Example 2
A branch and bound strategy that goes depth-first, but occasionally chooses to evaluate the node with the best lower bound value.
set_task_add_mode( ADD_TO_BEGIN );
set_task_retrieval_mode ( GET_FROM_BEGIN );
set_task_key_function ( &taskKey1 );
// In act_on_completed_task()
set_task_retrieval_mode( GET_BY_KEY );
set_task_retrieval_mode( GET_FROM_BEGIN );