std::regex_constants::error_type
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                    |   Defined in header <regex.h>
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|   typedef /*implementation defined*/ error_type;  | 
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|   static constexpr error_type error_collate;  | 
Th expression contains an invalid collating element name. | |
|   static constexpr error_type error_ctype;  | 
The expression contains an invalid character class name. | |
|   static constexpr error_type error_escape;  | 
The expression contains an invalid escaped character or a trailing escape. | |
|   static constexpr error_type error_backref;  | 
The expression contains an invalid back reference. | |
|   static constexpr error_type error_brack;  | 
The expression contains mismatched square brackets ([ and ]). | |
|   static constexpr error_type error_paren;  | 
The expression contains mismatched parentheses (( and )). | |
|   static constexpr error_type error_brace;  | 
The expression contains mismatched curly braces ({ and }). | |
|   static constexpr error_type error_badbrace;  | 
The expression contains an invalid range in a {} expression. | |
|   static constexpr error_type error_range;  | 
The expression contains an invalid character range (e.g. [b-a]). | |
|   static constexpr error_type error_space;  | 
There was not enough memory to convert the expression into a finite state machine. | |
|   static constexpr error_type error_badrepeat;  | 
One of *?+{ was not preceded by a valid regular expression. | |
|   static constexpr error_type error_complexity;  | 
The complexity of an attempted match exceeded a predefined level. | |
|   static constexpr error_type error_stack;  | 
There was not enough memory to perform a match. | |
The error_type is a type that describes errors that may occur during regular expression parsing.
[edit] See also
|     (class)  | |