frexpf(3) · carta

Usage

double frexp(double x, int *e); float frexpf(float x, int *e); long double frexpl(long double x, int *e);

_ISOC99_SOURCE { | | _POSIX_C_SOURCE >= 200112L}

Library

Math library (libm, -lm)

Overview

These functions are used to split the number x into a normalized fraction and an exponent which is stored in e.

Return value

These functions return the normalized fraction. If the argument x is not zero, the normalized fraction is x times a power of two, and its absolute value is always in the range 1/2 (inclusive) to 1 (exclusive), that is, [0.5,1).

If x is zero, then the normalized fraction is zero and zero is stored in e.

If x is a NaN, a NaN is returned, and the value of *e is unspecified.

If x is positive infinity (negative infinity), positive infinity (negative infinity) is returned, and the value of *e is unspecified.

Errors

No errors occur.

Attributes

For an explanation of the terms used in this section, see attributes(7).

Interface	Attribute	Value
frexp(), frexpf(), frexpl()	Thread safety	MT-Safe

Examples

The program below produces results such as the following:

$ ./a.out 2560
frexp(2560, &e) = 0.625: 0.625 * 2^12 = 2560
$ ./a.out -4
frexp(-4, &e) = -0.5: -0.5 * 2^3 = -4

Program source

#include <float.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
int
main(int argc, char *argv[])
{
    double x, r;
    int e;
    x = strtod(argv[1], NULL);
    r = frexp(x, &e);
    printf("frexp(%g, &e) = %g: %g * %d^%d = %g\n", x, r, r, 2, e, x);
    exit(EXIT_SUCCESS);
}

History

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