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():

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 thread-safe.

CONFORMING TO¶

C99, POSIX.1-2001. 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¶

This page is part of release 3.74 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at http://www.kernel.org/doc/man-pages/.