This subclause defines requirements on classes representing regular expression traits. [ Note: The class template regex_traits, defined in Clause [re.traits], satisfies these requirements. — end note ]
The class template basic_regex, defined in Clause [re.regex], needs a set of related types and functions to complete the definition of its semantics. These types and functions are provided as a set of member typedefs and functions in the template parameter traits used by the basic_regex class template. This subclause defines the semantics guaranteed by these members.
To specialize class template basic_regex for a character container CharT and its related regular expression traits class Traits, use basic_regex<CharT, Traits>.
In Table [tab:re:RegexpTraits] X denotes a traits class defining types and functions for the character container type charT; u is an object of type X; v is an object of type const X; p is a value of type const charT*; I1 and I2 are Input Iterators; F1 and F2 are forward iterators; c is a value of type const charT; s is an object of type X::string_type; cs is an object of type const X::string_type; b is a value of type bool; I is a value of type int; cl is an object of type X::char_class_type, and loc is an object of type X::locale_type.
|Expression||Return type||Assertion/note pre-/post-condition|
|X::char_type||charT||The character container type used in the implementation of class template basic_regex.|
|X::locale_type||A copy constructible type||A type that represents the locale used by the traits class.|
|X::char_class_type||A bitmask type ([bitmask.types]).||A bitmask type representing a particular character classification.|
|X::length(p)||std::size_t||Yields the smallest i such that p[i] == 0. Complexity is linear in i .|
|v.translate(c)||X::char_type||Returns a character such that for any character d that is to be considered equivalent to c then v.translate(c) == v.translate(d).|
|v.translate_nocase(c)||X::char_type||For all characters C that are to be considered equivalent to c when comparisons are to be performed without regard to case, then v.translate_nocase(c) == v.translate_nocase(C).|
|v.transform(F1, F2)||X::string_type||Returns a sort key for the character sequence designated by the iterator range [F1,F2) such that if the character sequence [G1,G2) sorts before the character sequence [H1,H2) then v.transform(G1, G2) < v.transform(H1, H2).|
|v.transform_primary(F1, F2)||X::string_type||Returns a sort key for the character sequence designated by the iterator range [F1,F2) such that if the character sequence [G1,G2) sorts before the character sequence [H1,H2) when character case is not considered then v.transform_primary(G1, G2) < v.transform_primary(H1, H2).|
|v.lookup_collatename(F1, F2)||X::string_type||Returns a sequence of characters that represents the collating element consisting of the character sequence designated by the iterator range [F1,F2). Returns an empty string if the character sequence is not a valid collating element.|
|v.lookup_classname(F1, F2, b)||X::char_class_type||Converts the character sequence designated by the iterator range [F1,F2) into a value of a bitmask type that can subsequently be passed to isctype. Values returned from lookup_classname can be bitwise or'ed together; the resulting value represents membership in either of the corresponding character classes. If b is true, the returned bitmask is suitable for matching characters without regard to their case. Returns 0 if the character sequence is not the name of a character class recognized by X. The value returned shall be independent of the case of the characters in the sequence.|
|v.isctype(c, cl)||bool||Returns true if character c is a member of one of the character classes designated by cl, false otherwise.|
|v.value(c, I)||int||Returns the value represented by the digit c in base I if the character c is a valid digit in base I; otherwise returns -1. [ Note: The value of I will only be 8, 10, or 16. — end note ]|
|u.imbue(loc)||X::locale_type||Imbues u with the locale loc and returns the previous locale used by u if any.|
|v.getloc()||X::locale_type||Returns the current locale used by v, if any.|