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Changing move function signature to match state method in preparation for next presentation

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This commit is contained in:
Logan McGrath 2021-10-06 12:19:22 -07:00
parent 6d5e78c0a9
commit cd9b71c03e
1 changed files with 8 additions and 6 deletions
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14
lib/Homework/Ch01/Hanoi.hs
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@ -1,5 +1,7 @@
module Homework.Ch01.Hanoi where module Homework.Ch01.Hanoi where
import Data.Maybe
newtype Peg = Peg () newtype Peg = Peg ()
data Move = Move {moveFrom :: String, moveTo :: String} deriving (Eq, Show) data Move = Move {moveFrom :: String, moveTo :: String} deriving (Eq, Show)
@ -15,9 +17,9 @@ hanoi numDisks pegLabelA pegLabelB pegLabelC =
(pegLabelB, []), (pegLabelB, []),
(pegLabelC, []) (pegLabelC, [])
] ]
in Right $ snd $ move pegs in Right . return . fromJust . fst $ move pegs
move :: Pegs -> (Pegs, [Move]) move :: Pegs -> (Maybe Move, Pegs)
move pegs = move pegs =
let (firstPegLabel, firstPeg) = head pegs let (firstPegLabel, firstPeg) = head pegs
(lastPegLabel, lastPeg) = last pegs (lastPegLabel, lastPeg) = last pegs
@ -26,13 +28,13 @@ move pegs =
canMove = firstPegDisc < lastPegDisc canMove = firstPegDisc < lastPegDisc
in if canMove in if canMove
then then
( [ (firstPegLabel, init firstPeg), ( Just $ Move firstPegLabel lastPegLabel,
[ (firstPegLabel, init firstPeg),
head $ tail pegs, head $ tail pegs,
(lastPegLabel, lastPeg <> [firstPegDisc]) (lastPegLabel, lastPeg <> [firstPegDisc])
], ]
[Move firstPegLabel lastPegLabel]
) )
else (pegs, []) else (Nothing, [])
fillPegWithDiscs :: Int -> [Disc] fillPegWithDiscs :: Int -> [Disc]
fillPegWithDiscs numDisks = Disc <$> reverse [1 .. numDisks] fillPegWithDiscs numDisks = Disc <$> reverse [1 .. numDisks]