Re: Line breaks and brackets in LaTeX export

[Juan Manuel Macías]

Ihor Radchenko writes:

> I haven't seen any publication rule that prevents using valid LaTeX
> commands like this. Do you have concrete examples? If not, one could
> argue that any auto-generated output could break some imaginary rule.

No, I don't have any concrete example. But it is one thing to use a
valid LaTeX command and another to use it unnecessarily. It's like
putting \vspace{0pt} between each paragraph.

> I am also wondering how LaTeX documents generated from LyX or TeXmacs
> look like. Are they not using some obvious machine-generated constructs?

I don't know, because I haven't seen them. But I'd bet (at the risk of
losing the bet) that none of those machine-generated constructs produce
anything as unnecessary as Org's present solution. The situation now
becomes the following:

Pandoc: selective solution. In specific cases it returns {[}...{]}

Org: non-selective solution = ugly LaTeX code.

>> Anyway. As for the compilation, it is highly unlikely that \empty will
>> cause any unexpected error. But LaTeX and its over 6000 packages is
>> unpredictable. It also seemed unlikely that \relax would cause any
>> problems, and catching up on the last discussion, it had to be replaced
>> by \empty because it returned an error just before \hline. \relax is one
>> of the recommended solutions from LaTeX, because it tells LaTeX that the
>> previous macro has finished expanding, but it is recommended keeping in
>> mind that the user will apply it only when needed, not everywhere. And
>> before \hline it doesn't make sense because there will never be an
>> '\\[...]' error. So, in the current situation, we can ask ourselves: is
>> \empty everywhere safe? Everything points to yes. Can we be 100% sure?
>> ...?
>
> My answer is: "\\" is 100% not universally safe. Simply because we have
> that bug report with [ ... ] items in tables.
> So, anything with no concrete counter-example is better as long as we
> are reasonably sure that we are not breaking LaTeX conventions.

As I said, this is a known LaTeX problem that occurs in a rare case, for
which there is a known solution (or several), which should be applied in
the specific case. And Org already provides the necessary tools to apply
it.

>> The only thing I can think of, for a non-selective solution like the
>> current one, is the following: if \\ has an optional argument that must
>> be a length, then let's give it, but with a value of zero: \\[0pt], which
>> is equivalent to putting the value by default (zero) explicitly.
>
> This has been proposed and then rejected by Max in
> https://list.orgmode.org/orgmode/ti5tdb$rd2$1@ciao.gmane.io/ and he
> concluded that some side effects are present when using \\[0pt]:
>
> Max>       \\[0pt]
> Max> 
> Max> causes insertion of some code for negative vertical skip (of zero height 
> Max> this case). It should not be really harmful, but I would avoid this

I would like to see some concrete example where this solution was
problematic. \\[0pt] is exactly the same as \\ (as for the effects).
Redundant but valid.