Add Haskell port

haskell/src/GildedRose.hs

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+module GildedRose where
+
+type GildedRose = [Item]
+
+data Item = Item String Int Int
+  deriving (Eq)
+
+instance Show Item where
+  show (Item name sellIn quality) =
+    name ++ ", " ++ show sellIn ++ ", " ++ show quality
+
+updateQuality :: GildedRose -> GildedRose
+updateQuality = map updateQualityItem
+  where
+    updateQualityItem (Item name sellIn quality) =
+      let
+        quality' =
+          if name /= "Aged Brie"
+             && name /= "Backstage passes to a TAFKAL80ETC concert"
+          then
+            if quality > 0
+            then
+              if name /= "Sulfuras, Hand of Ragnaros"
+              then quality - 1
+              else quality
+            else quality
+          else
+            if quality < 50
+            then
+              quality + 1 +
+                (if name == "Backstage passes to a TAFKAL80ETC concert"
+                 then
+                   if sellIn < 11
+                   then
+                     if quality < 49
+                     then
+                       1 + (if sellIn < 6
+                            then
+                              if quality < 48
+                              then 1
+                              else 0
+                            else 0)
+                     else 0
+                   else 0
+                 else 0)
+            else quality
+
+        sellIn' =
+          if name /= "Sulfuras, Hand of Ragnaros"
+          then sellIn - 1
+          else sellIn
+      in
+        if sellIn' < 0
+        then
+          if name /= "Aged Brie"
+          then
+            if name /= "Backstage passes to a TAFKAL80ETC concert"
+            then
+              if quality' > 0
+              then
+                if name /= "Sulfuras, Hand of Ragnaros"
+                then (Item name sellIn' (quality' - 1))
+                else (Item name sellIn' quality')
+              else (Item name sellIn' quality')
+            else (Item name sellIn' (quality' - quality'))
+          else
+            if quality' < 50
+            then (Item name sellIn' (quality' + 1))
+            else (Item name sellIn' quality')
+        else (Item name sellIn' quality')

haskell/src/Main.hs

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+module Main where
+
+import System.Environment
+import GildedRose
+
+
+main :: IO ()
+main = do
+  putStrLn "OMGHAI!"
+
+  let inventoriesWithDay = inventories `zip` [0..]
+      inventories = iterate updateQuality initialInventory
+
+  numberOfDays <- daysFromArg
+  mapM_ printUpdate (take numberOfDays inventoriesWithDay)
+
+  where
+    printUpdate :: (GildedRose, Int) -> IO ()
+    printUpdate (items, day) = do
+      putStrLn ("-------- day " ++ show day ++ " --------")
+      putStrLn "name, sellIn, quality"
+      mapM_ (putStrLn . show) items
+      putStrLn ""
+
+    daysFromArg :: IO Int
+    daysFromArg = do
+      args <- getArgs
+      return $ if length args > 0
+                  then read (head args)
+                  else 20
+
+    initialInventory :: GildedRose
+    initialInventory =
+      [ Item "+5 Dexterity Vest"                          10  20
+      , Item "Aged Brie"                                   2   0
+      , Item "Elixir of the Mongoose"                      5   7
+      , Item "Sulfuras, Hand of Ragnaros"                  0  80
+      , Item "Sulfuras, Hand of Ragnaros"                (-1) 80
+      , Item "Backstage passes to a TAFKAL80ETC concert"  15  20
+      , Item "Backstage passes to a TAFKAL80ETC concert"  10  49
+      , Item "Backstage passes to a TAFKAL80ETC concert"   5  49
+      -- this conjured item does not work properly yet
+      , Item "Conjured Mana Cake"                          3   6
+      ]