commita96d53bb8633c9f0590f46a9f45e32379737d25cparentb561ca30f9b8c2e0ddbeb22983726f6556322151Author:Jared Tobin <jared@jtobin.io>Date:Thu, 6 Apr 2023 18:31:35 +0400 Generics work.Diffstat:

M | lib/Okasaki/Heap/Class.hs | | | 65 | ++++++++++++++++++++++++++++++++++++++++++++++++++++++----------- |

1 file changed, 54 insertions(+), 11 deletions(-)diff --git a/lib/Okasaki/Heap/Class.hs b/lib/Okasaki/Heap/Class.hs@@ -1,18 +1,61 @@ +{-# OPTIONS_GHC -Wall #-} module Okasaki.Heap.Class where +import Data.Kind (Type) import qualified Okasaki.Heap.Binomial as B -import qualified Okasaki.Heap.Leftist as L -import qualified Okasaki.Heap.Leftist.Weighted as W -class Heap (h :: * -> *) where - bot :: Ord a => h a -> Maybe a - put :: Ord a => a -> h a -> h a - mer :: Ord a => h a -> h a -> h a - cut :: Ord a => h a -> h a +-- NB these need to be newtyped to be made proper instances +-- import qualified Okasaki.Heap.Leftist as L +-- import qualified Okasaki.Heap.Leftist.Weighted as W + +-- exercise 3.7: generic explicit-min heap +class Heap (h :: Type -> Type) where + data Pile h :: Type -> Type + + via :: Ord a => h a -> Pile h a + bot :: Ord a => Pile h a -> Maybe a + put :: Ord a => a -> Pile h a -> Pile h a + cut :: Ord a => Pile h a -> Pile h a + mer :: Ord a => Pile h a -> Pile h a -> Pile h a + out :: Pile h a -> h a instance Heap B.Heap where - bot = B.bot - put = B.put - mer = B.mer - cut = B.cut + data Pile B.Heap a = + Nib + | Bin a (B.Heap a) + + via = \case + B.Heap [] -> Nib + h -> let b = B.bot h + in case b of + Nothing -> Nib + Just a -> Bin a h + + bot = \case + Nib -> Nothing + Bin a _ -> Just a + + put a = \case + Nib -> Bin a (B.put a B.lef) + Bin m h + | a < m -> Bin a (B.put a h) + | otherwise -> Bin m (B.put a h) + + cut h = case h of + Nib -> Nib + Bin _ t -> + let c = B.cut t + in case B.bot c of + Nothing -> Nib + Just a -> Bin a c + + mer h l = case (h, l) of + (Nib, _) -> l + (_, Nib) -> h + (Bin a s, Bin b t) -> Bin (min a b) (B.mer s t) + + out = \case + Nib -> B.lef + Bin _ h -> h +