[re.err]

# 28 Text processing library [[text]](./#text)

## 28.6 Regular expressions library [[re]](re#err)

### 28.6.4 Namespace std​::​regex_constants [[re.const]](re.const#re.err)

#### 28.6.4.4 Implementation-defined error_type [re.err]

[ð](#lib:error_type)

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*;}

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/text.tex#L9885)

The type error_type is an implementation-defined enumerated type ([[enumerated.types]](enumerated.types "16.3.3.3.2 Enumerated types"))[.](#1.sentence-1)

Values of type error_type represent the error
conditions described in Table [120](#tab:re.err "Table 120: error_­type values in the C locale"):

Table [120](#tab:re.err) — error_type values in the C locale [[tab:re.err]](./tab:re.err)  

| [ð](#tab:re.err-row-1)<br>**Value** | **Error condition** |
| --- | --- |
| [ð](#tab:re.err-row-2)<br>error_collate | The expression contains an invalid collating element name[.](#tab:re.err-row-2-column-2-sentence-1) |
| [ð](#tab:re.err-row-3)<br>error_ctype | The expression contains an invalid character class name[.](#tab:re.err-row-3-column-2-sentence-1) |
| [ð](#tab:re.err-row-4)<br>error_escape | The expression contains an invalid escaped character, or a trailing escape[.](#tab:re.err-row-4-column-2-sentence-1) |
| [ð](#tab:re.err-row-5)<br>error_backref | The expression contains an invalid back reference[.](#tab:re.err-row-5-column-2-sentence-1) |
| [ð](#tab:re.err-row-6)<br>error_brack | The expression contains mismatched `[` and `]`[.](#tab:re.err-row-6-column-2-sentence-1) |
| [ð](#tab:re.err-row-7)<br>error_paren | The expression contains mismatched `(` and `)`[.](#tab:re.err-row-7-column-2-sentence-1) |
| [ð](#tab:re.err-row-8)<br>error_brace | The expression contains mismatched `{` and `}`[.](#tab:re.err-row-8-column-2-sentence-1) |
| [ð](#tab:re.err-row-9)<br>error_badbrace | The expression contains an invalid range in a `{}` expression[.](#tab:re.err-row-9-column-2-sentence-1) |
| [ð](#tab:re.err-row-10)<br>error_range | The expression contains an invalid character range, such as `[b-a]` in most encodings[.](#tab:re.err-row-10-column-2-sentence-1) |
| [ð](#tab:re.err-row-11)<br>error_space | There is insufficient memory to convert the expression into a finite state machine[.](#tab:re.err-row-11-column-2-sentence-1) |
| [ð](#tab:re.err-row-12)<br>error_badrepeat | One of `*?+{` is not preceded by a valid regular expression[.](#tab:re.err-row-12-column-2-sentence-1) |
| [ð](#tab:re.err-row-13)<br>error_complexity | The complexity of an attempted match against a regular expression exceeds a pre-set level[.](#tab:re.err-row-13-column-2-sentence-1) |
| [ð](#tab:re.err-row-14)<br>error_stack | There is insufficient memory to determine whether the regular expression matches the specified character sequence[.](#tab:re.err-row-14-column-2-sentence-1) |