std::regex_constants Namespace Reference
Regular Expressions

## 5.1 Regular Expression Syntax Options

enum | __syntax_option { _S_icase, _S_nosubs, _S_optimize, _S_collate, _S_ECMAScript, _S_basic, _S_extended, _S_awk, _S_grep, _S_egrep, _S_syntax_last }
enum | syntax_option_type : unsigned int { icase, nosubs, optimize, collate, ECMAScript, basic, extended, awk, grep, egrep }
constexpr syntax_option_type | operator& (syntax_option_type __a, syntax_option_type __b)
constexpr syntax_option_type | operator| (syntax_option_type __a, syntax_option_type __b)
constexpr syntax_option_type | operator^ (syntax_option_type __a, syntax_option_type __b)
constexpr syntax_option_type | operator~ (syntax_option_type __a)
syntax_option_type & | operator&= (syntax_option_type &__a, syntax_option_type __b)
syntax_option_type & | operator|= (syntax_option_type &__a, syntax_option_type __b)
syntax_option_type & | operator^= (syntax_option_type &__a, syntax_option_type __b)

## 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 { _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 }
enum | match_flag_type : unsigned int { match_default, match_not_bol, match_not_eol, match_not_bow, match_not_eow, match_any, match_not_null, match_continuous, match_prev_avail, format_default, format_sed, format_no_copy, format_first_only }
constexpr match_flag_type | operator& (match_flag_type __a, match_flag_type __b)
constexpr match_flag_type | operator| (match_flag_type __a, match_flag_type __b)
constexpr match_flag_type | operator^ (match_flag_type __a, match_flag_type __b)
constexpr match_flag_type | operator~ (match_flag_type __a)
match_flag_type & | operator&= (match_flag_type &__a, match_flag_type __b)
match_flag_type & | operator|= (match_flag_type &__a, match_flag_type __b)
match_flag_type & | operator^= (match_flag_type &__a, match_flag_type __b)

## 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 }
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)

## Detailed Description

ISO C++-0x entities sub namespace for regex.

## Enumeration Type Documentation

enum std::regex_constants::__match_flag

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.

Definition at line 213 of file regex_constants.h.

enum std::regex_constants::__syntax_option

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.

Definition at line 54 of file regex_constants.h.

enum std::regex_constants::error_type

The expression contained an invalid collating element name.

Definition at line 49 of file regex_error.h.

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.

Enumerator
match_default | The default matching rules.
match_not_bol | 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).
match_not_eol | 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).
match_not_bow | The expression \b is not matched against the sub-sequence [first,first).
match_not_eow | The expression \b should not be matched against the sub-sequence [last,last).
match_any | If more than one match is possible then any match is an acceptable result.
match_not_null | The expression does not match an empty sequence.
match_continuous | The expression only matches a sub-sequence that begins at first .
match_prev_avail | –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 regular expression algorithms 28.11 and iterators 28.12.

format_default

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.

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

Definition at line 236 of file regex_constants.h.

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.

Enumerator
icase | Specifies that the matching of regular expressions against a character sequence shall be performed without regard to case.
nosubs | 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.
optimize | 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.
collate | Specifies that character ranges of the form [a-b] should be locale sensitive.
ECMAScript | 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.
basic | 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].
extended | 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.
awk | 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).
grep | 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.
egrep | 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.

Definition at line 80 of file regex_constants.h.

## Function Documentation

constexpr error_type std::regex_constants::error_backref | ( | _S_error_backref |  | ) |

The expression contained an invalid back reference.

constexpr error_type std::regex_constants::error_badbrace | ( | _S_error_badbrace |  | ) |

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

constexpr error_type std::regex_constants::error_badrepeat | ( | _S_error_badrepeat |  | ) |

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

constexpr error_type std::regex_constants::error_brace | ( | _S_error_brace |  | ) |

The expression contained mismatched { and }

constexpr error_type std::regex_constants::error_brack | ( | _S_error_brack |  | ) |

The expression contained mismatched [ and ].

constexpr error_type std::regex_constants::error_collate | ( | _S_error_collate |  | ) |

The expression contained an invalid collating element name.

constexpr error_type std::regex_constants::error_complexity | ( | _S_error_complexity |  | ) |

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 |  | ) |

The expression contained an invalid character class name.

constexpr error_type std::regex_constants::error_escape | ( | _S_error_escape |  | ) |

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

constexpr error_type std::regex_constants::error_paren | ( | _S_error_paren |  | ) |

The expression contained mismatched ( and ).

constexpr error_type std::regex_constants::error_range | ( | _S_error_range |  | ) |

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 |  | ) |

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

constexpr error_type std::regex_constants::error_stack | ( | _S_error_stack |  | ) |

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

constexpr syntax_option_type std::regex_constants::operator& | ( | syntax_option_type | __a,
|  | syntax_option_type | __b
| ) |  |

inline

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.

Definition at line 164 of file regex_constants.h.

constexpr match_flag_type std::regex_constants::operator& | ( | match_flag_type | __a,
|  | match_flag_type | __b
| ) |  |

inline

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.

Definition at line 343 of file regex_constants.h.

syntax_option_type& std::regex_constants::operator&= | ( | syntax_option_type & | __a,
|  | syntax_option_type | __b
| ) |  |

inline

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.

Definition at line 189 of file regex_constants.h.

match_flag_type& std::regex_constants::operator&= | ( | match_flag_type & | __a,
|  | match_flag_type | __b
| ) |  |

inline

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.

Definition at line 368 of file regex_constants.h.

constexpr syntax_option_type std::regex_constants::operator^ | ( | syntax_option_type | __a,
|  | syntax_option_type | __b
| ) |  |

inline

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.

Definition at line 178 of file regex_constants.h.

constexpr match_flag_type std::regex_constants::operator^ | ( | match_flag_type | __a,
|  | match_flag_type | __b
| ) |  |

inline

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.

Definition at line 357 of file regex_constants.h.

syntax_option_type& std::regex_constants::operator^= | ( | syntax_option_type & | __a,
|  | syntax_option_type | __b
| ) |  |

inline

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.

Definition at line 197 of file regex_constants.h.

match_flag_type& std::regex_constants::operator^= | ( | match_flag_type & | __a,
|  | match_flag_type | __b
| ) |  |

inline

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.

Definition at line 376 of file regex_constants.h.

constexpr syntax_option_type std::regex_constants::operator| | ( | syntax_option_type | __a,
|  | syntax_option_type | __b
| ) |  |

inline

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.

Definition at line 171 of file regex_constants.h.

constexpr match_flag_type std::regex_constants::operator| | ( | match_flag_type | __a,
|  | match_flag_type | __b
| ) |  |

inline

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.

Definition at line 350 of file regex_constants.h.

syntax_option_type& std::regex_constants::operator|= | ( | syntax_option_type & | __a,
|  | syntax_option_type | __b
| ) |  |

inline

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.

Definition at line 193 of file regex_constants.h.

match_flag_type& std::regex_constants::operator|= | ( | match_flag_type & | __a,
|  | match_flag_type | __b
| ) |  |

inline

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.

Definition at line 372 of file regex_constants.h.

constexpr syntax_option_type std::regex_constants::operator~ | ( | syntax_option_type | __a | ) |

inline

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.

Definition at line 185 of file regex_constants.h.

constexpr match_flag_type std::regex_constants::operator~ | ( | match_flag_type | __a | ) |

inline

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.

Definition at line 364 of file regex_constants.h.