如何创建一个结合了Parser和Lexer的程序

Question

我想使用Ocamllex/Ocamlyacc构建一个编译器，我想创建一个主程序来结合我的OcamlParser和OcamlLexer。问题是，我知道如何在命令行中使用如下代码的输入来实现:

let _ =
  try
    let lexbuf = Lexing.from_channel stdin in
    while true do
      let result = Parser.main Lexer.token lexbuf in
      print_int result; print_newline(); flush stdout
    done
  with Lexer.Eof ->
    exit 0

但是如果我想使用一个文件作为输入，我该怎么做?我尝试这样做:

let file ="add.txt"
    let _ =
     let ic = open_in file in 
      try
        let lexbuf = Lexing.from_channel file in
        while true do
          let result = Parser.main Lexer.token lexbuf in
          print_int result; print_newline(); flush stdout
        done
      with Lexer.Eof ->
        exit 0

但它并没有真正起作用。

Answer 1

下面的代码适合我。在你的版本中，你有一些语法错误。

let _ =
      let file ="add.txt" in
      let i = open_in file in 
      try
        let lexbuf = Lexing.from_channel i in
        while true do
          let result = Parser.main Lexer.token lexbuf in
          print_int result; print_newline(); flush stdout
        done
      with Lexer.Eof ->
        exit 0

将1+2放入"add.txt"中得到3。