std::regex_traits::lookup_classname
| template< class ForwardIt > char_class_type lookup_classname( ForwardIt first, |
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If the character sequence [first, last) represents the name of a valid character class in the currently imbued locale (that is, the string between [: and :] in POSIX regular expressions), returns the implementation-defined value representing this character class. Otherwise, returns zero.
If the parameter icase is true, the character class ignores character case, e.g. the regex [:lower:] with std::regex_constants::icase generates a call to regex_traits<>::lookup_classname() with [first, last) indicating the string "lower" and icase == true. This call returns the same bitmask as the call generated by the regex [:alpha:] with icase == false.
The following character classes are always recognized, in both narrow and wide character forms, and the classifications returned (with icase == false) correspond to the matching classifications obtained by the std::ctype facet of the imbued locale, as follows:
| character class | std::ctype classification |
| "alnum" | std::ctype_base::alnum |
| "alpha" | std::ctype_base::alpha |
| "blank" | std::ctype_base::blank |
| "cntrl" | std::ctype_base::cntrl |
| "digit" | std::ctype_base::digit |
| "graph" | std::ctype_base::graph |
| "lower" | std::ctype_base::lower |
| "print" | std::ctype_base::print |
| "punct" | std::ctype_base::punct |
| "space" | std::ctype_base::space |
| "upper" | std::ctype_base::upper |
| "xdigit" | std::ctype_base::xdigit |
| "d" | std::ctype_base::digit |
| "s" | std::ctype_base::space |
| "w" | std::ctype_base::alnum with '_' optionally added |
The classification returned for the string "w" may be exactly the same as "alnum", in which case isctype() adds '_' explicitly.
Contents |
[edit] Parameters
| first, last | - | a pair of iterators which determines the sequence of characters that represents a name of a character class |
| icase | - | if true, ignores the upper/lower case distinction in the character classification |
| Type requirements | ||
-ForwardIt must meet the requirements of ForwardIterator.
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[edit] Return value
The bitmask representing the character classification determined by the given character class, or zero if the class is unknown.
[edit] Example
| This section is incomplete Reason: no example |
[edit] See also
| indicates membership in a character class (public member function) | |
