# FREXP

NAME

SYNOPSIS

DESCRIPTION

RETURN VALUE

ERRORS

ATTRIBUTES

CONFORMING TO

EXAMPLE

SEE ALSO

COLOPHON

## 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 versions <= 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.

## EXAMPLE

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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