anchor.diff:  	       collect (let ((parent1 (select *population* relative-scores))
   			     (parent2 (select *population* relative-scores)))
   			 ;; crossover and mutation
  -			 (mutate (crossover parent1 parent2))))))
  +			 (mutate (crossover parent1 parent2) 0.1)))))
       (run app)))
   
   ;;;; genetic operations
  
positive.code:        (when (> current pick)
  	 (return chromosome))))
  
  (defun crossover (parent1 parent2))
  
  (defun mutate (chromosome))
  
  ;;;; helpers
  (defun make-chromosome (chromosome-length &optional (range 1000) (straight-prob 0.1))
  
negative.code:      collect (make-chromosome chromosome-length)))
  
  (defun evaluate (candidate target)
    "Candidate is array of lists, target is zpb-ttf:glyph."
    (let ((index 0)
  	(score 0))
      (zpb-ttf:do-contours (contour target)
  