Multiplication tables: Difference between revisions

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@@ Line 2,242: / Line 2,242: @@
 =={{header|Haskell}}==
-<lang haskell>import Control.Monad
+<lang haskell>multTable :: Int -> [[Maybe Int]]
+multTable n =
-import Text.Printf
+  (\x ->
+      Just x :
-main = do
+      Nothing :
-    putStrLn $ "   x" ++ concatMap fmt [1..12]
+      ((\y ->
-    zipWithM_ f [1..12] $ iterate ("    " ++) ""
+           if y < x
-  where f n s = putStrLn $ fmt n ++ s ++ concatMap (fmt . (*n)) [n..12]
-        fmt n = printf "%4d" (n :: Int)</lang>
+             then Nothing
+             else Just (x * y)) <$>
+       range)) <$>
+  range
-Or, making do without imports beyond the Prelude, and separating data from formatting:
+  where
+    range = [1 .. n]
-<lang Haskell>multTable :: Int -> [[Maybe Int]]
-multTable n =
-    (\x ->   Just x    : Nothing : (
-    (\y -> if y < x then Nothing else Just (x * y))
-        <$> range))
-        <$> range
-      where range = [1..n]
 tableString :: [[Maybe Int]] -> String
-tableString tbl =
+tableString tbl = unlines $ (concat . (fmt <$>)) <$> tbl
+  where
-    unlines $ (concat . (fmt <$>)) <$> tbl
+    pad = "    "
+    fmt Nothing = pad
+    fmt (Just n) = drop (length s) (pad ++ s)
       where
-        pad          = "    "
+        s = show n
-        fmt  Nothing = pad
-        fmt (Just n) = drop (length s) (pad ++ s)
-          where
-            s = show n
 main :: IO ()