-- | Variant of 'choices' that only approximates the number of choices,
-- using 'llength'.
lchoices :: Tree a -> Int
lchoices (PChoice    _ _     ts) = P.llength (P.filter active ts)
lchoices :: Tree a -> Int
lchoices (PChoice    _ _     ts) = P.llength (P.filter active ts)
lchoices (PChoice    _ _     ts) = P.llength (P.filter active ts)