Year 2015 Day 2 Part 2

src/Years/Y2015/Day2.idr

@@ -22,6 +22,16 @@ record Box where
 (.slack) (MkBox length width height) =
   foldl1 min [length * width, width * height, length * height]
 
+(.ribbon) : Box -> Integer
+(.ribbon) (MkBox length width height) =
+  foldl1 min [2 * (length + width), 2 * (length + height), 2 * (width + height)]
+
+(.bow) : Box -> Integer
+(.bow) (MkBox length width height) = length * width * height
+
+totalRibbon : Box -> Integer
+totalRibbon x = x.ribbon + x.bow
+
 paperNeeded : Box -> Integer
 paperNeeded x = x.area + x.slack
 
@@ -35,13 +45,16 @@ parseBox str = do
   height <- note "Failed parsing height: \{show h}" $ parsePositive h
   pure $ MkBox length width height
 
-part1 : Eff (PartEff String) (Integer, ())
+part1 : Eff (PartEff String) (Integer, List Box)
 part1 = do
   input <- map lines $ askAt "input"
   boxes <- traverse parseBox input
   let output = sum . map paperNeeded $ boxes
-  pure (output, ())
+  pure (output, boxes)
+
+part2 : (boxes : List Box) -> Eff (PartEff String) Integer
+part2 boxes = pure . sum . map totalRibbon $ boxes
 
 public export
 day2 : Day
-day2 = First 2 part1
+day2 = Both 2 part1 part2