Community
The 'n' argument is for the possibility that they might want to filter for what is in some position in the sub-lists *other than the second item*, usable with a list of lists that presumably could sometimes be longer than two items. Their example used n=2 for the second item, but that wouldn't always be what they need. That's why they have
(nth (1- n) itm)
instead of
(cadr itm)
inside their original code.
The (vl-remove-if-not) function seems a more accurate "description" of what they want to do. Adjusting their optional item position into your sorted approach, but with the remove-if-not variety:
{code}
(defun FLOLI (lst n flt); for Filter List Of Lists by Item
(vl-sort
(vl-remove-if-not
'(lambda (x) (= (nth (1- n) x) flt))
lst
)
'(lambda (x y)
(< (car x) (car y))
)
)
)
{code}
But their original code leaves the list items that pass the test in their order in the original list, without sorting. If sorting is not required, it can be a lot shorter:
{code}
(defun FLOLI (lst n flt)
(vl-remove-if-not
'(lambda (x) (= (nth (1- n) x) flt))
lst
)
)
{code}
--
Kent Cooper
Some Buddy wrote...
....I could have the same result if I remove every item list in your general list which doesn't have "D" as second element and then sort the resulting list, but then I don't understand what is the 'n' argument for....
(nth (1- n) itm)
instead of
(cadr itm)
inside their original code.
The (vl-remove-if-not) function seems a more accurate "description" of what they want to do. Adjusting their optional item position into your sorted approach, but with the remove-if-not variety:
{code}
(defun FLOLI (lst n flt); for Filter List Of Lists by Item
(vl-sort
(vl-remove-if-not
'(lambda (x) (= (nth (1- n) x) flt))
lst
)
'(lambda (x y)
(< (car x) (car y))
)
)
)
{code}
But their original code leaves the list items that pass the test in their order in the original list, without sorting. If sorting is not required, it can be a lot shorter:
{code}
(defun FLOLI (lst n flt)
(vl-remove-if-not
'(lambda (x) (= (nth (1- n) x) flt))
lst
)
)
{code}
--
Kent Cooper
Some Buddy wrote...
....I could have the same result if I remove every item list in your general list which doesn't have "D" as second element and then sort the resulting list, but then I don't understand what is the 'n' argument for....
Kent Cooper, AIA 
It works either way, or by any valid way of making the List, except that the arguments need to be in a different order [list before position number]....
Command: ( FLOLI 2 sl "D" )
; error: bad argument type: listp 2
Command: ( FLOLI sl 2 "D" )
(("1" "D") ("2" "D"))
It even works if not all the sub-lists have "enough" items in them:
Command: (setq sl '((3 4 5) ("yes" 3 8 pi) (89.2 4 "whatever") (T "this" "that" 4)))
Command: (floli sl 4 4)
((T "this" "that" 4))
But if it matters, I found, in experimenting with the same list, that if pi is the element in a list that you're filtering for, you have to "do it right" with a preceding apostrophe to get what you want:
Command: (floli sl 4 pi)
nil
But:
Command: (floli sl 4 'pi)
(("yes" 3 8 PI))
That's not required with the symbols T or nil as elements in the sub-lists. I'm not sure whether there might be other things that would require some kind of special handling, as pi does.
--
Kent Cooper
stevor wrote...
Seems to work with the input list trewritten to lake lists:
(setq sl ( list (list "1" "X") (list"1" "D") (list "2" "D") ) ) ; input list
(setq rl ( FLOLI 2 sl "D" ) ) ; result list
Command: ( FLOLI 2 sl "D" )
; error: bad argument type: listp 2
Command: ( FLOLI sl 2 "D" )
(("1" "D") ("2" "D"))
It even works if not all the sub-lists have "enough" items in them:
Command: (setq sl '((3 4 5) ("yes" 3 8 pi) (89.2 4 "whatever") (T "this" "that" 4)))
Command: (floli sl 4 4)
((T "this" "that" 4))
But if it matters, I found, in experimenting with the same list, that if pi is the element in a list that you're filtering for, you have to "do it right" with a preceding apostrophe to get what you want:
Command: (floli sl 4 pi)
nil
But:
Command: (floli sl 4 'pi)
(("yes" 3 8 PI))
That's not required with the symbols T or nil as elements in the sub-lists. I'm not sure whether there might be other things that would require some kind of special handling, as pi does.
--
Kent Cooper
stevor wrote...
Seems to work with the input list trewritten to lake lists:
(setq sl ( list (list "1" "X") (list"1" "D") (list "2" "D") ) ) ; input list
(setq rl ( FLOLI 2 sl "D" ) ) ; result list
Kent Cooper, AIA
![Autodesk Design & Make Report](https://forums.autodesk.com/t5/image/serverpage/image-id/1350519iCB55845EBFC43016/image-size/large?v=v2&px=999" "Autodesk Design & Make Report")
