On Monday, 3 July 2017 at 03:50:14 UTC, Saurabh Das wrote:
Consider this snippet:
void main()
{
import std.stdio;
auto a = 6.2151;
auto b = a * 10000;
auto c = cast(ulong)b;
writeln("a: ", typeof(a).stringof, " ", a);
writeln("b: ", typeof(b).stringof, " ", b);
writeln("c: ", typeof(c).stringof, " ", c);
auto x = 62151.0;
auto y = cast(ulong)x;
writeln("x: ", typeof(x).stringof, " ", x);
writeln("y: ", typeof(y).stringof, " ", y);
}
The output is:
a: double 6.2151
b: double 62151
c: ulong 62150
x: double 62151
y: ulong 62151
Why does c round off from 62151 to 62150 when casting to ulong?
Thanks,
Saurabh
6.251 has no perfect double representation. It's real value is:
6.21509999999999962483343551867E0
Hence when you cast to ulong after the product by 10_000, this is
the equivalent of
trunc(62150.9999999999962483343551867E0)
which gives 62150
CQFD ;-]
