next_base

Given a leaf_type and a root_type which is contained in its ancestry, return the type that root_type is the immediate parent of.

In other words, this function determines the type that is derived directly from root_type which is also a base class of leaf_type. Given a root type and a leaf type, this function can be used to determine the types and order in which the leaf type is descended from the root type.

Parameters:

root_type	immediate parent of the returned type
leaf_type	descendant of root_type and the type to be returned

Returns:

immediate child of root_type and ancestor of leaf_type