KeepIf 指令

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KeepIf[ <Condition>, <List> ]

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KeepIf[Condition, List]

Creates a new list that only contains those elements of the initial list that fulfil the condition.

範例： KeepIf[x<3, {1, 2, 3, 4, 1, 5, 6}] returns the new list {1, 2, 1}.

備註： For list of numbers arbitrary condition may be used. For list of other objects one can use only conditions of the form x==constant or x!=constant.