exception VarUndef of string let rec eval_expr env = function Cst x -> x | Var x -> (try List.assoc x env with Not_found -> raise(VarUndef x)) | Sum(e1,e2) -> (eval_expr env e1) + (eval_expr env e2) | Diff(e1,e2) -> (eval_expr env e1) - (eval_expr env e2) | Prod(e1,e2) -> (eval_expr env e1) * (eval_expr env e2) | Quot(e1,e2) -> (eval_expr env e1) / (eval_expr env e2) | Letin(x,e1,e2) -> let t = eval_expr env e1 in eval_expr ((x,t)::env) e2