[Aldor-l] Using Aldor or SPAD

[Ralf Hemmecke]

> The only thing I know of the Aldor compiler
> is that long time ago my "intern-mate" Yannis was working on it at
> Sophia Antipolis...

Ah, Yannis Chicha worked with you... This world is so small...

> | I think we should not wait any longer. I'm currently interested in two
> | projects:
> | 
> | * species, together with Ralf and Nicolas
> | 
> | * symmetric functions
> | 
> | Both of these projects depend *heavily* on types being first class
> | objects, and on allowing dependent types. Both of these features are
> | missing in SPAD. 
> 
> Indeed.  You have mentioned dependent types many times.  I would like
> to know more about what you mean.  For example, if we go full
> dependent types, I suspect it would be very difficult to evaluate
> all categories at compile-time.  So, I'm interested in the kind of
> dependency you want.

Currently, in aldor-combinat I am going to define something like...

define CombinatorialSpecies(L: LabelType): Category == with {
         <<exports: CombinatorialSpecies>>
}
CharacteristicSpecies(n:Integer)(L:LabelType): CombinatorialSpecies L == 
add {
         Rep == Set L;
         import from Rep;
         <<implementation: CharacteristicSpecies>>
}
EmptySetSpecies(L: LabelType): CombinatorialSpecies L == {
         CharacteristicSpecies(0$Integer)(L) add;
}

As you see, EmptySetSpecies is a function and its result type depends on 
its input type L.

But I think what you mention about categories is not really connected to 
dependent or not dependent types. I actually don't know how one can 
construct a category at runtime and later use it.

For example,

define Cat: Category == if odd? random() then {with {foo: () -> ()}}
                                          else {with {bar: () -> ()}}

I could define a domain

Dom: Cat == add {
    foo(): () == {}
    bar(): () == {}
}

But how would I use it? At compile time the compiler cannot decide whether

foo()$Dom;

is actually available.

> [ For example, C++ has dependent types at its "template systems" but
>   values are limited to integers and addresses of toplevel entities ]

Could you provide some example code? A link?

> | In fact, there are two things missing in Axiom:
> | 
> | 1) a replacement for SPAD that allows one to use the Aldor language

> Can anyone familiar with integrating SPAD with foreign languages
> educate me about the thorny issues?

What exactly do you mean here?

Ralf