SML/NJ

Modify the function below to print out the value of x, fibonacci(x-1) and fibonacci(x-2) in every iteration of the function call:

fun fibonacci (x:int) =

if (x = 0 orelse x = 1)

then x

else fibonacci(x-1) + fibonacci(x-2)

The expression

fibonacci 5;

would produce the output:

x = 1

x = 0

x = 2 f(x-1) = 1 f(x-2) = 0

x = 1

x = 3 f(x-1) = 1 f(x-2) = 1

x = 1

x = 0

x = 2 f(x-1) = 1 f(x-2) = 0

x = 4 f(x-1) = 2 f(x-2) = 1

x = 1

x = 0

x = 2 f(x-1) = 1 f(x-2) = 0

x = 1

x = 3 f(x-1) = 1 f(x-2) = 1

x = 5 f(x-1) = 3 f(x-2) = 2

val it = 5 : int