entrytree_map_path :: Entry a => 
    (EntryTree a -> Maybe [EntryTree a] -> Loc -> Maybe [EntryTree a])
    -> [EntryTree a] -> Loc -> Maybe [EntryTree a]
entrytree_map_path f et (Loc ll) = entrytree_map_path_ f et ll [0]
entrytree_map_path :: Entry a => 
    (EntryTree a -> Maybe [EntryTree a] -> Loc -> Maybe [EntryTree a])
    -> [EntryTree a] -> Loc -> Maybe [EntryTree a]
entrytree_map_path f et (Loc ll) = entrytree_map_path_ f et ll [0]
entrytree_map_path f et (Loc ll) = entrytree_map_path_ f et ll [0]