[Aldor-l] Special casing...

[Christian Aistleitner]

Hello,

> do you think that something like (i.e., achieving the same or a similar  
> effect as) the following is possible in Aldor (or in improved SPAD):
>
> I'd like the compiler to allow something like
>
> ---------------------------------------------------------------------------
> f(a: S): T == { generic implementation }
>
> f(specialValueOfTypeS): T == { special implementation for  
> specialValueOfTypeS }
> f(otherSpecialValueOfTypeS): T == { special imp. for  
> otherSpecialValueOfTypeS }
>
> g(c: T, d: T): T == { ... f(c) ... f(d) ...}
> ---------------------------------------------------------------------------
>
> So, if c happens to be specialValueOfTypeS, then the special  
> implementation is
> used, and so on.

without further machinery, I'll doubt that this is possible. And I  
strongly disadvise you to use such a design.
You are mixing different programming paradigms here. But I am sure you  
thought about this problem and the arising confusion and problems.

If your domain S provides equality checks (PrimitiveType for Aldor), you  
can get something not too far from what you wanted to have while still  
being extensible. For example by using dictionaries (the value of s being  
the key and the various special implementations of f the values). Hiding  
the use of dictionaries within macros should give you the possibility to  
cancel them out and eliminate the overhead, if Aldor chooses to allow  
this  type of programming.
Whether such a design is really applicable depends on how badly you need  
extensibility.

Kind regards,
Christian