orChildren :: T.Tree (Feature a) -> [Feature a]
orChildren ftree = concat [children f | f <- subtrees ftree, isOrFeature (fnode f)]
orChildren :: T.Tree (Feature a) -> [Feature a]
orChildren ftree = concat [children f | f <- subtrees ftree, isOrFeature (fnode f)]
orChildren ftree = concat [children f | f <- subtrees ftree, isOrFeature (fnode f)]