sunfloor_stripped

// floor(x)
// Return x rounded toward -inf to integral value
// Method: Bit twiddling.
// Exception: Inexact flag raised if x not equal to floor(x)

#include <iostream>
#include <bitset>
using namespace std;

double florr(double x)

{
    int i0,i1,j0;

    unsigned int i;

    i0 =  *(1 + (int*)&x);

    i1 =  *(int*)&x;

    j0 = ((i0 >> 20) & 0x7ff) - 0x3ff;

    i = (0x000fffff) >> j0;

    i0 += (0x00100000) >> j0;

    i0 &= (~i);

    i1=0;

    *(1 + (int*)&x) = i0;

    *(int*)&x = i1;

    return x;

}

int main() {

    double x = -4.5; // 11000000 00010010 00000000 00000000 00000000 00000000 00000000 00000000

    double y = florr(x);

    cout << "the floor of " << x << " is " << y << endl; // Prints -5

    return 0;
}