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Opposite signs

General and Gameplay Programming Programming

Started by Stonicus March 23, 2004 04:08 PM

2 comments, last by Stonicus 20 years ago

Stonicus

157

Author

March 23, 2004 04:08 PM

What''s the most efficient way to determine if two integers are of different signs?


bool DiffSigns(int i, int j)
{
  if(((i > 0) && (j < 0)) || ((i < 0) && (j > 0)))
    return true;
  return false;
}

This will work, it''s the first function that comes to mind (it ignores the zero case as the purpose I need it for will handle it ahead of time) but it seems there is always a more efficient way than the first method you can think of. So any ideas?

Oluseyi

2,123

March 23, 2004 04:15 PM

bool diffSigns(const int a, const int b){  return bool(int(a < 0) ^ int(b < 0));}

Evil, but it works.

[edited by - Oluseyi on March 23, 2004 5:18:26 PM]

LousyPhreak

133

March 23, 2004 04:23 PM

bool DiffSigns(int i, int j){  return (bool)((i^j)&0x8000000)}

now THAT''s evil

(should work assuming the compiler takes all non 0 values as true)

http://mitglied.lycos.de/lousyphreak/

dalleboy

324

March 23, 2004 04:31 PM

Not as evil...

bool diffSigns(const int a, const int b)
{
   return (a < 0) != (b < 0);
}

[edited by - dalleboy on March 23, 2004 5:32:01 PM]

Opposite signs

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Opposite signs

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