28 Text processing library [text] (original) (raw)

28.6 Regular expressions library [re]

28.6.2 Requirements [re.req]

This subclause defines requirements on classes representing regular expression traits.

[Note 1:

The class templateregex_traits, defined in [re.traits], meets these requirements.

— _end note_]

The class template basic_regex, defined in[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 typedef-names and functions in the template parameter traits used by the basic_regex class template.

This subclause defines the semantics of 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 the following requirements,

• 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 ([input.iterators]);
• F1 and F2 are forward iterators ([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.

A traits class X meets the regular expression traits requirements if the following types and expressions are well-formed and have the specified semantics.

Result: charT, the character container type used in the implementation of class template basic_regex.

Result: basic_string<charT>

Result: A copy constructible type that represents the locale used by the traits class.

typename X::char_class_type

Result: A bitmask type ([bitmask.types]) representing a particular character classification.

Returns: The smallest i such that p[i] == 0.

Returns: A character such that for any character dthat is to be considered equivalent to cthen v.translate(c) == v.translate(d).

Returns: For all characters C that are to be considered equivalent to cwhen comparisons are to be performed without regard to case, then v.translate_nocase(c) == v.translate_nocase(C).

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)

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)

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)

Result: X​::​char_class_type

Returns: 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 0if 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.

Returns: Returns true if character c is a member of one of the character classes designated by cl,false otherwise.

Returns: 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 2:

The value of I will only be 8, 10, or 16.

— _end note_]

Effects: Imbues u with the locale loc and returns the previous locale used by u if any.

Returns: Returns the current locale used by v, if any.

[Note 3:

Class template regex_traits meets the requirements for a regular expression traits class when it is specialized forchar or wchar_t.

This class template is described in the header , and is described in [re.traits].

— _end note_]