Martin,
> The only slight awkwardness I can imagine is as follows: If I export, say, in
> Polynomial
>
> coefficientRing: () -> Ring
>
> then the result of baseRing will be a Ring, and may have "forgotten" all the
> other categories it possibly satisfies. Hm, it seems I will never understand
> "has" completely - Ralf, could you remind me why the following output is
> produced by Aldor?
Maybe you google for something like
+"static type" +"dynamic type" +aldor
Christian's remarks should be correct.
It is as simple as this: with "has" you refer to all the exports of a
domain. So if
A: with {foo: () -> ()} == add {foo(): () == {}}
B: with {bar: () -> ()} == A add {bar(): () == {}}
then B (statically) only exports bar, but if you look at the right hand
side of the definition of B then there is a (anonymous) domain
A add {bar(): () == {}}
which is of type
with {
foo: () -> ()
bar: () -> ()
}
and all this can be seen by "has" from B, too.
So
B has with {foo: () -> ()}
returns true.
I don't say that I like that since one can easily produce code that
looks typesafe but is completely wrong (see end of mail). Note that
suddenly, -1 is a member of NNI.
Ralf
---BEGIN HasSemantics.as
#include "aldor"
#include "aldorio"
NNI: with {
+: (%, %) -> %;
coerce: Integer -> %;
<<: (TextWriter, %) -> TextWriter;
} == Integer add {
Rep == Integer;
import from Rep;
coerce(x: Integer): % == per x;
(p: TextWriter) << (x: %): TextWriter == p << rep x;
}
main(): () == {
import from Integer;
stdout << "NNI has with -: % -> % ---- ";
stdout << (NNI has with {-:%->%}) << newline;
a: NNI := 1::NNI;
if NNI has with {-:%->%} then {
b: NNI := -a;
stdout << "-([EMAIL PROTECTED]) = " << b << newline;
}
stdout << "INT has IntegerType --- ";
stdout << (Integer has IntegerType) << newline;
stdout << "NNI has IntegerType --- ";
stdout << (NNI has IntegerType) << newline;
stdout << "NNI has OrderedArithmeticType --- ";
stdout << (NNI has OrderedArithmeticType) << newline;
stdout << "NNI has with <: (%,%) -> Boolean ---- ";
stdout << (NNI has with {<:(%,%)->Boolean}) << newline;
}
main();
---END HasSemantics.as
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