Subject: Re: plugins and lisp
From: Erik Naggum <>
Date: 02 Feb 2004 21:35:12 +0000
Newsgroups: comp.lang.lisp
Message-ID: <>

* Pieter
| How will a plugin type thing work on lisp?

  The usual issues, loading binary code and making it possible for it to
  call already loaded code, are trivial.  The loading and linking phases
  of Common Lisp environments are entirely transparent.

  However, you need to think about how you wish to «register» your code
  so that the system can call it.  One common way to do this is via hook
  variables -- lists of functions to call with no arguments and only for
  effect at known points in the code.  Another common way is to use CLOS
  methods with :BEFORE, :AROUND, and :AFTER qualifiers.  You need to
  plan for either way.  Other ways are possible, such as replacing a
  function entirely, but then it may be difficult to load more than one
  plugin that does this, even if you store the old definition in some
  variable and call it at the appropriate time.

| In c++ I would make a nice base class with a bunch of pure virtuals.
| The .so or .dll will return a pointer to an instance of the base class
| and so the story goes.  Is the approach in Lisp similar?

  Generally, no, but you could certainly arrange for something like it.

Erik Naggum | Oslo, Norway                                      2004-033

Act from reason, and failure makes you rethink and study harder.
Act from faith, and failure makes you blame someone and push harder.