float_t, double_t

Defined in header `<math.h>`
`typedef /implementation defined/ float_t`		(since C99)
`typedef /implementation defined/ double_t`		(since C99)

The types float_t and double_t are floating types at least as wide as float and double, respectively, and such that double_t is at least as wide as float_t. The value of FLT_EVAL_METHOD determines the types of float_t and double_t.

FLT_EVAL_METHOD	Explanation
`0`	`float_t` and `double_t` are equivalent to `float` and `double`, respectively
`1`	both `float_t` and `double_t` are equivalent to `double`
`2`	both `float_t` and `double_t` are equivalent to `long double`
`other`	both `float_t` and `double_t` are implementation defined

Example

#include <float.h>
#include <math.h>
#include <stdio.h>
 
int main(void)
{
    printf("%d\n", FLT_EVAL_METHOD);
    printf("%zu  %zu\n", sizeof(float),sizeof(float_t));
    printf("%zu  %zu\n", sizeof(double),sizeof(double_t));
    return 0;
}

Possible output:

0
4  4
8  8

References

C11 standard (ISO/IEC 9899:2011):

7.12 Mathematics (p: 231)

C99 standard (ISO/IEC 9899:1999):

7.12 Mathematics (p: 212)

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