let merge_acc acc1 acc2 =
{
p_hyp = acc1.p_hyp @ acc2.p_hyp;
p_goal = acc1.p_goal @ acc2.p_goal;
p_both = acc1.p_both @ acc2.p_both;
p_cut = acc1.p_cut @ acc2.p_cut;
call_hyp = acc1.call_hyp @ acc2.call_hyp;
call_pre = acc1.call_pre @ acc2.call_pre;
a_goal = WpPropId.merge_assign_info acc1.a_goal acc2.a_goal;
a_hyp = WpPropId.merge_assign_info acc1.a_hyp acc2.a_hyp;
a_call = WpPropId.merge_assign_info acc1.a_call acc2.a_call;
}