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 (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
",
		  x, r, r, FLT_RADIX, exp, x);
	   exit(EXIT_SUCCESS);
       }

SEE ALSO

       ldexp(3), modf(3)

COLOPHON

       This page is part of release 3.44 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)