fancy types (was Re: [Caml-list] ocaml killer)

[William Lovas <wlovas@stwing.upenn.edu>]

On Thu, Jan 29, 2004 at 09:52:31AM +0100, Thomas Fischbacher wrote:
> On Wed, 28 Jan 2004, Chet Murthy wrote:
> 
> > These are the things that matter in a language.  The fact that CAML
> > has fancy types, well, -I- like it, but it isn't why I wrote some of
> > my most complex systems in it, and it will never be enough to push
> > CAML into the mainstream.
> 
> At least, it is nice to be able to use the FFI to define a function 
> believe_me: 'a -> 'b which is just the identity, so that one can pass as 
> an argument a function to itself. There _are_ some situations where things 
> are best handled by using the fixed-point principle at a deep level.

I've passed functions to themselves before without ever having to make use
of such a function (which already exists in the standard library, it being
mysteriously named Obj.magic and its use being highly discouraged).  In all
of my scenarios, regular old parametric polymorphism was able to handle the
typing.  In what sort of situation have you needed this identity function?

William

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