OCaml"else"语法错误

Question

我是第一次学习OCaml,而且我遇到了一个非常模糊的"语法错误".在定义函数时generateboxes如此:

let rec generateboxes a b = 
    if a = (add1 b) then (force_newline ()); (print_sting "Done!")
    else if [1] = (Array.get finalarray a) then (populatebox
    (numbertoposition a) a); (generateboxes (add1 a) b)
    else (generateboxes (add1 a) b);;

编译器给出错误消息:"语法错误",它指向第一个else.我的代码输出这样的消息有什么明显的错误吗？(我意识到代码是脱离上下文的,但如果它的语法错误那么它应该无关紧要).

Answer 1

let rec generateboxes a b = 
    if a = add1 b then (force_newline (); print_sting "Done!")
    else if [1] = Array.get finalarray a then
      (populatebox (numbertoposition a) a; generateboxes (add1 a) b)
    else generateboxes (add1 a) b;;

如果a then或else子句中有多个语句,则需要将它们放在括号内.或者,您可以放置begin ... end它们:

let rec generateboxes a b = 
    if a = add1 b
    then begin
      force_newline ();
      print_sting "Done!" end
    else if [1] = Array.get finalarray a
    then begin
      populatebox (numbertoposition a) a;
      generateboxes (add1 a) b end
    else generateboxes (add1 a) b;;

(请注意,我还删除了一些不必要的括号,以使代码更清晰.)