open Ast

let binop_to_func : type a b. (a, b) Ast.binop -> (a -> a -> b) = function
  | Add -> Int.add
  | Sub -> Int.sub
  | Mul -> Int.mul
  | Div -> Int.div
  | Eq -> (=)

let rec eval : type a. a Ast.t -> a = function
  | Value (Int t) -> t
  | Value Unit -> ()
  | Binop (l, op, r) ->
    let f = binop_to_func op in
    f (eval l) (eval r)
  | Set_binop_pre (op, l) ->
    Hashtbl.replace Parser.precedence
      (Ast.binop_to_string op) (eval l)