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

NAME         top

       frexp,  frexpf, frexpl - convert floating-point number to fractional and inte-
       gral components

SYNOPSIS         top

       #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         top

       The frexp() function is used to split the number x into a normalized fraction
       and an exponent which is stored in exp.

RETURN VALUE         top

       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         top

       No errors occur.

CONFORMING TO         top

       C99, POSIX.1-2001.  The variant returning double also conforms to SVr4,
       4.3BSD, C89.

EXAMPLE         top

       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         top

       ldexp(3), modf(3)

COLOPHON         top

       This page is part of release 3.32 of the Linux man-pages project.  A
       description of the project, and information about reporting bugs, can be found
       at http://www.kernel.org/doc/man-pages/.

                                      2010-09-20                             FREXP(3)

HTML rendering created 2010-12-03 by Michael Kerrisk, author of The Linux Programming Interface

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