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frexpl

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

This page is part of release 3.24 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/.