Question

我是ocaml的新手并尝试使用Ocaml的图形库移动一个圆圈。这就是我所做的，但它不起作用。它应该继续无限时间，因为“虽然真实”，但它不起作用，我无法给出输入。

#load "graphics.cma";;
#load "unix.cma";;

Graphics.open_graph " 800x250";;
Graphics.remember_mode true;;
Graphics.set_color 100;;
Graphics.foreground;;

let player = [|40;80;10|];;

Graphics.fill_circle player.(0) player.(1) player.(2);;

let rec check button = 
    if button = 'w'
    then
    player.(0) <- player.(0) + 50;
    Graphics.fill_circle player.(0) player.(1) player.(2);

while true do
    let s = Graphics.wait_next_event [Graphics.Button_down; Graphics.Key_pressed]
    and bo=Graphics.key_pressed ()
    in if not bo then check s.Graphics.key;
    done;;

Answer 1

以下是问题的原因：

 Graphics.fill_circle player.(0) player.(1) player.(2);
                                                 ^^^^^^^
                       here should be a double semicolon

没有第二个分号，while表达式被认为是 check函数的一部分，正确的缩进澄清了这一点：

let rec check button = 
  if button = 'w'
  then
    player.(0) <- player.(0) + 50;
  Graphics.fill_circle player.(0) player.(1) player.(2);

  while true do
    let s = Graphics.wait_next_event [Graphics.Button_down; Graphics.Key_pressed]
    and bo=Graphics.key_pressed ()
    in if not bo then check s.Graphics.key;
  done

所以，你刚刚定义了一个函数检查，并且从未调用它，这就是为什么没有发生这种情况。

此外，OCaml是一种编程语言，因此最好尝试编写OCaml程序，而不是脚本。将以下内容放在graph.ml文件中，

let player = [|40;80;10|]

let init () = 
  Graphics.open_graph " 800x250";
  Graphics.remember_mode true;
  Graphics.set_color 100;
  Graphics.fill_circle player.(0) player.(1) player.(2)

let rec check button = 
  if button = 'w'
  then
    player.(0) <- player.(0) + 50;
  Graphics.fill_circle player.(0) player.(1) player.(2)

let run () = 
  while true do
    let s = Graphics.wait_next_event [
        Graphics.Button_down;
        Graphics.Key_pressed
      ] in
    let bo = Graphics.key_pressed () in
    if not bo then check s.Graphics.key;
  done


let () =
  init ();
  run ()

使用以下命令编译并运行它

 ocamlbuild -pkg graphics graph.native --

尝试使用图形库Ocaml移动圆圈

1 个答案: