【scala初学】collections Sets

        

Set，与Seq, Map并列

Set是没有重复元素的Iterable,方法分为以下几类：

• Test 

  方法：contains, apply, subsetOf

   contains方法询问是否set包含了yield被给与的元素.

   apply同contains,即 set(elem) 等同于 set contains elem

For example

scala> val fruit = Set("apple", "orange", "peach", "banana")
fruit: scala.collection.immutable.Set[java.lang.String] = Set(apple, orange, peach, banana)
scala> fruit("peach")
res0: Boolean = true
scala> fruit("potato")
res1: Boolean = false

• Additions

  方法：+ and ++

   增长一个或者多个元素

• Removals

  方法: - , --

   删除一个或者多个元素

• Set operations

  方法：union, intersection, diff

   这些方法有两种形式，字母和字符。

   

intersect	&
union	|
diff	&~

 继承自Traversable的++方法有点相似unoin。（后面略，没意义）

Class Set 操做

WHAT IT IS	WHAT IT DOES
Tests:
xs contains x	测试 xs是否包含x
xs(x)	同上
xs subsetOf ys	测试xs是不是ys的子集
Additions:
xs + x	Set xs 添加元素x ，返回Set(子类可能重写)
xs + (x, y, z)	Set xs 添加括号中的元素 返回Set
xs ++ ys	xs ys合并后的全部元素 返回 Set
Removals
xs - x	Set 包含xs中除去x的全部元素
xs - (x, y, z)	Set 包含xs出去括号中元素的全部元素
xs -- ys	Set 包含xs中除去ys中元素的全部元素
xs.empty	清空xs
Binary Operations:
xs & ys	xs和ys的交集
xs intersect ys
xs | ys	xs和ys的并集
xs union ys
xs &~ ys	xs和ys的区别
xs diff ys