18_a_1: Add missing module CountEntries from the examples

1 files changed, 22 insertions, 0 deletions

diff --git a/ch18/CountEntries.hs b/ch18/CountEntries.hs
new file mode 100644
index 0000000..706bec2
--- /dev/null
+++ b/ch18/CountEntries.hs
@@ -0,0 +1,22 @@
+{-- snippet countEntriesTrad --}

+module CountEntries (listDirectory, countEntriesTrad) where

+

+import System.Directory (doesDirectoryExist, getDirectoryContents)

+import System.FilePath ((</>))

+import Control.Monad (forM, liftM)

+

+listDirectory :: FilePath -> IO [String]

+listDirectory = liftM (filter notDots) . getDirectoryContents

+    where notDots p = p /= "." && p /= ".."

+

+countEntriesTrad :: FilePath -> IO [(FilePath, Int)]

+countEntriesTrad path = do

+  contents <- listDirectory path

+  rest <- forM contents $ \name -> do

+            let newName = path </> name

+            isDir <- doesDirectoryExist newName

+            if isDir

+              then countEntriesTrad newName

+              else return []

+  return $ (path, length contents) : concat rest

+{-- /snippet countEntriesTrad --}