# FREXP

## NAME

frexp, frexpf, frexpl - convert floating-point number to fractional and integral components

## SYNOPSIS

**#include <math.h>**

**double frexp(double** *x***, int ****exp***);**

float frexpf(float *x***, int ****exp***);**

long double frexpl(long double *x***, int ****exp***);**

Link with *-lm*.

Feature Test Macro Requirements for glibc (see **feature_test_macros(7)**):

**frexpf**(), **frexpl**():

_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L

|| /* Since glibc 2.19: */ _DEFAULT_SOURCE

|| /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

## DESCRIPTION

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

## 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 *exp*.

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

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

## ERRORS

No errors occur.

## ATTRIBUTES

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

## CONFORMING TO

C99, POSIX.1-2001, POSIX.1-2008.

The variant returning *double* also conforms to SVr4, 4.3BSD, C89.

## 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 <math.h>

#include <float.h>

#include <stdio.h>

#include <stdlib.h>

int

main(int argc, char *argv[])

{

double x, r;

int exp;

x = strtod(argv[1], NULL);

r = frexp(x, &exp);

printf("frexp(%g, &e) = %g: %g * %d^%d = %g\n",

x, r, r, FLT_RADIX, exp, x);

exit(EXIT_SUCCESS);

}

## SEE ALSO

**ldexp(3)**, **modf(3)**

## COLOPHON

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