Jan Burse, created Aug 17. 2019
* This module allows accessing the continuation queue and the verify flag.
* The predicate sys_assume_cont/1 will push a delayed goal. This predicate
* will also place an undo handler on the trail that will pop the
* delayed goal upon backtracking.
* When the verify flag allows it the whole continuation queue is executed
* either on the next exit port of a builtin or the next unification port of
* a defined predicate. The verify flag is automatically disabled during
* execution of an attribute variable hook.
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* The predicate temporarily pushes the goal G on the continuation queue.
* The predicate succeeds whenever A succeeds. The goal A is
* invoked with the verify flag temporarily set to off.