add interp from EoC

ocaml_yacc/calc.ml

@@ -1,15 +1,48 @@
+exception Exc of string
+
 (* File calc.ml *)
 let rec ast_to_string ast = match ast with 
 | Ast.Leaf s -> s
+| Ast.Int i -> string_of_int i
 | Ast.Node ls -> "[" ^ String.concat " " (List.map ast_to_string ls) ^ "]"
 ;;
 
+(** interpreter for interp_int*)
+class interp_int x_init =
+    object (self)
+      val mutable x = x_init
+      method interp code = match code with
+		| Ast.Int x -> x
+		| Ast.Node [Ast.Leaf "+"; lhs; rhs] ->
+			let x1 = self#interp lhs in
+			let x2 = self#interp rhs in
+			x1+x2 
+		| Ast.Node [Ast.Leaf "-"; lhs; rhs] ->
+			let x1 = self#interp lhs in
+			let x2 = self#interp rhs in
+			x1-x2 
+		| Ast.Node [Ast.Leaf "-"; x] ->
+			let x1 = self#interp x in
+			0-x1 
+		| Ast.Node [Ast.Leaf "%apply" ; Ast.Leaf "read"; Ast.Int 0] ->
+			let input = read_int_opt () in
+			match input with
+			| Some(y) -> y
+			| _ -> raise (Exc "input invalid number")
+		| _ -> raise (Exc "unsupported")
+    end;;
+
+
+
+
+(**main body*)
         let _ =
           try
             let lexbuf = Lexing.from_channel stdin in
+			let interp = new interp_int 0 in
             while true do
               let result = Parser.main Lexer.token lexbuf in
-                Printf.printf "%s" (ast_to_string result); print_newline(); flush stdout
+                Printf.printf "%d" (interp#interp result); print_newline(); flush stdout
             done
           with Lexer.Eof ->
             exit 0