expl3 par and sequences

Question

Having been exploring expl3 I have been updating some of my code to it, and I ran into a interesting issue that I was not predicting.

I get a strange error that I think is from trying to store multiple paragraphs into a sequence. I didnt find anything in the interface3 manual, does anyone know of an way around this?

I put my old method and new trail method for variable storage below for those who are interested.

Here is my old code.

\newcommand{\@supernote}{}
\newcommand{\supernote}[1]{\renewcommand\@supernote{#1}}

And here is my new code.

\seq_new:N \itemsupernote
\NewDocumentCommand{\supernote}{sm} {
    \seq_put_right:Nn \itemsupernote {#2}
}

Calling the function works the same way for both

\supernote{Here is my example

and here is the other half}

Here is my error for the new method in case it helps.

runaway argument? {here is my example Paragraph ended before \supernote was omplete.
<to be read again> \par l.109 

Answer 1

The issue is not with the code layer (which is all 'long'), but with your interface set up. As the more common case for document commands is that they should only take short pieces of text, xparse creates 'short' commands as-standard. To make an argument 'long' you need to mark it as such with a +

\NewDocumentCommand \supernote { s +m }
  {
    \seq_put_right:Nn \itemsupernote {#2}
  }

Notice that xparse deals with long/short arguments on an argument-by-argument basis rather than switching all of them in one go.