a FOR loop and floating variables

[Martin Drašar]

Dne 2.5.2013 20:14, Carlos napsal(a):
> I have this code :
>
> import std.stdio;
> import std.c.stdlib;
> void main()
> {
> int fahr;
> write("F\tC\n");
> for (fahr = 0; fahr <= 300; fahr = fahr + 20)
> write(fahr, "\t", (5.0/9.0)*(fahr-32), "\n");
> write("Done!\n");
> exit (0);
> }
>   Which works. but if I change the "5.0" for "5" I get cero on the
> celsius side.
>
> import std.stdio;
> import std.c.stdlib;
> void main()
> {
> int fahr;
> write("F\tC\n");
> for (fahr = 0; fahr <= 300; fahr = fahr + 20)
> write(fahr, "\t", (5/9)*(fahr-32), "\n");
> write("Done!\n");
> exit (0);
> }
>
> So why is this ?

Hi Carlos,

the second code performs integral division which very much behave like 
floating-point division, but the fractional part is chopped off.

  5/9 ~ 0.556 => 0
10/9 ~ 1.111 => 1

If you want precise (i.e. floating point) results, you have to have at 
least one float or double in your equation.

This would work:

write(fahr, "\t", (5.0/9)*(fahr-32), "\n");

Regards,
Martin