An 'a Cutoff.t is a function that returns true if propagation of changes should
be cutoff at a node based on the old value and the (possible) new value of the
node.
include sig ... endval sexp_of_t : ('a ‑> Sexplib.Sexp.t) ‑> 'a t ‑> Sexplib.Sexp.tinclude Core_kernel.Invariant.S1 with type a t := a tval invariant : 'a Base__.Invariant_intf.inv ‑> 'a t Base__.Invariant_intf.invval create : (old_value:'a ‑> new_value:'a ‑> bool) ‑> 'a tval of_compare : ('a ‑> 'a ‑> int) ‑> 'a tval always : _ tval never : _ tval phys_equal : _ tval poly_equal : _ tval should_cutoff : 'a t ‑> old_value:'a ‑> new_value:'a ‑> bool