memoize

[bearophile]

Andrei:

> Often you want to say "this entity is pure/const/immutable/safe... if 
> this other entity is the same, or generally if this Boolean is true". So 
> I was thinking of introducing e.g. a constrained pure:
> 
> template memoize( alias fn ) {
>      pure(isPure!fn) auto memoize( ParameterTypeTuple!fn ) {
>          ...
>      }
> }

http://d.puremagic.com/issues/show_bug.cgi?id=5125

Bye,
bearophile