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frexp (3)
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.
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). If x is zero, then the normalized fraction is zero and zero is
stored in exp.
CONFORMING TO
SVr4, 4.3BSD, C89. The float and long double variants are C99 require-
ments.
EXAMPLE
#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 */
This program 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
SEE ALSO
ldexp(3), modf(3)
2002-07-27 FREXP(3)
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