escape \o must be followed by a sequence of octal digits, enclosed in braces. An error occurs if this is not the case. This escape is a recent addition to Perl; it provides way of specifying character code points as octal numbers greater than 0777, and it also allows octal numbers and back references to be unambiguously specified.
For greater clarity and unambiguity, it is best to avoid following \ by a digit greater than zero. Instead, use \o<> or \x<> to specify character numbers, and \g<> to specify back references. The following paragraphs describe the old, ambiguous syntax.
The handling of a backslash followed by a digit other than 0 is complicated, and Perl has changed in recent releases, causing PCRE also to change. Outside a character class, PCRE reads the digit and any following digits as a decimal number. If the number is < 8, or if there have been at least that many previous capturing left parentheses in the expression, the entire sequence is taken as a back reference . A description of how this works is provided later, following the discussion of parenthesized subpatterns.
Inside a character class, or if the decimal number following \ is > 7 and there have not been that many capturing subpatterns, PCRE handles \8 and \9 as the literal characters "8" and "9", and otherwise re-reads up to three octal digits following the backslash, and using them to generate a data character. Any subsequent digits stand for themselves. Por exemplo:
\040 Another way of writing an ASCII space \40 The same, provided there are < 40 previous capturing subpatterns \7 Always a back reference \11 Can be a back reference, or another way of writing a tab \011 Always a tab \0113 A tab followed by character "3" \113 Can be a back reference, otherwise the character with octal code 113 \377 Can be a back reference, otherwise value 255 (decimal) \81 Either a back reference, or the two characters "8" and "1"
Notice that octal values >= 100 that are specified using this syntax must not be introduced by a leading zero, as no more than three octal digits are ever read.
Characters whose value is less than 256 can be defined by either of the two syntaxes for \x. There is no difference in the way they are handled. For example, \xdc is exactly the same as \x .
Constraints on character values.
Characters that are specified using octal or hexadecimal numbers are limited to certain values, as follows:
& lt; 0x10ffff and a valid codepoint.
Invalid Unicode codepoints are the range 0xd800 to 0xdfff (the so-called "surrogate" codepoints), and 0xffef.
Escape sequences in character classes.
All the sequences that define a single character value can be used both inside and outside character classes. Also, inside a character class, \b is interpreted as the backspace character (hex 08).
\N is not allowed in a character class. \B, \R, and \X are not special inside a character class. Like other unrecognized escape sequences, they are treated as the literal characters "B", "R", and "X". Outside a character class, these sequences have different meanings.
Unsupported Escape Sequences.
In Perl, the sequences \l, \L, \u, and \U are recognized by its string handler and used to modify the case of following characters. PCRE does not support these escape sequences.
Absolute and Relative Back References.
The sequence \g followed by an unsigned or a negative number, optionally enclosed in braces, is an absolute or relative back reference. A named back reference can be coded as \g . Back references are discussed later, following the discussion of parenthesized subpatterns.
Absolute and Relative Subroutine Calls.
For compatibility with Oniguruma, the non-Perl syntax \g followed by a name or a number enclosed either in angle brackets or single quotes, is alternative syntax for referencing a subpattern as a "subroutine". Details are discussed later. Notice that \g (Perl syntax) and \g<. & gt; (Oniguruma syntax) are not synonymous. The former is a back reference and the latter is a subroutine call.
Another use of backslash is for specifying generic character types:
\d Any decimal digit \D Any character that is not a decimal digit \h Any horizontal whitespace character \H Any character that is not a horizontal whitespace character \s Any whitespace character \S Any character that is not a whitespace character \v Any vertical whitespace character \V Any character that is not a vertical whitespace character \w Any "word" character \W Any "non-word" character.
There is also the single sequence \N, which matches a non-newline character. This is the same as the "." metacharacter when dotall is not set. Perl also uses \N to match characters by name, but PCRE does not support this.
Each pair of lowercase and uppercase escape sequences partitions the complete set of characters into two disjoint sets. Any given character matches one, and only one, of each pair. The sequences can appear both inside and outside character classes. They each match one character of the appropriate type. If the current matching point is at the end of the subject string, all fail, as there is no character to match.
For compatibility with Perl, \s did not used to match the VT character (code 11), which made it different from the the POSIX "space" class. However, Perl added VT at release 5.18, and PCRE followed suit at release 8.34. The default \s characters are now HT (9), LF (10), VT (11), FF (12), CR (13), and space (32), which are defined as white space in the "C" locale. This list may vary if locale-specific matching is taking place. For example, in some locales the "non-breaking space" character (\xA0) is recognized as white space, and in others the VT character is not.
A "word" character is an underscore or any character that is a letter or a digit. By default, the definition of letters and digits is controlled by the PCRE low-valued character tables, in Erlang's case (and without option unicode ), the ISO Latin-1 character set.
By default, in unicode mode, characters with values > 255, that is, all characters outside the ISO Latin-1 character set, never match \d, \s, or \w, and always match \D, \S, and \W. These sequences retain their original meanings from before UTF support was available, mainly for efficiency reasons. However, if option ucp is set, the behavior is changed so that Unicode properties are used to determine character types, as follows:
\d Any character that \p matches (decimal digit) \s Any character that \p or \h or \v \w Any character that matches \p or \p matches, plus underscore.
The uppercase escapes match the inverse sets of characters. Notice that \d matches only decimal digits, while \w matches any Unicode digit, any Unicode letter, and underscore. Notice also that ucp affects \b and \B, as they are defined in terms of \w and \W. Matching these sequences is noticeably slower when ucp is set.
The sequences \h, \H, \v, and \V are features that were added to Perl in release 5.10. In contrast to the other sequences, which match only ASCII characters by default, these always match certain high-valued code points, regardless if ucp is set.
The following are the horizontal space characters:
U+0009 Horizontal tab (HT) U+0020 Space U+00A0 Non-break space U+1680 Ogham space mark U+180E Mongolian vowel separator U+2000 En quad U+2001 Em quad U+2002 En space U+2003 Em space U+2004 Three-per-em space U+2005 Four-per-em space U+2006 Six-per-em space U+2007 Figure space U+2008 Punctuation space U+2009 Thin space U+200A Hair space U+202F Narrow no-break space U+205F Medium mathematical space U+3000 Ideographic space.
The following are the vertical space characters:
U+000A Line feed (LF) U+000B Vertical tab (VT) U+000C Form feed (FF) U+000D Carriage return (CR) U+0085 Next line (NEL) U+2028 Line separator U+2029 Paragraph separator.
In 8-bit, non-UTF-8 mode, only the characters with code points < 256 are relevant.
Outside a character class, by default, the escape sequence \R matches any Unicode newline sequence. In non-UTF-8 mode, \R is equivalent to the following:
This is an example of an "atomic group", details are provided below.
This particular group matches either the two-character sequence CR followed by LF, or one of the single characters LF (line feed, U+000A), VT (vertical tab, U+000B), FF (form feed, U+000C), CR (carriage return, U+000D), or NEL (next line, U+0085). The two-character sequence is treated as a single unit that cannot be split.
In Unicode mode, two more characters whose code points are > 255 are added: LS (line separator, U+2028) and PS (paragraph separator, U+2029). Unicode character property support is not needed for these characters to be recognized.
\R can be restricted to match only CR, LF, or CRLF (instead of the complete set of Unicode line endings) by setting option bsr_anycrlf either at compile time or when the pattern is matched. (BSR is an acronym for "backslash R".) This can be made the default when PCRE is built; if so, the other behavior can be requested through option bsr_unicode . These settings can also be specified by starting a pattern string with one of the following sequences:
(*BSR_ANYCRLF) CR, LF, or CRLF only (*BSR_UNICODE) Any Unicode newline sequence.
These override the default and the options specified to the compiling function, but they can themselves be overridden by options specified to a matching function. Notice that these special settings, which are not Perl-compatible, are recognized only at the very start of a pattern, and that they must be in upper case. If more than one of them is present, the last one is used. They can be combined with a change of newline convention; for example, a pattern can start with:
They can also be combined with the (*UTF8), (*UTF), or (*UCP) special sequences. Inside a character class, \R is treated as an unrecognized escape sequence, and so matches the letter "R" by default.
Unicode Character Properties.
Three more escape sequences that match characters with specific properties are available. When in 8-bit non-UTF-8 mode, these sequences are limited to testing characters whose code points are < 256, but they do work in this mode. The following are the extra escape sequences:
The property names represented by xx above are limited to the Unicode script names, the general category properties, "Any", which matches any character (including newline), and some special PCRE properties (described in the next section). Other Perl properties, such as "InMusicalSymbols", are currently not supported by PCRE. Notice that \P does not match any characters and always causes a match failure.
Sets of Unicode characters are defined as belonging to certain scripts. A character from one of these sets can be matched using a script name, for example:
Those that are not part of an identified script are lumped together as "Common". The following is the current list of scripts:
Each character has exactly one Unicode general category property, specified by a two-letter acronym. For compatibility with Perl, negation can be specified by including a circumflex between the opening brace and the property name. For example, \p is the same as \P .
If only one letter is specified with \p or \P, it includes all the general category properties that start with that letter. In this case, in the absence of negation, the curly brackets in the escape sequence are optional. The following two examples have the same effect:
The following general category property codes are supported:
The special property L& is also supported. It matches a character that has the Lu, Ll, or Lt property, that is, a letter that is not classified as a modifier or "other".
The Cs (Surrogate) property applies only to characters in the range U+D800 to U+DFFF. Such characters are invalid in Unicode strings and so cannot be tested by PCRE. Perl does not support the Cs property.
The long synonyms for property names supported by Perl (such as \p ) are not supported by PCRE. It is not permitted to prefix any of these properties with "Is".
No character in the Unicode table has the Cn (unassigned) property. This property is instead assumed for any code point that is not in the Unicode table.
Specifying caseless matching does not affect these escape sequences. For example, \p always matches only uppercase letters. This is different from the behavior of current versions of Perl.
Matching characters by Unicode property is not fast, as PCRE must do a multistage table lookup to find a character property. That is why the traditional escape sequences such as \d and \w do not use Unicode properties in PCRE by default. However, you can make them do so by setting option ucp or by starting the pattern with (*UCP).
Extended Grapheme Clusters.
The \X escape matches any number of Unicode characters that form an "extended grapheme cluster", and treats the sequence as an atomic group (see below). Up to and including release 8.31, PCRE matched an earlier, simpler definition that was equivalent to (?>\PM\pM*) . That is, it matched a character without the "mark" property, followed by zero or more characters with the "mark" property. Characters with the "mark" property are typically non-spacing accents that affect the preceding character.
This simple definition was extended in Unicode to include more complicated kinds of composite character by giving each character a grapheme breaking property, and creating rules that use these properties to define the boundaries of extended grapheme clusters. In PCRE releases later than 8.31, \X matches one of these clusters.
\X always matches at least one character. Then it decides whether to add more characters according to the following rules for ending a cluster:
End at the end of the subject string.
Do not end between CR and LF; otherwise end after any control character.
Do not break Hangul (a Korean script) syllable sequences. Hangul characters are of five types: L, V, T, LV, and LVT. An L character can be followed by an L, V, LV, or LVT character. An LV or V character can be followed by a V or T character. An LVT or T character can be followed only by a T character.
Do not end before extending characters or spacing marks. Characters with the "mark" property always have the "extend" grapheme breaking property.
Do not end after prepend characters.
Otherwise, end the cluster.
PCRE Additional Properties.
In addition to the standard Unicode properties described earlier, PCRE supports four more that make it possible to convert traditional escape sequences, such as \w and \s to use Unicode properties. PCRE uses these non-standard, non-Perl properties internally when the ucp option is passed. However, they can also be used explicitly. The properties are as follows:
Any alphanumeric character. Matches characters that have either the L (letter) or the N (number) property.
Any Posix space character. Matches the characters tab, line feed, vertical tab, form feed, carriage return, and any other character that has the Z (separator) property.
Any Perl space character. Matches the same as Xps, except that vertical tab is excluded.
Any Perl "word" character. Matches the same characters as Xan, plus underscore.
Perl and POSIX space are now the same. Perl added VT to its space character set at release 5.18 and PCRE changed at release 8.34.
Xan matches characters that have either the L (letter) or the N (number) property. Xps matches the characters tab, linefeed, vertical tab, form feed, or carriage return, and any other character that has the Z (separator) property. Xsp is the same as Xps; it used to exclude vertical tab, for Perl compatibility, but Perl changed, and so PCRE followed at release 8.34. Xwd matches the same characters as Xan, plus underscore.
There is another non-standard property, Xuc, which matches any character that can be represented by a Universal Character Name in C++ and other programming languages. These are the characters $, @, ` (grave accent), and all characters with Unicode code points >= U+00A0, except for the surrogates U+D800 to U+DFFF. Notice that most base (ASCII) characters are excluded. (Universal Character Names are of the form \uHHHH or \UHHHHHHHH, where H is a hexadecimal digit. Notice that the Xuc property does not match these sequences but the characters that they represent.)
Resetting the Match Start.
The escape sequence \K causes any previously matched characters not to be included in the final matched sequence. For example, the following pattern matches "foobar", but reports that it has matched "bar":
This feature is similar to a lookbehind assertion (described below). However, in this case, the part of the subject before the real match does not have to be of fixed length, as lookbehind assertions do. The use of \K does not interfere with the setting of captured substrings. For example, when the following pattern matches "foobar", the first substring is still set to "foo":
Perl documents that the use of \K within assertions is "not well defined". In PCRE, \K is acted upon when it occurs inside positive assertions, but is ignored in negative assertions. Note that when a pattern such as (?=ab\K) matches, the reported start of the match can be greater than the end of the match.
The final use of backslash is for certain simple assertions. An assertion specifies a condition that must be met at a particular point in a match, without consuming any characters from the subject string. The use of subpatterns for more complicated assertions is described below. The following are the backslashed assertions:
\b Matches at a word boundary. \B Matches when not at a word boundary. \A Matches at the start of the subject. \Z Matches at the end of the subject, and before a newline at the end of the subject. \z Matches only at the end of the subject. \G Matches at the first matching position in the subject.
Inside a character class, \b has a different meaning; it matches the backspace character. If any other of these assertions appears in a character class, by default it matches the corresponding literal character (for example, \B matches the letter B).
A word boundary is a position in the subject string where the current character and the previous character do not both match \w or \W (that is, one matches \w and the other matches \W), or the start or end of the string if the first or last character matches \w, respectively. In UTF mode, the meanings of \w and \W can be changed by setting option ucp . When this is done, it also affects \b and \B. PCRE and Perl do not have a separate "start of word" or "end of word" metasequence. However, whatever follows \b normally determines which it is. For example, the fragment \ba matches "a" at the start of a word.
The \A, \Z, and \z assertions differ from the traditional circumflex and dollar (described in the next section) in that they only ever match at the very start and end of the subject string, whatever options are set. Thus, they are independent of multiline mode. These three assertions are not affected by options notbol or noteol , which affect only the behavior of the circumflex and dollar metacharacters. However, if argument startoffset of run/3 is non-zero, indicating that matching is to start at a point other than the beginning of the subject, \A can never match. The difference between \Z and \z is that \Z matches before a newline at the end of the string and at the very end, while \z matches only at the end.
The \G assertion is true only when the current matching position is at the start point of the match, as specified by argument startoffset of run/3 . It differs from \A when the value of startoffset is non-zero. By calling run/3 multiple times with appropriate arguments, you can mimic the Perl option /g , and it is in this kind of implementation where \G can be useful.
Notice, however, that the PCRE interpretation of \G, as the start of the current match, is subtly different from Perl, which defines it as the end of the previous match. In Perl, these can be different when the previously matched string was empty. As PCRE does only one match at a time, it cannot reproduce this behavior.
If all the alternatives of a pattern begin with \G, the expression is anchored to the starting match position, and the "anchored" flag is set in the compiled regular expression.
Circumflex and Dollar.
The circumflex and dollar metacharacters are zero-width assertions. That is, they test for a particular condition to be true without consuming any characters from the subject string.
Outside a character class, in the default matching mode, the circumflex character is an assertion that is true only if the current matching point is at the start of the subject string. If argument startoffset of run/3 is non-zero, circumflex can never match if option multiline is unset. Inside a character class, circumflex has an entirely different meaning (see below).
Circumflex needs not to be the first character of the pattern if some alternatives are involved, but it is to be the first thing in each alternative in which it appears if the pattern is ever to match that branch. If all possible alternatives start with a circumflex, that is, if the pattern is constrained to match only at the start of the subject, it is said to be an "anchored" pattern. (There are also other constructs that can cause a pattern to be anchored.)
The dollar character is an assertion that is true only if the current matching point is at the end of the subject string, or immediately before a newline at the end of the string (by default). Notice however that it does not match the newline. Dollar needs not to be the last character of the pattern if some alternatives are involved, but it is to be the last item in any branch in which it appears. Dollar has no special meaning in a character class.
The meaning of dollar can be changed so that it matches only at the very end of the string, by setting option dollar_endonly at compile time. This does not affect the \Z assertion.
The meanings of the circumflex and dollar characters are changed if option multiline is set. When this is the case, a circumflex matches immediately after internal newlines and at the start of the subject string. It does not match after a newline that ends the string. A dollar matches before any newlines in the string, and at the very end, when multiline is set. When newline is specified as the two-character sequence CRLF, isolated CR and LF characters do not indicate newlines.
For example, the pattern /^abc$/ matches the subject string "def\nabc" (where \n represents a newline) in multiline mode, but not otherwise. So, patterns that are anchored in single-line mode because all branches start with ^ are not anchored in multiline mode, and a match for circumflex is possible when argument startoffset of run/3 is non-zero. Option dollar_endonly is ignored if multiline is set.
Notice that the sequences \A, \Z, and \z can be used to match the start and end of the subject in both modes. If all branches of a pattern start with \A, it is always anchored, regardless if multiline is set.
Full Stop (Period, Dot) and \N.
Outside a character class, a dot in the pattern matches any character in the subject string except (by default) a character that signifies the end of a line.
When a line ending is defined as a single character, dot never matches that character. When the two-character sequence CRLF is used, dot does not match CR if it is immediately followed by LF, otherwise it matches all characters (including isolated CRs and LFs). When any Unicode line endings are recognized, dot does not match CR, LF, or any of the other line-ending characters.
The behavior of dot regarding newlines can be changed. If option dotall is set, a dot matches any character, without exception. If the two-character sequence CRLF is present in the subject string, it takes two dots to match it.
The handling of dot is entirely independent of the handling of circumflex and dollar, the only relationship is that both involve newlines. Dot has no special meaning in a character class.
The escape sequence \N behaves like a dot, except that it is not affected by option PCRE_DOTALL . That is, it matches any character except one that signifies the end of a line. Perl also uses \N to match characters by name but PCRE does not support this.
Matching a Single Data Unit.
Outside a character class, the escape sequence \C matches any data unit, regardless if a UTF mode is set. One data unit is one byte. Unlike a dot, \C always matches line-ending characters. The feature is provided in Perl to match individual bytes in UTF-8 mode, but it is unclear how it can usefully be used. As \C breaks up characters into individual data units, matching one unit with \C in a UTF mode means that the remaining string can start with a malformed UTF character. This has undefined results, as PCRE assumes that it deals with valid UTF strings.
PCRE does not allow \C to appear in lookbehind assertions (described below) in a UTF mode, as this would make it impossible to calculate the length of the lookbehind.
The \C escape sequence is best avoided. However, one way of using it that avoids the problem of malformed UTF characters is to use a lookahead to check the length of the next character, as in the following pattern, which can be used with a UTF-8 string (ignore whitespace and line breaks):
A group that starts with (?| resets the capturing parentheses numbers in each alternative (see section Duplicate Subpattern Numbers ). The assertions at the start of each branch check the next UTF-8 character for values whose encoding uses 1, 2, 3, or 4 bytes, respectively. The individual bytes of the character are then captured by the appropriate number of groups.
Square Brackets and Character Classes.
An opening square bracket introduces a character class, terminated by a closing square bracket. A closing square bracket on its own is not special by default. However, if option PCRE_JAVASCRIPT_COMPAT is set, a lone closing square bracket causes a compile-time error. If a closing square bracket is required as a member of the class, it is to be the first data character in the class (after an initial circumflex, if present) or escaped with a backslash.
A character class matches a single character in the subject. In a UTF mode, the character can be more than one data unit long. A matched character must be in the set of characters defined by the class, unless the first character in the class definition is a circumflex, in which case the subject character must not be in the set defined by the class. If a circumflex is required as a member of the class, ensure that it is not the first character, or escape it with a backslash.
For example, the character class [aeiou] matches any lowercase vowel, while [^aeiou] matches any character that is not a lowercase vowel. Notice that a circumflex is just a convenient notation for specifying the characters that are in the class by enumerating those that are not. A class that starts with a circumflex is not an assertion; it still consumes a character from the subject string, and therefore it fails if the current pointer is at the end of the string.
In UTF-8 mode, characters with values > 255 (0xffff) can be included in a class as a literal string of data units, or by using the \x.
When caseless matching is set, any letters in a class represent both their uppercase and lowercase versions. For example, a caseless [aeiou] matches "A" and "a", and a caseless [^aeiou] does not match "A", but a caseful version would. In a UTF mode, PCRE always understands the concept of case for characters whose values are < 256, so caseless matching is always possible. For characters with higher values, the concept of case is supported only if PCRE is compiled with Unicode property support. If you want to use caseless matching in a UTF mode for characters >=, ensure that PCRE is compiled with Unicode property support and with UTF support.
Characters that can indicate line breaks are never treated in any special way when matching character classes, whatever line-ending sequence is in use, and whatever setting of options PCRE_DOTALL and PCRE_MULTILINE is used. A class such as [^a] always matches one of these characters.
The minus (hyphen) character can be used to specify a range of characters in a character class. For example, [d-m] matches any letter between d and m, inclusive. If a minus character is required in a class, it must be escaped with a backslash or appear in a position where it cannot be interpreted as indicating a range, typically as the first or last character in the class, or immediately after a range. For example, [b-d-z] matches letters in the range b to d, a hyphen character, or z.
The literal character "]" cannot be the end character of a range. A pattern such as [W-]46] is interpreted as a class of two characters ("W" and "-") followed by a literal string "46]", so it would match "W46]" or "-46]". However, if "]" is escaped with a backslash, it is interpreted as the end of range, so [W-\]46] is interpreted as a class containing a range followed by two other characters. The octal or hexadecimal representation of "]" can also be used to end a range.
An error is generated if a POSIX character class (see below) or an escape sequence other than one that defines a single character appears at a point where a range ending character is expected. For example, [z-\xff] is valid, but [A-\d] and [A-[:digit:]] are not.
Ranges operate in the collating sequence of character values. They can also be used for characters specified numerically, for example, [\000-\037]. Ranges can include any characters that are valid for the current mode.
If a range that includes letters is used when caseless matching is set, it matches the letters in either case. For example, [W-c] is equivalent to [][\\^_`wxyzabc], matched caselessly. In a non-UTF mode, if character tables for a French locale are in use, [\xc8-\xcb] matches accented E characters in both cases. In UTF modes, PCRE supports the concept of case for characters with values > 255 only when it is compiled with Unicode property support.
The character escape sequences \d, \D, \h, \H, \p, \P, \s, \S, \v, \V, \w, and \W can appear in a character class, and add the characters that they match to the class. For example, [\dABCDEF] matches any hexadecimal digit. In UTF modes, option ucp affects the meanings of \d, \s, \w and their uppercase partners, just as it does when they appear outside a character class, as described in section Generic Character Types earlier. The escape sequence \b has a different meaning inside a character class; it matches the backspace character. The sequences \B, \N, \R, and \X are not special inside a character class. Like any other unrecognized escape sequences, they are treated as the literal characters "B", "N", "R", and "X".
A circumflex can conveniently be used with the uppercase character types to specify a more restricted set of characters than the matching lowercase type. For example, class [^\W_] matches any letter or digit, but not underscore, while [\w] includes underscore. A positive character class is to be read as "something OR something OR . " and a negative class as "NOT something AND NOT something AND NOT . ".
Only the following metacharacters are recognized in character classes:
Backslash Hyphen (only where it can be interpreted as specifying a range) Circumflex (only at the start) Opening square bracket (only when it can be interpreted as introducing a Posix class name, or for a special compatibility feature; see the next two sections) Terminating closing square bracket.
However, escaping other non-alphanumeric characters does no harm.
Posix Character Classes.
Perl supports the Posix notation for character classes. This uses names enclosed by [: and :] within the enclosing square brackets. PCRE also supports this notation. For example, the following matches "0", "1", any alphabetic character, or "%":
The following are the supported class names:
alnum Letters and digits alpha Letters ascii Character codes 0-127 blank Space or tab only cntrl Control characters digit Decimal digits (same as \d) graph Printing characters, excluding space lower Lowercase letters print Printing characters, including space punct Printing characters, excluding letters, digits, and space space Whitespace (the same as \s from PCRE 8.34) upper Uppercase letters word "Word" characters (same as \w) xdigit Hexadecimal digits.
The default "space" characters are HT (9), LF (10), VT (11), FF (12), CR (13), and space (32). If locale-specific matching is taking place, the list of space characters may be different; there may be fewer or more of them. "Space" used to be different to \s, which did not include VT, for Perl compatibility. However, Perl changed at release 5.18, and PCRE followed at release 8.34. "Space" and \s now match the same set of characters.
The name "word" is a Perl extension, and "blank" is a GNU extension from Perl 5.8. Another Perl extension is negation, which is indicated by a ^ character after the colon. For example, the following matches "1", "2", or any non-digit:
PCRE (and Perl) also recognize the Posix syntax [.ch.] and [=ch=] where "ch" is a "collating element", but these are not supported, and an error is given if they are encountered.
By default, characters with values > 255 do not match any of the Posix character classes. However, if option PCRE_UCP is passed to pcre_compile() , some of the classes are changed so that Unicode character properties are used. This is achieved by replacing certain Posix classes by other sequences, as follows:
Negated versions, such as [:^alpha:], use \P instead of \p. Three other POSIX classes are handled specially in UCP mode:
This matches characters that have glyphs that mark the page when printed. In Unicode property terms, it matches all characters with the L, M, N, P, S, or Cf properties, except for:
Arabic Letter Mark.
Mongolian Vowel Separator.
This matches the same characters as [:graph:] plus space characters that are not controls, that is, characters with the Zs property.
This matches all characters that have the Unicode P (punctuation) property, plus those characters whose code points are less than 128 that have the S (Symbol) property.
The other POSIX classes are unchanged, and match only characters with code points less than 128.
Compatibility Feature for Word Boundaries.
In the POSIX.2 compliant library that was included in 4.4BSD Unix, the ugly syntax [[:<:]] and [[:>:]] is used for matching "start of word" and "end of word". PCRE treats these items as follows:
is converted to \b(?=\w)
is converted to \b(?<=\w)
Only these exact character sequences are recognized. A sequence such as [a[:<:]b] provokes error for an unrecognized POSIX class name. This support is not compatible with Perl. It is provided to help migrations from other environments, and is best not used in any new patterns. Note that \b matches at the start and the end of a word (see "Simple assertions" above), and in a Perl-style pattern the preceding or following character normally shows which is wanted, without the need for the assertions that are used above in order to give exactly the POSIX behaviour.
Vertical Bar.
Vertical bar characters are used to separate alternative patterns. For example, the following pattern matches either "gilbert" or "sullivan":
Any number of alternatives can appear, and an empty alternative is permitted (matching the empty string). The matching process tries each alternative in turn, from left to right, and the first that succeeds is used. If the alternatives are within a subpattern (defined in section Subpatterns ), "succeeds" means matching the remaining main pattern and the alternative in the subpattern.
Internal Option Setting.
The settings of the Perl-compatible options caseless , multiline , dotall , and extended can be changed from within the pattern by a sequence of Perl option letters enclosed between "(?" and ")". The option letters are as follows:
For example, (?im) sets caseless, multiline matching. These options can also be unset by preceding the letter with a hyphen. A combined setting and unsetting such as (?im-sx) , which sets caseless and multiline , while unsetting dotall and extended , is also permitted. If a letter appears both before and after the hyphen, the option is unset.
The PCRE-specific options dupnames , ungreedy , and extra can be changed in the same way as the Perl-compatible options by using the characters J, U, and X respectively.
When one of these option changes occurs at top-level (that is, not inside subpattern parentheses), the change applies to the remainder of the pattern that follows.
An option change within a subpattern (see section Subpatterns ) affects only that part of the subpattern that follows it. So, the following matches abc and aBc and no other strings (assuming caseless is not used):
By this means, options can be made to have different settings in different parts of the pattern. Any changes made in one alternative do carry on into subsequent branches within the same subpattern. Por exemplo:
matches "ab", "aB", "c", and "C", although when matching "C" the first branch is abandoned before the option setting. This is because the effects of option settings occur at compile time. There would be some weird behavior otherwise.
Other PCRE-specific options can be set by the application when the compiling or matching functions are called. Sometimes the pattern can contain special leading sequences, such as (*CRLF), to override what the application has set or what has been defaulted. Details are provided in section Newline Sequences earlier.
The (*UTF8) and (*UCP) leading sequences can be used to set UTF and Unicode property modes. They are equivalent to setting options unicode and ucp , respectively. The (*UTF) sequence is a generic version that can be used with any of the libraries. However, the application can set option never_utf , which locks out the use of the (*UTF) sequences.
Subpatterns.
Subpatterns are delimited by parentheses (round brackets), which can be nested. Turning part of a pattern into a subpattern does two things:
It localizes a set of alternatives. For example, the following pattern matches "cataract", "caterpillar", or "cat":
Without the parentheses, it would match "cataract", "erpillar", or an empty string.
It sets up the subpattern as a capturing subpattern. That is, when the complete pattern matches, that portion of the subject string that matched the subpattern is passed back to the caller through the return value of run/3 .
Opening parentheses are counted from left to right (starting from 1) to obtain numbers for the capturing subpatterns. For example, if the string "the red king" is matched against the following pattern, the captured substrings are "red king", "red", and "king", and are numbered 1, 2, and 3, respectively:
It is not always helpful that plain parentheses fulfill two functions. Often a grouping subpattern is required without a capturing requirement. If an opening parenthesis is followed by a question mark and a colon, the subpattern does not do any capturing, and is not counted when computing the number of any subsequent capturing subpatterns. For example, if the string "the white queen" is matched against the following pattern, the captured substrings are "white queen" and "queen", and are numbered 1 and 2:
The maximum number of capturing subpatterns is 65535.
As a convenient shorthand, if any option settings are required at the start of a non-capturing subpattern, the option letters can appear between "?" and ":". Thus, the following two patterns match the same set of strings:
As alternative branches are tried from left to right, and options are not reset until the end of the subpattern is reached, an option setting in one branch does affect subsequent branches, so the above patterns match both "SUNDAY" and "Saturday".
Duplicate Subpattern Numbers.
Perl 5.10 introduced a feature where each alternative in a subpattern uses the same numbers for its capturing parentheses. Such a subpattern starts with (?| and is itself a non-capturing subpattern. For example, consider the following pattern:
As the two alternatives are inside a (?| group, both sets of capturing parentheses are numbered one. Thus, when the pattern matches, you can look at captured substring number one, whichever alternative matched. This construct is useful when you want to capture a part, but not all, of one of many alternatives. Inside a (?| group, parentheses are numbered as usual, but the number is reset at the start of each branch. The numbers of any capturing parentheses that follow the subpattern start after the highest number used in any branch. The following example is from the Perl documentation; the numbers underneath show in which buffer the captured content is stored:
A back reference to a numbered subpattern uses the most recent value that is set for that number by any subpattern. The following pattern matches "abcabc" or "defdef":
In contrast, a subroutine call to a numbered subpattern always refers to the first one in the pattern with the given number. The following pattern matches "abcabc" or "defabc":
If a condition test for a subpattern having matched refers to a non-unique number, the test is true if any of the subpatterns of that number have matched.
An alternative approach using this "branch reset" feature is to use duplicate named subpatterns, as described in the next section.
Named Subpatterns.
Identifying capturing parentheses by number is simple, but it can be hard to keep track of the numbers in complicated regular expressions. Also, if an expression is modified, the numbers can change. To help with this difficulty, PCRE supports the naming of subpatterns. This feature was not added to Perl until release 5.10. Python had the feature earlier, and PCRE introduced it at release 4.0, using the Python syntax. PCRE now supports both the Perl and the Python syntax. Perl allows identically numbered subpatterns to have different names, but PCRE does not.
In PCRE, a subpattern can be named in one of three ways: (?<name>. ) or (?'name'. ) as in Perl, or (?P<name>. ) as in Python. References to capturing parentheses from other parts of the pattern, such as back references, recursion, and conditions, can be made by name and by number.
Names consist of up to 32 alphanumeric characters and underscores, but must start with a non-digit. Named capturing parentheses are still allocated numbers as well as names, exactly as if the names were not present. The capture specification to run/3 can use named values if they are present in the regular expression.
By default, a name must be unique within a pattern, but this constraint can be relaxed by setting option dupnames at compile time. (Duplicate names are also always permitted for subpatterns with the same number, set up as described in the previous section.) Duplicate names can be useful for patterns where only one instance of the named parentheses can match. Suppose that you want to match the name of a weekday, either as a 3-letter abbreviation or as the full name, and in both cases you want to extract the abbreviation. The following pattern (ignoring the line breaks) does the job:
There are five capturing substrings, but only one is ever set after a match. (An alternative way of solving this problem is to use a "branch reset" subpattern, as described in the previous section.)
For capturing named subpatterns which names are not unique, the first matching occurrence (counted from left to right in the subject) is returned from run/3 , if the name is specified in the values part of the capture statement. The all_names capturing value matches all the names in the same way.
You cannot use different names to distinguish between two subpatterns with the same number, as PCRE uses only the numbers when matching. For this reason, an error is given at compile time if different names are specified to subpatterns with the same number. However, you can specify the same name to subpatterns with the same number, even when dupnames is not set.
Repetition.
Repetition is specified by quantifiers, which can follow any of the following items:
A literal data character The dot metacharacter The \C escape sequence The \X escape sequence The \R escape sequence An escape such as \d or \pL that matches a single character A character class A back reference (see the next section) A parenthesized subpattern (including assertions) A subroutine call to a subpattern (recursive or otherwise)
The general repetition quantifier specifies a minimum and maximum number of permitted matches, by giving the two numbers in curly brackets (braces), separated by a comma. The numbers must be < 65536, and the first must be less than or equal to the second. For example, the following matches "zz", "zzz", or "zzzz":
A closing brace on its own is not a special character. If the second number is omitted, but the comma is present, there is no upper limit. If the second number and the comma are both omitted, the quantifier specifies an exact number of required matches. Thus, the following matches at least three successive vowels, but can match many more:
The following matches exactly eight digits:
An opening curly bracket that appears in a position where a quantifier is not allowed, or one that does not match the syntax of a quantifier, is taken as a literal character. For example, is not a quantifier, but a literal string of four characters.
In Unicode mode, quantifiers apply to characters rather than to individual data units. Thus, for example, \x matches two characters, each of which is represented by a 2-byte sequence in a UTF-8 string. Similarly, \X matches three Unicode extended grapheme clusters, each of which can be many data units long (and they can be of different lengths).
The quantifier is permitted, causing the expression to behave as if the previous item and the quantifier were not present. This can be useful for subpatterns that are referenced as subroutines from elsewhere in the pattern (but see also section Defining Subpatterns for Use by Reference Only ). Items other than subpatterns that have a quantifier are omitted from the compiled pattern.
For convenience, the three most common quantifiers have single-character abbreviations:
Infinite loops can be constructed by following a subpattern that can match no characters with a quantifier that has no upper limit, for example:
Earlier versions of Perl and PCRE used to give an error at compile time for such patterns. However, as there are cases where this can be useful, such patterns are now accepted. However, if any repetition of the subpattern matches no characters, the loop is forcibly broken.
By default, the quantifiers are "greedy", that is, they match as much as possible (up to the maximum number of permitted times), without causing the remaining pattern to fail. The classic example of where this gives problems is in trying to match comments in C programs. These appear between /* and */. Within the comment, individual * and / characters can appear. An attempt to match C comments by applying the pattern.
fails, as it matches the entire string owing to the greediness of the .* item.
However, if a quantifier is followed by a question mark, it ceases to be greedy, and instead matches the minimum number of times possible, so the following pattern does the right thing with the C comments:
The meaning of the various quantifiers is not otherwise changed, only the preferred number of matches. Do not confuse this use of question mark with its use as a quantifier in its own right. As it has two uses, it can sometimes appear doubled, as in.
which matches one digit by preference, but can match two if that is the only way the remaining pattern matches.
If option ungreedy is set (an option that is not available in Perl), the quantifiers are not greedy by default, but individual ones can be made greedy by following them with a question mark. That is, it inverts the default behavior.
When a parenthesized subpattern is quantified with a minimum repeat count that is > 1 or with a limited maximum, more memory is required for the compiled pattern, in proportion to the size of the minimum or maximum.
If a pattern starts with .* or . and option dotall (equivalent to Perl option /s ) is set, thus allowing the dot to match newlines, the pattern is implicitly anchored, because whatever follows is tried against every character position in the subject string. So, there is no point in retrying the overall match at any position after the first. PCRE normally treats such a pattern as if it was preceded by \A.
In cases where it is known that the subject string contains no newlines, it is worth setting dotall to obtain this optimization, or alternatively using ^ to indicate anchoring explicitly.
However, there are some cases where the optimization cannot be used. When .* is inside capturing parentheses that are the subject of a back reference elsewhere in the pattern, a match at the start can fail where a later one succeeds. Consider, for example:
If the subject is "xyz123abc123", the match point is the fourth character. Therefore, such a pattern is not implicitly anchored.
Another case where implicit anchoring is not applied is when the leading .* is inside an atomic group. Once again, a match at the start can fail where a later one succeeds. Consider the following pattern:
It matches "ab" in the subject "aab". The use of the backtracking control verbs (*PRUNE) and (*SKIP) also disable this optimization.
When a capturing subpattern is repeated, the value captured is the substring that matched the final iteration. For example, after.
has matched "tweedledum tweedledee", the value of the captured substring is "tweedledee". However, if there are nested capturing subpatterns, the corresponding captured values can have been set in previous iterations. For example, after.
matches "aba", the value of the second captured substring is "b".
Atomic Grouping and Possessive Quantifiers.
With both maximizing ("greedy") and minimizing ("ungreedy" or "lazy") repetition, failure of what follows normally causes the repeated item to be re-evaluated to see if a different number of repeats allows the remaining pattern to match. Sometimes it is useful to prevent this, either to change the nature of the match, or to cause it to fail earlier than it otherwise might, when the author of the pattern knows that there is no point in carrying on.
Consider, for example, the pattern \d+foo when applied to the following subject line:
After matching all six digits and then failing to match "foo", the normal action of the matcher is to try again with only five digits matching item \d+, and then with four, and so on, before ultimately failing. "Atomic grouping" (a term taken from Jeffrey Friedl's book) provides the means for specifying that once a subpattern has matched, it is not to be re-evaluated in this way.
If atomic grouping is used for the previous example, the matcher gives up immediately on failing to match "foo" the first time. The notation is a kind of special parenthesis, starting with (?> as in the following example:
This kind of parenthesis "locks up" the part of the pattern it contains once it has matched, and a failure further into the pattern is prevented from backtracking into it. Backtracking past it to previous items, however, works as normal.
An alternative description is that a subpattern of this type matches the string of characters that an identical standalone pattern would match, if anchored at the current point in the subject string.
Atomic grouping subpatterns are not capturing subpatterns. Simple cases such as the above example can be thought of as a maximizing repeat that must swallow everything it can. So, while both \d+ and \d+? are prepared to adjust the number of digits they match to make the remaining pattern match, (?>\d+) can only match an entire sequence of digits.
Atomic groups in general can contain any complicated subpatterns, and can be nested. However, when the subpattern for an atomic group is just a single repeated item, as in the example above, a simpler notation, called a "possessive quantifier" can be used. This consists of an extra + character following a quantifier. Using this notation, the previous example can be rewritten as.
Notice that a possessive quantifier can be used with an entire group, for example:
Possessive quantifiers are always greedy; the setting of option ungreedy is ignored. They are a convenient notation for the simpler forms of an atomic group. However, there is no difference in the meaning of a possessive quantifier and the equivalent atomic group, but there can be a performance difference; possessive quantifiers are probably slightly faster.
The possessive quantifier syntax is an extension to the Perl 5.8 syntax. Jeffrey Friedl originated the idea (and the name) in the first edition of his book. Mike McCloskey liked it, so implemented it when he built the Sun Java package, and PCRE copied it from there. It ultimately found its way into Perl at release 5.10.
PCRE has an optimization that automatically "possessifies" certain simple pattern constructs. For example, the sequence A+B is treated as A++B, as there is no point in backtracking into a sequence of A:s when B must follow.
When a pattern contains an unlimited repeat inside a subpattern that can itself be repeated an unlimited number of times, the use of an atomic group is the only way to avoid some failing matches taking a long time. O padrão.
matches an unlimited number of substrings that either consist of non-digits, or digits enclosed in <>, followed by ! or ?. When it matches, it runs quickly. However, if it is applied to.
it takes a long time before reporting failure. This is because the string can be divided between the internal \D+ repeat and the external * repeat in many ways, and all must be tried. (The example uses [!?] rather than a single character at the end, as both PCRE and Perl have an optimization that allows for fast failure when a single character is used. They remember the last single character that is required for a match, and fail early if it is not present in the string.) If the pattern is changed so that it uses an atomic group, like the following, sequences of non-digits cannot be broken, and failure happens quickly:
Back References.
Outside a character class, a backslash followed by a digit > 0 (and possibly further digits) is a back reference to a capturing subpattern earlier (that is, to its left) in the pattern, provided there have been that many previous capturing left parentheses.
However, if the decimal number following the backslash is < 10, it is always taken as a back reference, and causes an error only if there are not that many capturing left parentheses in the entire pattern. That is, the parentheses that are referenced do need not be to the left of the reference for numbers < 10. A "forward back reference" of this type can make sense when a repetition is involved and the subpattern to the right has participated in an earlier iteration.
It is not possible to have a numerical "forward back reference" to a subpattern whose number is 10 or more using this syntax, as a sequence such as \50 is interpreted as a character defined in octal. For more details of the handling of digits following a backslash, see section Non-Printing Characters earlier. There is no such problem when named parentheses are used. A back reference to any subpattern is possible using named parentheses (see below).
Another way to avoid the ambiguity inherent in the use of digits following a backslash is to use the \g escape sequence. This escape must be followed by an unsigned number or a negative number, optionally enclosed in braces. The following examples are identical:
An unsigned number specifies an absolute reference without the ambiguity that is present in the older syntax. It is also useful when literal digits follow the reference. A negative number is a relative reference. Considere o seguinte exemplo:
The sequence \g is a reference to the most recently started capturing subpattern before \g, that is, it is equivalent to \2 in this example. Similarly, \g would be equivalent to \1. The use of relative references can be helpful in long patterns, and also in patterns that are created by joining fragments containing references within themselves.
A back reference matches whatever matched the capturing subpattern in the current subject string, rather than anything matching the subpattern itself (section Subpattern as Subroutines describes a way of doing that). So, the following pattern matches "sense and sensibility" and "response and responsibility", but not "sense and responsibility":
If caseful matching is in force at the time of the back reference, the case of letters is relevant. For example, the following matches "rah rah" and "RAH RAH", but not "RAH rah", although the original capturing subpattern is matched caselessly:
There are many different ways of writing back references to named subpatterns. The syntax \k and the Perl syntax \k<name> or \k'name' are supported, as is the Python syntax (?P=name) . The unified back reference syntax in Perl 5.10, in which \g can be used for both numeric and named references, is also supported. The previous example can be rewritten in the following ways:
A subpattern that is referenced by name can appear in the pattern before or after the reference.
There can be more than one back reference to the same subpattern. If a subpattern has not been used in a particular match, any back references to it always fails. For example, the following pattern always fails if it starts to match "a" rather than "bc":
As there can be many capturing parentheses in a pattern, all digits following the backslash are taken as part of a potential back reference number. If the pattern continues with a digit character, some delimiter must be used to terminate the back reference. If option extended is set, this can be whitespace. Otherwise an empty comment (see section Comments ) can be used.
Recursive Back References.
A back reference that occurs inside the parentheses to which it refers fails when the subpattern is first used, so, for example, (a\1) never matches. However, such references can be useful inside repeated subpatterns. For example, the following pattern matches any number of "a"s and also "aba", "ababbaa", and so on:
At each iteration of the subpattern, the back reference matches the character string corresponding to the previous iteration. In order for this to work, the pattern must be such that the first iteration does not need to match the back reference. This can be done using alternation, as in the example above, or by a quantifier with a minimum of zero.
Back references of this type cause the group that they reference to be treated as an atomic group. Once the whole group has been matched, a subsequent matching failure cannot cause backtracking into the middle of the group.
Assertions.
An assertion is a test on the characters following or preceding the current matching point that does not consume any characters. The simple assertions coded as \b, \B, \A, \G, \Z, \z, ^, and $ are described in the previous sections.
More complicated assertions are coded as subpatterns. There are two kinds: those that look ahead of the current position in the subject string, and those that look behind it. An assertion subpattern is matched in the normal way, except that it does not cause the current matching position to be changed.
Assertion subpatterns are not capturing subpatterns. If such an assertion contains capturing subpatterns within it, these are counted for the purposes of numbering the capturing subpatterns in the whole pattern. However, substring capturing is done only for positive assertions. (Perl sometimes, but not always, performs capturing in negative assertions.)
If a positive assertion containing one or more capturing subpatterns succeeds, but failure to match later in the pattern causes backtracking over this assertion, the captures within the assertion are reset only if no higher numbered captures are already set. This is, unfortunately, a fundamental limitation of the current implementation, and as PCRE1 is now in maintenance-only status, it is unlikely ever to change.
For compatibility with Perl, assertion subpatterns can be repeated. However, it makes no sense to assert the same thing many times, the side effect of capturing parentheses can occasionally be useful. In practice, there are only three cases:
If the quantifier is , the assertion is never obeyed during matching. However, it can contain internal capturing parenthesized groups that are called from elsewhere through the subroutine mechanism.
If quantifier is , where n > 0, it is treated as if it was . At runtime, the remaining pattern match is tried with and without the assertion, the order depends on the greediness of the quantifier.
If the minimum repetition is > 0, the quantifier is ignored. The assertion is obeyed only once when encountered during matching.
Lookahead assertions start with (?= for positive assertions and (?! for negative assertions. For example, the following matches a word followed by a semicolon, but does not include the semicolon in the match:
The following matches any occurrence of "foo" that is not followed by "bar":
Notice that the apparently similar pattern.
does not find an occurrence of "bar" that is preceded by something other than "foo". It finds any occurrence of "bar" whatsoever, as the assertion (?!foo) is always true when the next three characters are "bar". A lookbehind assertion is needed to achieve the other effect.
If you want to force a matching failure at some point in a pattern, the most convenient way to do it is with (?!), as an empty string always matches. So, an assertion that requires there is not to be an empty string must always fail. The backtracking control verb (*FAIL) or (*F) is a synonym for (?!).
Lookbehind assertions start with (?<= for positive assertions and (?<! for negative assertions. For example, the following finds an occurrence of "bar" that is not preceded by "foo":
The contents of a lookbehind assertion are restricted such that all the strings it matches must have a fixed length. However, if there are many top-level alternatives, they do not all have to have the same fixed length. Thus, the following is permitted:
The following causes an error at compile time:
Branches that match different length strings are permitted only at the top-level of a lookbehind assertion. This is an extension compared with Perl, which requires all branches to match the same length of string. An assertion such as the following is not permitted, as its single top-level branch can match two different lengths:
However, it is acceptable to PCRE if rewritten to use two top-level branches:
Sometimes the escape sequence \K (see above) can be used instead of a lookbehind assertion to get round the fixed-length restriction.
The implementation of lookbehind assertions is, for each alternative, to move the current position back temporarily by the fixed length and then try to match. If there are insufficient characters before the current position, the assertion fails.
In a UTF mode, PCRE does not allow the \C escape (which matches a single data unit even in a UTF mode) to appear in lookbehind assertions, as it makes it impossible to calculate the length of the lookbehind. The \X and \R escapes, which can match different numbers of data units, are not permitted either.
"Subroutine" calls (see below), such as (?2) or (?&X), are permitted in lookbehinds, as long as the subpattern matches a fixed-length string. Recursion, however, is not supported.
Possessive quantifiers can be used with lookbehind assertions to specify efficient matching of fixed-length strings at the end of subject strings. Consider the following simple pattern when applied to a long string that does not match:
As matching proceeds from left to right, PCRE looks for each "a" in the subject and then sees if what follows matches the remaining pattern. If the pattern is specified as.
the initial .* matches the entire string at first. However, when this fails (as there is no following "a"), it backtracks to match all but the last character, then all but the last two characters, and so on. Once again the search for "a" covers the entire string, from right to left, so we are no better off. However, if the pattern is written as.
there can be no backtracking for the .*+ item; it can match only the entire string. The subsequent lookbehind assertion does a single test on the last four characters. If it fails, the match fails immediately. For long strings, this approach makes a significant difference to the processing time.
Using Multiple Assertions.
Many assertions (of any sort) can occur in succession. For example, the following matches "foo" preceded by three digits that are not "999":
Notice that each of the assertions is applied independently at the same point in the subject string. First there is a check that the previous three characters are all digits, and then there is a check that the same three characters are not "999". This pattern does not match "foo" preceded by six characters, the first of which are digits and the last three of which are not "999". For example, it does not match "123abcfoo". A pattern to do that is the following:
This time the first assertion looks at the preceding six characters, checks that the first three are digits, and then the second assertion checks that the preceding three characters are not "999".
Assertions can be nested in any combination. For example, the following matches an occurrence of "baz" that is preceded by "bar", which in turn is not preceded by "foo":
The following pattern matches "foo" preceded by three digits and any three characters that are not "999":
Conditional Subpatterns.
It is possible to cause the matching process to obey a subpattern conditionally or to choose between two alternative subpatterns, depending on the result of an assertion, or whether a specific capturing subpattern has already been matched. The following are the two possible forms of conditional subpattern:
If the condition is satisfied, the yes-pattern is used, otherwise the no-pattern (if present). If more than two alternatives exist in the subpattern, a compile-time error occurs. Each of the two alternatives can itself contain nested subpatterns of any form, including conditional subpatterns; the restriction to two alternatives applies only at the level of the condition. The following pattern fragment is an example where the alternatives are complex:
There are four kinds of condition: references to subpatterns, references to recursion, a pseudo-condition called DEFINE, and assertions.
Checking for a Used Subpattern By Number.
If the text between the parentheses consists of a sequence of digits, the condition is true if a capturing subpattern of that number has previously matched. If more than one capturing subpattern with the same number exists (see section Duplicate Subpattern Numbers earlier), the condition is true if any of them have matched. An alternative notation is to precede the digits with a plus or minus sign. In this case, the subpattern number is relative rather than absolute. The most recently opened parentheses can be referenced by (?(-1), the next most recent by (?(-2), and so on. Inside loops, it can also make sense to refer to subsequent groups. The next parentheses to be opened can be referenced as (?(+1), and so on. (The value zero in any of these forms is not used; it provokes a compile-time error.)
Consider the following pattern, which contains non-significant whitespace to make it more readable (assume option extended ) and to divide it into three parts for ease of discussion:
The first part matches an optional opening parenthesis, and if that character is present, sets it as the first captured substring. The second part matches one or more characters that are not parentheses. The third part is a conditional subpattern that tests whether the first set of parentheses matched or not. If they did, that is, if subject started with an opening parenthesis, the condition is true, and so the yes-pattern is executed and a closing parenthesis is required. Otherwise, as no-pattern is not present, the subpattern matches nothing. That is, this pattern matches a sequence of non-parentheses, optionally enclosed in parentheses.
If this pattern is embedded in a larger one, a relative reference can be used:
This makes the fragment independent of the parentheses in the larger pattern.
Checking for a Used Subpattern By Name.
Perl uses the syntax (?(<name>). ) or (?('name'). ) to test for a used subpattern by name. For compatibility with earlier versions of PCRE, which had this facility before Perl, the syntax (?(name). ) is also recognized.
Rewriting the previous example to use a named subpattern gives:
If the name used in a condition of this kind is a duplicate, the test is applied to all subpatterns of the same name, and is true if any one of them has matched.
Checking for Pattern Recursion.
If the condition is the string (R), and there is no subpattern with the name R, the condition is true if a recursive call to the whole pattern or any subpattern has been made. If digits or a name preceded by ampersand follow the letter R, for example:
the condition is true if the most recent recursion is into a subpattern whose number or name is given. This condition does not check the entire recursion stack. If the name used in a condition of this kind is a duplicate, the test is applied to all subpatterns of the same name, and is true if any one of them is the most recent recursion.
At "top-level", all these recursion test conditions are false. The syntax for recursive patterns is described below.
Defining Subpatterns for Use By Reference Only.
If the condition is the string (DEFINE), and there is no subpattern with the name DEFINE, the condition is always false. In this case, there can be only one alternative in the subpattern. It is always skipped if control reaches this point in the pattern. The idea of DEFINE is that it can be used to define "subroutines" that can be referenced from elsewhere. (The use of subroutines is described below.) For example, a pattern to match an IPv4 address, such as "192.168.23.245", can be written like this (ignore whitespace and line breaks):
The first part of the pattern is a DEFINE group inside which is a another group named "byte" is defined. This matches an individual component of an IPv4 address (a number < 256). When matching takes place, this part of the pattern is skipped, as DEFINE acts like a false condition. The remaining pattern uses references to the named group to match the four dot-separated components of an IPv4 address, insisting on a word boundary at each end.
If the condition is not in any of the above formats, it must be an assertion. This can be a positive or negative lookahead or lookbehind assertion. Consider the following pattern, containing non-significant whitespace, and with the two alternatives on the second line:
The condition is a positive lookahead assertion that matches an optional sequence of non-letters followed by a letter. That is, it tests for the presence of at least one letter in the subject. If a letter is found, the subject is matched against the first alternative, otherwise it is matched against the second. This pattern matches strings in one of the two forms dd-aaa-dd or dd-dd-dd, where aaa are letters and dd are digits.
There are two ways to include comments in patterns that are processed by PCRE. In both cases, the start of the comment must not be in a character class, or in the middle of any other sequence of related characters such as (?: or a subpattern name or number. The characters that make up a comment play no part in the pattern matching.
The sequence (?# marks the start of a comment that continues up to the next closing parenthesis. Nested parentheses are not permitted. If option PCRE_EXTENDED is set, an unescaped # character also introduces a comment, which in this case continues to immediately after the next newline character or character sequence in the pattern. Which characters are interpreted as newlines is controlled by the options passed to a compiling function or by a special sequence at the start of the pattern, as described in section Newline Conventions earlier.
Notice that the end of this type of comment is a literal newline sequence in the pattern; escape sequences that happen to represent a newline do not count. For example, consider the following pattern when extended is set, and the default newline convention is in force:
On encountering character #, pcre_compile() skips along, looking for a newline in the pattern. The sequence \n is still literal at this stage, so it does not terminate the comment. Only a character with code value 0x0a (the default newline) does so.
Recursive Patterns.
Consider the problem of matching a string in parentheses, allowing for unlimited nested parentheses. Without the use of recursion, the best that can be done is to use a pattern that matches up to some fixed depth of nesting. It is not possible to handle an arbitrary nesting depth.
For some time, Perl has provided a facility that allows regular expressions to recurse (among other things). It does this by interpolating Perl code in the expression at runtime, and the code can refer to the expression itself. A Perl pattern using code interpolation to solve the parentheses problem can be created like this:
Item (?p ) interpolates Perl code at runtime, and in this case refers recursively to the pattern in which it appears.
Obviously, PCRE cannot support the interpolation of Perl code. Instead, it supports special syntax for recursion of the entire pattern, and for individual subpattern recursion. After its introduction in PCRE and Python, this kind of recursion was later introduced into Perl at release 5.10.
A special item that consists of (? followed by a number > 0 and a closing parenthesis is a recursive subroutine call of the subpattern of the given number, if it occurs inside that subpattern. (If not, it is a non-recursive subroutine call, which is described in the next section.) The special item (?R) or (?0) is a recursive call of the entire regular expression.
This PCRE pattern solves the nested parentheses problem (assume that option extended is set so that whitespace is ignored):
First it matches an opening parenthesis. Then it matches any number of substrings, which can either be a sequence of non-parentheses or a recursive match of the pattern itself (that is, a correctly parenthesized substring). Finally there is a closing parenthesis. Notice the use of a possessive quantifier to avoid backtracking into sequences of non-parentheses.
If this was part of a larger pattern, you would not want to recurse the entire pattern, so instead you can use:
The pattern is here within parentheses so that the recursion refers to them instead of the whole pattern.
In a larger pattern, keeping track of parenthesis numbers can be tricky. This is made easier by the use of relative references. Instead of (?1) in the pattern above, you can write (?-2) to refer to the second most recently opened parentheses preceding the recursion. That is, a negative number counts capturing parentheses leftwards from the point at which it is encountered.
It is also possible to refer to later opened parentheses, by writing references such as (?+2). However, these cannot be recursive, as the reference is not inside the parentheses that are referenced. They are always non-recursive subroutine calls, as described in the next section.
An alternative approach is to use named parentheses instead. The Perl syntax for this is (?&name). The earlier PCRE syntax (?P>name) is also supported. We can rewrite the above example as follows:
If there is more than one subpattern with the same name, the earliest one is used.
This particular example pattern that we have studied contains nested unlimited repeats, and so the use of a possessive quantifier for matching strings of non-parentheses is important when applying the pattern to strings that do not match. For example, when this pattern is applied to.
it gives "no match" quickly. However, if a possessive quantifier is not used, the match runs for a long time, as there are so many different ways the + and * repeats can carve up the subject, and all must be tested before failure can be reported.
At the end of a match, the values of capturing parentheses are those from the outermost level. If the pattern above is matched against.
the value for the inner capturing parentheses (numbered 2) is "ef", which is the last value taken on at the top-level. If a capturing subpattern is not matched at the top level, its final captured value is unset, even if it was (temporarily) set at a deeper level during the matching process.
Do not confuse item (?R) with condition (R), which tests for recursion. Consider the following pattern, which matches text in angle brackets, allowing for arbitrary nesting. Only digits are allowed in nested brackets (that is, when recursing), while any characters are permitted at the outer level.
Here (?(R) is the start of a conditional subpattern, with two different alternatives for the recursive and non-recursive cases. Item (?R) is the actual recursive call.
Differences in Recursion Processing between PCRE and Perl.
Recursion processing in PCRE differs from Perl in two important ways. In PCRE (like Python, but unlike Perl), a recursive subpattern call is always treated as an atomic group. That is, once it has matched some of the subject string, it is never re-entered, even if it contains untried alternatives and there is a subsequent matching failure. This can be illustrated by the following pattern, which means to match a palindromic string containing an odd number of characters (for example, "a", "aba", "abcba", "abcdcba"):
The idea is that it either matches a single character, or two identical characters surrounding a subpalindrome. In Perl, this pattern works; in PCRE it does not work if the pattern is longer than three characters. Consider the subject string "abcba".
At the top level, the first character is matched, but as it is not at the end of the string, the first alternative fails, the second alternative is taken, and the recursion kicks in. The recursive call to subpattern 1 successfully matches the next character ("b"). (Notice that the beginning and end of line tests are not part of the recursion.)
Back at the top level, the next character ("c") is compared with what subpattern 2 matched, which was "a". This fails. As the recursion is treated as an atomic group, there are now no backtracking points, and so the entire match fails. (Perl can now re-enter the recursion and try the second alternative.) However, if the pattern is written with the alternatives in the other order, things are different:
This time, the recursing alternative is tried first, and continues to recurse until it runs out of characters, at which point the recursion fails. But this time we have another alternative to try at the higher level. That is the significant difference: in the previous case the remaining alternative is at a deeper recursion level, which PCRE cannot use.
To change the pattern so that it matches all palindromic strings, not only those with an odd number of characters, it is tempting to change the pattern to this:
Again, this works in Perl, but not in PCRE, and for the same reason. When a deeper recursion has matched a single character, it cannot be entered again to match an empty string. The solution is to separate the two cases, and write out the odd and even cases as alternatives at the higher level:
If you want to match typical palindromic phrases, the pattern must ignore all non-word characters, which can be done as follows:
If run with option caseless , this pattern matches phrases such as "A man, a plan, a canal: Panama!" and it works well in both PCRE and Perl. Notice the use of the possessive quantifier *+ to avoid backtracking into sequences of non-word characters. Without this, PCRE takes much longer (10 times or more) to match typical phrases, and Perl takes so long that you think it has gone into a loop.
The palindrome-matching patterns above work only if the subject string does not start with a palindrome that is shorter than the entire string. For example, although "abcba" is correctly matched, if the subject is "ababa", PCRE finds palindrome "aba" at the start, and then fails at top level, as the end of the string does not follow. Once again, it cannot jump back into the recursion to try other alternatives, so the entire match fails.
The second way in which PCRE and Perl differ in their recursion processing is in the handling of captured values. In Perl, when a subpattern is called recursively or as a subpattern (see the next section), it has no access to any values that were captured outside the recursion. In PCRE these values can be referenced. Consider the following pattern:
In PCRE, it matches "bab". The first capturing parentheses match "b", then in the second group, when the back reference \1 fails to match "b", the second alternative matches "a", and then recurses. In the recursion, \1 does now match "b" and so the whole match succeeds. In Perl, the pattern fails to match because inside the recursive call \1 cannot access the externally set value.
Subpatterns as Subroutines.
If the syntax for a recursive subpattern call (either by number or by name) is used outside the parentheses to which it refers, it operates like a subroutine in a programming language. The called subpattern can be defined before or after the reference. A numbered reference can be absolute or relative, as in the following examples:
An earlier example pointed out that the following pattern matches "sense and sensibility" and "response and responsibility", but not "sense and responsibility":
If instead the following pattern is used, it matches "sense and responsibility" and the other two strings:
Another example is provided in the discussion of DEFINE earlier.
All subroutine calls, recursive or not, are always treated as atomic groups. That is, once a subroutine has matched some of the subject string, it is never re-entered, even if it contains untried alternatives and there is a subsequent matching failure. Any capturing parentheses that are set during the subroutine call revert to their previous values afterwards.
Processing options such as case-independence are fixed when a subpattern is defined, so if it is used as a subroutine, such options cannot be changed for different calls. For example, the following pattern matches "abcabc" but not "abcABC", as the change of processing option does not affect the called subpattern:
Oniguruma Subroutine Syntax.
For compatibility with Oniguruma, the non-Perl syntax \g followed by a name or a number enclosed either in angle brackets or single quotes, is alternative syntax for referencing a subpattern as a subroutine, possibly recursively. Here follows two of the examples used above, rewritten using this syntax:
PCRE supports an extension to Oniguruma: if a number is preceded by a plus or minus sign, it is taken as a relative reference, for example:
Notice that \g (Perl syntax) and \g<. & gt; (Oniguruma syntax) are not synonymous. The former is a back reference; the latter is a subroutine call.
Backtracking Control.
Perl 5.10 introduced some "Special Backtracking Control Verbs", which are still described in the Perl documentation as "experimental and subject to change or removal in a future version of Perl". It goes on to say: "Their usage in production code should be noted to avoid problems during upgrades." The same remarks apply to the PCRE features described in this section.
The new verbs make use of what was previously invalid syntax: an opening parenthesis followed by an asterisk. They are generally of the form (*VERB) or (*VERB:NAME). Some can take either form, possibly behaving differently depending on whether a name is present. A name is any sequence of characters that does not include a closing parenthesis. The maximum name length is 255 in the 8-bit library and 65535 in the 16-bit and 32-bit libraries. If the name is empty, that is, if the closing parenthesis immediately follows the colon, the effect is as if the colon was not there. Any number of these verbs can occur in a pattern.
The behavior of these verbs in repeated groups, assertions, and in subpatterns called as subroutines (whether or not recursively) is described below.
Optimizations That Affect Backtracking Verbs.
PCRE contains some optimizations that are used to speed up matching by running some checks at the start of each match attempt. For example, it can know the minimum length of matching subject, or that a particular character must be present. When one of these optimizations bypasses the running of a match, any included backtracking verbs are not processed. processed. You can suppress the start-of-match optimizations by setting option no_start_optimize when calling compile/2 or run/3 , or by starting the pattern with (*NO_START_OPT).
Experiments with Perl suggest that it too has similar optimizations, sometimes leading to anomalous results.
Verbs That Act Immediately.
The following verbs act as soon as they are encountered. They must not be followed by a name.
This verb causes the match to end successfully, skipping the remainder of the pattern. However, when it is inside a subpattern that is called as a subroutine, only that subpattern is ended successfully. Matching then continues at the outer level. If (*ACCEPT) is triggered in a positive assertion, the assertion succeeds; in a negative assertion, the assertion fails.
If (*ACCEPT) is inside capturing parentheses, the data so far is captured. For example, the following matches "AB", "AAD", or "ACD". When it matches "AB", "B" is captured by the outer parentheses.
The following verb causes a matching failure, forcing backtracking to occur. It is equivalent to (?!) but easier to read.
The Perl documentation states that it is probably useful only when combined with (?<>) or (??<>). Those are Perl features that are not present in PCRE.
A match with the string "aaaa" always fails, but the callout is taken before each backtrack occurs (in this example, 10 times).
Recording Which Path Was Taken.
The main purpose of this verb is to track how a match was arrived at, although it also has a secondary use in with advancing the match starting point (see (*SKIP) below).
In Erlang, there is no interface to retrieve a mark with run/2,3 , so only the secondary purpose is relevant to the Erlang programmer.
The rest of this section is therefore deliberately not adapted for reading by the Erlang programmer, but the examples can help in understanding NAMES as they can be used by (*SKIP).
A name is always required with this verb. There can be as many instances of (*MARK) as you like in a pattern, and their names do not have to be unique.
When a match succeeds, the name of the last encountered (*MARK:NAME), (*PRUNE:NAME), or (*THEN:NAME) on the matching path is passed back to the caller as described in section "Extra data for pcre_exec() " in the pcreapi documentation. In the following example of pcretest output, the /K modifier requests the retrieval and outputting of (*MARK) data:
The (*MARK) name is tagged with "MK:" in this output, and in this example it indicates which of the two alternatives matched. This is a more efficient way of obtaining this information than putting each alternative in its own capturing parentheses.
If a verb with a name is encountered in a positive assertion that is true, the name is recorded and passed back if it is the last encountered. This does not occur for negative assertions or failing positive assertions.
After a partial match or a failed match, the last encountered name in the entire match process is returned, for example:
Notice that in this unanchored example, the mark is retained from the match attempt that started at letter "X" in the subject. Subsequent match attempts starting at "P" and then with an empty string do not get as far as the (*MARK) item, nevertheless do not reset it.
Verbs That Act after Backtracking.
The following verbs do nothing when they are encountered. Matching continues with what follows, but if there is no subsequent match, causing a backtrack to the verb, a failure is forced. That is, backtracking cannot pass to the left of the verb. However, when one of these verbs appears inside an atomic group or an assertion that is true, its effect is confined to that group, as once the group has been matched, there is never any backtracking into it. In this situation, backtracking can "jump back" to the left of the entire atomic group or assertion. (Remember also, as stated above, that this localization also applies in subroutine calls.)
These verbs differ in exactly what kind of failure occurs when backtracking reaches them. The behavior described below is what occurs when the verb is not in a subroutine or an assertion. Subsequent sections cover these special cases.
The following verb, which must not be followed by a name, causes the whole match to fail outright if there is a later matching failure that causes backtracking to reach it. Even if the pattern is unanchored, no further attempts to find a match by advancing the starting point take place.
If (*COMMIT) is the only backtracking verb that is encountered, once it has been passed, run/2,3 is committed to find a match at the current starting point, or not at all, for example:
This matches "xxaab" but not "aacaab". It can be thought of as a kind of dynamic anchor, or "I've started, so I must finish". The name of the most recently passed (*MARK) in the path is passed back when (*COMMIT) forces a match failure.
If more than one backtracking verb exists in a pattern, a different one that follows (*COMMIT) can be triggered first, so merely passing (*COMMIT) during a match does not always guarantee that a match must be at this starting point.
Notice that (*COMMIT) at the start of a pattern is not the same as an anchor, unless the PCRE start-of-match optimizations are turned off, as shown in the following example:
For this pattern, PCRE knows that any match must start with "a", so the optimization skips along the subject to "a" before applying the pattern to the first set of data. The match attempt then succeeds. In the second call the no_start_optimize disables the optimization that skips along to the first character. The pattern is now applied starting at "x", and so the (*COMMIT) causes the match to fail without trying any other starting points.
The following verb causes the match to fail at the current starting position in the subject if there is a later matching failure that causes backtracking to reach it:
If the pattern is unanchored, the normal "bumpalong" advance to the next starting character then occurs. Backtracking can occur as usual to the left of (*PRUNE), before it is reached, or when matching to the right of (*PRUNE), but if there is no match to the right, backtracking cannot cross (*PRUNE). In simple cases, the use of (*PRUNE) is just an alternative to an atomic group or possessive quantifier, but there are some uses of (*PRUNE) that cannot be expressed in any other way. In an anchored pattern, (*PRUNE) has the same effect as (*COMMIT).
The behavior of (*PRUNE:NAME) is the not the same as (*MARK:NAME)(*PRUNE). It is like (*MARK:NAME) in that the name is remembered for passing back to the caller. However, (*SKIP:NAME) searches only for names set with (*MARK).
The fact that (*PRUNE:NAME) remembers the name is useless to the Erlang programmer, as names cannot be retrieved.
The following verb, when specified without a name, is like (*PRUNE), except that if the pattern is unanchored, the "bumpalong" advance is not to the next character, but to the position in the subject where (*SKIP) was encountered.
(*SKIP) signifies that whatever text was matched leading up to it cannot be part of a successful match. Consider:
If the subject is "aaaac. ", after the first match attempt fails (starting at the first character in the string), the starting point skips on to start the next attempt at "c". Notice that a possessive quantifier does not have the same effect as this example; although it would suppress backtracking during the first match attempt, the second attempt would start at the second character instead of skipping on to "c".
When (*SKIP) has an associated name, its behavior is modified:
When this is triggered, the previous path through the pattern is searched for the most recent (*MARK) that has the same name. If one is found, the "bumpalong" advance is to the subject position that corresponds to that (*MARK) instead of to where (*SKIP) was encountered. If no (*MARK) with a matching name is found, (*SKIP) is ignored.
Notice that (*SKIP:NAME) searches only for names set by (*MARK:NAME). It ignores names that are set by (*PRUNE:NAME) or (*THEN:NAME).
The following verb causes a skip to the next innermost alternative when backtracking reaches it. That is, it cancels any further backtracking within the current alternative.
The verb name comes from the observation that it can be used for a pattern-based if-then-else block:
If the COND1 pattern matches, FOO is tried (and possibly further items after the end of the group if FOO succeeds). On failure, the matcher skips to the second alternative and tries COND2, without backtracking into COND1. If that succeeds and BAR fails, COND3 is tried. If BAZ then fails, there are no more alternatives, so there is a backtrack to whatever came before the entire group. If (*THEN) is not inside an alternation, it acts like (*PRUNE).
The behavior of (*THEN:NAME) is the not the same as (*MARK:NAME)(*THEN). It is like (*MARK:NAME) in that the name is remembered for passing back to the caller. However, (*SKIP:NAME) searches only for names set with (*MARK).
The fact that (*THEN:NAME) remembers the name is useless to the Erlang programmer, as names cannot be retrieved.
A subpattern that does not contain a | character is just a part of the enclosing alternative; it is not a nested alternation with only one alternative. The effect of (*THEN) extends beyond such a subpattern to the enclosing alternative. Consider the following pattern, where A, B, and so on, are complex pattern fragments that do not contain any | characters at this level:
If A and B are matched, but there is a failure in C, matching does not backtrack into A; instead it moves to the next alternative, that is, D. However, if the subpattern containing (*THEN) is given an alternative, it behaves differently:
The effect of (*THEN) is now confined to the inner subpattern. After a failure in C, matching moves to (*FAIL), which causes the whole subpattern to fail, as there are no more alternatives to try. In this case, matching does now backtrack into A.
Notice that a conditional subpattern is not considered as having two alternatives, as only one is ever used. That is, the | character in a conditional subpattern has a different meaning. Ignoring whitespace, consider:
If the subject is "ba", this pattern does not match. As .*? is ungreedy, it initially matches zero characters. The condition (?=a) then fails, the character "b" is matched, but "c" is not. At this point, matching does not backtrack to .*? as can perhaps be expected from the presence of the | character. The conditional subpattern is part of the single alternative that comprises the whole pattern, and so the match fails. (If there was a backtrack into .*?, allowing it to match "b", the match would succeed.)
The verbs described above provide four different "strengths" of control when subsequent matching fails:
(*THEN) is the weakest, carrying on the match at the next alternative.
(*PRUNE) comes next, fails the match at the current starting position, but allows an advance to the next character (for an unanchored pattern).
(*SKIP) is similar, except that the advance can be more than one character.
(*COMMIT) is the strongest, causing the entire match to fail.
More than One Backtracking Verb.
If more than one backtracking verb is present in a pattern, the one that is backtracked onto first acts. For example, consider the following pattern, where A, B, and so on, are complex pattern fragments:
If A matches but B fails, the backtrack to (*COMMIT) causes the entire match to fail. However, if A and B match, but C fails, the backtrack to (*THEN) causes the next alternative (ABD) to be tried. This behavior is consistent, but is not always the same as in Perl. It means that if two or more backtracking verbs appear in succession, the last of them has no effect. Considere o seguinte exemplo:
If there is a matching failure to the right, backtracking onto (*PRUNE) causes it to be triggered, and its action is taken. There can never be a backtrack onto (*COMMIT).
Backtracking Verbs in Repeated Groups.
PCRE differs from Perl in its handling of backtracking verbs in repeated groups. For example, consider:
If the subject is "abac", Perl matches, but PCRE fails because the (*COMMIT) in the second repeat of the group acts.
Backtracking Verbs in Assertions.
(*FAIL) in an assertion has its normal effect: it forces an immediate backtrack.
(*ACCEPT) in a positive assertion causes the assertion to succeed without any further processing. In a negative assertion, (*ACCEPT) causes the assertion to fail without any further processing.
The other backtracking verbs are not treated specially if they appear in a positive assertion. In particular, (*THEN) skips to the next alternative in the innermost enclosing group that has alternations, regardless if this is within the assertion.
Negative assertions are, however, different, to ensure that changing a positive assertion into a negative assertion changes its result. Backtracking into (*COMMIT), (*SKIP), or (*PRUNE) causes a negative assertion to be true, without considering any further alternative branches in the assertion. Backtracking into (*THEN) causes it to skip to the next enclosing alternative within the assertion (the normal behavior), but if the assertion does not have such an alternative, (*THEN) behaves like (*PRUNE).
Backtracking Verbs in Subroutines.
These behaviors occur regardless if the subpattern is called recursively. The treatment of subroutines in Perl is different in some cases.
(*FAIL) in a subpattern called as a subroutine has its normal effect: it forces an immediate backtrack.
(*ACCEPT) in a subpattern called as a subroutine causes the subroutine match to succeed without any further processing. Matching then continues after the subroutine call.
(*COMMIT), (*SKIP), and (*PRUNE) in a subpattern called as a subroutine cause the subroutine match to fail.
(*THEN) skips to the next alternative in the innermost enclosing group within the subpattern that has alternatives. If there is no such group within the subpattern, (*THEN) causes the subroutine match to fail.
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Chevy 350 pequeno bloco em Murray Lawn Mower!
Bloco pequeno insano de Chevy 350 em Murray Riding Lawn Mower!
Este 350 bloco pequeno Chevy em um gramado mais é louco! Por que colocar um V8 em um cortador de grama? Bem, porque não?! Ouça esta coisa & # 8230;
Gramado e Jardim & raquo;
Como crescer hortênsia de cortes.
Chevy 350 pequeno bloco em Murray Lawn Mower!
Repower Your Scag Exmark Toro Lesco Caminhe atrás do cortador com um novo motor.
Primavera é aqui! Tempo de ajuste para o seu equipamento!
Postos de gasolina que vendem 100% de gasolina & # 8211; Sem etanol.
Especial Pré-Temporada: 50% de Desconto em Todas as Lâminas de Corte com Serviço Completo!
Go Kart, carrinho de golfe, gramado e jardim, serviço de cortador de grama, reparação de motores pequenos & raquo;
MowerPartsZone abre loja de varejo!
A MowerPartsZone acaba de anunciar a abertura de sua loja de varejo em 7130 Oak Ridge Highway, em Knoxville, TN. Eles estão localizados no antigo local da ProGreen Plus.
A MowerPartsZone tem uma linha completa de peças, incluindo carburadores, pneus, baterias, correias, pás, acionadores de partida, cordas de fixação, embreagens de tomada de força e muito mais. Temos peças para TODAS AS MARCAS de equipamentos de energia, incluindo Craftsman, John Deere, Cadet Cub, Honda, Troy Bilt, Murray, Snapper além de marcas comerciais como Scag e Exmark. Temos peças de motor para Briggs e Stratton, Tecumseh, Kohler, Honda, Kawasaki.
A MowerPartsZone também possui uma linha completa de peças de kart, incluindo correntes de roletes, embreagens, faixas de freio, peças de motor, pneus e muito mais!
A MowerPartsZone acabou de adicionar uma ampla seleção de peças para carrinhos de golfe que também cobrem marcas como EZ-Go, Yamaha, Club Car e outras.
Ligue-nos para mais informações em 865.235.1799.
Serviço de cortador de grama & raquo;
Toro Sulky Velky apenas $ 289 frete grátis!
Sulky Velky apenas $ 289 w / FREE Shipping!
NOVO Mower sulky / velky para os cortadores comerciais da Toro. Compre agora e aproveite nossas promoções especiais de verão!
Bloqueios em um & # 8220; levantado & # 8221; posição de armazenamento sem anexos extras.
Guarnições de graxa protegidas.
Construção em aço resistente.
Pinos de liberação rápida.
Facilmente anexa em minutos para a maioria dos cortadores comerciais de tamanho médio.
Suporte de pivô vertical patenteado com rolamentos de rolos de aço.
Parafusos diretamente para a maioria dos cortadores comerciais.
Acabamento em pó durável.
Plataforma de pé extra larga.
Garantia limitada de dois anos.
Adapta-se à Exmark, Lesco, John Deere, Scag, Toro e a maioria dos outros cortadores de relva comerciais.
Não importa como você diz "velky, sulky, velkie, ou sulkie", ProGreen Plus tem a melhor seleção de sulky e velkeys ao redor!
Toro Sulky Velky apenas US $ 289.
Chevy 350 pequeno bloco em Murray Lawn Mower!
Bloco pequeno insano de Chevy 350 em Murray Riding Lawn Mower!
Este 350 bloco pequeno Chevy em um gramado mais é louco! Por que colocar um V8 em um cortador de grama? Bem, porque não?! Ouça esta coisa & # 8230;
Repower Your Scag Exmark Toro Lesco Caminhe atrás do cortador com um novo motor.
Troque sua Kawasaki por um novo motor.
Repower seu Scag, Exmark, Gravely, Toro, Lesco, ou outro cortador de caminhada comercial atrás com um novo motor Briggs and Stratton 17,5 cavalos de potência.
Este é um ótimo mecanismo de substituição para muitos & # 8230;
Primavera é aqui! Tempo de ajuste para o seu equipamento!
A primavera está chegando em Knoxville! Nossa loja de varejo e oficina estão em plena explosão para a temporada!
Obtenha seu equipamento no início para bater a corrida da primavera. Atendemos todas as marcas de equipamentos de energia, incluindo & # 8230;
Postos de gasolina que vendem 100% de gasolina & # 8211; Sem etanol.
Postos de gasolina que vendem 100% de gasolina.
Gasolina com etanol pode prejudicar o seu poder & # 8230;
Especial Pré-Temporada: 50% de Desconto em Todas as Lâminas de Corte com Serviço Completo!
Agora é o momento PERFEITO para obter o seu cortador de empurrar ou montar o cortador de manutenção. Não espere até a primavera, quando a espera será longa. Além disso, não é bom que o seu equipamento seja armazenado & # 8230;
Serviço de Gerador, Peças e Reparos.
Atendemos TODAS AS MARCAS de geradores incluindo Honda, Generac, Briggs e Stratton e muito mais!
Nós também carregamos peças de motor para Honda, Briggs e Stratton, Yamaha, Kohler, Subaru, Tecumseh, Onan e muito mais. Carburadores, motores de arranque, filtros de ar, combustível & # 8230;
Venda Pré-Temporada! Cintos 50% de desconto!
Confira nossos excelentes especiais de pré-temporada! Neste momento, todos os cintos de estoque estão com 50% de desconto no preço já baixo da MowerPartsZone! Visite nossa loja de varejo em 7130 Oak Ridge Highway, Knoxville, TN 37931.
Problemas de arranque com o seu cortador? Como verificar a bateria do seu cortador de grama e escolher a bateria do tamanho certo para o seu cortador.
Sede de bateria e cortador de peças elétricas!
É nessa época do ano que você sai para tentar iniciar o seu cortador pela primeira vez na temporada, mas vira a chave e nada acontece. & # 8230;
Peças de cortador de grama: prepare-se agora para a sega da primavera!
Cortador de grama peças para todas as marcas.
Agora é a hora de preparar seu cortador e equipamento de força para a estação de corte!
Nós carregamos peças para TODAS AS MARCAS de cortadores e equipamentos de energia, incluindo Scag, Exmark, John Deere, & # 8230;
Toro Sulky Velky apenas $ 289 frete grátis!
Sulky Velky apenas $ 289 w / FREE Shipping!
NOVO Mower sulky / velky para os cortadores comerciais da Toro. Compre agora e aproveite nossas promoções especiais de verão!
Bloqueios em um & # 8220; levantado & # 8221; posição de armazenamento sem anexos extras.
Peças para todas as marcas! Clique para visitar nossa loja de peças.
Serviço de cortador de grama & raquo;
Chevy 350 pequeno bloco em Murray Lawn Mower!
Bloco pequeno insano de Chevy 350 em Murray Riding Lawn Mower!
Este 350 bloco pequeno Chevy em um gramado mais é louco! Por que colocar um V8 em um cortador de grama? Bem, porque não?! Ouça esta coisa & # 8230;
Repower Your Scag Exmark Toro Lesco Caminhe atrás do cortador com um novo motor.
Troque sua Kawasaki por um novo motor.
Repower seu Scag, Exmark, Gravely, Toro, Lesco, ou outro cortador de caminhada comercial atrás com um novo motor Briggs and Stratton 17,5 cavalos de potência.
Este é um ótimo mecanismo de substituição para muitos & # 8230;
Todos os veículos terrestres (ATV & # 8217; s) & raquo;
Postos de gasolina que vendem 100% de gasolina & # 8211; Sem etanol.
Postos de gasolina que vendem 100% de gasolina.
Gasolina com etanol pode prejudicar o seu poder & # 8230;
John Deere Gator 6 x 4 e # 8211; Sim! Nós trabalhamos nesses!
A ProGreen Plus pode atender todas as marcas de ATVs, incluindo os John Deere Gators! Aqui está um exemplo de um que acabamos de concluir esta semana.
Este Gator foi trazido porque estava soprando LOTES & # 8230;
Gramado e Jardim & raquo;
Como crescer hortênsia de cortes.
Como crescer hortênsia de cortes.
As hortênsias são plantas decíduas floríferas que podem variar em tamanho, desde pequenos arbustos até grandes variedades de árvores. Se você quiser cultivar suas próprias plantas de hortênsias, você pode produzir novas plantas de hortaliças & # 8230;
Chevy 350 pequeno bloco em Murray Lawn Mower!
Bloco pequeno insano de Chevy 350 em Murray Riding Lawn Mower!
Este 350 bloco pequeno Chevy em um gramado mais é louco! Por que colocar um V8 em um cortador de grama? Bem, porque não?! Ouça esta coisa & # 8230;
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