frexp()

break a floating-point number into a normalized fraction and an integral power of 2

Synopsis:

#include <math.h>
double frexp( double value, int *exp );

Description:

The frexp() function breaks a floating-point number into a normalized fraction and an integral power of 2. It stores the integral power of 2 in the int object pointed to by exp.

Returns:

The value of x, such that x is a double with magnitude in the interval [0.5, 1) or 0, and value equals x times 2 raised to the power *exp. If value is 0, then both parts of the result are 0.

Examples:

#include <stdio.h>
#include <math.h>

void main()
  {
    int    expon;
    double value;

    value = frexp(  4.25, &expon );
    printf( "%f %d\n", value, expon );
    value = frexp( -4.25, &expon );
    printf( "%f %d\n", value, expon );
  }

produces the output

0.531250 3
-0.531250 3

Classification:

ANSI

See also:

ldexp(), modf()