LispForum

Posted: **Fri Oct 12, 2012 6:49 am**

HI
I'm very newbie also in programming, and I'm trying to learn CL

ok, I have just a problem with this exercize that ask me : "define a function that takes a list as an argument and returns true if one of its elements is a list.

OK,I just studied dolist, then:

Code: Select all

(defun use_dol (lst)
	   (dolist (x lst)
	     (if (listp x)
		 t)))

(use_dol  '(a b '(c d) e))

but NIL raise...why? ther's a nested list in list arg for use_dol func... I can't understand why!

thanks in advance for help!

Posted: **Sat Oct 13, 2012 11:35 pm**

DOLIST returns NIL as long as there is no explicit RESULT-FORM defined. See the the examples on the DOLIST page what this means.

- edgar

Posted: **Sun Oct 14, 2012 1:27 am**

thanks!

Posted: **Sun Oct 14, 2012 5:14 pm**

(if (listp x) t) doesn't terminate the loop; it just keeps looping, and eventually returns nil. Use (return t)

Posted: **Mon Oct 15, 2012 7:42 am**

good, thanks

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