September 2017 Update

Task/Floyds-triangle/Haskell/floyds-triangle-1.hs

@@ -1,12 +1,17 @@
-import Data.List
-import Control.Monad
-import Control.Arrow
+import Control.Monad (liftM2)
+
+floydTriangle =
+  liftM2
+    (zipWith (liftM2 (.) enumFromTo ((pred .) . (+))))
+    (scanl (+) 1)
+    id
+    [1 ..]
 
 alignR :: Int -> Integer -> String
-alignR n = (\s -> replicate (n - length s) ' ' ++ s). show
+alignR n = (\s -> replicate (n - length s) ' ' ++ s) . show
 
-floydTriangle = liftM2 (zipWith (liftM2 (.) enumFromTo ((pred.). (+)))) (scanl (+) 1) id [1..]
-
-formatFT n = mapM_ (putStrLn. unwords. zipWith alignR ws) t where
-  t = take n floydTriangle
-  ws = map (length. show) $ last t
+formatFT :: Int -> IO ()
+formatFT n = mapM_ (putStrLn . unwords . zipWith alignR ws) t
+  where
+    t = take n floydTriangle
+    ws = map (length . show) $ last t

Task/Floyds-triangle/Haskell/floyds-triangle-3.hs

@@ -0,0 +1,21 @@
+import Data.List (mapAccumL)
+
+floyd :: Int -> [[Int]]
+floyd n =
+  snd $
+  mapAccumL
+    (\start row -> (start + succ row, [start .. start + row]))
+    1
+    [0 .. pred n]
+
+-- TEST -----------------------------------------------------------------------
+showFloyd :: [[Int]] -> String
+showFloyd xs =
+  let padRight n = length >>= (<$> mappend (replicate n ' ')) . drop
+  in unlines $
+     (concat .
+      zipWith ((. show) . padRight) ((succ . length . show) <$> last xs)) <$>
+     xs
+
+main :: IO ()
+main = mapM_ putStrLn $ (showFloyd . floyd) <$> [5, 14]