[handle the case when there are no enums to declare
John Meacham <john@repetae.net>**20070510080759] hunk ./C/FromGrin2.hs 86
-    enum_tag_t = text "enum {" $$ nest 4 (P.vcat (punctuate P.comma $ map (uncurry f) (Map.toList wenum) ++ (zipWith f (Set.toList (Set.map nodeTagName ts)) [0 ..]))) $$ text "};" where
-        f t n = tshow t <> text " = " <> tshow (n :: Int)
+    enum_tag_t | null enums = mempty
+               | otherwise  = text "enum {" $$ nest 4 (P.vcat (punctuate P.comma $ enums)) $$ text "};"
+        where
+            f t n = tshow t <> text " = " <> tshow (n :: Int)
+            enums =  map (uncurry f) (Map.toList wenum) ++ (zipWith f (Set.toList (Set.map nodeTagName ts)) [0 ..])