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FAQ: Lisp Frequently Asked Questions 3/7 [Monthly posting]
Section - [3-9] Closures don't seem to work properly when referring to the iteration variable in DOLIST, DOTIMES, DO and LOOP.

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DOTIMES, DOLIST, DO and LOOP all use assignment instead of binding to
update the value of the iteration variables. So something like
   
   (let ((l nil))
     (dotimes (n 10)
       (push #'(lambda () n)
	     l)))

will produce 10 closures over the same value of the variable N. To
avoid this problem, you'll need to create a new binding after each
assignment: 

   (let ((l nil))
     (dotimes (n 10)
	(let ((n n))
	  (push #'(lambda () n)
		l))))

Then each closure will be over a new binding of n.

This is one reason why programmers who use closures prefer MAPC and
MAPCAR to DOLIST.




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