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FREXP
Linux Programmer's Manual (3)
20130806
NAME
frexp, frexpf, frexpl  convert floatingpoint 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():

_BSD_SOURCE  _SVID_SOURCE  _XOPEN_SOURCE >= 600  _ISOC99_SOURCE 
_POSIX_C_SOURCE >= 200112L;
or
cc std=c99
DESCRIPTION
The
frexp()
function is used to split the number
x
into a
normalized fraction and an exponent which is stored in
exp.
RETURN VALUE
The
frexp()
function returns 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
Multithreading (see pthreads(7))
The
frexp(),
frexpf(),
and
frexpl()
functions are threadsafe.
CONFORMING TO
C99, POSIX.12001.
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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Index
 NAME

 SYNOPSIS

 DESCRIPTION

 RETURN VALUE

 ERRORS

 ATTRIBUTES

 Multithreading (see pthreads(7))

 CONFORMING TO

 EXAMPLE

 Program source

 SEE ALSO

 COLOPHON

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