funclang series5: Added freevars function for ass12.

funclang-taddeus/series5/ass12.ml

@@ -43,19 +43,35 @@ let rec expr2string =
     | Cond (cond, e1, e2) -> "if " ^ expr2string(cond)
                              ^ " then " ^ expr2string(e1)
                              ^ " else " ^ expr2string(e2)
-    | Fun (arg, e) -> "fun " ^ arg ^ " -> " ^ expr2string(e)
+    | Fun (arg, e) -> "func " ^ arg ^ " -> " ^ expr2string(e)
     | FunAp (e1, e2) -> "(" ^ expr2string(e1) ^ " " ^ expr2string(e2) ^ ")"
     | Let (var, e1, e2) -> "let " ^ var ^ " = " ^ expr2string(e1)
                            ^ " in " ^ expr2string(e2)
     | LetRec (var, e1, e2) -> "let rec " ^ var ^ " = " ^ expr2string(e1)
                               ^ " in " ^ expr2string(e2)
-;;
 
-(* let a = 1 in b *)
-print_endline (expr2string (Let ("a", (Num 1), (Var "b"))));;
-
-(* a + 3 *)
-print_endline (expr2string (BinopAp (Add, Var "a", Num 3)));;
+let freevars e =
+    let rec free_vars bound_vars = function
+          Num _ | Bool _ -> []
+        | Var v when List.mem v bound_vars -> []
+        | Var v -> [v]
+        | MonopAp (_, e) -> free_vars bound_vars e
+        | BinopAp (_, e1, e2)
+        | FunAp (e1, e2) -> free_vars bound_vars e1 @ free_vars bound_vars e2
+        | Cond (cond, e1, e2) -> free_vars bound_vars cond
+                                 @ free_vars bound_vars e1
+                                 @ free_vars bound_vars e2
+        | Fun (arg, e) -> free_vars (arg::bound_vars) e
+        | Let (v, e1, e2) -> free_vars (v::bound_vars) e2
+                             @ free_vars bound_vars e1
+        | LetRec (v, e1, e2) -> let bound = v::bound_vars in
+                                free_vars bound e2 @ free_vars bound e1
+    in
+    free_vars [] e
 
-(* -a *)
-print_endline (expr2string (MonopAp (Neg, Var "a")));;
+(*let rec subs e var replacement =
+    let free = freevars e in
+    match e with
+    | Num _ | Bool _ -> e
+    | Var v when List.mem v bound_vars -> []
+    | Var v -> [v]*)