Evolve

最有意思的就是其中的genes,不同的动物会有不同的genes还会遗传和变异!!!

mapc和mapcar的区别查了一下,mapc返回原始的list而mapcar会把结果cons,如果是利用side effect话mapc比较省时间.

还有一个问题,就是对于下面的代码

(defparameter *list* '(1 2 3 4))

(mapc (lambda (x) (incf x)) *list*)

我原本以为会直接把*list*上的每一个数都加一但是并没有,mapcar也一样

但是下面的代码却可以把每一个list元素中的第一个数改变

(defparameter *l* '((1 2) (2 3) (3 4)))

(mapc (lambda (x) (incf (car x))) *l*)

我想会不会是这一章前面提到过的浅复制的原因,对于symbol和integer等这些简单的元素传参数时是完全复制,没有共享的结构

但是对于后者传的是个list,是共享的.所以side effec会影响原始的值

;;;;

(defparameter *width* 100)
(defparameter *height* 30)
(defparameter *jungle* '(45 10 10 10))
(defparameter *plant-energy* 80)

;;;;growing plants in our world

(defparameter *plants* (make-hash-table :test #'equal))

(defun random-plant (left top width height)
	(let ((pos (cons (+ left (random width)) (+ top (random height)))))
		(setf (gethash pos *plants*) t)))

(defun add-plants ()
	(apply #'random-plant *jungle*)
	(random-plant 0 0 *width* *height*))


;;;;create animals

(defstruct animal x y energy dir genes)

(defparameter *animals*
	(list (make-animal 
		:x (ash *width* -1)
		:y (ash *height* -1)
		:energy 1000
		:dir 0
		:genes (loop repeat 8
			collecting (1+ (random 10))))))


;;;;handling animal motion

(defun move (animal)
	(let ((dir (animal-dir animal))
		(x (animal-x animal))
		(y (animal-y animal)))
	(setf (animal-x animal) (mod (+ x
		(cond ((and (>= dir 2) (< dir 5)) 1)
			((or (= dir 1) (= dir 5)) 0)
			(t -1))
		*width*)
	*width*))
	(setf (animal-y animal) (mod (+ y
		(cond ((and (>= dir 0) (< dir 3)) -1)
			((and (>= dir 4) (< dir 7)) 1)
			(t 0))
		*height*)
	*height*))
	(decf (animal-energy animal))))


;;;;handling animal turning

(defun turn (animal)
	(let ((x (random (apply #'+ (animal-genes animal)))))
		(labels ((angle (genes x)
			(let ((xnu (- x (car genes))))
				(if (< xnu 0)
					0
					(1+ (angle (cdr genes) xnu))))))
		(setf (animal-dir animal)
			(mod (+ (animal-dir animal) (angle (animal-genes animal) x))
				8)))))


;;;;handling animal eating

(defun eat (animal)
	(let ((pos (cons (animal-x animal) (animal-y animal))))
		(when (gethash pos *plants*)
			(incf (animal-energy animal) *plant-energy*)
			(remhash pos *plants*))))


;;;;handling animal reproduction

(defparameter *reproduction-energy* 200)

(defun reproduce (animal)
	(let ((e (animal-energy animal)))
		(when (>= e *reproduction-energy*)
			(setf (animal-energy animal) (ash e -1))
			(let ((animal-nu (copy-structure animal))
				(genes (copy-list (animal-genes animal)))
				(mutation (random 8)))
			(setf (nth mutation genes) (max 1 (+ (nth mutation genes) (random 3) -1)))
			(setf (animal-genes animal-nu) genes)
			(push animal-nu *animals*)))))


;;;;simulating a day in our world

(defun update-world ()
	(setf *animals* (remove-if (lambda (animal)
									(<= (animal-energy animal) 0))
								*animals*))
	(mapc (lambda (animal)
		(turn animal)
		(move animal)
		(eat animal)
		(reproduce animal))
	*animals*)
	(add-plants))


;;;;drawing our world

(defun draw-world ()
	(loop for y
		below *height*
		do (progn (fresh-line)
				  (princ "|")
				  (loop for x
				  	below *width*
				  	do (princ (cond ((some (lambda (animal)
				  							(and (= (animal-x animal) x)
				  								 (= (animal-y animal) y)))
				  							*animals*)
				  						#M)
				  					((gethash (cons x y) *plants*) #*)
				  					(t #space))))
				  (princ "|"))))


;;;;creating a user interface

(defun evolution ()
	(draw-world)
	(fresh-line)
	(let ((str (read-line)))
		(cond ((equal str "quit") ())
			(t (let ((x (parse-integer str :junk-allowed t)))
				(if x
					(loop for i
						below x
						do (update-world)
						if (zerop (mod i 1000))
						do (princ #.))
					(update-world))
				(evolution))))))