combine_strees
a_T_b_T = combine_strees(a_T, a_T_b_fake, __pop_cond_true_stack());
a_T_b_F = combine_strees(a_T, a_T_b_fake, __pop_cond_false_stack());
a_F_c_T = combine_strees(a_F, a_F_c_fake, __pop_cond_true_stack());
a_F_c_F = combine_strees(a_F, a_F_c_fake, __pop_cond_false_stack());