Re: CAR/CDR vs FIRST/REST

On 2024-09-12, B. Pym <Nobody447095@here-nor-there.org> wrote:

Barry Margolin wrote:
>

      (mapcan #'(lambda (x) (and (numberp x) (list x))) list)

 

      (loop for x in list
              when (numberp x) collect x)

 
I agree with this example.  Once I learned LOOP I never used the
above idiom again.

>
(filter number? '(a b c 1 2 3))
===>
(1 2 3)

Also, once you realize that "remove-if-not" is "keep-if":

  (remove-if-not #'numberp list)

then you also will not use the poor "idiom":

  (mapcan #'(lambda (x) (and (numberp x) (list x))) list)

Not to mention that once you learn that (lambda ...) is
a macro which writes #'(lambda ...) for you, you will tend
not to use the latter again.

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