Compile-time exceptions

[Denis Koroskin]

On Mon, 24 Nov 2008 13:15:36 +0300, bearophile <bearophileHUGS at lycos.com>  
wrote:

> This is a generic example of a small function template (it's similar to  
> a function with the same name in Mathematica. It that returns the result  
> of the callable 'func' applied n times to 'item'):
>
>
> TyItem nest(TyFun, TyItem)(TyFun func, TyItem item, int n) {
>     static assert(IsCallable!(TyFun), "nest(): func must be a callable");
>     static assert(CastableTypes!(ReturnType!(TyFun), TyItem),
>                   "nest(): func must return a type castable to item.");
>     if (n < 0)
>         throw new ArgumentException("nestList(): n must be >= 0");
>
>     for (int i = 1; i <= n; i++)
>         item = func(item);
>     return item;
> } // End of nest()
>
>
> Its unit tests contain the following stuff too, because raising that  
> exception is part of the user interface of that function:
>
> unittest {
>     ...
>     assert(Throws!(ArgumentException)(nest(&sin, 0.1, -1)));
>     ...
>     //nest("hello", 0.1, -1); // static asserts
>     ...
> }
>
> (I'm waiting to have a better Throws!() in the std lib that doesn't  
> require to be put into an assert()).
> But at the moment I haven't found ways to unit test the first two static  
> asserts, so I just put tests in the unittest for them, and I comment  
> them out to make the unittest run.
>
> That problem may be solved with a "static try" and "static catch", that  
> work at compile time :-)
> (I think this isn't related with the Java static exceptions).
>
> static try
>     deleg();
> static catch (StaticAssert a) {
>     ...
> }
>
> Bye,
> bearophile

This has already been discussed:
http://digitalmars.com/d/archives/digitalmars/D/static_try_catch_construct_would_be_helpful_66794.html