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std::regex_traits< _Ch_type >(3) Library Functions Manual std::regex_traits< _Ch_type >(3)

NAME

std::regex_traits< _Ch_type > - Describes aspects of a regular expression.

SYNOPSIS

Public Types


typedef _RegexMask char_class_type
typedef _Ch_type char_type
typedef std::locale locale_type
typedef std::basic_string< char_type > string_type

Public Member Functions


regex_traits ()
Constructs a default traits object. locale_type getloc () const
Gets a copy of the current locale in use by the regex_traits object. locale_type imbue (locale_type __loc)
Imbues the regex_traits object with a copy of a new locale. bool isctype (_Ch_type __c, char_class_type __f) const
Determines if c is a member of an identified class. template<typename _Fwd_iter > char_class_type lookup_classname (_Fwd_iter __first, _Fwd_iter __last, bool __icase=false) const
Maps one or more characters to a named character classification. template<typename _Fwd_iter > string_type lookup_collatename (_Fwd_iter __first, _Fwd_iter __last) const
Gets a collation element by name. template<typename _Fwd_iter > string_type transform (_Fwd_iter __first, _Fwd_iter __last) const
Gets a sort key for a character sequence. template<typename _Fwd_iter > string_type transform_primary (_Fwd_iter __first, _Fwd_iter __last) const
Gets a sort key for a character sequence, independent of case. char_type translate (char_type __c) const
Performs the identity translation. char_type translate_nocase (char_type __c) const
Translates a character into a case-insensitive equivalent. int value (_Ch_type __ch, int __radix) const
Converts a digit to an int.

Static Public Member Functions


static std::size_t length (const char_type *__p)
Gives the length of a C-style string starting at __p.

Protected Attributes


locale_type _M_locale

Detailed Description

template<typename _Ch_type>

class std::regex_traits< _Ch_type >" Describes aspects of a regular expression.

A regular expression traits class that satisfies the requirements of section [28.7].

The class regex is parameterized around a set of related types and functions used to complete the definition of its semantics. This class satisfies the requirements of such a traits class.

Constructor & Destructor Documentation

template<typename _Ch_type > std::regex_traits< _Ch_type >::regex_traits () [inline]

Constructs a default traits object.

Member Function Documentation

template<typename _Ch_type > locale_type std::regex_traits< _Ch_type >::getloc () const [inline]

Gets a copy of the current locale in use by the regex_traits object.

template<typename _Ch_type > locale_type std::regex_traits< _Ch_type >::imbue (locale_type __loc) [inline]

Imbues the regex_traits object with a copy of a new locale.

Parameters

__loc A locale.

Returns

a copy of the previous locale in use by the regex_traits object.

Note

Calling imbue with a different locale than the one currently in use invalidates all cached data held by *this.

References std::swap().

template<typename _Ch_type > bool std::regex_traits< _Ch_type >::isctype (_Ch_type __c, char_class_type __f) const

Determines if c is a member of an identified class.

Parameters

__c a character.
__f a class type (as returned from lookup_classname).

Returns

true if the character __c is a member of the classification represented by __f, false otherwise.

Exceptions

std::bad_cast if the current locale does not have a ctype facet.

template<typename _Ch_type > static std::size_t std::regex_traits< _Ch_type >::length (const char_type * __p) [inline], [static]

Gives the length of a C-style string starting at __p.

Parameters

__p a pointer to the start of a character sequence.

Returns

the number of characters between *__p and the first default-initialized value of type char_type. In other words, uses the C-string algorithm for determining the length of a sequence of characters.

template<typename _Ch_type > template<typename _Fwd_iter > char_class_type std::regex_traits< _Ch_type >::lookup_classname (_Fwd_iter __first, _Fwd_iter __last, bool __icase = false) const

Maps one or more characters to a named character classification.

Parameters

__first beginning of the character sequence.
__last one-past-the-end of the character sequence.
__icase ignores the case of the classification name.

Returns

an unspecified value that represents the character classification named by the character sequence designated by the iterator range [__first, __last). If icase is true, the returned mask identifies the classification regardless of the case of the characters to be matched (for example, [[:lower:]] is the same as [[:alpha:]]), otherwise a case-dependent classification is returned. The value returned shall be independent of the case of the characters in the character sequence. If the name is not recognized then returns a value that compares equal to 0.

At least the following names (or their wide-character equivalent) are supported.

  • d
  • w
  • s
  • alnum
  • alpha
  • blank
  • cntrl
  • digit
  • graph
  • lower
  • print
  • punct
  • space
  • upper
  • xdigit

template<typename _Ch_type > template<typename _Fwd_iter > string_type std::regex_traits< _Ch_type >::lookup_collatename (_Fwd_iter __first, _Fwd_iter __last) const

Gets a collation element by name.

Parameters

__first beginning of the collation element name.
__last one-past-the-end of the collation element name.

Returns

a sequence of one or more characters that represents the collating element consisting of the character sequence designated by the iterator range [__first, __last). Returns an empty string if the character sequence is not a valid collating element.

template<typename _Ch_type > template<typename _Fwd_iter > string_type std::regex_traits< _Ch_type >::transform (_Fwd_iter __first, _Fwd_iter __last) const [inline]

Gets a sort key for a character sequence.

Parameters

__first beginning of the character sequence.
__last one-past-the-end of the character sequence.

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).

What this really does is provide a more efficient way to compare a string to multiple other strings in locales with fancy collation rules and equivalence classes.

Returns

a locale-specific sort key equivalent to the input range.

Exceptions

std::bad_cast if the current locale does not have a collate facet.

References std::basic_string< _CharT, _Traits, _Alloc >::data(), and std::basic_string< _CharT, _Traits, _Alloc >::size().

Referenced by std::regex_traits< _Ch_type >::transform_primary().

template<typename _Ch_type > template<typename _Fwd_iter > string_type std::regex_traits< _Ch_type >::transform_primary (_Fwd_iter __first, _Fwd_iter __last) const [inline]

Gets a sort key for a character sequence, independent of case.

Parameters

__first beginning of the character sequence.
__last one-past-the-end of the character sequence.

Effects: if typeid(use_facet<collate<_Ch_type> >) == typeid(collate_byname<_Ch_type>) and the form of the sort key returned by collate_byname<_Ch_type>::transform(__first, __last) is known and can be converted into a primary sort key then returns that key, otherwise returns an empty string.

Todo

Implement this function correctly.

References std::vector< _Tp, _Alloc >::data(), std::vector< _Tp, _Alloc >::size(), and std::regex_traits< _Ch_type >::transform().

template<typename _Ch_type > char_type std::regex_traits< _Ch_type >::translate (char_type __c) const [inline]

Performs the identity translation.

Parameters

__c A character to the locale-specific character set.

Returns

__c.

template<typename _Ch_type > char_type std::regex_traits< _Ch_type >::translate_nocase (char_type __c) const [inline]

Translates a character into a case-insensitive equivalent.

Parameters

__c A character to the locale-specific character set.

Returns

the locale-specific lower-case equivalent of __c.

Exceptions

std::bad_cast if the imbued locale does not support the ctype facet.

template<typename _Ch_type > int std::regex_traits< _Ch_type >::value (_Ch_type __ch, int __radix) const

Converts a digit to an int.

Parameters

__ch a character representing a digit.
__radix the radix if the numeric conversion (limited to 8, 10, or 16).

Returns

the value represented by the digit __ch in base radix if the character __ch is a valid digit in base radix; otherwise returns -1.

Author

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Mon Dec 18 2023 libstdc++