Done task 5

[summerofcode2018soln.git] / src / task5 / task5.hs

diff --git a/src/task5/task5.hs b/src/task5/task5.hs
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+{-# LANGUAGE OverloadedStrings #-}
+
+import Data.Text (Text)
+import qualified Data.Text as T
+import qualified Data.Text.IO as TIO
+import Data.Char (isSpace)
+
+
+main :: IO ()
+main = do 
+        text <- TIO.readFile "data/05-instructions.txt"
+        let uncommented = deComment text
+        let expanded = expand uncommented
+        print $ countNonSpace uncommented
+        print $ countNonSpace expanded
+
+
+countNonSpace :: Text -> Int
+countNonSpace = T.length . T.filter (\c -> not (isSpace c))
+
+
+-- Remove comments
+deComment :: Text -> Text
+deComment text = deComment' (extractFirstComment text) text
+
+-- If there are no comments, return the text as-is
+-- If there is a first comment, decomment the rest
+deComment' :: Maybe (Text, Text) -> Text -> Text
+deComment' Nothing text = text
+deComment' (Just (prefix, suffix)) _ = prefix `T.append` (deComment suffix)
+
+-- Monad notation to string togeether all the Maybes
+extractFirstComment :: Text -> Maybe (Text, Text)
+extractFirstComment text = 
+    do (prefix, commentSuffix) <- maybeBreakOn "<" text
+       (_, suffix) <- maybeBreakOn ">" commentSuffix
+       return (prefix, suffix)
+
+
+-- Expand compression
+expand :: Text -> Text
+expand text = expand' (extractFirstExpander text) text
+
+-- If there are no compression markers, return the text
+-- If there's one, expand it, and try again.
+expand' :: Maybe (Text, Int, Int, Text) -> Text -> Text
+expand' Nothing text = text
+expand' (Just (prefix, expandLen, expandCount, suffix)) _ =
+    expand (expandedPrefix `T.append` suffix)
+    where unexpandedPrefix = T.dropEnd expandLen prefix
+          group = T.takeEnd expandLen prefix
+          expanded  = T.replicate expandCount group
+          expandedPrefix = unexpandedPrefix `T.append` expanded
+
+extractFirstExpander :: Text -> Maybe (Text, Int, Int, Text)
+extractFirstExpander text = 
+    do (prefix, suffix) <- maybeBreakOn ":" text
+       (expanderLenT, suffix') <- maybeBreakOn ":" suffix
+       (expanderCountT, suffix'') <- maybeBreakOn ":" suffix'
+       let expanderLen = read $ T.unpack expanderLenT
+       let expanderCount = read $ T.unpack expanderCountT
+       return (prefix, expanderLen, expanderCount, suffix'')
+
+
+-- Uses Text.breakOn, but puts the result in a Maybe
+-- Also drops the needle from the returned suffix.
+maybeBreakOn :: Text -> Text -> Maybe (Text, Text)
+maybeBreakOn needle haystack =
+    if T.null suffix
+    then Nothing
+    else Just (prefix, T.drop (T.length needle) suffix)
+    where (prefix, suffix) = T.breakOn needle haystack