Programming tricks (and former trade secrets)

[PhilBot]

Originally Posted by WesleyC

The code goes something like this:

output = (input * input / 127) * (input > 0) ? 1 : -1;

This is a great piece of math, but when I tried it, it didn't work...
It only served to reinforce my motto "when in doubt, add parenthesis".

It appears that the compiler gives greater precedence to * than it does to ?

So what the code was doing was this:

output = ((input * input / 127) * (input > 0)) ? 1 : -1;

not this:

output = (input * input / 127) * ((input > 0) ? 1 : -1);


As written, the code only returned +/- 1. With parenthesis added as in the second example, the code did what was intended.

The other cool by-product of this code is that it adds in a small dead-band to the joystick. Any offset less than 13 returns a zero after interger math truncation.