M76 Posted March 3, 2010 Share Posted March 3, 2010 Hi, I'm trying to construct a list of points, but when I try to add a new element to the list with cons, the result is not what I expect. Example: list looks like this: ((50.0 40.0)) I have one point as a list in a list. I try to add to the list with cons for example (20.0 30.0) I get this as a result: (((20.0 30.0)) 50.0 40.0) why? Quote Link to comment Share on other sites More sharing options...
MSasu Posted March 3, 2010 Share Posted March 3, 2010 Use APPEND statement instead. (setq List1st '((1 2) (3 4) (5 6) (7 )) (setq List2nd '()) (foreach thePoint List1st (setq List2nd (append List2nd (list thePoint))) ) Regards, Quote Link to comment Share on other sites More sharing options...
Lee Mac Posted March 3, 2010 Share Posted March 3, 2010 I'm not sure of the desired result, but cons should return like this: (cons '(20 30) '((40 50))) ==> ((20 30) (40 50)) Quote Link to comment Share on other sites More sharing options...
David Bethel Posted March 3, 2010 Share Posted March 3, 2010 I think Lee's example is used lot more ( cons ) is a lot lot faster than ( append ) but it does make the final list in reverse order at times. I use this a lot (setq l1 '(40 50)) (setq l1 (cons '(20 30) l1) (setq l1 (reverse l1)) -David Quote Link to comment Share on other sites More sharing options...
Lee Mac Posted March 3, 2010 Share Posted March 3, 2010 Not really a conclusive test, but just as an example: (defun cons-it nil (cons '(40 50) '((20 30)))) (defun append-it nil (append '((40 50)) '((20 30)))) (Benchmark '((cons-it) (append-it))) Benchmarking ...................Elapsed milliseconds / relative speed for 65536 iteration(s): (CONS-IT).......1357 / 1.06 <fastest> (APPEND-IT).....1436 / 1.00 <slowest> Quote Link to comment Share on other sites More sharing options...
M76 Posted March 3, 2010 Author Share Posted March 3, 2010 I'm not sure of the desired result, but cons should return like this: (cons '(20 30) '((40 50))) ==> ((20 30) (40 50)) Yes it should but it does not. And I don't know why. I can use append, speed is not an issue now. Quote Link to comment Share on other sites More sharing options...
Lee Mac Posted March 3, 2010 Share Posted March 3, 2010 Yes it should but it does not. And I don't know why. What code are you using? Quote Link to comment Share on other sites More sharing options...
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