Scala

Unit01

scala> val arr = Array[Int](1,2,3,4,5)
arr: Array[Int] = Array(1, 2, 3, 4, 5)

scala> for (i<-arr){}

scala> for (i<-arr){println(i)}
1
2
3
4
5

角標來取值
scala> arr(2)
res2: Int = 3

scala> var idx = Array(0,1,2,3,4)
idx: Array[Int] = Array(0, 1, 2, 3, 4)

scala> for(i<-idx){println(arr(i))}


scala> 1 to 10
res4: scala.collection.immutable.Range.Inclusive = Range(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)

scala> 1.to(10)
res5: scala.collection.immutable.Range.Inclusive = Range(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)


scala> 0 until 5
res7: scala.collection.immutable.Range = Range(0, 1, 2, 3, 4)


scala> for(ele <- 0 to 5) println(arr(ele))
1
2
3
4
5
java.lang.ArrayIndexOutOfBoundsException: 5
  at $anonfun$1.apply$mcVI$sp(<console>:13)
  at scala.collection.immutable.Range.foreach$mVc$sp(Range.scala:160)
  ... 32 elided


scala> for (ele <- 0 until arr.length) println(arr(ele))
1
2
3
4
5

scala> arr
res9: Array[Int] = Array(1, 2, 3, 4, 5)

scala> for (ele <- arr){
     | if (ele%2==0) println(ele)
     | }
2
4

scala> for (ele <- arr;if ele%2==0) println(ele)
2
4

scala> for (ele <- arr if ele%2==0) println(ele)
2
4

雙層for循環
scala> for(i <- 1 to 3;j <- 1 to 3 if i != j) println(10*i+j)
12
13
21
23
31
32

scala> for(i <- 1 to 3;j <- 1 to 3 if i != j) yield(10*i+j)
res15: scala.collection.immutable.IndexedSeq[Int] = Vector(12, 13, 21, 23, 31, 32)

運算符重載
操做符重載成方法
scala> 1.+(2)
res16: Int = 3