+setMainIs :: String -> IO ()
+setMainIs arg
+ | not (null main_mod) -- The arg looked like "Foo.baz"
+ = do { writeIORef v_MainFunIs (Just main_fn) ;
+ writeIORef v_MainModIs (Just main_mod) }
+
+ | isUpper (head main_fn) -- The arg looked like "Foo"
+ = writeIORef v_MainModIs (Just main_fn)
+
+ | otherwise -- The arg looked like "baz"
+ = writeIORef v_MainFunIs (Just main_fn)
+ where
+ (main_mod, main_fn) = split_longest_prefix arg (== '.')
+
+