Identity and constant are straightforward functions. The identity function returns the same value provided as parameter; similar to additive and multiplicative identity property, adding 0 to any number is still the same number.
The constant<T, R>(t: T) function returns a new function that will always return the t value:
fun main(args: Array<String>) {
val oneToFour = 1..4
println("With identity: ${oneToFour.map(::identity).joinToString()}") //1, 2, 3, 4
println("With constant: ${oneToFour.map(constant(1)).joinToString()}") //1, 1, 1, 1
}
We can rewrite our fizzBuzz value using constant:
fun main(args: Array<String>) {
val fizz = PartialFunction({ n: Int -> n % 3 == 0 }, constant("FIZZ"))
val buzz = PartialFunction({ n: Int -> n % 5 == 0 }, constant("BUZZ"))
val...
