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std::regex_constants::syntax_option_type

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C++
 
Espressioni regolari libreria
Classi
Original:
Classes
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basic_regex(C++11)
sub_match(C++11)
match_results(C++11)
Algoritmi
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Algorithms
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regex_match(C++11)
regex_search(C++11)
regex_replace(C++11)
Iteratori
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Iterators
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regex_iterator(C++11)
regex_token_iterator(C++11)
Eccezioni
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Exceptions
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regex_error(C++11)
Tratti
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Traits
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regex_traits(C++11)
Costanti
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Constants
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syntax_option_type(C++11)
match_flag_type(C++11)
error_type(C++11)
 
Elemento definito nell'header <regex>
typedef /*unspecified*/ syntax_option_type;

static constexpr syntax_option_type icase = /*unspecified*/;
static constexpr syntax_option_type nosubs = /*unspecified*/;
static constexpr syntax_option_type optimize = /*unspecified*/;
static constexpr syntax_option_type collate = /*unspecified*/;
static constexpr syntax_option_type ECMAScript = /*unspecified*/;
static constexpr syntax_option_type basic = /*unspecified*/;
static constexpr syntax_option_type extended = /*unspecified*/;
static constexpr syntax_option_type awk = /*unspecified*/;
static constexpr syntax_option_type grep = /*unspecified*/;

static constexpr syntax_option_type egrep = /*unspecified*/;
Il syntax_option_type è un BitmaskType che contiene le opzioni che governano il modo le espressioni regolari si comportano.
Original:
The syntax_option_type is a BitmaskType that contains options that govern how regular expressions behave.
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I valori possibili per questo tipo (icase, optimize, ecc) sono duplicati all'interno std :: basic_regex.
Original:
The possible values for this type (icase, optimize, etc.) are duplicated inside std :: basic_regex.
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Indice

[modifica] Costanti

Valore
Original:
Value
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 Effect(s)
icase Character matching should be performed without regard to case.
nosubs When performing matches, no sub-expression matches should be stored in the supplied std::regex_match structure.
optimize 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 Character ranges of the form "[a-b]" will be locale sensitive.
ECMAScript 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 Use the basic POSIX regular expression grammar (grammar documentation).
extended Use the extended POSIX regular expression grammar (grammar documentation).
awk Use the regular expression grammar used by the awk utility in POSIX (grammar documentation)
grep 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.
egrep 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 '|'.

[modifica] Note

Perché POSIX usa "più a sinistra lungo" regola corrispondente (la più lunga sottosequenza corrispondente viene abbinato, e se ci sono diverse sottosequenze questi, il primo è abbinato), non è adatto, ad esempio, per l'analisi dei linguaggi di markup: una regex POSIX come "<tag[^>]*>.*</tag>" corrisponderà tutto, dalla prima alla "<tag" "</tag>" scorso, in particolare ogni "</tag>" "<tag>" e mezzo. D'altra parte, ECMAScript favore della non avidi partite, e il ECMAScript regex "<tag[^>]*>.*?</tag>" dovrebbe corrispondere solo fino al primo tag di chiusura.
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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[modifica] Esempio

Illustra la differenza tra l'algoritmo di corrispondenza ECMAScript e le espressioni regolari 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';
}

Output: 

Searching for .*(a|xayy) in zzxayyzz:
 ECMA (depth first search) match: zzxa
 POSIX (leftmost longest)  match: zzxayy

[modifica] Vedi anche

(C++11)
Espressione oggetto regolare
Original:
regular expression object
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(classe template) [modifica]
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