Hi Alex, I missed to include it... (de null (X) (not X))
Thanks! for the suggestions. I tried the pairlis alternatives. Much better. 'extract' will be very useful. I'll have to work with nond a bit more to get how/when use that. /Lindsay On Thu, Feb 9, 2017 at 3:17 AM, Alexander Burger <a...@software-lab.de> wrote: > Hi Lindsay, > > > # pairlis2: gives a list of pairs of corresponding elements > > # of the lists x and y, and appends this to the list a. > > # (pairlis '(A B C) '(1 2) () ) -> ((A . 1) (B . 2)) > > > > (de pairlis2 (X Y A) > > (cond > > ((null X) A) > > ((null Y) A) > > (T > > (cons > > (cons (car X) (car Y)) > > (pairlis2 (cdr X) (cdr Y) A) ) ) ) ) > > Sorry, I have not tested, but 'null' should be undefined. You could > replace it > with 'not'. But then 'nond' is better than 'cond', avoiding it completely > (see > discussion here in this list). > > > In general, using recursion here is quite an overkill. A simpler form > could be > > (de pairlis (X Y A) > (conc (mapcar cons X Y) A) ) > > or, if you want to handle the case where the first list is longer than the > second, > > (de pairlis (X Y A) > (conc > (extract > '((A B) (and A B (cons A B))) > X > Y ) > A ) ) > > ♪♫ Alex > -- > UNSUBSCRIBE: mailto:picolisp@software-lab.de?subject=Unsubscribe >
