scala> ////////////////////////////////////////////////////////////////
scala> // Typed Pattern : Pattern Matching a Type
scala> ////////////////////////////////////////////////////////////////
scala> def patternFn(x: Any) = x match {
| //
| case b: List[_] => println("List...")
|
| // This do not work because of type erasure #318
| case c: Map[Int, Int] => println("This is wrong...")
|
| case d: Map[_, _] => println("Map: This does work")
|
| // We dot have issue of Type Erasure with Array
| case e: Array[Int] => println("Array of Int...")
|
| case f: Array[_] => println("Array of other types...")
| }
<console>:28: warning: non-variable type argument Int in type pattern scala.collection.immutable.Map[Int,Int] (the underlying of Map[Int,Int]) is unchecked since it is eliminated by erasure
case c: Map[Int, Int] => println("This is wrong...")
^
<console>:30: warning: unreachable code
case d: Map[_, _] => println("Map: This does work")
^
patternFn: (x: Any)Unit
scala>
scala> // Not expected result because of type erasure
scala> patternFn(Map[Int, String](1 -> "a", 2 -> "b"))
This is wrong...
scala> // Expected result : For Array we do not have the issue of
scala> // type erasure
scala> patternFn(Array[Int](1, 2, 3))
Array of Int...
scala> patternFn(Array[Double](1.2, 2,2))
Array of other types...
scala> // Concatenate an array : Example #236
scala> val a1 = Array(1, 2, 3)
a1: Array[Int] = Array(1, 2, 3)
scala> val a2 = Array(5, 6, 7, 8, 9)
a2: Array[Int] = Array(5, 6, 7, 8, 9)
scala>
scala> val result = a1 ++ a2
result: Array[Int] = Array(1, 2, 3, 5, 6, 7, 8, 9)
scala>
scala> // zip operator : Example #236
scala> // zip can be used to create an array of Pairs
scala> // Note : Unmatched elements are left out
scala> val zipped = a1.zip(a2)
zipped: Array[(Int, Int)] = Array((1,5), (2,6), (3,7))
scala>
scala> for {
| (e1, e2) <- zipped
| }{
| println("e1 -> " + e1 + ", e2 -> " + e2)
| }
e1 -> 1, e2 -> 5
e1 -> 2, e2 -> 6
e1 -> 3, e2 -> 7
scala> // Parameterize Class instance with Value & Type
scala>
scala> /*******************************************
| Creating & Initializing an Array #77
| *******************************************/
| //Option 1
| // Here 'String' is Parameterized Type
| // '2' is a Parameterized Value
| // Square Bracket ([]) is used to Parameterize a Type
| val subject:Array[String] = new Array[String](2)
subject: Array[String] = Array(null, null)
scala> subject.update(0, "english")
scala> subject.update(1, "math")
scala>
scala> //Option 2
scala> val subject = new Array[String](3)
subject: Array[String] = Array(null, null, null)
scala> // During assignment Parenthesis calls the 'update()' method
scala> // passing both the Array index & value assigned
scala> subject(0) = "english"
scala> subject(1) = "math"
scala>
scala> // Option 3
scala> // Here Parenthesis in 'Array' calls the apply() factory
scala> // method of the Companion Object (Here Array is a
scala> // Companion Object rather than the Class)
scala> val subject = Array("english", "math")
subject: Array[String] = Array(english, math)
scala> /*******************************************
| Accessing an Array #77
| *******************************************/
|
| //Option 1
| for(i <- (0).to(1)) {
| // Note : Parenthesis is used to access an Array element
| // unlike Square brackets that is used in Java
| // #79
| print(subject.apply(i))
| }
englishmath
scala>
scala> //Option 2
scala> // If a method ('to' in our case) takes only 1 parameter
scala> // '.' and Parenthesis cna be omitted (We should also have a
scala> // receiver for the method call...in our case 'i')
scala> for(i <- 0 to 1) {
| //Note here..the apply() method is called implicitly
| print(subject(i))
| }
englishmath