On Wed, Oct 27, 2004 at 01:19:29PM -0600, Luke Palmer wrote: > Stéphane Payrard writes: > > That would allow to implement typechecking in imcc. > > > > .sym Scalar a > > a = new .PerlInt # ok. Perlint is derived from Scalar > > Ugh, yeah, but what does that buy you? In dynamic languages pure > derivational typechecking is very close to useless. The reason C++[1] > has pure derivational semantics is because of implementation. The > vtable functions have the same relative address, so you can use a > derived object interchangably. In a language where methods are looked > up by name, such strictures are more often over-restrictive than > helpful.
So, still thinking (too?) statically, I should probably worry about what "does" a pmc instead on what it is derived from. In that case, I would not have to worry about abstract pmc classes. So abstract classes missing from the enum of core_pmcs.h, which prompted that subthread, becomes a moot point. > > Anyway, that's just my rant. If such a thing is to be in imcc, it > _must_ be optional without loss of feature. I have quibble with the > automatic typechecking of .param variables for the same reason. Declaring a symreg just as a pmc would do that anyway. > > Luke > > [1] And the reason Java has it is because C++ did. Great design work, > guys. > -- stef
