Maybe the following piece of code is interesting. If one wraps "element" thick
enough, one can use dependent types. Aldor does not realize though that
getit(OutputType, ...) has OutputType.
#include "aldor"
#include "aldorio"
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;
}
------------------------------------------------------------------
getit(T: Category, L: Tuple T, i: MachineInteger): T == add {
import from Tuple T;
element(L, i);
}
MyTuple(T: Category, L: Tuple T): with {
new: List Object -> %;
get: (i: MachineInteger, %) -> getit(T, L, i);
} == add {
Rep == List Object;
import from Rep;
new(a: List Object): % == per a;
get(i: MachineInteger, x: %): getit(T, L, i) == {
X: List Object := rep x;
(U, u) == avail(X.i);
u pretend getit(T, L, i);
}
}
------------------------------------------------------------------
import from Integer, Object, List Object, Boolean, MachineInteger;
t: Tuple OutputType == (Integer, Boolean);
li : List Object := [object(Integer, 17), object(Boolean, true)];
m: MyTuple(OutputType, t) == new li;
p: getit(OutputType, t, 1) := get(1, m)$MyTuple(OutputType, t);
stdout << p pretend Integer << newline;
-- note that the following results in an "export not found":
-- if getit(OutputType, t, 1) has OutputType
-- then stdout << p << newline;
------------------------------------------------------------------
all the best,
Martin
-------------------------------------------------------------------------
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