> How come last one should be same? Aren't they different types? I'd expect
> `Array[Int] ~~ Positional[Numeric]` to give False
They are different types, but one could logically be considered a "subtype" of
the other (and would be in some programming languages).
E.g. in C#, a class Foo which takes a type parameter can define whether it
wants to be, with regard to that parameter (using Perl 6 notation):
covariant: Foo[Dog] ~~ Foo[Animal]
contravariant: Foo[Animal] ~~ Foo[Dog]
invariant: neither
(Or at least that's how I understand it, I'm just starting to learn C#.)
It appears that in Perl 6, currently only *Invariance* is supported for
parameterized types.
Whether that is a conscious design choice ("keeping it simple"), or something
that might be extended in the future given sufficient demand/tuits, is
something that jnthn should be able to answer, since if I'm not mistaken he's
done much of the Perl 6 OO work and is also a C#/Java expert.
