def combinator &b
  lambda do |f|
    lambda{|x|lambda{|y| f[x[x]] [y]}}[
      lambda{|x|lambda{|y| f[x[x]] [y]}}]
  end[ lambda{|f|lambda{|n| b[n , &f] }}]
end
 
a = combinator do | n , &f |
  if n == 0
    1
  else
    n * f.call(n-1)
  end
end
 
p a.call 7
 
 
 
def recursion &block
  lambda do |*h|
    g = lambda{|*h| block.call(*h , &g)}
    g.call(*h)
  end
end
 
a = recursion do |n , &rec|
  if n == 0
    1
  else
    n * rec.call(n-1)
  end
end
p a.call 7
 

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