[Rd] Feature request: Allow comma after last element in a list

[Duncan Murdoch]

This is a great suggestion.  BTW, I think it would be possible to do 
this in RStudio as well.  See their Addins page here: 
https://rstudio.github.io/rstudioaddins/ .

Duncan Murdoch

On 2026-04-30 1:44 p.m., Tomek Gieorgijewski wrote:
> Hi Manfred!
> 
> As I can see that you already maintain the habit to have one element per
> line,
> I would like to propose that you incorporate some editing scripts in your
> editor
> to help ease your frustration.
> I believe trying to change R parser will only add more of that feeling :)
> I don't know your editor but if it's vim, I can propose this edit to .vimrc
> file:
> " ----
> function! ListCommas() range
>         if a:firstline < a:lastline
>             " Add commas at the end from first to second to last line if
> there's no comma yet
>             execute a:firstline . "," . (a:lastline - 1) . 's/[^,]$/&,/e'
>         endif
>          " Delete comma from last line (if matched)
>         execute a:lastline . 's/,$//e'
>     endfunction
> 
>     vnoremap <leader>, :call ListCommas()<CR>
> " ---
> 
> So, now if you rerun vim on your file you can swap, add, delete lines from
> the list as you wish,
> and at the end you can highlight all elements lines of your list in visual
> mode and execute ListCommas
> function on those lines with <leader>, shortcut.
> 
> Of course only if you maintain your structure of element per line and
> trailing parenthesis at a seperate line.
> 
> I'm sure VS Code, Emacs and some other editors have similar abilities to
> help you.
> Unfortunately I don't know of any such possibility in RStudio.
> 
> regards,
> Tomek.
> 
> pt., 24 kwi 2026 o 13:35 Manfred Kooistra <manfred.kooistra using gmail.com>
> napisał(a):
> 
>> I've always been irritated that R doesn't allow a comma after the last
>> element in a "list":
>>
>>> a <- c(
>> +     1,
>> +     2,
>> +     3
>> + )
>>> a
>> [1] 1 2 3
>>> b <- c(
>> +     1,
>> +     2,
>> +     3,
>> + )
>> Error in c(1, 2, 3, ) : argument 4 is empty
>>
>> This makes updating lists unnecessarily cumbersome, which I find I
>> frequently do, either when I test code and want to run it with lists of
>> varying elements or varying orders of elements or when I maintain lists
>> manually over time and have to add or delete elements from them.
>>
>> Is there a reason for this behavior in R and might it not be a good idea
>> to change it?
>> ______________________________________________
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>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>
> 
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