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