Summary:
Add support for nary predicates, not just unary ones. Many operations
don't make much sense for nullary predicates, and are generally treated
as no-ops. The first argument is treated specially, as the "anchor" of
the predicate application. For example, adding or removing an attribute
uses the anchor to identify the atom to operate on. Also, abstraction
and normalization operations treat the anchor specially.
Reviewed By: cristianoc
Differential Revision: D3669391
fbshipit-source-id: 3d142ea
Josh Berdine
4185bda8ba