1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
|
{-# LANGUAGE GeneralizedNewtypeDeriving #-}
-- Here we allow it to succeed (No SAFE)
-- | We use newtype to create an isomorphic type to Int
-- with a reversed Ord dictionary. We now use the MinList
-- API of Y1 to create a new MinList. Then we use newtype
-- deriving to convert the newtype MinList to an Int
-- MinList. This final result breaks the invariants of
-- MinList which shouldn't be possible with the exposed
-- API of Y1.
module Main where
import SafeLang06_A
class IntIso t where
intIso :: c t -> c Int
instance IntIso Int where
intIso = id
newtype Down a = Down a deriving (Eq, Show, IntIso)
instance Ord a => Ord (Down a) where
compare (Down a) (Down b) = compare b a
forceInt :: MinList Int -> MinList Int
forceInt = id
a1, a2 :: MinList Int
a1 = foldl insertMinList (newMinList $ head nums) (tail nums)
a2 = forceInt $ intIso $ foldl (\x y -> insertMinList x $ Down y) (newMinList $ Down $ head nums) (tail nums)
nums :: [Int]
nums = [1,4,0,1,-5,2,3,5,-1,2,0,0,-4,-3,9]
main = do
printIntMinList a1
printIntMinList a2
|
