backtrack

Resumes this choice point: restores its saved executionContext (carrying over context's current step counter, flags and knowledge bases), advances alternatives to the next one, and returns the resulting ClassicExecutionContext, ready to be handed to it.unibo.tuprolog.solve.classic.fsm.StatePrimitiveExecution or it.unibo.tuprolog.solve.classic.fsm.StateRuleExecution depending on the concrete subtype.