title: Even maximums in Lisp
body: <p>I am trying to find the even maximums from a list in Lisp.</p>
  <pre><code>(defun m(L)
      (cond
          ((numberp L) L)
          ((atom L) most-negative-fixnum)
          (T (apply #'max (mapcar #'m L)))
      )
  )
  </code></pre>
  <p>This &quot;m&quot; works for the maximum of a list(of lists) and the next to find the even maximums:</p>
  <pre><code>
  (defun _list (L)
      (mapcan #'((lambda (v)
                  (cond
                      ((= 0 (mod v 2)) (list v))
                      (t nil)
                  )
                 ) (m L)
                 )
      L
      )
  )
  </code></pre>
  <p>I get the error <code> ((LAMBDA (V) (COND ((= 0 (MOD V 2)) (LIST V)) (T NIL))) (M L)) should be a lambda expression</code>
  And I can't figure out why. I played with the paranthesis a lot but still nothing. Can somebody give me some better ideas why this happens?</p>