Added assertMaybe

2 files changed, 8 insertions, 1 deletions

diff --git a/Spear.lkshw b/Spear.lkshw
index 2dd5288..f062526 100644
--- a/Spear.lkshw
+++ b/Spear.lkshw
@@ -1,7 +1,7 @@
 Version of workspace file format:
                1
 Time of storage:
-               "Thu Aug 30 20:54:09 CEST 2012"
+               "Thu Aug 30 20:57:58 CEST 2012"
 Name of the workspace:
                "Spear"
 File paths of contained packages:
diff --git a/Spear/Setup.hs b/Spear/Setup.hs
index cfe379c..e7917cf 100644
--- a/Spear/Setup.hs
+++ b/Spear/Setup.hs
@@ -8,6 +8,7 @@ module Spear.Setup
 ,   runSetup_
 ,   setupError
 ,   setupIO
+,   assertMaybe
 )
 where
 
@@ -50,3 +51,9 @@ setupError = MT.lift . throwError
 -- | Lift the given IO action into the 'Setup' monad.
 setupIO :: IO a -> Setup a
 setupIO = MT.lift . MT.lift
+
+
+-- | Throw the given error string if given 'Nothing'.
+assertMaybe :: Maybe a -> String -> Setup ()
+assertMaybe Nothing err = setupError err
+assertMaybe _ _ = return ()