Re: [possible patch] Remove the '\\[0pt]' string from the last line of a verse block in LaTeX export

[Juan Manuel Macías]

Ihor Radchenko writes:

> The very reason we use \\[0pt] is because it supposed to prevent
> interpreting [...] at the new line/transcoded element as argument.
>
> You demonstrated that it is yet not always safe enough.
>
> May it be better to use something like
>
> \newcommand\nothing{}
> \newcommand{\safenewline}{\\\nothing}
>
> And then use \safenewline instead of \\[0pt]
>
> In my tests,
>
> \begin{center}
> \begin{tabular}{ll}
> [t] & s\safenewline
> [I] & A\safenewline
> [m] & kg\safenewline
> \end{tabular}
> \end{center}
>
> Does not suffer from misinterpreting new line as argument.

I remember the thread where these issues were discussed and the long
discussion where many alternatives were proposed. After all, the \\[0pt]
solution still seems the safest to me. It seems that the problem is
located only in the verse environment, probably due to some particular
redefinition of the \\ macro that makes that environment.

In any case, square brackets are a problematic character in LaTeX
(think, e.g., of some environment that takes an optional argument). I
think pandoc chooses to always export them as {[}{]}:

#+begin_src sh :results latex
str="[hello world] [foo] [bar]"
pandoc -f org -t latex <<< $str
#+end_src

#+RESULTS:
#+begin_export latex
{[}hello world{]} {[}foo{]} {[}bar{]}
#+end_export

We could do the same, but I'm afraid it's too late if
org-latex-line-break-safe already exists... I don't remember if
something similar was proposed in that discussion, and it was rejected
for some reason.

> `org-latex-verse-block' already has a giant regexp replacement:
>
>       ;; In a verse environment, add a line break to each newline
>       ;; character and change each white space at beginning of a line
>       ;; into a normal space, calculated with `\fontdimen2\font'.  One
>       ;; or more blank lines between lines are exported as a single
>       ;; blank line.  If the `:lines' attribute is used, the last
>       ;; verse of each stanza ends with the string `\\!', according to
>       ;; the syntax of the `verse' package. The separation between
>       ;; stanzas can be controlled with the length `\stanzaskip', of
>       ;; the aforementioned package.  If the `:literal' attribute is
>       ;; used, all blank lines are preserved and exported as
>       ;; `\vspace*{\baselineskip}', including the blank lines before
>       ;; or after CONTENTS.
>
> We may as well strip the trailing \\[0pt] there.

I think it would be best to remove the last \\[0pt] in the verse block.
I can prepare a patch, but I'm afraid that org-latex-verse-block is
becoming an homage to replace-regexp-in-string...

Best regards,

Juan Manuel