On 05/01/2007 12:29 PM, Martin Rubey wrote:
> Ralf Hemmecke <[EMAIL PROTECTED]> writes:
>
>> I wonder why
>>
>> > getit(T: Category, L: Tuple T, i: MachineInteger): T == add {
>> > import from Tuple T;
>> > element(L, i);
>> > }
>>
>> compiles.
>>
>> add {...} is an anonymous domain, that exports *nothing*. T is a category.
>
> I do not understand. In what way is that different from
>
> CharacteristicSpecies(n:Integer)(L:LabelType): CombinatorialSpecies L == add {
> Rep == SetSpecies L;
> import from Rep;
> nn: I == machine n;
> <<implementation: CharacteristicSpecies>>
> }
>
> ??? I would have thought that CombinatorialSpecies L is also a category. Take
> the example
>
> getit(OutputType, (Boolean, Integer), 1)
>
> I would expect that it returns a domain of type OutputType, which happens to
> be
> Boolean, although we do not export that knowledge.
Oh, I am terribly sorry, I must have been totally unawake. Of course
your getit returns a domain. But still, I don't know why it compiles.
As I said. Your "add {...}" thing considered as an anonymous domain
exports *nothing*. Since putting into a context
A: CatA == add {...}
can only make the list of exports smaller. So that construction can
never have any export.
What you probably want is
getit(T: Category, L: Tuple T, i: MachineInteger): T == {
import from Tuple T;
element(L, i);
}
without the "add" or perhaps (if the former does not work) somthing like
... == {
import from Tuple T;
element(L, i) add;
}
but I don't know whether that is something that is supposed to work.
Note that "A with {B}" is equivalent to "with {A; B}", but that does not
apply if you replace "with" by "add".
Ralf
PS: What you do is to construct a domain whose exports are computed at
runtime. There should be no problem, but if you look at some references
at Axiom-Portal, there are some papers that discuss the semantics of
runtime-computed categories.
Ralf
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