Hi Martin,
I haven't tested it, but that should somehow work.
printObject(tw: TextWriter)(T: PrimitiveType, t: T): TextWriter == {
if T has OutputType then tw << t else tw << "<unprintable>";
}
printObjects(l: List Object): () == {
for x in l repeat printObject(stdout)(avail x);
}
Does that mean that one cannot access the element? I am pretty sure that
your "problem" is a non-problem.
And if I remember correctly what we talked about today, then the use of
Object in FiniteProduct might involve some "pretend", but that would be
local to that domain. Wait a bit until I find some time to actually
implement what we have discussed today.
Ralf
On 04/30/2007 09:03 PM, Martin Rubey wrote:
> Dear Christian, Ralf,
>
> I just realized what sort of problem I had with my code below, and what might
> pose a difficulty in future: namely, we cannot "deconstruct" an element of
> this
> type. More precisely:
>
> Object: with {
> object: (T: PrimitiveType, T) -> %;
> avail: % -> (T: PrimitiveType, T);
> }
> == add {
> Rep == Record(T: PrimitiveType, val: T);
> import from Rep;
> object (T: PrimitiveType, t: T) : % == per [T, t];
> avail (ob: %) : (T: PrimitiveType, T) == explode rep ob;
> }
>
> Multiset(T: Type, L: Tuple T): with {
> new: List Object -> %;
> get: (i: MachineInteger, %) -> Object;
> } == add {
> Rep == List Object;
> import from Rep;
> new(a: List Object): % == per a;
> get(i: MachineInteger, x: %): Object == {
> X: List Object := rep x;
> X.i;
> }
> }
>
> works, but, as you can see, we can only "get" an Object, not the element
> itself.
>
> I'm not sure whether this is a problem, however.
>
> All the best,
>
> Martin
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