[Aldor-l] Special casing...

[Martin Rubey]

Dear Christian, Dear Gaby,

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.

As criterion for equality, identical memory location would be sufficient for
me. Of course, f should be allowed to be type-valued.

In the axiom interpreter, the above is allowed for ordinary functions, i.e.,
functions that return an element of a domain.

For example, one can define

f: Integer -> Integer
f 0 == 1
f 1 == 1
f n == f(n-1) + f(n-2)

I guess it is possible to define

f(a: S): T == { 
    if a = specialValueOfTypeS then 
        { special implementation for specialValueOfTypeS }
    else if a = otherSpecialValueOfTypeS then 
        { special imp. for otherSpecialValueOfTypeS }
    else { generic implementation }
}

but this would not really be very extensible...

Martin