Data commit

Task/Box-the-compass/Haskell/box-the-compass.hs

@@ -0,0 +1,70 @@
+import Data.Char (toUpper)
+
+import Data.Maybe (fromMaybe)
+
+import Text.Printf (PrintfType, printf)
+
+dirs :: [String]
+dirs =
+  [ "N"
+  , "NbE"
+  , "N-NE"
+  , "NEbN"
+  , "NE"
+  , "NEbE"
+  , "E-NE"
+  , "EbN"
+  , "E"
+  , "EbS"
+  , "E-SE"
+  , "SEbE"
+  , "SE"
+  , "SEbS"
+  , "S-SE"
+  , "SbE"
+  , "S"
+  , "SbW"
+  , "S-SW"
+  , "SWbS"
+  , "SW"
+  , "SWbW"
+  , "W-SW"
+  , "WbS"
+  , "W"
+  , "WbN"
+  , "W-NW"
+  , "NWbW"
+  , "NW"
+  , "NWbN"
+  , "N-NW"
+  , "NbW"
+  ]
+
+-- Index between 0 and 31 ->  the corresponding compass point name.
+pointName :: Int -> String
+pointName = capitalize . concatMap (fromMaybe "?" . fromChar) . (dirs !!)
+  where
+    fromChar c =
+      lookup
+        c
+        [ ('N', "north")
+        , ('S', "south")
+        , ('E', "east")
+        , ('W', "west")
+        , ('b', " by ")
+        , ('-', "-")
+        ]
+    capitalize (c:cs) = toUpper c : cs
+
+-- Degrees -> compass point index between 0 and 31.
+pointIndex :: Double -> Int
+pointIndex d = (round (d * 1000) + 5625) `mod` 360000 `div` 11250
+
+printPointName :: PrintfType t => String -> t
+printPointName d =
+  let deg = read d :: Double
+      idx = pointIndex deg
+  in printf "%2d  %-18s  %6.2f°\n" (idx + 1) (pointName idx) deg
+
+main :: IO ()
+main = mapM_ (printPointName . show) [0 .. 31]