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std::regex_constants::syntax_option_type

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C++
 
Reguläre Ausdrücke Bibliothek
Classes
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Classes
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basic_regex(C++11)
sub_match(C++11)
match_results(C++11)
Algorithmen
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Algorithms
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regex_match(C++11)
regex_search(C++11)
regex_replace(C++11)
Iteratoren
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Iterators
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regex_iterator(C++11)
regex_token_iterator(C++11)
Ausnahmen
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Exceptions
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regex_error(C++11)
Traits
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Traits
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regex_traits(C++11)
Konstanten
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Constants
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syntax_option_type(C++11)
match_flag_type(C++11)
error_type(C++11)
 
definiert in 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*/;
Die syntax_option_type ist ein BitmaskType die Optionen, wie reguläre Ausdrücke verhalten regeln enthält .
Original:
The syntax_option_type is a BitmaskType that contains options that govern how regular expressions behave.
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Die möglichen Werte für diese Art (icase, optimize, etc.) sind im Inneren std :: basic_regex vervielfältigt .
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The possible values for this type (icase, optimize, etc.) are duplicated inside std :: basic_regex.
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Inhaltsverzeichnis

[Bearbeiten] Konstanten

Value
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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 '|'.

[Bearbeiten] Notes

Weil der POSIX verwendet "linke längsten" übereinstimmende Regel (die längste übereinstimmende Teilfolge abgestimmt ist, und wenn es mehrere solcher Teilsequenzen, die erste abgestimmt ist), ist es nicht geeignet, zum Beispiel für das Parsen von Markup-Sprachen: a POSIX regex wie "<tag[^>]*>.*</tag>" würde passen alles von der ersten "<tag" zum letzten "</tag>", einschließlich aller "</tag>" und "<tag>" dazwischen. Auf der anderen Seite unterstützt ECMAScript non-greedy Spiele, und die ECMAScript regex "<tag[^>]*>.*?</tag>" würde nur bis zum ersten Abschluss tag .
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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[Bearbeiten] Beispiel

Zeigt den Unterschied in der Matching-Algorithmus zwischen ECMAScript und POSIX reguläre Ausdrücke
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

[Bearbeiten] Siehe auch

(C++11)
regulären Ausdrucks
Original:
regular expression object
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