1 TEST OF DEFACTORISATION FOR FUNCTIONS THAT DROP
5 > data Boolean = FF | TT
6 > data Pair a b = MkPair a b
7 > data LList alpha = Nill | Conss alpha (LList alpha)
8 > data Nat = Zero | Succ Nat
9 > data Tree x = Leaf x | Node (Tree x) (Tree x)
10 > data A a = MkA a (A a)
12 > append :: LList a -> LList a -> LList a
13 > append xs ys = case xs of
15 > Conss z zs -> Conss z (append zs ys)
17 The following function drops @b@.
19 > flat :: Tree (Pair a b) -> LList a
21 > Leaf (MkPair a b) -> Conss a Nill
22 > Node l r -> append (flat l) (flat r)
24 > fl :: Boolean -> LList Boolean
25 > fl x = flat (Leaf (MkPair TT Zero))