ocaml

Jane Street's Core lib has such a function: Fn.const . https://github.com/janestreet/core_kernel/blob/master/lib/fn.ml let const c = (); fun _ -> c val const : 'a -> 'b -> 'a produces a function that just returns its first argument I really don't understand it. What's the purpose of this function? In what scenario we have to use it? Why put (); first? Why not write it as let const c = fun () -> c ? this will give a function taking unit as parameter and always returns initial c . If I do let f = const 5 , f will become a function which takes '_a as parameter. What's the purpose of returning a

Here's a simple example of using the library Cohttp: open Lwt open Cohttp open Cohttp_lwt_unix let body = Client.get (Uri.of_string "http://www.reddit.com/") >>= fun (resp, body) -> let code = resp |> Response.status |> Code.code_of_status in Printf.printf "Response code: %d\n" code; Printf.printf "Headers: %s\n" (resp |> Response.headers |> Header.to_string); body |> Cohttp_lwt.Body.to_string >|= fun body -> Printf.printf "Body of length: %d\n" (String.length body); body let () = let body = Lwt_main.run body in print_endline ("Received body\n" ^ body) I'm trying to compile it ocaml my_test1

Recently I was given the code List.fold_left (fun acc x -> raise x ; acc) 3 I'm completely fine with this partial application having a functional value of type exn list -> int , and the fact it yields a warning isn't surprising. I am, however, not certain what half of the warning means: Warning 21: this statement never returns (or has an unsound type.) I can't actually find any reference to this warning where it isn't the result of a non-returning statement. Even the man page for ocamlc only mentions non-returning statements for this warning, and warnings.ml refers to it merely as Nonreturning

I recently decided to organize the files in my project directory. I moved the parsers I had for a few different file types into their own directory and also decided to use ocamlbuild (the as the project was getting more complicated and the simple shell script was not sufficient any longer). I was able to successfully include external projects by modifying myocamlbuild with some basic rules (calling ocaml_lib , I'll use ocamlfind some other time), but I am stuck on how to include the folder as a module into the project properly. I created a parser.mlpack file and filled it with the proper

Could someone explain what the |> operator does? This code was taken from the reference here : let m = PairsMap.(empty |> add (0,1) "hello" |> add (1,0) "world") I can see what it does, but I wouldn't know how to apply the |> operator otherwise. For that matter, I have no idea what the Module.() syntax is doing either. An explanation on that would be nice too. Module.(e) is equivalent to let open Module in e . It is a shorthand syntax to introduce things in scope. The operator |> is defined in module Pervasives as let (|>) x f = f x . (In fact, it is defined as an external primitive, easier to