Ackermann Function

# title: Ackermann Function
# source: https://rosettacode.org/wiki/Ackermann_function
# category: Rosetta Code Popular
# difficulty: Intermediate
# summary: Evaluate the classic Ackermann function for a few small inputs to demonstrate deep recursion.
# tags: popular, recursion, math
# vibe: 0.2

def ackermann(m, n)
  if m == 0
    n + 1
  elsif n == 0
    ackermann(m - 1, 1)
  else
    ackermann(m - 1, ackermann(m, n - 1))
  end
end

def run
  {
    a_0_0: ackermann(0, 0),
    a_2_2: ackermann(2, 2),
    a_3_2: ackermann(3, 2)
  }
end