ocaml

问题 When compiling this program: module type Inc = sig type t val inc : t -> t end module type Dec = sig type t val dec : t -> t end module Merger (I : Inc) (D : Dec with type t = I.t) = struct let merge x = x |> I.inc |> D.dec end module IntInc : Inc = struct type t = int let inc x = x + 10 end module IntDec : Dec = struct type t = int let dec x = x - 8 end module Combiner = Merger (IntInc) (IntDec) I get the following error: File "simple.ml", line 30, characters 35-41: Error: Signature mismatch

问题 Imagine I've a C library called libcat for interacting with my cat fluffy. I'm therefore writing bindings for OCaml to simplify interactions with fluffy. module type CAT = sig type cat val find : ... -> cat val feed : cat -> unit ... end ;; module Cat : CAT = ... There is considerable memory management already built into libcat, like say caching, freeing destroyed toys, and maybe even a limited scope garbage collector for emptying the litter. Yet, overall libcat requires that users explicitly

问题 I am currently working on a website project written in OCaml and compiled to javascript using js_of_ocaml. It works pretty well as long as I have only one source file using the command ocamlfind ocamlc -package js_of_ocaml -package js_of_ocaml.syntax -syntax camlp4o -linkpkg -o file.byte file.ml but I would like to include several modules in my project. How can I do that ? The other modules are actually a lexer and a parser poduced by ocamllex and menhir. I have read a tutorial on how to use

问题 The following code does not compile: let x = "hello" in Printf.printf x The error is: Error: This expression has type string but an expression was expected of type ('a, out_channel, unit) format = ('a, out_channel, unit, unit, unit, unit) format6 1) Can someone give an explanation of the error message? 2) And why would a string cannot be passed to printf ? 回答1: The first argument to printf must be of type ('a, out_channel, unit) format not string. String literals can be automatically

问题 I'm cross-compiling a touchscreen driver, which comes with an ocaml calibration application. I'm trying to compile the driver and the application for ARM, in particular, the Beagleboard, running Angström. It goes like this: ^_^[raziel@Bebop zytouch-driver-20081121]$ source /usr/local/angstrom/arm/environment-setup ^_^[raziel@Bebop zytouch-driver-20081121]$ make CC=arm-angstrom-linux-gnueabi-gcc arm-angstrom-linux-gnueabi-gcc -std=gnu99 -g -O2 -Wall -Wextra -Werror -Wstrict-prototypes

问题 I have been on learning Ocaml for a week, some things got clear, the others rather not. I'm trying to compose a simple Tic-Tac-Toe server accepting connections via telnet. Just for a word. I have to use Lwt and rigth now it seems for me a darken place because I had faced too much of language pecularities. The begining of the code: let sock = Lwt_unix.socket Unix.PF_INET Unix.SOCK_STREAM 0 let setting_up_server_socket = let sockaddr = (Unix.ADDR_INET(Unix.inet_addr_of_string "127.0.0.1", 23233

问题 Is there a good way to get the line number of exception in OCaml without debugging symbols? Certainly, if we turn on debugging symbols and run with OCAMLRUNPARAM=b , we can get the backtrace. However, I don't really need the whole backtrace and I'd like a solution without debugging symbols. At the moment, we can write code like try assert false with x -> failwith (Printexc.to_string x ^ "\nMore useful message") in order to get the file and line number from assert, but this seems awkward. Is

问题 I'm trying to learn OCaml through the Real World OCaml book. They have a guide by which I am supposed to install the Core package and utop. However, while I seem to be successfully installing both of these using Opam, neither of them works when I try to use them. I know that they're installed, because when I try to install them again, I get this message: $ opam install utop core [NOTE] Package utop is already installed (current version is 1.10). [NOTE] Package core is already installed

问题 I'm trying to learn OCaml through the Real World OCaml book. They have a guide by which I am supposed to install the Core package and utop. However, while I seem to be successfully installing both of these using Opam, neither of them works when I try to use them. I know that they're installed, because when I try to install them again, I get this message: $ opam install utop core [NOTE] Package utop is already installed (current version is 1.10). [NOTE] Package core is already installed

问题 The Unix.sleep function can suspend the program for whole seconds, but how can you suspend it for less than a second? 回答1: The classical Unix solution for this is to use select() with no file descriptors: let minisleep (sec: float) = ignore (Unix.select [] [] [] sec) 回答2: The Thread.delay function pauses the thread for the given number of seconds, but it takes a float, allowing you to pause the thread for less than a second. 回答3: from Unix module val sleepf : float -> unit Stop execution for