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# std::regex_constants::error_type

From cppreference.com
< cpp‎ | regex

Defined in header `<regex>` |  |
typedef /*implementation defined*/ error_type; |  | (since C++11)
constexpr error_type error_collate = /*unspecified*/; constexpr error_type error_ctype = /*unspecified*/; constexpr error_type error_escape = /*unspecified*/; constexpr error_type error_backref = /*unspecified*/; constexpr error_type error_brack = /*unspecified*/; constexpr error_type error_paren = /*unspecified*/; constexpr error_type error_brace = /*unspecified*/; constexpr error_type error_badbrace = /*unspecified*/; constexpr error_type error_range = /*unspecified*/; constexpr error_type error_space = /*unspecified*/; constexpr error_type error_badrepeat = /*unspecified*/; constexpr error_type error_complexity = /*unspecified*/; constexpr error_type error_stack = /*unspecified*/; |  | (since C++11)

The `error_type` is a type that describes errors that may occur during regular expression parsing.

### [edit] Constants

Constant | Explanation
`error_collate` | the expression contains an invalid collating element name
`error_ctype` | the expression contains an invalid character class name
`error_escape` | the expression contains an invalid escaped character or a trailing escape
`error_backref` | the expression contains an invalid back reference
`error_brack` | the expression contains mismatched square brackets ('[' and ']')
`error_paren` | the expression contains mismatched parentheses ('(' and ')')
`error_brace` | the expression contains mismatched curly braces ('{' and '}')
`error_badbrace` | the expression contains an invalid range in a {} expression
`error_range` | the expression contains an invalid character range (e.g. [b-a])
`error_space` | there was not enough memory to convert the expression into a finite state machine
`error_badrepeat` | one of *?+{ was not preceded by a valid regular expression
`error_complexity` | the complexity of an attempted match exceeded a predefined level
`error_stack` | there was not enough memory to perform a match

### [edit] Notes

In C++11, these constants were specified with redundant keyword `static`, which was removed by C++14 via LWG issue 2053

### [edit] See also

regex_error (C++11) | reports errors generated by the regular expressions library (class) [edit]

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