float_t, double_t

typedef /* implementation-defined */ float_t

typedef /* implementation-defined */ double_t

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.

Example

#include <float.h>
#include <math.h>
#include <stdio.h>

#define SHOW(expr) printf("%s = %d\n", #expr, (int)(expr))

int main()
{
    SHOW(FLT_EVAL_METHOD);
    SHOW(sizeof(float));
    SHOW(sizeof(float_t));
    SHOW(sizeof(double));
    SHOW(sizeof(double_t));
}

FLT_EVAL_METHOD = 1
sizeof(float) = 4
sizeof(float_t) = 8
sizeof(double) = 8
sizeof(double_t) = 8

References

• C23 standard (ISO/IEC 9899:2024):
• 7.12 Mathematics <math.h> (p: TBD)
• C17 standard (ISO/IEC 9899:2018):
• 7.12 Mathematics <math.h> (p: TBD)
• C11 standard (ISO/IEC 9899:2011):
• 7.12 Mathematics <math.h> (p: 231)
• C99 standard (ISO/IEC 9899:1999):
• 7.12 Mathematics <math.h> (p: 212)

See also