[Camllist] dynamically loading C functions
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Date:  20010306 (00:16) 
From:  Chris Hecker <checker@d...> 
Subject:  Re: [Camllist] dynamically loading C functions 
>You can provide combinators to build the type information: Wow, that's pretty cool. I'm not that familiar with abstract types and modules in caml (or any functional language), so this was kind of an eye opener. I think I understand how they work a bit more now, thanks. I do have one thing I can't figure out. Here's my test module: module C: sig type 'a t val int_t : int t val float_t : float t (* Begins with @ so it's rightassociative :) *) val (@>) : 'a t > 'b t > ('a > 'b) t val get_function : string > 'a t > 'a val conv : 'a t > int list end = struct type 'a t = T of int  Tl of int list let int_t = T 1 let float_t = T 2 let (@>) a b = match a,b with (T a,T b) > Tl [a;b]  (T a,Tl b) > Tl (a :: b)  (Tl a,Tl b) > Tl (a @ b)  (Tl a,T b) > Tl (a @ [b]) let get_function s l = Obj.magic s (* just get it to compile *) let conv (Tl a) = a end The way I've done 'a t is as a variant int list. This works, but my @> flattens nested lists because of the pattern match, so while the type system differentiates between # (float_t @> int_t @> float_t @> float_t @> int_t);;  : (float > int > float > float > int) C.t = <abstr> and (note the nested parens): # (float_t @> (int_t @> float_t @> float_t) @> int_t);;  : (float > (int > float > float) > int) C.t = <abstr> my internal representation doesn't: # conv (float_t @> int_t @> float_t @> float_t @> int_t);;  : int list = [2; 1; 2; 2; 1] # conv (float_t @> (int_t @> float_t @> float_t) @> int_t);;  : int list = [2; 1; 2; 2; 1] I thought I could fix this by saying type 'a t = T of int  Tl of 'a t list, but that seems to constrain (@>) to be 'a t > 'a t > 'a t and I lose the cruicial ('a > 'b) t combinator (not sure if I'm using that word correctly) and I get a type error. Any idea how I could get it to nest? Chris  To unsubscribe, mail camllistrequest@inria.fr. Archives: http://caml.inria.fr