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From: Wojtek Narczynski <wojtek@power.com.pl>
Newsgroups: comp.lang.ada
Subject: Re: Formal and informal type systems? (Was: ADA Popularity Discussion
 Request)
Date: Tue, 28 Sep 2004 22:03:13 +0200
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Date: 2004-09-28T22:03:13+02:00
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On Tue, 28 Sep 2004 10:14:37 +0200, Jacob Sparre Andersen wrote:

> In what way is the OCAML (I don't know Haskell) type system formal in
> contrast to that of Ada?

OCaml is not the best example, as it is ML with 'informal' extensions. ML
type system (Hindley-Milner) is formal in that it's definition is a set of
mathematical hieroglyps, in contrast to textual description in Ada RM.

Haskel type system is much more than that of ML, as it has 'type classes',
very powerfull. So does Aldor type system.

> And is that good?

It is good to typecheck with a term rewriting system, yes.

But then, the more 'potent' (more commonly referred as 'expressive') the
type system is, the more complex.

Regards,
Wojtek