title: Name of this function in built-in Emacs Lisp library?
body: <p>The following Emacs Lisp function takes a list of lists and returns a list in which the items of the inner lists have been concatenated to one big list. It is pretty straight-forward and I am convinced something like this must already be part of the standard function library.</p>
  
  <pre><code>(defun flatten (LIST)
    (if LIST
        (append (car LIST) (flatten (cdr LIST)))
      nil))
  </code></pre>
  
  <p>I am looking for a function that will take a single list of lists as its argument and then append all the inner lists. </p>
  
  <pre><code>(flatten '((a b) (c d)))
  </code></pre>
  
  <p>will give</p>
  
  <pre><code>(a b c d)
  </code></pre>
  
  <p>Does anyone know whether this function is already built in, and if so, under which name?</p>
  
  <p>Thanks!</p>