Cons (which stands for construct) takes two arguments, the node data and the list that the bottom half of the pair will point to.
cons(代表construct)获得两个参数,即节点数据以及pair的下半部分将要指向的列表。
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They are slightly different from the node structures I showed you in c, above, because the bottom half of a pair doesn't have to be a pointer to a list node.
Other studies have already shown that tumor biology can change. One study, for example, showed that half of cancers change when they spread to the sentinel node.