[challenge] Bounded types

[Philippe Sigaud]

On Sun, Oct 10, 2010 at 23:24, Adam D. Ruppe <destructionator at gmail.com> wrote:
> I saw it on the Phobos list and whipped together a first try.

Cool! Thanks, Adam.

>        static string runCheckCode() { return q{
>                asm {
>                        jo overflow;
>                }
>                if(_payload < min) goto overflow;
>                if(_payload > max) goto overflow;
>
>                goto ok;
>
>                overflow:
>                        throw new BoundedOverflowException("Overflow at "~file~":"~to!string(line)~"
> (payload: " ~ to!string(_payload) ~ ")");
>                ok:
>                        ;
>                };
>        }

Could you explain what asm { jo overflow;} does?


>        T opBinary(string op, string file = __FILE__, int line = __LINE__)(T rhs) {
>
>        T opOpAssign(string op, string file = __FILE__, int line = __LINE__)(T rhs) {
>
>        T opAssign(T rhs, string file = __FILE__, int line = __LINE__) {
>
>        string toString() {
>
>        alias _payload this;

Yeah, this challenge is like re-inventing typedef. I wonder if most of
this code could be lift off to a mixin of its own, that we could use
for any type that wraps another one.


> It uses a mixin to do the check, so the jo instruction works so it catches
> wrapping overflow too.

Could you explain that part?



> I'm sure it is broken with types other than int right now, but it might be a
> starting point.

Some people downthread raise a point about performance. I don't have a
D compiler right now, do you think you could compare Bounded to a
regular int, for example?

Philippe