/* * Return the number of decisions after solving. * * If its >0, a solution of the Request was found. * * If its ==0, and 'Solver.problems?' returns +true+, the Request couldn't be solved. * * If its ==0, and 'Solver.problems?' returns +false+, the Request is trivially solved. * * call-seq: * solver.decision_count -> int * */ int decision_count()