1 // Mart Lubbers s4109503, Camil Staps s4498062
3 implementation module RefactorX
7 //Start = map toString [E1,E2,E3,E4,E5]
8 //Start = map free [E1,E2,E3,E4,E5]
9 //Start = map toString (map remove_unused_lets [E1,E2,E3,E4,E5])
10 Start = map eval [E1,E2,E3,E4,E5]
12 E1 = OP (LET "x" (OP (NR 42) MIN (NR 3)) (OP (VAR "x") DIV (NR 0))) PLUS (LET "y" (NR 6) (OP (VAR "y") MUL (VAR "y")))
13 E2 = LET "x" (NR 42) (OP (VAR "x") PLUS (LET "x" (NR 58) (VAR "x")))
14 E3 = LET "x" (NR 1) (LET "y" (NR 2) (LET "x" (NR 3) (NR 4)))
15 E4 = LET "x" (NR 1) (OP (VAR "x") PLUS (VAR "y"))
16 E5 = OP (LET "x" (NR 1) (VAR "x")) MUL (VAR "x")
18 (<+) infixl 9 :: String a -> String | toString a
19 (<+) str a = str +++ toString a
21 instance toString Operator where
27 instance toString Expr where
28 toString (NR n) = toString n
30 toString (LET n e1 e2) = "(let " <+ n <+ "=" <+ e1 <+ " in " <+ e2 <+ ")"
31 toString (OP e1 o e2) = bracket e1 <+ o <+ bracket e2
33 bracket :: Expr -> String
34 bracket (OP e1 o e2) = "(" <+ (OP e1 o e2) <+ ")"
35 bracket e = toString e
40 free (OP e1 o e2) = removeDup (free e1 ++ free e2)
41 free (LET n e1 e2) = removeMember n (free e2)
43 remove_unused_lets:: Expr -> Expr
44 remove_unused_lets (LET n e1 e2)
45 | isMember n (free e2) = (LET n (remove_unused_lets e1) (remove_unused_lets e2))
46 | otherwise = remove_unused_lets e2
47 remove_unused_lets (OP e1 o e2) = (OP (remove_unused_lets e1) o (remove_unused_lets e2))
48 remove_unused_lets e = e
50 apply:: Operator Val Val -> Val
51 apply _ Undef _ = Undef
52 apply _ _ Undef = Undef
53 apply DIV _ (Result 0) = Undef
54 apply o (Result e1) (Result e2) = Result (apply` o e1 e2)
56 apply`:: Operator -> Int Int -> Int
65 eval`:: Expr [(Name, Val)] -> Val
66 eval` (NR n) _ = Result n
67 eval` (VAR v) [] = Undef
68 eval` (VAR v) [(n, e):xs]
70 | otherwise = eval` (VAR v) xs
71 eval` (OP e1 o e2) xs = apply o (eval` e1 xs) (eval` e2 xs)
72 eval` (LET n e1 e2) xs = eval` e2 [(n, eval` e1 xs):xs]