With my library, you set up some versions and a variable to track the current version:

(method-versions:define-method-version :v1.0)
(method-versions:define-method-version :v1.1 :v1.0)
 
(declaim (special *protocol-version*))
(defparameter *protocol-version* :v1.0)

In ContextL, you just set up some layers:

(contextl:deflayer :v1.0)
(contextl:deflayer :v1.1 (:v1.0))

In my library, you then set up a generic function that uses a special method combination that keys off of the special variable:

(defgeneric send-cmd (cmd)
  (:method-combination method-versions:method-versions-method-combination
                       *protocol-version*))

In ContextL, you declare a layered function:

(contextl:define-layered-function (cmd))

In my library, you then declare different methods using the version as a method qualifier.

(defmethod send-cmd ((cmd login-cmd))
  (send-string (login-name cmd))
  (send-string (login-password cmd)))
 
(defmethod send-cmd :v1.0 ((cmd login-cmd))
  (send-string (login-name cmd))
  (send-string (login-password cmd))
  (send-string (login-location cmd)))

In ContextL, you declare layered methods specifying which layer the functions belong to:

(contextl:define-layered-method send-cmd ((cmd login-cmd))
  (send-string (login-name cmd))
  (send-string (login-password cmd)))
 
(contextl:define-layered-method send-cmd :in :v1.0 ((cmd login-cmd))
  (send-string (login-name cmd))
  (send-string (login-password cmd))
  (send-string (login-location cmd)))

In my library, you set your special variable appropriately and invoke the method:

(let ((*protocol-version* :v1.1))
  (send-cmd cmd))

In ContextL, you declare which layer you want to be active when you go to invoke the method:

(contextl:with-active-layers (:v1.1)
  (send-cmd cmd))

My library does not let you specify other method qualifiers like :around or :after. ContextL does.

I am going to leave my library published because I think it is a reasonably understandable, yet non-trivial, use of non-standard method combinations. However, I am going to end up using ContextL for the projects that I had intended for my library.

• Here is the new tarball: fft_1.4.2011.03.24.tar.gz
• and its GPG signature: fft_1.4.2011.03.24.tar.gz.asc

Thank you!

Here is the source tarball: cl-growl_1.1.2010.04.29.tar.gz and the corresponding GPG signature: cl-growl_1.1.2010.04.29.tar.gz.asc. For other ways to access this code, see the CL-Growl page.

Thank you, Alex!

• Corrected spelling of siete (Spanish for seven)
• Corrected spelling of colores (Spanish for colors)

Today, I am working on adding animal drawings.