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

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 || _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  (exclu-
       sive), 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 (nega-
       tive 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);
       }
SEE ALSO
       ldexp(3), modf(3)
COLOPHON
       This page is part of release 3.53 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)