Re: [Axiom-mail] Equivalence between named domain and %

[Gabriel Dos Reis]

Waldek Hebisch <address@hidden> writes:

| Gabriel Dos Reis wrote:
| > If my understanding is correct, this problem touches upon the fact
| > that the SPAD compiler does not know (at the moment) how to properly
| > resolve recursive declaration/definitions of types.  Is that correct?
| > 
| > Since, under the hood, almost everything is a pointer, why is the
| > compiler having trouble admitting recursion?
| > 
| 
| AFAICS Spad types are global and separately compiled. Recursive
| dependencies are painful when you want separate compilation.

I don't think so.  This is recursive definition in the *same unit*.

Check out Haskell, or  the excellent book
"The implementation of Functional Languages", by Simon Peyton Jones.

| Also, during type checking compiler traverses varoius links (references)
| between types -- on has to be careful to avoid infinite loops
| (and when loop is detected how to give sane semantic to the loop).

Yes, so?

| I am not sure if just telling "recursive type definitons are OK" is
| a good idea.  Some restrictions on recursion are clearily needed,
| and with such restrictions old-fashioned techniqe of forward
| declarations may work well.

certainly some restrictions may be needed; I don't believe the current
ones make sense.

-- Gaby