| Insert into . | | if () then | | Keep in . | | if () then | | Keep in . | | else | | if () then | | Delete from . (Suppose , and . The projection of and | | in the primitive direction is the same point.) | | else | | Keep in . | | end if | | end if | | else | | if () then | | Insert into , and delete from at the same time. (Suppose , | | and .) | | else | | if () then | | Keep in . | | else | | if () then | | Delete from . (Suppose , and ) | | else | | Keep in . | | end if | | end if | | end if | | end if |
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