title: How does lambda multiplication works?
body: <p><a href="http://www.inf.fu-berlin.de/lehre/WS03/alpi/lambda.pdf" rel="nofollow">A Tutorial Introduction to the Lambda Calculus</a></p>
  
  <p>This article introduces the multiplication function</p>
  
  <blockquote>
    <p>The multiplication of two numbers x and y can be computed using the following
    function:<p>(λxyz.x(yz))</p><p>The product of 2 by 2 is then:</p><p>(λxyz.x(yz))22</p><p>which reduces to</p><p>(λz.2(2z))</p><p>The reader can verify that by further reducing this expression, we can obtain the expected result 4.</p></p>
  </blockquote>
  
  <p>I have no idea how  can  (λz.2(2z))  reduce to 4. Can anyone show me the process?</p>
  
  <p>the 2 in lambda function is λsz.s(s(z)), and the 4 is λsz.s(s(s(s(z)))).</p>