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authorjao <jao@gnu.org>2018-11-21 23:51:41 +0000
committerjao <jao@gnu.org>2018-11-21 23:51:41 +0000
commit50134d5b5c4baabdfb35c0aeb8bf53d29f009c4d (patch)
treea710ee9a8e9ea9e46951d371af29081e1c72f502 /src/lib/Xmobar/Plugins/Utils.hs
parent7674145b878fd315999558075edcfc5e09bdd91c (diff)
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+------------------------------------------------------------------------------
+-- |
+-- Module: Plugins.Utils
+-- Copyright: (c) 2010 Jose Antonio Ortega Ruiz
+-- License: BSD3-style (see LICENSE)
+--
+-- Maintainer: Jose A Ortega Ruiz <jao@gnu.org>
+-- Stability: unstable
+-- Portability: unportable
+-- Created: Sat Dec 11, 2010 20:55
+--
+--
+-- Miscellaneous utility functions
+--
+------------------------------------------------------------------------------
+
+
+module Xmobar.Plugins.Utils (expandHome, changeLoop, safeHead) where
+
+import Control.Monad
+import Control.Concurrent.STM
+
+import System.Environment
+import System.FilePath
+
+
+expandHome :: FilePath -> IO FilePath
+expandHome ('~':'/':path) = fmap (</> path) (getEnv "HOME")
+expandHome p = return p
+
+changeLoop :: Eq a => STM a -> (a -> IO ()) -> IO ()
+changeLoop s f = atomically s >>= go
+ where
+ go old = do
+ f old
+ go =<< atomically (do
+ new <- s
+ guard (new /= old)
+ return new)
+
+safeHead :: [a] -> Maybe a
+safeHead [] = Nothing
+safeHead (x:_) = Just x