September 2017 Update

Task/Map-range/Haskell/map-range.hs

@@ -1,21 +1,28 @@
 import Data.Ratio
-import Text.Printf
+import Text.Printf (PrintfType, printf)
 
 -- Map a value from the range [a1,a2] to the range [b1,b2].  We don't check
 -- for empty ranges.
-mapRange :: (Fractional a) => (a, a) -> (a, a) -> a -> a
-mapRange (a1,a2) (b1,b2) s = b1+(s-a1)*(b2-b1)/(a2-a1)
+mapRange
+  :: Fractional a
+  => (a, a) -> (a, a) -> a -> a
+mapRange (a1, a2) (b1, b2) s = b1 + (s - a1) * (b2 - b1) / (a2 - a1)
 
-main = do
-  -- Perform the mapping over floating point numbers.
+main :: IO ()
+main
+-- Perform the mapping over floating point numbers.
+ = do
   putStrLn "---------- Floating point ----------"
-  mapM_ (\n -> prtD n . mapRange (0,10) (-1,0) $ fromIntegral n) [0..10]
-
+  mapM_ (\n -> prtD n . mapRange (0, 10) (-1, 0) $ fromIntegral n) [0 .. 10]
   -- Perform the same mapping over exact rationals.
   putStrLn "---------- Rationals ----------"
-  mapM_ (\n -> prtR n . mapRange (0,10) (-1,0) $ n%1) [0..10]
-
-    where prtD :: PrintfType r => Integer -> Double -> r
-          prtD n x = printf "%2d -> %6.3f\n" n x
-          prtR :: PrintfType r => Integer -> Rational -> r
-          prtR n x = printf "%2d -> %s\n" n (show x)
+  mapM_ (\n -> prtR n . mapRange (0, 10) (-1, 0) $ n % 1) [0 .. 10]
+  where
+    prtD
+      :: PrintfType r
+      => Integer -> Double -> r
+    prtD = printf "%2d -> %6.3f\n"
+    prtR
+      :: PrintfType r
+      => Integer -> Rational -> r
+    prtR n x = printf "%2d -> %s\n" n (show x)