Disable implicit conversion

[Stewart Gordon]

On 07/03/2011 16:40, Jesse Phillips wrote:
> KennyTM~ Wrote:
>
>> On Mar 7, 11 18:33, Eugene wrote:
>>> Hi!
>>>
>>> What I want to do is pretty simple.  I need to subtract a ubyte from a
>>> ubyte and store the result in a ubyte.  The problem is that DMD
>>> implicitly wants to convert the ubytes into an integer, so it fails
>>> when attempting to store the result into a ubyte.  (Int cannot be
>>> converted to ubyte?)

I've been bitten by that annoyance while doing Java stuff in the past.
http://d.puremagic.com/issues/show_bug.cgi?id=1977

<snip>
> Not only that but the operation isn't any safer than a cast, if overflow didn't matter
> and you just need it to fit then this would be good.
>
> Lastly overflow does matter and if it happens the code will continue to silently work.
> I recommend using std.conv.to because it will throw an exception if an overflow were to
> happen.

If overflow of a ubyte matters, surely so does overflow of an int or long?

In the OP's case, the only possible overflow is a negative result.  As such, if overflow 
matters, one will do something like

     if (u2 < u1) {
         // ...
     } else {
         u3 = cast(ubyte) (u2 - u1);
     }

For such simple cases as this, using a library function to convert an overflow into an 
exception might be overkill.

Stewart.