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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():
       _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L
           || /* Since glibc 2.19: */ _DEFAULT_SOURCE
           || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION

   These functions are used to  split  the  number  x  into  a  normalized
   fraction and an exponent which is stored in exp.

RETURN VALUE

   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.

ERRORS

   No errors occur.

ATTRIBUTES

   For  an  explanation  of  the  terms  used   in   this   section,   see
   attributes(7).

   
   Interface                    Attribute      Value   
   
   frexp(), frexpf(), frexpl()  Thread safety  MT-Safe

CONFORMING TO

   C99, POSIX.1-2001, POSIX.1-2008.

   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 4.09 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
   https://www.kernel.org/doc/man-pages/.

                              2016-03-15                          FREXP(3)



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