On Fri, Sep 11, 2015 at 11:21:56AM +0100, Joseph Wright wrote:
>On 11/09/2015 11:17, Alexander Grahn wrote:
>> On Fri, Sep 11, 2015 at 11:06:08AM +0100, Joseph Wright wrote:
>>> On 11/09/2015 10:46, Alexander Grahn wrote:
>>>> consider the following example:
>>>>
>>>> \documentclass{article}
>>>> \usepackage{expl3}
>>>>
>>>> \begin{document}
>>>> \ExplSyntaxOn
>>>> \clist_set:Nn\l_tmpa_clist{,,foo,bar,}
>>>> \typeout{\clist_count:N\l_tmpa_clist} %expected: 5, I get 2.
>>>> \typeout{\clist_item:Nn\l_tmpa_clist{3}} %expected: `foo`, I get `'.
>>>> \typeout{\clist_item:Nn\l_tmpa_clist{4}} %expected: `bar`, I get `'.
>>>> \ExplSyntaxOff
>>>> \end{document}
>>>>
>>>> Why does \clist_set:Nn ignore empty items when initialising a clist
>>>> variable from a token list? Is this intended behaviour? Is there a
>>>> work-around?
>>
>>> This is by-design. Comma lists can't contain empty items, commas, etc.:
>>> sequences can. The reason is comma lists are 'close' to the user level,
>>> and there stray empty entries are normally best ignored.
>>
>> This is very unfortunate, because I want to be able to correctly process
>> user input of comma sparated items which /may/ contain empty items.
>>
>> With \@for from LaTeX2e I can easily process such input properly:
>>
>> \documentclass{article}
>>
>> \begin{document}
>> \makeatletter
>> \@for\listitem:=,,foo,bar,\do{
>> \typeout{item:\listitem}
>> }
>> \makeatother
>> \end{document}
>>
>> Now I am looking for an L3 equivalent of \@for.
>>
>> Alexander
>
>Can of course be done using a sequence
>
> \input expl3-generic %
> \ExplSyntaxOn
> \seq_set_split:Nnn \l_tmpa_seq { , } { ,,foo,bar, }
> \seq_show:N \l_tmpa_seq
>
Perfect! Thanks a lot!
Alexander
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