Applying the evaluate-object operator
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The evaluate-object operator, as with all other operators, can apply either
directly or in a subgoal.  To apply it directly, domain-dependent productions
must augment the operator's evaluation object with a value.

If a no-change impasse arises after an instance of evaluate-object has been
selected, the evaluation will be computed in the resulting subgoal.  The
{evaluation subgoal} is discussed in Section See Computing evaluations on
page See Computing evaluations.  Once subgoals have been used to compute
evaluations, chunks that have been built from the subgoals can directly
compute the evaluations.

Terminating the operator is done automatically by the default productions
once the evaluation object has a value.  If the evaluation produced by the
operator does not lead to the termination of the multi-choice subgoal, the
reconsider preference will lead to the selection of another evaluate-object
operator.