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patched 2020-19 in haskell

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This commit is contained in:
Julien Dessaux 2023-05-05 23:01:55 +02:00
parent ee4fa81423
commit dc4363d9e7
Signed by: adyxax
GPG key ID: F92E51B86E07177E
1 changed files with 3 additions and 3 deletions
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6
2020/19-Monster_Messages/first.hs
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@ -3,7 +3,6 @@ module Main (main) where
import Control.Monad (void, when)
import Data.Either
import Data.List (foldl')
import Data.Maybe (isJust)
import Data.Map qualified as M
import Data.Void (Void)
import Text.Megaparsec
@ -70,11 +69,12 @@ compute (Input rules messages) = length . filter id $ map isValid messages
Just "" -> True
otherwise -> False
matches :: RuleID -> Message -> Maybe Message
matches _ [] = Nothing
matches ruleId msg = case rules M.! ruleId of
Left c -> if head msg == c then (Just $ tail msg) else Nothing
Right actions -> case map (processAction msg) actions of
Nothing:a:_ -> a
a:_ -> a
Just a:_ -> Just a
Nothing:Just a:_ -> Just a
otherwise -> Nothing
processAction :: Message -> Action -> Maybe Message
processAction msg action = foldl' step (Just msg) action