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C++ concepts: RegexTraits

From cppreference.com
< cpp‎ | concept
 
 
 

RegexTraits is a traits class that abstracts operations needed for a given character type when as template type parameters for std::basic_regex.

[edit] Requirements

Given

  • CharT, a character type
  • X, a RegexTraits type for type CharT
  • u, an object of type X
  • v, an object of type const X
  • p, a value of type const CharT*
  • I1, I2, input iterators
  • F1, F2, forward iterators
  • c, a value of type const CharT
  • s, an object of type X::string_type
  • cs, an object of type const X::string_type
  • b, a value of type bool
  • I, a value of type int
  • cl, an object of type X::char_class_type
  • loc, an object of type X::locale_type


expression return type semantics
X::char_type CharT Used to refer to the character type.
X::string_type std::basic_string<CharT>
X::locale_type A CopyConstructible type that represents the locale used by the traits class.
X::char_class_type A BitmaskType type that represents a particular character classification.
X::length(p) std::size_t Returns: 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 considered to be equivalent to c, then v.translate(c) == v.translate(d).
v.translate_nocase(c) X::char_type Returns: a character such that for any character C considered to be equivalent to c 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) without regard to case, then v.transform_primary(G1, G2) < v.transform_primary(H1, H2).
v.lookup_collatename(F1, F2) X::string_type Returns:
  • An empty string if the character sequence is not a valid collating element
  • A sequence of characters that represents the collating element consisting of the character sequence designated by the iterator range [F1, F2) otherwise
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 BitmaskType 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: whether c is a member of one of the character classes designated by cl or not.
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
  • -1 otherwise
u.imbue(loc) X::locale_type
  • Imbues u with the locale loc
  • Returns: The previous locale used by u if any
v.getloc() X::locale_type Returns: The previous locale used by v if any.


[edit] Standard library

RegexTraits is satisfied by the following standard library classes:

template<> class regex_traits<char>;
template<> class regex_traits<wchar_t>;
(since C++11)
(since C++11)