frexp, frexpf, frexpl - convert floating-point number to fractional and integral
components
#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
These functions are used to split the number
x into a normalized fraction
and an exponent which is stored in
exp.
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.
No errors occur.
For an explanation of the terms used in this section, see
attributes(7).
Interface |
Attribute |
Value |
frexp (), frexpf (), frexpl () |
Thread safety |
MT-Safe |
C99, POSIX.1-2001, POSIX.1-2008.
The variant returning
double also conforms to SVr4, 4.3BSD, C89.
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
#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);
}
ldexp(3),
modf(3)