Scala:Type parameterization

Polymorphism in Scala can be achieved through type parameterization. Let us define class g with attributes x,y as integers as

scala> class g(val x:Int, val y:Int)
defined class g

We can use Type parameter like follows

scala> class g[T](val x:T, val y:T)
defined class g

scala> val obj=new g[Char]('a','b')
obj: g[Char] = g@a53564

scala> obj.x
res11: Char = a

scala> obj.y
res12: Char = b

We need not specify the type parameter explicitly like that, the Scala compiler  can infer the Type from function parameters

scala> val obj=new g('a','b')
obj: g[Char] = g@a53564

scala> obj.x
res3: Char = a
scala> val obj1=new g(1,2)
obj1: g[Int] = g@a53564

scala> obj1.y
res3: Char = 2

Now we can play a bit

scala> val obj=new g(1,true)          
obj: g[AnyVal] = g@11d95

scala> obj.x
res1: AnyVal = 1

scala> obj.y
res2: AnyVal = true

Notice that  val obj=new g(1,true) doesn't cause a type mismatch error even Value 1 is of type Int and true is of Boolean while both parameters are expected to be of same type. The reason is that, Boolean, Char, Int etc. are Subtypes of AnyValue.Here The compiler inferred the type as AnyValue looking at the parameters passed.

We can also have multiple Type parameters as follows

scala> class g[T,H](val x:T, val y:H)
defined class g

scala> val obj=new g('A',9)
obj: g[Char,Int] = g@14f7121

scala> obj.x
res10: Char = A

scala> obj.y
res11: Int = 9

We can define functions of parameterized type like follows

scala> def f[T](x:T):Unit=print(x)
f: [T](T)Unit

scala> f[Int](6)                  
6

scala> f(6)                  
6

scala> f("ssss")                  
ssss