Fixed width floating-point types (since C++23) (original) (raw)

If the implementation supports any of the following ISO 60559 types as an extended floating-point type, then:

the corresponding macro is defined as 1 to indicate support,
the corresponding floating-point literal suffix is available, and
the corresponding type alias name is provided:

TypesDefined in header	Literal suffix	Predefined macro	C language type	Type properties
bits of storage	bits of precision	bits of exponent	max exponent
float16_t	f16 or F16	__STDCPP_FLOAT16_T__	_Float16	16	11	5	15
float32_t	f32 or F32	__STDCPP_FLOAT32_T__	_Float32	32	24	8	127
float64_t	f64 or F64	__STDCPP_FLOAT64_T__	_Float64	64	53	11	1023
float128_t	f128 or F128	__STDCPP_FLOAT128_T__	_Float128	128	113	15	16383
bfloat16_t	bf16 or BF16	__STDCPP_BFLOAT16_T__	(N/A)	16	8	8	127

[edit] Notes

The type std::bfloat16_t is known as Brain Floating-Point.

Unlike the fixed width integer types, which may be aliases to standard integer types, the fixed width floating-point types must be aliases to extended floating-point types (not float / double / long double), therefore not drop-in replacements for standard floating-point types.

[edit] Example

#include #if STDCPP_FLOAT64_T != 1 #error "64-bit float type required" #endif int main() { std::float64_t f = 0.1f64; }

[edit] References

C++23 standard (ISO/IEC 14882:2024):
6.8.3 Optional extended floating-point types [basic.extended.fp]

[edit] See also

Fundamental types