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Date:         Wed, 26 Jan 2011 09:12:46 -0500
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From: Bruno Le Floch <blflatex@GMAIL.COM>
Subject: Re: \clist_length:N and \clist_nth:N
To: LATEX-L@listserv.uni-heidelberg.de
In-Reply-To:  <A56E7BB9-DA26-44C0-9E48-A109A1259C15@hp.com>
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Status: R

> I don't have any issue with element or elt (having been exposed to lisp long
> time ago) but my feeling is that "length" is rather a good name for the
> concept, but then we should use it in other places too and get rid of
> elt_count there.
>
> For _nth I think _element is ok, but I'm not so sure why _item would be bad.
> Don't see that there would be a conflict with other "items" of LaTeX. In
> fact it is the same concept, so why choose different names?

I agree with Frank: the "only" difference between clists and
list-based environment is the separator: comma in one case, \item in
the other.

Bruno

> Am 25.01.2011 um 10:37 schrieb "Robin Fairbairns"
> <Robin.Fairbairns@CL.CAM.AC.UK>:
>
>> Joseph Wright <joseph.wright@MORNINGSTAR2.CO.UK> wrote:
>>
>>> On 24/01/2011 14:01, Lars Hellström wrote:
>>>> Isn't this "elt" an implementation detail for that type of list (various
>>>> \@elt tokens in 2e come to mind), and thus something that should be kept
>>>> internal rather than canonised in a public interface? The clean solution
>>>> for *both* types of list is rather to use "length".
>>>
>>> Seems reasonable: one would normally talk about 'a long list of things
>>> to do', so lists to have 'length' :-)
>>
>> in some ways of looking at a list, it has 'length'.
>>
>> in plain english, i would say lists have "items" (or just "things")
>> rather than "elements", but "item" is already heavily overloaded in
>> the user's level latex-ese.  i don't have a problem with "element" (or
>> "elt" in command names).
>>
>>>> Moreover, I get a vague impression that the term `elt' is part of the
>>>> pseudo-LISP heritage of LaTeX (emphasis on the "La"). If so, then that
>>>> is IMHO another reason to avoid it, as that heritage is full of square
>>>> pegs trying to fit in round holes.
>>>
>>> Not being familiar with Lisp, I can only go on things like LaTeX2e's
>>> \@cdr, etc., which have much more sensible names in expl3.
>>
>> the "lisp heritage" is no more than simple use of some lisp names for
>> some latex internal operations (e.g., car, cdr).  it's a long time (>40
>> years) since i learned lisp, but i don't remember a special name for
>> items in a lisp list.
>>
>>>>> I didn't write "clist_nth" with a view of it being the permanent name,
>>>>> but
>>>>> now that I've written it I can't think of a (good) alternative. Any
>>>>> thoughts?
>>>>
>>>> I think the verb you're looking for is "index", i.e., the command name
>>>> would be clist_index.
>>
>> hmm.  index works, but i don't think it supports the "plain english" test.
>>
>>> I'd imagine 'index' to be the other way around:
>>>
>>>  \clist_index:Nn \l_some_clist { item } => Number
>>
>> agreed.
>>
>>> whereas what Will has implemented gives the 'entry', 'element', 'item'
>>> or some such name. ('element' seems to be discouraged based on the first
>>> part of your e-mail, so perhaps 'item' is better.)
>>
>> i think element is as good as it gets, in this context.
>>
>>>> first: Return index of first occurrence of a particular item within a
>>>> clist,
>>>>        or -1 (given 0-based indices) if the item does not occur therein.
>>>> last:  Return index of last occurrence of a particular item within a
>>>> clist,
>>>>        or -1 (given 0-based indices) if the item does not occur therein.
>>>>        (Note: Slightly trickier to implement.)
>>>
>>> Both of these look relatively easy to do.
>>>
>>>> range: Return a subrange of the clist, i.e., if \a_clist is "a,b,c,d"
>>>> then
>>>>        \clist_range:Nnn\a_clist{1}{2} returns "b,c". (I don't have an
>>>>        opinion as to what might be the best sense of "return" in this
>>>> case.)
>>>> replace: Replace the material in a subrange of the clist by some other
>>>>        clist material.
>>>
>>> More tricky. Let's sort the others first :-)
>>
>> robin
>>
>> getting better every day.  very slightly.
>