On 6/1/15 5:29 PM, Oleg B wrote:
Hello. I found unexpected (for me) behavior of rounding double values at
casting to ulong:
$ cat roundtest.d
import std.stdio;
void main()
{
double a = 10, b = 0.01;
writeln( "int: ", cast(int)(a/b) );
writeln( "uint: ", cast(uint)(a/b) );
writeln( "long: ", cast(long)(a/b) );
writeln( "ulong: ", cast(ulong)(a/b) );
}
$ rdmd roundtest.d
int: 1000
uint: 1000
long: 1000
ulong: 999 <----- WTF?? -------
These are NOT roundings. They are truncations.
Note that for floating point 0.01 is not representable exactly. This is
the reason you get the error. On other systems, you may not get errors
for this one case, but you could get errors for other. Please read about
floating point error:
http://en.wikipedia.org/wiki/Floating_point#Accuracy_problems
-Steve
