Here is a list of all documented namespace variables with links to the namespaces they belong to:

### - _ -

- __multiline : std::regex_constants
- __polynomial : std::regex_constants
- _CASable_bits : __gnu_parallel
- _CASable_mask : __gnu_parallel

### - a -

- adopt_lock : std
- awk : std::regex_constants

### - b -

- basic : std::regex_constants

### - c -

- cerr : std
- cin : std
- clog : std
- collate : std::regex_constants
- cout : std

### - d -

- default_sentinel : std
- defer_lock : std
- destroying_delete : std

### - e -

- e_v : std::numbers
- ECMAScript : std::regex_constants
- egamma_v : std::numbers
- 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
- ignore : std
- in_place : std::experimental
- inv_pi_v : std::numbers
- inv_sqrt3_v : std::numbers
- inv_sqrtpi_v : std::numbers
- is_aggregate_v : std
- is_bind_expression_v : std::experimental
- is_bounded_array_v : std
- is_detected_convertible_v : std::experimental
- is_detected_exact_v : std::experimental
- is_detected_v : std::experimental
- is_layout_compatible_v : std
- is_nothrow_convertible_v : std
- is_nothrow_swappable_v : std
- is_nothrow_swappable_with_v : std
- is_placeholder_v : std::experimental
- is_pointer_interconvertible_base_of_v : std
- is_swappable_v : std
- is_swappable_with_v : std
- is_unbounded_array_v : std

### - l -

- ln10_v : std::numbers
- ln2_v : std::numbers
- log10e_v : std::numbers
- log2e_v : std::numbers

### - 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
- multiline : std::regex_constants

### - n -

- nosubs : std::regex_constants
- nullopt : std::experimental, std

### - o -

- optimize : std::regex_constants

### - p -

- phi_v : std::numbers
- pi_v : std::numbers
- piecewise_construct : std

### - s -

- sqrt2_v : std::numbers
- sqrt3_v : std::numbers

### - t -

- try_to_lock : std

### - w -

- wcerr : std
- wcin : std
- wclog : std
- wcout : std