### - a -

- awk : std::regex_constants

### - b -

- basic : std::regex_constants

### - c -

- collate : std::regex_constants

### - d -

- denorm_absent : std
- denorm_indeterminate : std
- denorm_present : std

### - e -

- ECMAScript : std::regex_constants
- egrep : std::regex_constants
- extended : std::regex_constants

### - f -

- format_default : std::regex_constants
- format_first_only : std::regex_constants
- format_no_copy : std::regex_constants
- format_sed : std::regex_constants

### - g -

- grep : std::regex_constants

### - i -

- icase : std::regex_constants

### - m -

- match_any : std::regex_constants
- match_continuous : std::regex_constants
- match_default : std::regex_constants
- match_not_bol : std::regex_constants
- match_not_bow : std::regex_constants
- match_not_eol : std::regex_constants
- match_not_eow : std::regex_constants
- match_not_null : std::regex_constants
- match_prev_avail : std::regex_constants

### - n -

- nosubs : std::regex_constants

### - o -

- optimize : std::regex_constants

### - p -

- parallel_balanced : __gnu_parallel
- parallel_omp_loop : __gnu_parallel
- parallel_omp_loop_static : __gnu_parallel
- parallel_taskqueue : __gnu_parallel
- parallel_unbalanced : __gnu_parallel

### - r -

- round_to_nearest : std
- round_toward_infinity : std
- round_toward_neg_infinity : std
- round_toward_zero : std

### - s -

- sequential : __gnu_parallel