title: Multithreading in sbcl
body: <p>I am newbie at programming in lisp.I am using sbcl.In one part of program thread is created as-</p>
  
  <pre><code>(sb-thread:make-thread
    (lambda ()
      (progn
        (sleep 0)
        (setf c (+ a b))
        (print "ADDITION:")
        (print c))))
  </code></pre>
  
  <p>I am not getting what <code>lambda()</code> and <code>progn(sleep 0)</code> does, and why it is written inside <code>sb-thread</code> bracket?</p>