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    std::regex_constants::match_flag_type

    From cppreference.com
     
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    Defined in header <regex>
    using match_flag_type = /* implementation-defined */;
    		 (1) (since C++11)
    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 */;
    		 (2) (since C++11)
    (inline since C++17)
    1) match_flag_type is a BitmaskType that specifies additional regular expression matching options.

    Constants

    See More

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

    Name 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) [edit]
    (C++11)
    		 general options controlling regex behavior
    (typedef) [edit]
    (C++11)
    		 describes different types of matching errors
    (typedef) [edit]