1 implementation module RefactorX
5 //Start = map toString [E1,E2,E3,E4,E5]
6 //Start = map free [E1,E2,E3,E4,E5]
7 //Start = map toString (map remove_unused_lets [E1,E2,E3,E4,E5])
8 Start = map eval [E1,E2,E3,E4,E5]
10 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")))
11 E2 = LET "x" (NR 42) (OP (VAR "x") PLUS (LET "x" (NR 58) (VAR "x")))
12 E3 = LET "x" (NR 1) (LET "y" (NR 2) (LET "x" (NR 3) (NR 4)))
13 E4 = LET "x" (NR 1) (OP (VAR "x") PLUS (VAR "y"))
14 E5 = OP (LET "x" (NR 1) (VAR "x")) MUL (VAR "x")
16 (<+) infixl 9 :: String a -> String | toString a
17 (<+) str a = str +++ toString a
19 instance toString Operator where
25 instance toString Expr where
26 toString (NR n) = toString n
28 toString (LET n e1 e2) = "(let " <+ n <+ "=" <+ e1 <+ " in " <+ e2 <+ ")"
29 toString (OP e1 o e2) = bracket e1 <+ o <+ bracket e2
31 bracket :: Expr -> String
32 bracket (OP e1 o e2) = "(" <+ (OP e1 o e2) <+ ")"
33 bracket e = toString e
38 free (OP e1 o e2) = removeDup (free e1 ++ free e2)
39 free (LET n e1 e2) = removeMember n (free e2)
41 remove_unused_lets:: Expr -> Expr
42 remove_unused_lets (LET n e1 e2)
43 | isMember n (free e2) = (LET n (remove_unused_lets e1) (remove_unused_lets e2))
44 | otherwise = remove_unused_lets e2
45 remove_unused_lets (OP e1 o e2) = (OP (remove_unused_lets e1) o (remove_unused_lets e2))
46 remove_unused_lets e = e
48 apply:: Operator Val Val -> Val
49 apply _ Undef _ = Undef
50 apply _ _ Undef = Undef
51 apply DIV _ (Result 0) = Undef
52 apply o (Result e1) (Result e2) = Result (apply` o e1 e2)
54 apply`:: Operator -> Int Int -> Int
63 eval`:: Expr [(Name, Val)] -> Val
64 eval` (NR n) _ = Result n
65 eval` (VAR v) [] = Undef
66 eval` (VAR v) [(n, e):xs]
68 | otherwise = eval` (VAR v) xs
69 eval` (OP e1 o e2) xs = apply o (eval` e1 xs) (eval` e2 xs)
70 eval` (LET n e1 e2) xs = eval` e2 [(n, eval` e1 xs):xs]