The documentation for make-derived-parameter appears incorrect.  It is at least somewhat misleading <a href="http://docs.plt-scheme.org/reference/parameters.html#(def._((quote._~23~25kernel)._make-derived-parameter))">http://docs.plt-scheme.org/reference/parameters.html#(def._((quote._~23~25kernel)._make-derived-parameter))</a> The docs say that the arguments to make-derived-parameter are:     v: any/c     guard: ...     wrap: ... which makes it looks like its an extended version of make-parameter, when in fact its real arguments appear to be:     p: parameter?     guard: ...     wrap: ... The first argument is a parameter not the initial value for a parameter. -- Christopher W. Bowron <<a href="mailto:chris@bowron.us">chris@bowron.us</a>> [ Nothing is exciting if you know what the outcome will be ]    - Joseph Campbell