# frexp

```FREXP(3)                   Linux Programmer's Manual                  FREXP(3)

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);

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  frac-
tion 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 (nega-
tive 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  at-
tributes(7).

+----------------------------+---------------+---------+
|Interface                   | Attribute     | Value   |
+----------------------------+---------------+---------+
|frexp(), frexpf(), frexpl() | Thread safety | MT-Safe |
+----------------------------+---------------+---------+
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);
}