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

< cpp‎ | types
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Runtime type information

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:
Type name
Defined in header
Literal suffix Predefined macro C language type Type properties
bits of storage bits of precision bits of exponent max exponent
std::float16_t f16 or F16 __STDCPP_FLOAT16_T__ _Float16 16 11 5 15
std::float32_t f32 or F32 __STDCPP_FLOAT32_T__ _Float32 32 24 8 127
std::float64_t f64 or F64 __STDCPP_FLOAT64_T__ _Float64 64 53 11 1023
std::float128_t f128 or F128 __STDCPP_FLOAT128_T__ _Float128 128 113 15 16383
std::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).

[edit] Example

#include <stdfloat>
#if __STDCPP_FLOAT64_T__ != 1
    #error "64-bit float type required"
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