Is this a bug or did I misunderstood arithmetic or cast()?

cast(int)(-5 * 1 * 0.41));  // result: -2
cast(int)(-5 * 1u);         // result: -5
cast(int)(-5 * 1u * 0.41)); // result: 1760936589

The last result seems strange to me. I use dmd 1.005.

Henning

Henning Hasemann wrote:
> Is this a bug or did I misunderstood arithmetic or cast()?
> 
> cast(int)(-5 * 1 * 0.41));  // result: -2
> cast(int)(-5 * 1u);         // result: -5
> cast(int)(-5 * 1u * 0.41)); // result: 1760936589
> 
> The last result seems strange to me. I use dmd 1.005.

This is caused by the type conversion rules: typeof(-5 * 1u) == uint, so -5 * 1u * 0.41 == cast(uint)-5 * 0.41 == 0xfffffffb * 0.41 == 1760936589.31 which rounds to 1760936589 when cast to an int.