58.scala编程思想笔记——序列

58.scala编程思想笔记——序列
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源码下载连接请见第一篇笔记。         

Vector是一种集合，可以在集合中存储事务。Vector还是一种序列，此外还有另一种基本序列，即List.  可以在不导入任何类的情况下使用它们，就像它们是语言中的固有类型一样。

         Vector和List继承自Seq序列，因此具有公共的操作，所以testSeq方法在其上都可以运行。

例如：

import com.atomicscala.AtomicTest._

 

testSeq(Vector(1, 7, 22, 11, 17))

testSeq(List(1, 7, 22, 11, 17))

 

def testSeq(s:Seq[Int]) = {

  // Is thereanything inside?

  s.isEmpty isfalse

  // How manyelements inside?

  s.length is 5

 

  // Appendingto the end:

  s :+ 99 isSeq(1, 7, 22, 11, 17, 99)

  // Insertingat the beginning:

  47 +: s isSeq(47, 1, 7, 22, 11, 17)

 

  // Get thefirst element:

  s.head is 1

  // Get therest after the first:

  s.tail isSeq(7, 22, 11, 17)

  // Get thelast element:

  s.last is 17

  // Get allelements after the 3rd:

  s.drop(3) isSeq(11, 17)

  // Get allelements except last 3:

 s.dropRight(3) is Seq(1, 7)

  // Get first3 elements:

  s.take(3) isSeq(1, 7, 22)

  // Get final3 elements:

 s.takeRight(3) is Seq(22, 11, 17)

  // Sectionfrom indices 2 up to 5:

  s.slice(2,5)is Seq(22, 11, 17)

 

  // Get valueat location 3:

  s(3) is 11

  // See if itcontains a value:

 s.contains(22) is true

  s.indexOf(22)is 2

  // Replacevalue at location 3:

  s.updated(3,16) is

    Seq(1, 7,22, 16, 17)

  // Removelocation 3:

  s.patch(3,Nil, 1) is

    Seq(1, 7,22, 17)

 

  // Append twosequences:

  val seq2 = s++ Seq(99, 88)

  seq2 isSeq(1, 7, 22, 11, 17, 99, 88)

  // Find theunique values and sort them:

 s.distinct.sorted is

    Seq(1, 7,11, 17, 22)

  // Reversethe order:

  s.reverse is

    Seq(17, 11,22, 7, 1)

  // Find thecommon elements:

 s.intersect(seq2) is Seq(1,7,22,11,17)

  // Smallestand largest values:

  s.min is 1

  s.max is 22

  // Does itbegin or end

  // with thesesequences?

 s.startsWith(Seq(1,7)) is true

  s.endsWith(Seq(11,17))is true

  // Total allthe values:

  s.sum is 58

  // Multiplytogether all the values:

  s.product is28798

  //"Set" forces unique values:

  s.toSet isSet(1, 17, 22, 7, 11)

}