(
    (defun filtermap_fun (process remaining init)
        (if remaining
            (assign next (a process (list (f remaining)))
                (if next 
                    (c next (filtermap process (r remaining) init))
                    (filtermap process (r remaining) init)
                )
            )
            init
        )
    )

    (defmac filtermap (process remaining . maybe_init)
        (if maybe_init
           (qq (filtermap_fun (unquote process) (unquote remaining) (unquote (f maybe_init))))
           (qq (filtermap_fun (unquote process) (unquote remaining) ()))
        )
    )
)