(* File calc.ml *)
let rec ast_to_string ast = match ast with 
| Ast.Leaf s -> s
| Ast.Node ls -> "[" ^ String.concat " " (List.map ast_to_string ls) ^ "]"
;;

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