blogs/cmm

From: Rahul Jain 
Subject: Symbols, the Universe, and Robert Paulson or, Redefined Meanings of Symbolic Expression and their Interpretation by a Programmer
Newsgroups: comp.lang.lisp
Organization: Rice University, Houston TX

“His name is Robert Paulson.''

If you are unfamiliar with that statement, please watch the movie
Fight Club. It's a great movie that everyone should watch anyway, and
it would be a waste to try to describe what that statement means
outside of the context of the movie.

Here is a rendition of what is happening in the movie into Lisp code:

(defpackage :real-world
  (:export #:person #:person-name #:person-live-p))

(defpackage :project-mayhem)

(in-package :real-world)

(cl:defclass person ()
  (live-p :initform t
          :accessor person-live-p)
  (name :initarg :name
        :accessor person-name))

(cl:defvar robert-paulson (cl:make-instance 'person “Robert Paulson”))

(cl:assert (cl:string= (person-name robert-paulson) “Robert Paulson”))

(cl:in-package :project-mayhem)

(cl:defclass person ()
  ())

(in-package :real-world)

(cl:assert (cl:string= (person-name robert-paulson) “Robert Paulson”))

(cl:in-package :project-mayhem)

(cl:import '(real-world:person-name real-world:person-live-p))

(cl:defclass person ()
  (live-p :initform t
          :reader person-live-p))

(cl:defclass dead-person (person)
  (live-p :initform nil
          :allocation :class
          :reader person-live-p)
  (name :initform “Robert Paulson”
        :allocation :class
        :reader person-name))

(cl:defvar robert-paulson)

(cl:defmethod (cl:setf person-live-p) ((value null) (person person))
  (cl:let ((robert-paulson person))
    (cl:change-class person 'dead-person)
    (cl:assert (cl:string= (person-name robert-paulson)
                           “Robert Paulson”))))