September 2017 Update

Task/Catamorphism/Haskell/catamorphism-1.hs

@@ -0,0 +1,8 @@
+main :: IO ()
+main =
+  putStrLn . unlines $
+  [ show . foldr (+)    0  -- sum
+  , show . foldr (*)    1  -- product
+  , foldr ((++) . show) "" -- concatenation
+  ] <*>
+  [[1 .. 10]]

Task/Catamorphism/Haskell/catamorphism-2.hs

@@ -0,0 +1,12 @@
+import Data.Monoid
+
+main :: IO ()
+main =
+  let xs = [1 .. 10]
+  in (putStrLn . unlines)
+       [ (show . getSum     . foldr (<>) mempty) (Sum     <$> xs)
+       , (show . getProduct . foldr (<>) mempty) (Product <$> xs)
+       , (show .              foldr (<>) mempty) (show    <$> xs)
+       , (show .              foldr (<>) mempty) (words
+                     "Love is one damned thing after each other")
+       ]

Task/Catamorphism/Haskell/catamorphism.hs

@@ -1,5 +0,0 @@
-nums = [1..10]
-
-summation = foldl (+) 0 nums
-product = foldl (*) 1 nums
-concatenation = foldr (\num s -> show num ++ s) "" nums