Eliminate assert and lazy from D?

[Robert Jacques]

On Tue, 13 Oct 2009 00:33:57 -0400, Andrei Alexandrescu  
<SeeWebsiteForEmail at erdani.org> wrote:

> Right now, the language has enough power to express assert as a library  
> function, as opposed to a primitive construct. (See e.g. enforce.) I  
> think it would be good to relegate assert to object.d.
>
> This also brings up "lazy", which seems to be quite botched. Are there  
> suggestions on how to replicate its functionality in a different way? I  
> even seem to recall lazy was discussed as a disadvantage in the recent  
> dialog on reddit, see
>
> http://www.reddit.com/r/programming/comments/9qf8i/i_wrote_some_d_today_and_its_completely_blowing/
>
> I personally believe it's useful to be able to pass an unevaluated  
> expression into a function, for example assert and enforce themselves  
> use that.
>
> But let's open this for discussion: should assert and/or lazy be  
> removed? If not, why not? It yes, why? How can we replicate their  
> functionality?
>
>
> Andrei

Well, a lazy 'variable' is really a delegate of an expression, so implicit  
conversion of an expression to a delegate would be one way to remove lazy.  
(Not sure how practical/easy that is though)

And then assert (I think) becomes

void assert( bool delegate() expr, string delegate() msg ) {
     debug {
         if(!expr)
             throw new Exception(msg);
     }
}