std::regex_traits

C++

Language

Headers

Freestanding and hosted implementations

Named requirements

Language support library

Concepts library (C++20)

Diagnostics library

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Filesystem library (C++17)

Technical Specifications

Regular expressions library

Classes

basic_regex (C++11)

sub_match (C++11)

match_results (C++11)

Algorithms

regex_match (C++11)

regex_search (C++11)

regex_replace (C++11)

Iterators

regex_iterator (C++11)

regex_token_iterator (C++11)

Exceptions

regex_error (C++11)

Traits

regex_traits (C++11)

Constants

syntax_option_type (C++11)

match_flag_type (C++11)

error_type (C++11)

Regex Grammar

Modified ECMAScript-262 (C++11)

std::regex_traits

Member Functions

regex_traits::regex_traits

regex_traits::length

regex_traits::translate

regex_traits::translate_nocase

regex_traits::transform

regex_traits::transform_primary

regex_traits::lookup_collatename

regex_traits::lookup_classname

regex_traits::isctype

regex_traits::value

regex_traits::imbue

regex_traits::getloc

Defined in header <regex>
template< class CharT > class regex_traits;		(since C++11)

The type trait template regex_traits supplies std::basic_regex with the set of types and functions necessary to operate on the type CharT.

Since many of regex operations are locale-sensitive (when std::regex_constants::collate flag is set), the regex_traits class typically holds an instance of a std::locale as a private member.

Standard specializations

Two specializations of std::regex_traits are defined by the standard library:

std::regex_traits<char>

std::regex_traits<wchar_t>

These specializations make it possible to use std::basic_regex<char> (aka std::regex) and std::basic_regex<wchar_t> (aka std::wregex). To use std::basic_regex with other character types (for example, char32_t), a user-provided trait class must be used.

Member types

Type	Definition
char_type	CharT
string_type	std::basic_string<CharT>
locale_type	The locale used for localized behavior in the regular expression. Must be CopyConstructible
char_class_type	Represents a character classification and is capable of holding an implementation specific set returned by lookup_classname. Must be a BitmaskType.

Member functions

(constructor)	constructs the regex_traits object (public member function)
length [static]	calculates the length of a null-terminated character string (public static member function)
translate	determines the equivalence key for a character (public member function)
translate_nocase	determines the case-insensitive equivalence key for a character (public member function)
transform	determines the sort key for the given string, used to provide collation order (public member function)
transform_primary	determines the primary sort key for the character sequence, used to determine equivalence class (public member function)
lookup_collatename	gets a collation element by name (public member function)
lookup_classname	gets a character class by name (public member function)
isctype	indicates membership in a localized character class (public member function)
value	translates the character representing a numeric digit into an integral value (public member function)
imbue	sets the locale (public member function)
getloc	gets the locale (public member function)