[bitc-dev] Bitc -> Polymorphic

[David Hopwood]

Jørgen Hermanrud Fjeld wrote:
> On Mon, Jan 31, 2005 at 07:56:52PM +0000, David Hopwood wrote:
> 
>>I don't see what is weird about this, at least from the given example.
>>It works as I would expect from recursive types in Haskell and other
>>languages.
> 
> The sample only illustrated how O'Caml does recursive types, for the record.
> You can find the example of weird recursive types in the O'Caml
> mailing list "http://caml.inria.fr/archives/200501/msg00337.html" in a post by Xavier.

Perhaps a warning message could be output, e.g.:

   # let f x = x :: x
   val f : ('a list as 'a) -> 'a list = <fun>
   Warning: check whether this type was intended to be recursive.

   # f [1;2;3];;
   Characters 3-4:
     f [1;2;3];;
        ^
   This expression has type int but is here used with type 'a list as 'a

but if this is the only problem, I don't think it's serious. Note that
the type ('a list as 'a) is perfectly valid:

   # f [];;
   - : ('a list as 'a) list = [[]]

-- 
David Hopwood <david.nospam.hopwood at blueyonder.co.uk>