<p>I've been attempting to write a Lisp macro that would perfom the equivalent of ++ in other programming languages for semantic reasons.  I've attempted to do this in several different ways, but none of them seem to work, and all are accepted by the interpreter, so I don't know if I have the correct syntax or not.  My idea of how this would be defined would be</p>

<pre><code>(defmacro ++ (variable)
  (incf variable))
</code></pre>

<p>but this gives me a SIMPLE-TYPE-ERROR when trying to use it.  What would make it work?</p>

Remember that a macro returns an expression to be evaluated. In order to do this, you have to backquote:
```
```
(defmacro ++ (variable)
   `(incf ,variable))
```
```