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std::regex_constants::match_flag_type

Defined in header <regex> 
using match_flag_type = /* implementation-defined */;
 (1) (since C++11)
(2) 
constexpr match_flag_type match_default =     {};
constexpr match_flag_type match_not_bol =     /* unspecified */;
constexpr match_flag_type match_not_eol =     /* unspecified */;
constexpr match_flag_type match_not_bow =     /* unspecified */;
constexpr match_flag_type match_not_eow =     /* unspecified */;
constexpr match_flag_type match_any =         /* unspecified */;
constexpr match_flag_type match_not_null =    /* unspecified */;
constexpr match_flag_type match_continuous =  /* unspecified */;
constexpr match_flag_type match_prev_avail =  /* unspecified */;
constexpr match_flag_type format_default =    {};
constexpr match_flag_type format_sed =        /* unspecified */;
constexpr match_flag_type format_no_copy =    /* unspecified */;
constexpr match_flag_type format_first_only = /* unspecified */;
 (since C++11)
(until C++17)		 
inline constexpr match_flag_type match_default =     {};
inline constexpr match_flag_type match_not_bol =     /* unspecified */;
inline constexpr match_flag_type match_not_eol =     /* unspecified */;
inline constexpr match_flag_type match_not_bow =     /* unspecified */;
inline constexpr match_flag_type match_not_eow =     /* unspecified */;
inline constexpr match_flag_type match_any =         /* unspecified */;
inline constexpr match_flag_type match_not_null =    /* unspecified */;
inline constexpr match_flag_type match_continuous =  /* unspecified */;
inline constexpr match_flag_type match_prev_avail =  /* unspecified */;
inline constexpr match_flag_type format_default =    {};
inline constexpr match_flag_type format_sed =        /* unspecified */;
inline constexpr match_flag_type format_no_copy =    /* unspecified */;
inline constexpr match_flag_type format_first_only = /* unspecified */;
 (since C++17)
1) match_flag_type is a BitmaskType that specifies additional regular expression matching options.

Constants

Note: [first, last) refers to the character sequence being matched.

Constant Explanation
match_not_bol The first character in [first, last) will be treated as if it is not at the beginning of a line
(i.e. ^ will not match [first, first)).
match_not_eol The last character in [first, last) will be treated as if it is not at the end of a line
(i.e. $ will not match [last, last)).
match_not_bow \b will not match [first, first).
match_not_eow \b will not match [last, last).
match_any If more than one match is possible, then any match is an acceptable result.
match_not_null Do not match empty sequences.
match_continuous Only match a sub-sequence that begins at first.
match_prev_avail --first is a valid iterator position.
When set, causes match_not_bol and match_not_bow to be ignored.
format_default Use ECMAScript rules to construct strings in std::regex_replace (syntax documentation).
format_sed Use POSIX sed utility rules in std::regex_replace (syntax documentation).
format_no_copy Do not copy un-matched strings to the output in std::regex_replace.
format_first_only Only replace the first match in std::regex_replace.

All constants, except for match_default and format_default, are bitmask elements. The match_default and format_default constants are empty bitmasks.

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR Applied to Behavior as published Correct behavior
LWG 2053 C++11 1. the constants were declared static
2. match_default and format_default were initialized from ​0​		 1. removed the static specifier
2. initialized from {}

See also

(C++11)
attempts to match a regular expression to an entire character sequence
(function template)
(C++11)
general options controlling regex behavior
(typedef)
(C++11)
describes different types of matching errors
(typedef)

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