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[Caml-list] currying...
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| Date: | -- (:) |
| From: | Thomas Colcombet <Thomas.Colcombet@i...> |
| Subject: | Re: [Caml-list] currying... |
As I understand the problem, may be the small following examples explain how CAML implements curryfication : # let f = fun x -> (Printf.printf "%d\n" x; fun y -> Printf.printf "%d\n" y);; val f : int -> int -> unit = <fun> # f 1;; 1 - : int -> unit = <fun> # f 1 2;; 1 2 - : unit = () This function does not behave as the following one : # let f = fun x y -> (Printf.printf "%d\n" x; Printf.printf "%d\n" y);; val f : int -> int -> unit = <fun> # f 1;; - : int -> unit = <fun> # f 1 2;; 1 2 - : unit = () In other words, a fun construct is evaluated only when all its argument are known. The notation "let f x y = ..." is just syntactic sugar for "let f = fun x y -> ...". Thomas Colcombet > How does caml know when to call a function? For example, say I have: > > val f: int -> int -> int -> unit > > and the definition of f is > > let f x y = Printf.printf "%d %d" x y;Printf.printf "%d" > > so f actually takes two ints, prints them, and then returns a function that takes an int and returns unit. From the val declaration above in a .cmi file, how can caml tell the difference between that f and this one: > > let f x y z = Printf.printf "%d %d %d" x y z > > How does it know "when" to call f, since you need a different number of parameters for the different definitions? The top f prints x y when it's called with two parms, so it doesn't wait until all three parms have been passed. > > I have a feeling I'm missing something fundamental here, or else the definition of a function internally has a field for its arity and it just partially applies until it reaches the total arity. I thought I remembered seeing some documentation on this months ago, but I can't find it now... > > It doesn't seem to partially evaluate the function or anything insane like that. > > Chris > > ------------------- > To unsubscribe, mail caml-list-request@inria.fr. Archives: http://caml.inria.fr ------------------- To unsubscribe, mail caml-list-request@inria.fr. Archives: http://caml.inria.fr