emulate \DontPrintSemicolon in algorithm2e.sty

[dginev]

Fixes dginev/ar5iv#423

Since algorithm2e.sty is emulated in Perl, with some very special considerations for the ends of lines, I think this is the best way to also support the \DontPrintSemicolon without losing the line endings.

There is probably a possible refactor that relies on the native interpretation more, but that could be deferred...

Running example:

\documentclass{article}
\usepackage{algorithm2e}
\begin{document}
\begin{algorithm}
\DontPrintSemicolon
line 1

line 2\;
line 3\;
\For{$t = 1, 2, \ldots, T$} {
    line 1\;
    line 2\;
    line 3\;
}
\end{algorithm}
\end{document}

[dginev]

I also made the printing switches global assignments and spotted a curious discrepancy - algorithm2e will also create a listing line if there is a regular \par in the flow, but our binding had deactivated \r (to a space), so the par breaks weren't getting seen.

I probably need to fetch some more tests before this is really solid, since the comments do a great job of warning there may be too many newlines created if one isn't careful.

[dginev]

As Bruce pointed out on the call today, this fixes the exact report from #2049

[brucemiller]

This looks plausible, I think. Is it ready for review?

[dginev]

Doing a quick run through the ctan examples... It looks like the PR introduces some extra trailing newlines at the ends of indented blocks. Except no, the same extra line-breaks exist in the master branch. So no visible regressions.

I think the minimal fix here is ready for review+merge, and there are certainly more details one can fine-tune to get the examples rendering perfectly. But maybe not for this release?

[dginev]

A comment for future reference (since I don't have an issue to attach it to):

Besides the empty trailing line, another detail that could be polished is the vertical algorithm bars, which are currently emulated via what seems to be | ascii art. I remembered that Twitter of all places has a nice solution for those using flexbox. I extracted it into a codepen (try horizontally shrinking/growing the window to demo the effect):
https://codepen.io/dginev/pen/QWoNgON

Maybe something to try a little later on.