一、映射定义精读1.映射是两个集合之间的一种对应关系,对应与集合一样,是一个原始概念,不能用更基本的概念来定义它.理解对应概念应注意下列两点: (1)A的元素都能在∫下确定至少一个元素属于B,即A的元素都“参加”; First, mapping definition Intensive reading 1. Mapping is a correspondence between two collections, correspondence and collection is a primitive concept, it can not be defined with a more basic concept. Understand the corresponding concept should pay attention to the following two points: ( 1) The elements of A can all determine that at least one element belongs to B, that is, the elements of A are all “participating”;