&& is_terrain_known(pos1.x, pos1.y))

        && is_terrain_known(pos1))

        && is_terrain_known(pos2.x, pos2.y))

        && is_terrain_known(pos2))

    // OK, now we guarantee the move.

    // Swap features and colours.

    // Swap traps.

    // Swap shops.

        set_terrain_changed(pos1.x, pos1.y);

        set_terrain_changed(pos1);

        set_terrain_changed(pos2.x, pos2.y);

        set_terrain_changed(pos2);

    const int i1 = igrd(pos1);
    const int i2 = igrd(pos2);

    // Swap items.
    for (stack_iterator si(pos1); si; ++si)
        si->pos = pos1;

    igrd(pos1) = i2;
    igrd(pos2) = i1;
    if (igrd(pos1) != NON_ITEM)
    {
        for (stack_iterator si(igrd(pos1)); si; ++si)
            si->pos = pos1;
    }
    if (igrd(pos2) != NON_ITEM)
    {
        for (stack_iterator si(igrd(pos2)); si; ++si)
            si->pos = pos2;
    }

    for (stack_iterator si(pos2); si; ++si)
        si->pos = pos2;

    // Swap monsters.
    // Note that trapping nets, etc., move together
    // with the monster/player, so don't clear them.

    // Swap clouds.

                                    : mon->pronoun(PRONOUN_CAP_POSSESSIVE).c_str();

                                    : mon->pronoun(PRONOUN_CAP_POSSESSIVE);

    mons_clear_trapping_net(monster);

    mons_clear_trapping_net(monster);

void monsters::moveto( const coord_def& c )

void monsters::moveto(const coord_def& c)

    if (c != pos() && in_bounds(pos()))
        mons_clear_trapping_net(this);

    position = newpos;

    moveto(newpos);

    // set new monster grid pointer to this monster.
    mgrd(newpos) = monster_index(this);

    // Set new monster grid pointer to this monster.
    mgrd(newpos) = mindex();

        mons_clear_trapping_net(mon);

    for (int x = 0; x < GXM; x++)
        for (int y = 0; y < GYM; y++)

    for (rectangle_iterator ri(1); ri; ++ri)
    {
        if (grid_stair_direction(grd(*ri)) == cmd)

             if (grid_stair_direction(grd[x][y]) == cmd)
             {
                stair_pos.set(x, y);
                break;
             }

            stair_pos = *ri;
            break;

    }

    clear_trapping_net();

    mons_clear_trapping_net(mon1);

    int mid2 = mgrd(moves.target);

    const int mid2 = mgrd(moves.target);

    {

        mons_clear_trapping_net(mon2);
    }

    // Shift all monsters & items to new area.

    // Shift all monsters and items to new area.

        move_item_stack_to_grid( *ri, newpos );

        move_item_stack_to_grid(*ri, newpos);

        if ( mgrd(*ri) != NON_MONSTER )

        if (mgrd(*ri) != NON_MONSTER)