method hiding (or not) in derived classes
Perl 6 has a concept of a "candidate list". The candidate list are those that could handle the call, typically inherited methods and multi variations. It seems that multi variations, at least with respect to the semicolon parameters, compare the actual type and drop out of the list if any don't match. What about ordinary methods (and ordinary parameters of multis)? Does the candidate list hold every method name that matches, or does it do simpler parameter matching based on number of arguments, required named arguments, etc.? If that is the case, then a derived method might not hide a base class method if the parameter list is seriously incompatible. More interestingly, left-to-right ordering of multiply-inherited base classes will be checked for applicability rather than arbitrarily taking the leftmost. --John
Critisizms on postcircumfix:<( )>
I think the idea of "The expected semantics of &.() is that of a type
coercion..." confuses the notion of function call and conversion. If anything
other than a Code object has one, it is acting as a functor, or function-like
object. The meaning of Dog(args) is seemingly a class method anyway, not a
normal instance method. It was elsewhere said that the type name as a listop
indicates conversion. I think that should be taken to mean that the compiler
uses whatever form of conversion function is available. I think $obj(args)
should mean whatever I want it to mean, like any other function. An (untyped)
variable $obj can call &.() with the same syntax it does with an object of type
Code, no problem.
We already use the method .new to mean "create one of these using these
arguments". Sometimes that =is= logically a conversion. In C++ that is
assumed by default. So why make a different function with different syntax?
I propose that any method that is logically a "conversion" can be marked with a
property to say so, and the implementation will draw upon those when asked to
perform a conversion.
our C multi method ^new (D $oldguy) is conversion { ... }
(er, the default inherited .new doesn't prevent me from making a multi new in
my class, right?)
Now I can say $c = C.new($d); and if I ever say $c = C $d; or my C $c = $d;
it will know that this is the function to call.
--John
