> i'm trying to write a function that takes two arguments - one is
> an ato the other is a list of lists - for each list within the
> list, if the atom matches its first memeber, i want it's second
> member to be added to a master list and finally returned- for
> example:
>
> (setq mylist '((a b)(a c)(a d)))
> (myfunc 'a lst)
>
> and myfunc would return
>
> (b c d)

Kenny Tilton wrote:

> I do not know of a one-step solution, but you could try:
>
> (defun cullCar (match lists)
> (delete-if #'null (mapcar #'(lambda (list)
> (when (eql match (car list))
> (cadr list)))
> lists)))
>
> This would be inefficent where many non-matches occur. Doesn't
> the loop macro have some neat features for this? (Don't use it
> myself.)

Scheme

(define (myfunc x lst)
(filter-map
(lambda(xs) (and (equal? x (car xs)) (cadr xs)))
lst))

(myfunc 'b '((b 2) (c 3) (b 4) (d 5) (b 6)))

===>
(2 4 6)

On 2024-07-02, B. Pym <No_spamming@noWhere_7073.org> wrote:
>> i'm trying to write a function that takes two arguments - one is
>> an ato the other is a list of lists - for each list within the
>> list, if the atom matches its first memeber, i want it's second
>> member to be added to a master list and finally returned- for
>> example:
>>
>> (setq mylist '((a b)(a c)(a d)))
>> (myfunc 'a lst)
>>
>> and myfunc would return
>>
>> (b c d)

1> (match @(coll (a @x)) '((a b) (a c) (a d) (x 0) (a e)) x)
(b c d e)

--
TXR Programming Language: http://nongnu.org/txr
Cygnal: Cygwin Native Application Library: http://kylheku.com/cygnal
Mastodon: @Kazinator@mstdn.ca

"B. Pym" <No_spamming@noWhere_7073.org> writes:
> (myfunc 'b '((b 2) (c 3) (b 4) (d 5) (b 6)))
> ===>
> (2 4 6)

(myfunc 'b '((b 2) (c 3) (b #f) (d 5) (b 6)))
===>
(2 6)

Should be (2 #f 6).

This works:

(define (m2 x lst)
(map cadr (filter (lambda (ys) (equal? (car ys) x)) lst)))