[Openmcl-devel] inverse function
raffaelcavallaro at mac.com
Sat Feb 13 16:19:25 UTC 2010
On Feb 13, 2010, at 7:20 AM, Taoufik Dachraoui wrote:
> Does someone know if there is any work done to generate an inverse of any given lisp function (if possible).
1. Side effects:
(defun had-a-great-fall (being)
(inverse #'had-a-great-fall) => #'put-together-again
(defparameter *humpty-dumpty* (make-instance 'being :name "humpty-dumpty"))
(funcall (inverse #'had-a-great-fall) (had-a-great-fall *humpty-dumpty*))
=> error: all the king's horses and all the kings men couldn't
put #<BEING #x3020015339FD>, humpty-dumpty, together again.
i.e., common lisp has side effects, some of which can't be undone.
2. Functions can produce the same value for different args:
(defun square (x)
(* x x))
(inverse #'square) => #'sqrt ;; or something very like sqrt
(funcall (inverse #'square) (square -3)) => 3 ;; i.e., not -3 as it you want it to
raffaelcavallaro at me.com
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