arc> (ssexpand 'a:.b)
(compose a .b)
arc> (ssexpand '.b)
So, we need to recurse in the f argument anyway. At a certain point, it seems like the anonymous & higher-order functions add layers of indirection on what should just be a straightforward recursive definition.
I get really annoyed at that, though, when working with trees in Arc. There always seems to be some underlying pattern that's just different enough that I can't abstract it into a higher-order function.