Calculation problem?

[zenox0]

Hey, im having a problem with a calculation. This is a sample of the code:

void main()
{
   double a = 1.16 / 1.45 * 1000.0;
   double b = 800.0;

   if ( a == b )
      printf("a equals b");
}

Now.. if you calculate this.. a = 800. and b = 800.
However.... the statement if ( a == b ) returns false.

Can anyone tell me why?

 

[drewdaman]

comparing doubles is a tricky business.. if even one digit is different, it will not eval to true... you should find a mechanism to set the precision you want.

 

[uolj]

Check out this link in the FAQ-Lite:

http://www.parashift.com/c++-faq-lite/newbie.html

and click on 29.17 for some insight on your problem and potential fixes.

 

[GMX]

Try to cout a and b as decimals and as hex values.