std::regex_constants::syntax_option_type
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| Definido no cabeçalho <regex>
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| typedef /*unspecified*/ syntax_option_type; static constexpr syntax_option_type icase = /*unspecified*/; |
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O
syntax_option_type é um BitmaskType que contém opções que determinam como se comportam expressões regulares.Original:
The
syntax_option_type is a BitmaskType that contains options that govern how regular expressions behave.The text has been machine-translated via Google Translate.
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Os valores possíveis para este tipo (
icase, optimize, etc) são duplicados dentro std :: basic_regex.Original:
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Índice |
[editar] Constantes
| Valor
Original: Value The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
Effect(s) |
icase
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Character matching should be performed without regard to case. |
nosubs
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When performing matches, no sub-expression matches should be stored in the supplied std::regex_match structure. |
optimize
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Instructs the regular expression engine to make matching faster, with the potential cost of making construction slower. For example, this might mean converting a non-deterministic FSA to a deterministic FSA. |
collate
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Character ranges of the form "[a-b]" will be locale sensitive. |
ECMAScript
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Use the ECMAScript (JavaScript) regular expression grammar (ECMA-262 grammar documentation), modified to support collating elements, character classes, and equivalence classes from POSIX, and the character class aliases \d, \D, \s, \S, \w, and \W are made locale-sensitive |
basic
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Use the basic POSIX regular expression grammar (grammar documentation). |
extended
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Use the extended POSIX regular expression grammar (grammar documentation). |
awk
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Use the regular expression grammar used by the awk utility in POSIX (grammar documentation) |
grep
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Use the regular expression grammar used by the grep utility in POSIX. This is effectively the same as the basic option with the addition of newline '\n' as an alternation separator.
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egrep
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Use the regular expression grammar used by the grep utility, with the -E option, in POSIX. This is effectively the same as the extended option with the addition of newline '\n' as an alternation separator in addtion to '|'.
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[editar] Notas
Porque o POSIX utiliza "o mais longo mais à esquerda" regra de correspondência (a subseqüência mais longa correspondência é correspondido, e se existem várias subseqüências tais, o primeiro é correspondido), não é adequado, por exemplo, para analisar linguagens de marcação: um regex POSIX, como "<tag[^>]*>.*</tag>" iria corresponder tudo, desde o primeiro até o "<tag" "</tag>" passado, incluindo todos os "</tag>" e inbetween "<tag>". Por outro lado, ECMAScript suporta não gananciosos partidas, eo ECMAScript regex "<tag[^>]*>.*?</tag>" corresponderia somente até a marca de fechamento primeira.
Original:
Because POSIX uses "leftmost longest" matching rule (the longest matching subsequence is matched, and if there are several such subsequences, the first one is matched), it is not suitable, for example, for parsing markup languages: a POSIX regex such as "<tag[^>]*>.*</tag>" would match everything from the first "<tag" to the last "</tag>", including every "</tag>" and "<tag>" inbetween. On the other hand, ECMAScript supports non-greedy matches, and the ECMAScript regex "<tag[^>]*>.*?</tag>" would match only until the first closing tag.
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[editar] Exemplo
Ilustra a diferença no algoritmo de correspondência entre ECMAScript e expressões regulares POSIX
Original:
Illustrates the difference in the matching algorithm between ECMAScript and POSIX regular expressions
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#include <iostream> #include <string> #include <regex> int main() { std::string str = "zzxayyzz"; std::regex re1(".*(a|xayy)"); // ECMA std::regex re2(".*(a|xayy)", std::regex::extended); // POSIX std::cout << "Searching for .*(a|xayy) in zzxayyzz:\n"; std::smatch m; std::regex_search(str, m, re1); std::cout << " ECMA (depth first search) match: " << m[0] << '\n'; std::regex_search(str, m, re2); std::cout << " POSIX (leftmost longest) match: " << m[0] << '\n'; }
Saída:
Searching for .*(a|xayy) in zzxayyzz: ECMA (depth first search) match: zzxa POSIX (leftmost longest) match: zzxayy
[editar] Veja também
| (C++11) |
objeto de expressão regular Original: regular expression object The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (modelo de classe) |
