frexp(), frexpf()

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 );

float frexpf( float value, 
              int* exp );

Arguments:

value

The value you want to break into a normalized fraction.

exp

A pointer to a location where the function can store the integral power of 2.

Library:

libm

Use the -l m option to qcc to link against this library.

Description:

These functions break a floating-point number into a normalized fraction and an integral power of 2. It stores the integral power of 2 in the int pointed to by exp.

Returns:

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 <stdlib.h>
#include <math.h>

int main( void )
{
    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 );

    return EXIT_SUCCESS;
}

produces the output:

0.531250 3
-0.531250 3

Classification:

ANSI, POSIX 1003.1

See also:

ldexp(), modf()