From d33f32d5cc06179e1367214100bb5e39ea4c02bf Mon Sep 17 00:00:00 2001
From: Jon Kristensen <jon.kristensen@nejla.com>
Date: Sat, 21 Apr 2012 19:23:48 +0200
Subject: [PATCH] removed head and tail

---
 src/Network/XMPP/Utilities.hs | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/Network/XMPP/Utilities.hs b/src/Network/XMPP/Utilities.hs
index 7841698..039924a 100644
--- a/src/Network/XMPP/Utilities.hs
+++ b/src/Network/XMPP/Utilities.hs
@@ -38,8 +38,11 @@ idGenerator prefix = atomically $ do
     next :: TVar [Text.Text] -> IO Text.Text
     next tvar = atomically $ do
         list <- readTVar tvar
-        writeTVar tvar $ tail list
-        return $ head list
+        case list of
+          [] -> error "empty list in Utilities.hs"
+          (x:xs) -> do
+            writeTVar tvar xs
+            return x
 
     -- Generates an infinite and predictable list of IDs, all beginning with the
     -- provided prefix.