(* op : binary operator *)
type op = Plus | Minus | Times | Divide

(* op_to_string : op -> string *)
let op_to_string op =
  match op with
  | Plus -> " + "
  | Minus -> " - "
  | Times -> " * "
  | Divide -> " / "

(* e : syntax *)
type e =
  | Num of int
  | Var of string
  | Op of e * op * e
  | Fun of string * e
  | App of e * e
  (*
  | Shift of string * e
  | Control of string * e
  | Shift0 of string * e
  | Control0 of string * e
  | Reset of e
  *)
  | Try of e * string * string * e
  | Perform of e
  | PerformShallow of e

(* to_string : e -> string *)
let rec to_string exp =
  match exp with
  | Num n -> string_of_int n
  | Var x -> x
  | Op (e0, op, e1) -> "(" ^ to_string e0 ^ op_to_string op ^ to_string e1 ^ ")"
  | Fun (x, e) -> "(fun " ^ x ^ " -> " ^ to_string e ^ ")"
  | App (e0, e1) -> "(" ^ to_string e0 ^ " " ^ to_string e1 ^ ")"
  (*
  | Shift (x, e) -> "(shift " ^ x ^ " -> " ^ to_string e ^ ")"
  | Control (x, e) -> "(control " ^ x ^ " -> " ^ to_string e ^ ")"
  | Shift0 (x, e) -> "(shift0 " ^ x ^ " -> " ^ to_string e ^ ")"
  | Control0 (x, e) -> "(control0 " ^ x ^ " -> " ^ to_string e ^ ")"
  | Reset e -> "reset (" ^ to_string e ^ ")"
  *)
  | Try (e0, n, k, e1) ->
      "(try " ^ to_string e0 ^ " with | effect " ^ n ^ ", " ^ k ^ " -> "
      ^ to_string e1 ^ ")"
  | Perform e -> "perform " ^ to_string e
  | PerformShallow e -> "perform_shallow " ^ to_string e

(* print : e -> unit *)
let print exp =
  let str = to_string exp in
  print_string str