Larry Wall wrote:
Anyway, I think the type constructors need to avoid overloading the
logic operators. Perl 6 is an operator-rich language because that
contributes to long-term clarity despite the short-term confusion.
OK. My main dog in this race is the idea of defining new roles
through the concepts of the intersection or difference between
existing roles (even the union was thrown in there mainly for the sake
of completion), with the consequent extension of the type system in
the opposite direction from the usual one (toward the more general);
the exact syntax used for this is less of an issue, as long as it is
straightforward and simple. Given that the set analogy is exactly
what I'm using, I'd be fine using the Set operators (presumably '\xAD\xFC'
and '\xAD\xFB') and their ASCII workarounds ('(|)' and '(&)'?) instead of '|'
and '&'. Presumably, '-' is still the "difference of Sets" operator.
And yes, this "roles as sets" paradigm would presumably mean that you
could examine roles using '⊂', '⊃', '∈', and so on. Given the
semantic aspect of roles, I don't think that I'd go along with saying
that 'A ⊃ B' is equivalent to 'A.does(B)' - although I _would_ agree
that if 'A.does(B)' then 'A ⊃ B'. Rather, I'd think of 'A ⊃ B' as
being the means that one would use for duck-typing, if one really
wanted to (presuming that one can mess with how perl 6 does
type-checking).
Likewise, 'm ∈ R' will match if 'R.can(m)'; but the definition of
'element' might be broader than just methods.
--
Jonathan "Dataweaver" Lang
