Restructure files, add new subsystems

OS/FileExt.hs

@@ -0,0 +1,34 @@
+{-# OPTIONS_HADDOCK ignore-exports #-}
+
+module OS.FileExt where
+
+
+-- |Compare the extension of a file with the given String.
+cmpExt :: String -> FilePath -> Bool
+cmpExt checkExt = (==) checkExt . getExt
+
+
+-- |Get the extension of a file.
+getExt :: FilePath -> String
+getExt fp
+  | hasExt fp = last   .
+      splitBy (== '.') .
+      last             .
+      splitBy (== '/') $
+      fp
+  | otherwise = ""
+
+
+-- |Check if the file has an extension.
+hasExt :: FilePath -> Bool
+hasExt = (>1) . length . splitBy (== '.')
+
+
+-- |Split an array into subarrays depending on a given condition.
+splitBy :: (a -> Bool) -- ^ condition
+        -> [a]         -- ^ array to split
+        -> [[a]]       -- ^ splitted array
+splitBy f s =  case dropWhile f s of
+                 [] -> []
+                 s' -> w : splitBy f s''
+                   where (w, s'') = break f s'