+ Just xx -> try_read sw xx
+
+
+try_read :: Read a => String -> String -> a
+-- (try_read sw str) tries to read s; if it fails, it
+-- bleats about flag sw
+try_read sw str
+ = case reads str of
+ ((x,_):_) -> x -- Be forgiving: ignore trailing goop, and alternative parses
+ [] -> ghcError (UsageError ("Malformed argument " ++ str ++ " for flag " ++ sw))
+ -- ToDo: hack alert. We should really parse the arugments
+ -- and announce errors in a more civilised way.