def listOfDuplicates[A](x: A, length: Int): List[A] = {
if (length < 1)
Nil
else
x :: listOfDuplicates(x, length - 1)
}
println(listOfDuplicates[Int](3, 4)) // List(3, 3, 3, 3)
println(listOfDuplicates("La", 8)) // List(La, La, La, La, La, La, La, La)
List(3, 3, 3, 3) List(La, La, La, La, La, La, La, La)
defined function listOfDuplicates
The method listOfDuplicates
takes a type parameter A
and value parameters x
and length
. Value x
is of type A
. If length < 1
we return an empty list. Otherwise we prepend x
to the the list of duplicates returned by the recursive call. (Note that ::
means prepend an element on the left to a list on the right.)
In first example call, we explicitly provide the type parameter by writing [Int]
. Therefore the first argument must be an Int
and the return type will be List[Int]
.
The second example call shows that you don't always need to explicitly provide the type parameter. The compiler can often infer it based on context or on the types of the value arguments. In this example, "La"
is a String
so the compiler knows A
must be String
.
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