static void identify_floor_missiles_matching(item_def mitem, int idflags)
{
    mitem.flags &= ~idflags;
    int item = NON_ITEM;
    for (int y = 0; y < GYM; ++y)
        for (int x = 0; x < GXM; ++x)
        {
            item = igrd[x][y];
            while (item != NON_ITEM)
            {
                item_def &i(mitm[item]);
                item = i.link;
                if ((i.flags & ISFLAG_THROWN) && items_stack(i, mitem))
                    i.flags |= idflags;
            }
        }
}

                identify_floor_missiles_matching(item, ISFLAG_KNOW_PLUSES);

            identify_floor_missiles_matching(item, ISFLAG_KNOW_PLUSES);