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

[Alex Baretta <alex@baretta.com>]

Thomas Fischbacher wrote:
> On Thu, 29 Jan 2004, William Lovas wrote:

> # let fac n = let do_rec specialist n = if n = 0 then 1 else n * specialist specialist (n-1) in do_rec do_rec n;;
> 
> Characters 74-84:
>   let fac n = let do_rec specialist n = if n = 0 then 1 else n * 
> specialist specialist (n-1) in do_rec do_rec n;;
>                                                                             
> ^^^^^^^^^^
> This expression has type 'a -> 'b -> 'c but is here used with type 'a
> 
> # let fac n = let do_rec specialist n = if n = 0 then 1 else n * (Obj.magic specialist) specialist (n-1) in do_rec do_rec n;;
> val fac : int -> int = <fun>
> 
> # fac 8;;
> - : int = 40320

As far as I can see you are asking for no more than recursive types.

[alex@alex graph]$ ocaml -rectypes
         Objective Caml version 3.07+2

# let fac n = let do_rec specialist n = if n = 0 then 1 else n * 
specialist specialist (n-1) in do_rec do_rec n;;
val fac : int -> int = <fun>
# fac 3;;
- : int = 6

This is kind of thread where an RTFL comment might be appropriate.

Alex

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