程序結束後的語法錯誤

Question

我正在做一個在ocaml中編寫玩具編譯器的實驗。目前，我正在嘗試爲我的詞法分析器實現offside rule。不過，我在ocaml語法方面遇到了一些麻煩（編譯器錯誤非常無法提供信息）。下面的代碼（它的33行）會導致第34行的錯誤超出源代碼的末尾。我不確定是什麼導致了這個錯誤。

open Printf 

let s = (Stack.create():int Stack.t); 

let rec check x = 
    (
     if Stack.is_empty s then 
      Stack.push x s 
     else if Stack.top s < x then 
      (
       Stack.push x s; 
       printf "INDENT\n"; 
      ) 
     else if Stack.top s > x then 
      (
       printf "DEDENT\n"; 
       Stack.pop s; 
       check x; 
      ) 
     else 
      printf "MATCHED\n"; 
    ); 

let main() = 
    (
     check 0; 
     check 4; 
     check 6; 
     check 8; 
     check 5; 
    ); 

let _ = Printexc.print main() 

ocaml的輸出：

File "lexer.ml", line 34, characters 0-0: 
Error: Syntax error 

有人可以幫助我的工作出了什麼錯誤是由引起的，幫助我對我的方式來修復它？

Answer 1

尾隨;主要定義,檢查和s是錯誤的。

用代替這3次出現;;如下：

let s = (Stack.create():int Stack.t);; 

let rec check x = 
    (
     (* ...sequence of imperative statements... *) 
);; 

let main() = 
    (
     (* ...sequence of imperative statements... *) 
);; 

;是在下列情況下使用：

• 測序命令語句
• 作爲
• 作爲
• 作爲記錄字段之間的隔板陣列元件之間的隔板的列表元素之間的隔板

一些例子：

let hello_world1() = 
    print_endline "Hello"; 
    print_endline "World !" 
;; 

let hello_world2() = 
    begin 
    print_endline "Hello"; 
    print_endline "World !" 
    end 
;; 

let hello_world3() = 
    (
    print_endline "Hello"; 
    print_endline "World !"; 
) 
;; 

let some_list = 
    [1; 2; 3] 
;; 

let some_array = 
    [| 'a'; 'b'; 'c' |] 
;; 

type my_process = 
    { 
    pid: int; 
    executable_path: string; 
    } 
;; 

let p1 = { pid = 142; executable_path = "./my_exec" };; 

Answer 2

剛取出;作品：

open Printf 

let (s:int Stack.t) = Stack.create() 

let rec check x = 
    (
     if Stack.is_empty s then 
      Stack.push x s 
     else if Stack.top s < x then 
      (
       Stack.push x s; 
       printf "INDENT\n"; 
      ) 
     else if Stack.top s > x then 
      (
       printf "DEDENT\n"; 
       Stack.pop s; 
       check x; 
      ) 
     else 
      printf "MATCHED\n"; 
    ) 

let main() = 
    (
     check 0; 
     check 4; 
     check 6; 
     check 8; 
     check 5; 
    ) 

let _ = 
    Printexc.print main() 

運行它：

gaius@debian:~/Projects/TestCase$ ./lexer 
INDENT 
INDENT 
INDENT 
DEDENT 
DEDENT 
INDENT