gistfile1.rb

#!/usr/bin/env ruby

def multifunc(msg, pos, b)
  puts "Calculating: #{msg}"
  b.call(pos)
end

puts multifunc("Fibonacci numb", 5,  f = lambda { |n| (n == 0 || n == 1) ? n : (f.call(n-1) + f.call(n-2))  })