5.1 Regular Expression Syntax Options¶

enum syntax_option_type : unsigned int { _S_icase, _S_nosubs, _S_optimize, _S_collate, _S_ECMAScript, _S_basic, _S_extended, _S_awk, _S_grep, _S_egrep, _S_polynomial, _S_multiline }
This is a bitmask type indicating how to interpret the regex. constexpr syntax_option_type icase
constexpr syntax_option_type nosubs
constexpr syntax_option_type optimize
constexpr syntax_option_type collate
constexpr syntax_option_type ECMAScript
constexpr syntax_option_type basic
constexpr syntax_option_type extended
constexpr syntax_option_type awk
constexpr syntax_option_type grep
constexpr syntax_option_type egrep
constexpr syntax_option_type multiline
constexpr syntax_option_type __multiline
Extension: Equivalent to regex_constants::multiline for C++11 and C++14. constexpr syntax_option_type __polynomial
constexpr syntax_option_type operator& (syntax_option_type __a, syntax_option_type __b) noexcept
This is a bitmask type indicating how to interpret the regex. constexpr syntax_option_type operator| (syntax_option_type __a, syntax_option_type __b) noexcept
This is a bitmask type indicating how to interpret the regex. constexpr syntax_option_type operator^ (syntax_option_type __a, syntax_option_type __b) noexcept
This is a bitmask type indicating how to interpret the regex. constexpr syntax_option_type operator~ (syntax_option_type __a) noexcept
This is a bitmask type indicating how to interpret the regex. constexpr syntax_option_type & operator&= (syntax_option_type &__a, syntax_option_type __b) noexcept
This is a bitmask type indicating how to interpret the regex. constexpr syntax_option_type & operator|= (syntax_option_type &__a, syntax_option_type __b) noexcept
This is a bitmask type indicating how to interpret the regex. constexpr syntax_option_type & operator^= (syntax_option_type &__a, syntax_option_type __b) noexcept
This is a bitmask type indicating how to interpret the regex.

5.2 Matching Rules¶

Matching a regular expression against a sequence of characters [first, last) proceeds according to the rules of the grammar specified for the regular expression object, modified according to the effects listed below for any bitmask elements set.
enum match_flag_type : unsigned int { _S_default, _S_not_bol, _S_not_eol, _S_not_bow, _S_not_eow, _S_any, _S_not_null, _S_continuous, _S_prev_avail, _S_sed, _S_no_copy, _S_first_only, _S_match_flag_last }
This is a bitmask type indicating regex matching rules. constexpr match_flag_type match_default
constexpr match_flag_type match_not_bol
constexpr match_flag_type match_not_eol
constexpr match_flag_type match_not_bow
constexpr match_flag_type match_not_eow
constexpr match_flag_type match_any
constexpr match_flag_type match_not_null
constexpr match_flag_type match_continuous
constexpr match_flag_type match_prev_avail
constexpr match_flag_type format_default
constexpr match_flag_type format_sed
constexpr match_flag_type format_no_copy
constexpr match_flag_type format_first_only
constexpr match_flag_type operator& (match_flag_type __a, match_flag_type __b) noexcept
This is a bitmask type indicating regex matching rules. constexpr match_flag_type operator| (match_flag_type __a, match_flag_type __b) noexcept
This is a bitmask type indicating regex matching rules. constexpr match_flag_type operator^ (match_flag_type __a, match_flag_type __b) noexcept
This is a bitmask type indicating regex matching rules. constexpr match_flag_type operator~ (match_flag_type __a) noexcept
This is a bitmask type indicating regex matching rules. constexpr match_flag_type & operator&= (match_flag_type &__a, match_flag_type __b) noexcept
This is a bitmask type indicating regex matching rules. constexpr match_flag_type & operator|= (match_flag_type &__a, match_flag_type __b) noexcept
This is a bitmask type indicating regex matching rules. constexpr match_flag_type & operator^= (match_flag_type &__a, match_flag_type __b) noexcept
This is a bitmask type indicating regex matching rules.

5.3 Error Types¶

enum error_type { _S_error_collate, _S_error_ctype, _S_error_escape, _S_error_backref, _S_error_brack, _S_error_paren, _S_error_brace, _S_error_badbrace, _S_error_range, _S_error_space, _S_error_badrepeat, _S_error_complexity, _S_error_stack, _S_null, _S_grammar }
constexpr error_type error_collate (_S_error_collate)
constexpr error_type error_ctype (_S_error_ctype)
constexpr error_type error_escape (_S_error_escape)
constexpr error_type error_backref (_S_error_backref)
constexpr error_type error_brack (_S_error_brack)
constexpr error_type error_paren (_S_error_paren)
constexpr error_type error_brace (_S_error_brace)
constexpr error_type error_badbrace (_S_error_badbrace)
constexpr error_type error_range (_S_error_range)
constexpr error_type error_space (_S_error_space)
constexpr error_type error_badrepeat (_S_error_badrepeat)
constexpr error_type error_complexity (_S_error_complexity)
constexpr error_type error_stack (_S_error_stack)

enum std::regex_constants::error_type¶

The expression contained an invalid collating element name.

enum std::regex_constants::match_flag_type : unsigned int¶

This is a bitmask type indicating regex matching rules. The match_flag_type is implementation defined but it is valid to perform bitwise operations on these values and expect the right thing to happen.

enum std::regex_constants::syntax_option_type : unsigned int¶

This is a bitmask type indicating how to interpret the regex. The syntax_option_type is implementation defined but it is valid to perform bitwise operations on these values and expect the right thing to happen.

A valid value of type syntax_option_type shall have exactly one of the elements ECMAScript, basic, extended, awk, grep, egrep set.

constexpr error_type std::regex_constants::error_backref (_S_error_backref) [inline], [constexpr]¶

The expression contained an invalid back reference.

constexpr error_type std::regex_constants::error_badbrace (_S_error_badbrace) [inline], [constexpr]¶

The expression contained an invalid range in a {} expression.

constexpr error_type std::regex_constants::error_badrepeat (_S_error_badrepeat) [inline], [constexpr]¶

One of *?+{ was not preceded by a valid regular expression.

constexpr error_type std::regex_constants::error_brace (_S_error_brace) [inline], [constexpr]¶

The expression contained mismatched { and }

constexpr error_type std::regex_constants::error_brack (_S_error_brack) [inline], [constexpr]¶

The expression contained mismatched [ and ].

constexpr error_type std::regex_constants::error_collate (_S_error_collate) [inline], [constexpr]¶

The expression contained an invalid collating element name.

constexpr error_type std::regex_constants::error_complexity (_S_error_complexity) [inline], [constexpr]¶

The complexity of an attempted match against a regular expression exceeded a pre-set level.

constexpr error_type std::regex_constants::error_ctype (_S_error_ctype) [inline], [constexpr]¶

The expression contained an invalid character class name.

constexpr error_type std::regex_constants::error_escape (_S_error_escape) [inline], [constexpr]¶

The expression contained an invalid escaped character, or a trailing escape.

constexpr error_type std::regex_constants::error_paren (_S_error_paren) [inline], [constexpr]¶

The expression contained mismatched ( and ).

constexpr error_type std::regex_constants::error_range (_S_error_range) [inline], [constexpr]¶

The expression contained an invalid character range, such as [b-a] in most encodings.

constexpr error_type std::regex_constants::error_space (_S_error_space) [inline], [constexpr]¶

There was insufficient memory to convert the expression into a finite state machine.

constexpr error_type std::regex_constants::error_stack (_S_error_stack) [inline], [constexpr]¶

There was insufficient memory to determine whether the regular expression could match the specified character sequence.

constexpr match_flag_type std::regex_constants::operator& (match_flag_type __a, match_flag_type __b) [constexpr], [noexcept]¶

This is a bitmask type indicating regex matching rules. The match_flag_type is implementation defined but it is valid to perform bitwise operations on these values and expect the right thing to happen.

constexpr syntax_option_type std::regex_constants::operator& (syntax_option_type __a, syntax_option_type __b) [constexpr], [noexcept]¶

This is a bitmask type indicating how to interpret the regex. The syntax_option_type is implementation defined but it is valid to perform bitwise operations on these values and expect the right thing to happen.

A valid value of type syntax_option_type shall have exactly one of the elements ECMAScript, basic, extended, awk, grep, egrep set.

constexpr match_flag_type & std::regex_constants::operator&= (match_flag_type & __a, match_flag_type __b) [inline], [constexpr], [noexcept]¶

This is a bitmask type indicating regex matching rules. The match_flag_type is implementation defined but it is valid to perform bitwise operations on these values and expect the right thing to happen.

constexpr syntax_option_type & std::regex_constants::operator&= (syntax_option_type & __a, syntax_option_type __b) [inline], [constexpr], [noexcept]¶

This is a bitmask type indicating how to interpret the regex. The syntax_option_type is implementation defined but it is valid to perform bitwise operations on these values and expect the right thing to happen.

A valid value of type syntax_option_type shall have exactly one of the elements ECMAScript, basic, extended, awk, grep, egrep set.

constexpr match_flag_type std::regex_constants::operator^ (match_flag_type __a, match_flag_type __b) [constexpr], [noexcept]¶

This is a bitmask type indicating regex matching rules. The match_flag_type is implementation defined but it is valid to perform bitwise operations on these values and expect the right thing to happen.

constexpr syntax_option_type std::regex_constants::operator^ (syntax_option_type __a, syntax_option_type __b) [constexpr], [noexcept]¶

This is a bitmask type indicating how to interpret the regex. The syntax_option_type is implementation defined but it is valid to perform bitwise operations on these values and expect the right thing to happen.

A valid value of type syntax_option_type shall have exactly one of the elements ECMAScript, basic, extended, awk, grep, egrep set.

constexpr match_flag_type & std::regex_constants::operator^= (match_flag_type & __a, match_flag_type __b) [inline], [constexpr], [noexcept]¶

This is a bitmask type indicating regex matching rules. The match_flag_type is implementation defined but it is valid to perform bitwise operations on these values and expect the right thing to happen.

constexpr syntax_option_type & std::regex_constants::operator^= (syntax_option_type & __a, syntax_option_type __b) [inline], [constexpr], [noexcept]¶

This is a bitmask type indicating how to interpret the regex. The syntax_option_type is implementation defined but it is valid to perform bitwise operations on these values and expect the right thing to happen.

A valid value of type syntax_option_type shall have exactly one of the elements ECMAScript, basic, extended, awk, grep, egrep set.

constexpr match_flag_type std::regex_constants::operator| (match_flag_type __a, match_flag_type __b) [constexpr], [noexcept]¶

This is a bitmask type indicating regex matching rules. The match_flag_type is implementation defined but it is valid to perform bitwise operations on these values and expect the right thing to happen.

constexpr syntax_option_type std::regex_constants::operator| (syntax_option_type __a, syntax_option_type __b) [constexpr], [noexcept]¶

This is a bitmask type indicating how to interpret the regex. The syntax_option_type is implementation defined but it is valid to perform bitwise operations on these values and expect the right thing to happen.

A valid value of type syntax_option_type shall have exactly one of the elements ECMAScript, basic, extended, awk, grep, egrep set.

constexpr match_flag_type & std::regex_constants::operator|= (match_flag_type & __a, match_flag_type __b) [inline], [constexpr], [noexcept]¶

This is a bitmask type indicating regex matching rules. The match_flag_type is implementation defined but it is valid to perform bitwise operations on these values and expect the right thing to happen.

constexpr syntax_option_type & std::regex_constants::operator|= (syntax_option_type & __a, syntax_option_type __b) [inline], [constexpr], [noexcept]¶

This is a bitmask type indicating how to interpret the regex. The syntax_option_type is implementation defined but it is valid to perform bitwise operations on these values and expect the right thing to happen.

A valid value of type syntax_option_type shall have exactly one of the elements ECMAScript, basic, extended, awk, grep, egrep set.

constexpr match_flag_type std::regex_constants::operator~ (match_flag_type __a) [constexpr], [noexcept]¶

This is a bitmask type indicating regex matching rules. The match_flag_type is implementation defined but it is valid to perform bitwise operations on these values and expect the right thing to happen.

constexpr syntax_option_type std::regex_constants::operator~ (syntax_option_type __a) [constexpr], [noexcept]¶

This is a bitmask type indicating how to interpret the regex. The syntax_option_type is implementation defined but it is valid to perform bitwise operations on these values and expect the right thing to happen.

A valid value of type syntax_option_type shall have exactly one of the elements ECMAScript, basic, extended, awk, grep, egrep set.

constexpr syntax_option_type std::regex_constants::__multiline [inline], [constexpr]¶

Extension: Equivalent to regex_constants::multiline for C++11 and C++14.

constexpr syntax_option_type std::regex_constants::__polynomial [inline], [constexpr]¶

Extension: Ensure both space complexity of compiled regex and time complexity execution are not exponential. If specified in a regex with back-references, the exception regex_constants::error_complexity will be thrown.

constexpr syntax_option_type std::regex_constants::awk [inline], [constexpr]¶

Specifies that the grammar recognized by the regular expression engine is that used by POSIX utility awk in IEEE Std 1003.1-2001. This option is identical to syntax_option_type extended, except that C-style escape sequences are supported. These sequences are: \\, \a, \b, \f, \n, \r, \t , \v, \&apos,, &apos,, and \ddd (where ddd is one, two, or three octal digits).

constexpr syntax_option_type std::regex_constants::basic [inline], [constexpr]¶

Specifies that the grammar recognized by the regular expression engine is that used by POSIX basic regular expressions in IEEE Std 1003.1-2001, Portable Operating System Interface (POSIX), Base Definitions and Headers, Section 9, Regular Expressions [IEEE, Information Technology -- Portable Operating System Interface (POSIX), IEEE Standard 1003.1-2001].

constexpr syntax_option_type std::regex_constants::collate [inline], [constexpr]¶

Specifies that character ranges of the form [a-b] should be locale sensitive.

constexpr syntax_option_type std::regex_constants::ECMAScript [inline], [constexpr]¶

Specifies that the grammar recognized by the regular expression engine is that used by ECMAScript in ECMA-262 [Ecma International, ECMAScript Language Specification, Standard Ecma-262, third edition, 1999], as modified in section [28.13]. This grammar is similar to that defined in the PERL scripting language but extended with elements found in the POSIX regular expression grammar.

constexpr syntax_option_type std::regex_constants::egrep [inline], [constexpr]¶

Specifies that the grammar recognized by the regular expression engine is that used by POSIX utility grep when given the -E option in IEEE Std 1003.1-2001. This option is identical to syntax_option_type extended, except that newlines are treated as whitespace.

constexpr syntax_option_type std::regex_constants::extended [inline], [constexpr]¶

Specifies that the grammar recognized by the regular expression engine is that used by POSIX extended regular expressions in IEEE Std 1003.1-2001, Portable Operating System Interface (POSIX), Base Definitions and Headers, Section 9, Regular Expressions.

constexpr match_flag_type std::regex_constants::format_default [inline], [constexpr]¶

When a regular expression match is to be replaced by a new string, the new string is constructed using the rules used by the ECMAScript replace function in ECMA- 262 [Ecma International, ECMAScript Language Specification, Standard Ecma-262, third edition, 1999], part 15.5.4.11 String.prototype.replace. In addition, during search and replace operations all non-overlapping occurrences of the regular expression are located and replaced, and sections of the input that did not match the expression are copied unchanged to the output string.

Format strings (from ECMA-262 [15.5.4.11]):

• $$ The dollar-sign itself ($)
• $& The matched substring.
• $` The portion of string that precedes the matched substring. This would be match_results::prefix().
• $' The portion of string that follows the matched substring. This would be match_results::suffix().
• $n The nth capture, where n is in [1,9] and $n is not followed by a decimal digit. If n <= match_results::size() and the nth capture is undefined, use the empty string instead. If n > match_results::size(), the result is implementation-defined.
• $nn The nnth capture, where nn is a two-digit decimal number on [01, 99]. If nn <= match_results::size() and the nth capture is undefined, use the empty string instead. If nn > match_results::size(), the result is implementation-defined.

constexpr match_flag_type std::regex_constants::format_first_only [inline], [constexpr]¶

When specified during a search and replace operation, only the first occurrence of the regular expression shall be replaced.

constexpr match_flag_type std::regex_constants::format_no_copy [inline], [constexpr]¶

During a search and replace operation, sections of the character container sequence being searched that do not match the regular expression shall not be copied to the output string.

constexpr match_flag_type std::regex_constants::format_sed [inline], [constexpr]¶

When a regular expression match is to be replaced by a new string, the new string is constructed using the rules used by the POSIX sed utility in IEEE Std 1003.1- 2001 [IEEE, Information Technology -- Portable Operating System Interface (POSIX), IEEE Standard 1003.1-2001].

constexpr syntax_option_type std::regex_constants::grep [inline], [constexpr]¶

Specifies that the grammar recognized by the regular expression engine is that used by POSIX utility grep in IEEE Std 1003.1-2001. This option is identical to syntax_option_type basic, except that newlines are treated as whitespace.

constexpr syntax_option_type std::regex_constants::icase [inline], [constexpr]¶

Specifies that the matching of regular expressions against a character sequence shall be performed without regard to case.

constexpr match_flag_type std::regex_constants::match_any [inline], [constexpr]¶

If more than one match is possible then any match is an acceptable result.

constexpr match_flag_type std::regex_constants::match_continuous [inline], [constexpr]¶

The expression only matches a sub-sequence that begins at first .

Referenced by std::regex_iterator< _Bi_iter, _Ch_type, _Rx_traits >::operator++().

constexpr match_flag_type std::regex_constants::match_default [inline], [constexpr]¶

The default matching rules.

constexpr match_flag_type std::regex_constants::match_not_bol [inline], [constexpr]¶

The first character in the sequence [first, last) is treated as though it is not at the beginning of a line, so the character (^) in the regular expression shall not match [first, first).

constexpr match_flag_type std::regex_constants::match_not_bow [inline], [constexpr]¶

The expression \b is not matched against the sub-sequence [first,first).

constexpr match_flag_type std::regex_constants::match_not_eol [inline], [constexpr]¶

The last character in the sequence [first, last) is treated as though it is not at the end of a line, so the character ($) in the regular expression shall not match [last, last).

constexpr match_flag_type std::regex_constants::match_not_eow [inline], [constexpr]¶

The expression \b should not be matched against the sub-sequence [last,last).

constexpr match_flag_type std::regex_constants::match_not_null [inline], [constexpr]¶

The expression does not match an empty sequence.

Referenced by std::regex_iterator< _Bi_iter, _Ch_type, _Rx_traits >::operator++().

constexpr match_flag_type std::regex_constants::match_prev_avail [inline], [constexpr]¶

--first is a valid iterator position. When this flag is set then the flags match_not_bol and match_not_bow are ignored by the algorithms regex_match, regex_search, and regex_replace, and by the iterators regex_iterator and regex_token_iterator.

Referenced by std::regex_iterator< _Bi_iter, _Ch_type, _Rx_traits >::operator++().

constexpr syntax_option_type std::regex_constants::multiline [inline], [constexpr]¶

Specifies that the ^ anchor matches at the beginning of a line, and the $ anchor matches at the end of a line, not only at the beginning/end of the input. Valid for the ECMAScript syntax, ignored otherwise.

Since

constexpr syntax_option_type std::regex_constants::nosubs [inline], [constexpr]¶

Specifies that when a regular expression is matched against a character container sequence, no sub-expression matches are to be stored in the supplied match_results structure.

constexpr syntax_option_type std::regex_constants::optimize [inline], [constexpr]¶

Specifies that the regular expression engine should pay more attention to the speed with which regular expressions are matched, and less to the speed with which regular expression objects are constructed. Otherwise it has no detectable effect on the program output.