[clean-list] About abstract synonym types...

[Fergus Henderson]

On 04-Feb-2004, Fabien TODESCATO <fabien.todescato@wanadoo.fr> wrote:
> The Clean home pages advertises the new 2.1 version as featuring 
> "abstract synonym types". I couldn't however find any explanations nor 
> any syntax definition in the relese 2.1 of the language report that 
> ships with the system.

I'm guessing that an "abstract synonym type" would be an abstract type
that is defined as a synonym type.  An abstract type is one whose
name is exported to other modules.

> Is this "abstract synonym types facility" the equivalent of the 
> "newtype" construction in Haskell ?

If my guess is right, then no, the two are not really equivalent.
The difference is that with Haskell's newtype, conversions between the
abstract type and its definition must be explicit.

> And if so, are recursive type definitions supported ?

I think the answer to that is probably no, because IIRC Clean does
not support recursive synonym types.

I have my own questions about abstract synonym types in Clean 2.1:

	- how do they interact with type classes?

	- how do they interact with separate compilation?
	  Does changing the definition of an abstact synonym type
	  require recompiling modules that import the module which
	  defines it?

	- has the Clean team considered how abstract synonym types
	  should be supported if compiling to a strongly-typed target
	  language that does not support abstract synonym types,
	  such as C++, Java, the JVM, or the .NET CLR?

-- 
Fergus Henderson <fjh@cs.mu.oz.au>  |  "I have always known that the pursuit
The University of Melbourne         |  of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.