[Qt-interest] Why 1/255 is 0 ?

[Dan White]

You are missing the significance of math operations with integers as opposed to floating point numbers.

Integer 1 / integer 255 = 0
1.0 / 255.0 = 0.003921569

the definition for the function you are using is qreal qPow ( qreal x, qreal y )

So your statement should read:
qPow( (qreal(i)/255.0),qreal(j) );

j/1 is wasted operation.

“Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us.”
Bill Waterson (Calvin & Hobbes)

----- Hannu Shemeikka <hps at shemeikka.org> wrote:
> Hi,
> 
> Could someone explain me this:
> 
> double c = 1/255; 
> 
> and c is 0 after watching it in debugger. It should be 0,003921569.
> I tried float and few others but no success.
> 
> The real thing where I need that division is qPow((i/255),(j/1)); //
> i<255 and j<8
> 
> What am I missing here? I'm using Ubuntu 10.10 and Qt 4.7
> 
> - Hannu
> 
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