2 % (c) The AQUA Project, Glasgow University, 1993-1998
5 This is useful, general stuff for the Native Code Generator.
7 Provide trees (of instructions), so that lists of instructions
8 can be appended in linear time.
13 nilOL, isNilOL, unitOL, appOL, consOL, snocOL, concatOL,
14 fromOL, toOL, foldrOL, foldlOL
23 | Two (OrdList a) (OrdList a)
28 isNilOL :: OrdList a -> Bool
30 unitOL :: a -> OrdList a
31 snocOL :: OrdList a -> a -> OrdList a
32 consOL :: a -> OrdList a -> OrdList a
33 appOL :: OrdList a -> OrdList a -> OrdList a
34 concatOL :: [OrdList a] -> OrdList a
38 snocOL as b = Two as (One b)
39 consOL a bs = Two (One a) bs
40 concatOL aas = foldr Two None aas
43 isNilOL (One _) = False
44 isNilOL (Two as bs) = isNilOL as && isNilOL bs
45 isNilOL (Many xs) = null xs
49 appOL as bs = Two as bs
51 foldrOL :: (a->b->b) -> b -> OrdList a -> b
53 foldrOL k z (One x) = k x z
54 foldrOL k z (Two b1 b2) = foldrOL k (foldrOL k z b2) b1
55 foldrOL k z (Many xs) = foldr k z xs
57 foldlOL :: (b->a->b) -> b -> OrdList a -> b
59 foldlOL k z (One x) = k z x
60 foldlOL k z (Two b1 b2) = foldlOL k (foldlOL k z b1) b2
61 foldlOL k z (Many xs) = foldl k z xs
63 fromOL :: OrdList a -> [a]
68 flat (One x) rest = x:rest
69 flat (Two a b) rest = flat a (flat b rest)
70 flat (Many xs) rest = xs ++ rest
72 toOL :: [a] -> OrdList a