30 Regular expressions library [re] (original) (raw)
The type match_flag_type is animplementation-defined bitmask type.
The constants of that type, except for match_default andformat_default, are bitmask elements.
The match_default andformat_default constants are empty bitmasks.
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 in Table 137 for any bitmask elements set.
Table 137: regex_constants::match_flag_type effects when obtaining a match against a character container sequence [first, last). [tab:re.matchflag]
| 🔗 | Element | Effect(s) if set |
|---|---|---|
| 🔗 | match_not_bol | The first character in the sequence [first, last) shall be 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) shall be 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" shall not match the sub-sequence [first, first). |
| 🔗 | match_not_eow | The expression "\\b" shall not match 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 shall not match an empty sequence. |
| 🔗 | match_continuous | The expression shall only match a sub-sequence that begins atfirst. |
| 🔗 | match_prev_avail | --first is a valid iterator position. When this flag is set the flags match_not_bol and match_not_bow shall be ignored by theregular expression algorithms and iterators. |
| 🔗 | format_default | When a regular expression match is to be replaced by a new string, the new string shall be constructed using the rules used by the ECMAScript replace function in ECMA-262, part 15.5.4.11 String.prototype.replace. In addition, during search and replace operations all non-overlapping occurrences of the regular expression shall be located and replaced, and sections of the input that did not match the expression shall be copied unchanged to the output string. |
| 🔗 | format_sed | When a regular expression match is to be replaced by a new string, the new string shall be constructed using the rules used by the sed utility in POSIX. |
| 🔗 | 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. |