which element of a list?

[Anonymous]

Hi!

I'm looking for a function, or a lisp routine, that is capable of this:
i have a list, for example (1 2 4 8), and i need to get, that "2" is the 1st element of this,"4" is the 2nd, and so on...
is there any function or stg that can do that?

thx in advance

[Anonymous]

(setq lst (list 1 2 3 4))
(1 2 3 4)
_$ (setq 1st (car lst))
1
_$ (vl-remove 1st lst)
(2 3 4)

[Anonymous]

Given a list: (1 2 4 8)

There are a few ways.

(setq lst (cdr lst)); returns (2 4 8)

(setq first (nth 0 lst)); returns 1

(setq second (nth 1 lst)); returns 2

(setq third (nth 2 lst)); returns 4

(setq first (car lst)); returns 1

(setq second (cadr lst)); returns 2



Bob

[Anonymous]

There MAY be some confusion about your
problem.

If you want to know what value is at a specific
index of your list you could use the nth function

ie;

(setq theList (list 1 2 4 8 16))

face=Arial size=2>

(setq valueAtPosition_3 (nth 3 theList))  ;=> 8 ;
value at index position 3 is 8

whereas if you want to know the index location of a specific value you
could use the  vl-position function

ie;

(setq LocationOFValue_4 (vl-position 4 theList)) ;=> 2 ; index position
of symbol 4 in list is 2

///kdub

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"sunchase" wrote in message
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href="news:6095721@di......

Hi!
I'm looking for a function, or a lisp routine, that is capable of this: i have
a list, for example (1 2 4 8), and i need to get, that "2" is the 1st element
of this,"4" is the 2nd, and so on... is there any function or stg that can do
that? thx in advance

[Anonymous]

Hi!

Thanks a lot for your help 🙂 you are right,the way I put my question was a bit confusing, but I noticed it only after receving some answers I had not really expected.
However you could catch my mind, and your tip seems to be the solution for my problem.

Thanks again:)

[Anonymous]

sunchase wrote:
> Hi! I'm looking for a function, or a lisp routine, that is capable of
> this: i have a list, for example (1 2 4 8), and i need to get, that "2"
> is the 1st element of this,"4" is the 2nd, and so on... is there any
> function or stg that can do that? thx in advance

As others have shown, vl-position is probably what you are after.

Your example is inconsistent, though: "2" is not included in your list,
neither is "4". (The numbers 2 and 4 are, "4" is not a number, it is a
string!)

So, if your data to compare is really strings, you need to have a type
conversion somewhere in your program. See ATOI.

--

[Anonymous]

(setq sample_list (list "first" "second" "third" "fourth"))

then

(length (member "second" (reverse sample_list)))

returns 2,

(length (member "third" (reverse sample_list)))

returns 3, and

(length (member "not_in_list" (reverse sample_list)))

returns 0.

[Anonymous]

Yes, that"s what I needed, you're right 🙂 and I'm sorry for the confusing outlook of my lines: I did not mean to emphasise that 2 or 4 are strings, of course they are numbers. The signs "" must have been embarrassing.