please give detailed code in Scala. (Functioning programming). all data types must be immutable.

A Fibonacci function is easy to define recursively, but done naively it is inefficient, re-computing the same Fibonacci value many times as it recursively descends down both recursive calls. For example, given a definition, def fib(n: Int ) : Int = { if (n R, t: Long = nanoTime) = (code, nanoTime - t) A Fibonacci function is easy to define recursively, but done naively it is inefficient, re-computing the same Fibonacci value many times as it recursively descends down both recursive calls. For example, given a definition, def fib(n: Int ) : Int = { if (n R, t: Long = nanoTime) = (code, nanoTime - t)