union of subsets

• 并集

union of subsets的用法和样例：

例句

1. This function returns the union of two or more specified sets.
   此函数返回两个或更多指定集的并集。
2. These include functions to move, shrink and inflate rects, find the union of two rects, and a variety of collision-detection functions.
   它们包括移动，收缩和膨胀矩形，找出两个矩形的并集，和一堆的碰撞检测函数。