Fibanacci assignment from SICP Meetup 1

lambda_fib.rb

puts "=========== Iterative ============"
def fib(n)
  i = 0
  f = 0
  s = 1
  puts f
  puts s
  while i < n - 2
    t = f
    f = s
    s = f + t
    puts s
    i += 1
  end
end
fib(20)

puts "=========== Recursive ============"
def fib_rec(n)
  if n > 2
    f, s = fib_rec(n - 1)
    puts f + s
    t = f
    f = s
    s = f + t
    [f, s]
  else
    puts 0
    puts 1
    [0, 1]
  end
end
fib_rec(20)

puts "=========== Lambda calculus ============"
->(l_fib){
  ->(num) { l_fib.(l_fib, num) }
}.(
  ->(g, n){
    if n > 2
      f, s = g.(g, n - 1)
      puts f + s
      t = f
      f = s
      s = f + t
      [f, s]
    else
      puts 0
      puts 1
      [0, 1]
    end
  }
).(20)