pub fn force_cycle<T: Hash + Eq + Debug + Clone + 'static>(
) -> T
Demands and observes the value of an
&Art<T>, returning a
(cloned) value of type
T, or the value of
cycle_out if the
force edge forms a cycle in the DCG.
Note that if the articulation
a is not a thunk, then
will not be used (cycles in the DCG are formed by thunks forcing
one another, not by reference cells).