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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(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600
       || _ISOC99_SOURCE; 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.

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);
       } /* main */

SEE ALSO

       ldexp(3), modf(3)

COLOPHON

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       description  of  the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.

                                  2008-10-29                          FREXP(3)