Re: [Toss-devel] Hierarchical Terms with Sharing

[Lukasz K. <luk...@gm...>]

Hi.

> I'm sorry, I still haven't finished the example with generating the
> board. In the drafts I have a description of matching as an algorithm
> to compute "ISA", therefore rewriting can be based on computing
> "subterm ISA pattern".

In the future, sure - but I think for now the rewriting we have is quite ok, no?

> As for "Var", it has so many parameters to be compatible with the
> current system, right? In the end it will most probably be "Var of
> string * term option ref". See "Term Rewriting and All That" section
> 4.8 "Unification of term graphs".

Just the contrary - the parameters of the variable are necessary,
also in principle, in any system I think. The reason is that we have
functional variables - and we certainly want them (map, fold, etc :).)
So variables take parameters when the var-function is applied, and
it must be like this. And the integer - current arity - is just to know if
we have a ternary function fully applied or rather a ternary function but
still as a functional variable - unapplied. Maybe this could be removed,
but I see no reason - it does not cost much, and is really useful some
times. So I guess the variables have to be like that. And maybe there
is some use of functional variables in the type system, or maybe not?

Lukasz