【scala初學】collections Sets

        

Set，與Seq, Map並列

Set是沒有重複元素的Iterable,方法分爲以下幾類：

• Test 

  方法：contains, apply, subsetOf

   contains方法詢問是否set包含了yield被給與的元素.

   apply同contains,即 set(elem) 等同於 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 ++

   增長一個或者多個元素

• Removals

  方法: - , --

   刪除一個或者多個元素

• Set operations

  方法：union, intersection, diff

   這些方法有兩種形式，字母和字符。

   

intersect	&
union	|
diff	&~

 繼承自Traversable的++方法有點相似unoin。（後面略，沒意義）

Class Set 操做

WHAT IT IS	WHAT IT DOES
Tests:
xs contains x	測試 xs是否包含x
xs(x)	同上
xs subsetOf ys	測試xs是不是ys的子集
Additions:
xs + x	Set xs 添加元素x ，返回Set(子類可能重寫)
xs + (x, y, z)	Set xs 添加括號中的元素 返回Set
xs ++ ys	xs ys合併後的全部元素 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出去括號中元素的全部元素
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的並集
xs union ys
xs &~ ys	xs和ys的區別
xs diff ys