31 Regular expressions library [re]

31.5 Namespace std​::​regex_­constants [re.const]

31.5.3 Implementation-defined error_­type [re.err]

namespace std::regex_constants {
  using error_type = T3;
  inline constexpr error_type error_collate = unspecified;
  inline constexpr error_type error_ctype = unspecified;
  inline constexpr error_type error_escape = unspecified;
  inline constexpr error_type error_backref = unspecified;
  inline constexpr error_type error_brack = unspecified;
  inline constexpr error_type error_paren = unspecified;
  inline constexpr error_type error_brace = unspecified;
  inline constexpr error_type error_badbrace = unspecified;
  inline constexpr error_type error_range = unspecified;
  inline constexpr error_type error_space = unspecified;
  inline constexpr error_type error_badrepeat = unspecified;
  inline constexpr error_type error_complexity = unspecified;
  inline constexpr error_type error_stack = unspecified;
}
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The type error_­type is an implementation-defined enumerated type. Values of type error_­type represent the error conditions described in Table 132:

Table 132 — error_­type values in the C locale
ValueError condition
error_­collate The expression contained an invalid collating element name.
error_­ctype The expression contained an invalid character class name.
error_­escape The expression contained an invalid escaped character, or a trailing escape.
error_­backref The expression contained an invalid back reference.
error_­brack The expression contained mismatched [ and ].
error_­paren The expression contained mismatched ( and ).
error_­brace The expression contained mismatched { and }
error_­badbrace The expression contained an invalid range in a {} expression.
error_­range The expression contained an invalid character range, such as [b-a] in most encodings.
error_­space There was insufficient 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 against a regular expression exceeded a pre-set level.
error_­stack There was insufficient memory to determine whether the regular expression could match the specified character sequence.