Initial import.

gp.asd

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+(asdf:defsystem :gp
+  :depends-on ()
+  :serial t
+  :components
+  ((:file "gp")))

gp.lisp

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+(defpackage #:gp.goof
+  (:use :cl)
+  (:documentation "Genetic programming is cool!"))
+
+(in-package :gp.goof)
+
+; Look! A Y Combinator.
+(defun Y (r)
+  ((lambda (f) (funcall f f))
+   (lambda (f)
+     (funcall r (lambda (x) (funcall (funcall f f) x))))))
+
+; So apparently labels is better than Y, but I'm keeping the Y.
+(defun mutate (form)
+  "Mutate takes a form and modifies the numbers randomly."
+  (let ((sign (let ((x (random 2)))
+                (if (= x 0) #'+ #'-))))
+    (mapcar (Y (lambda (fun)
+                 (lambda (n)
+                   (cond
+                     ((eq (class-of n) (find-class 'fixnum))
+                      (funcall sign (random 5) n))
+                     ((eq (class-of n) (find-class 'cons))
+                      (mapcar fun n))
+                     (t n)))))
+             form)))