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; 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 = %g0, x, r, r, FLT_RADIX, exp, x); exit(EXIT_SUCCESS); } /* main */

SEE ALSO ldexp(3), modf(3)

COLOPHON This page is part of release 3.22 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at

2008-10-29 FREXP(3)