HIWORD with negative values

[Derek Baker]

Can anyone tell me why y2 and y3 give different results, when y prior to shifting is negative (as in the values below)?

#include <cstdlib>
#include <iostream>

using namespace std;

int main()
{
    int iVertPos = 7;
    int yCaret = 7;
    int cyChar = 13;
    
    int y;
   
    y = (yCaret- 1- iVertPos) * cyChar;
    y = y << 16;
   
    int y2 = iVertPos + (HIWORD(y)) / cyChar;
    int y3 = iVertPos + (y >> 16) / cyChar;
   
   
    cout << "y: " << y << endl;
    cout << "y2: " << y2 << endl;
    cout << "y3: " << y3 << endl;
   
    cout << endl << endl;
    system("PAUSE");

return 0;
}

Thanks

Derek

[Derek Baker]

Sorted it out: dug out the answer on usenet.

Apparently HIWORD returns an unsigned word, so obviously wouldn't handle my negative value.

Casting to short does the trick:

y = iVertPos + (short(HIWORD(lParam)) / cyChar);

Derek