32 Regular expressions library [re]

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

32.4.3 Bitmask type match_flag_type [re.matchflag]

Table 138: 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 at first.
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 the regular 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.