Problem Statement

The Ackermann function is a classic example of a recursive function, notable especially because it is not a primitive recursive function. It grows very quickly in value, as does the size of its call tree.

The Ackermann function is usually defined as follows:

Its arguments are never negative and it always terminates.

Write a function which returns the value of

A ( m , n )

{\displaystyle A(m,n)}

. Arbitrary precision is preferred (since the function grows so quickly), but not required.

Let's start with the solution:

int A(int m, int n) => m==0 ? n+1 : n==0 ? A(m-1,1) : A(m-1,A(m,n-1));

main() {
  print(A(0,0));
  print(A(1,0));
  print(A(0,1));
  print(A(2,2));
  print(A(2,3));
  print(A(3,3));
  print(A(3,4));
  print(A(3,5));
  print(A(4,0));
}