Re: vertical space

[Nick Dokos <ndokos@gmail.com>]

Rustom Mody <rustompmody@gmail.com> writes:

> Im having an issue with inconsistent vertical space
>
> If I do latex export \\es at eol produce blank lines
> However with html export they appear in output but not consistently
> org version 8.2.5e
> emacs version 24.3.1
>
> Below a cut-down version from a file I see it happening
> ------------
> #+TITLE: Equational Reasoning in Logic
> #+AUTHOR: Rusi
> #+OPTIONS: toc:nil
> * Object and Meta language
> Look at the following proof
>
> #+ATTR_LATEX: :mode math :environment flalign
> P \wedge (Q \vee P)\\
> " \wedge distributes over \vee " \\
> = (P \wedge Q) \vee (P \wedge Q) \\
> " Idempotence of \vee " \\
> = P \wedge Q \\
> \\
> \\
>

This case is easy: just delete the last two \\ and you are done.  I take
it that your real case is more complicated.

Running org-element-parse-buffer on your buffer might be illuminating:
the "internal" \\ get parsed as

 (line-break (:begin 267 :end 270 :post-blank 0 :parent #3))

but the last one (I used a buffer with just one trailing \\, not two)
gets parsed as

#("\\\\
" 0 3 (:parent #3))

i.e. a string, so it gets copied to the output. When the output is
latex:

,----
| " Idempotence of \(\vee\) " \\
| = P \(\wedge\) Q \\
| \\
| % Emacs 24.3.50.2 (Org mode 8.2.5g)
| \end{document}
`----

the \\ are processed by pdflatex and become empty lines. When the output
is html:

,----
| " Idempotence of &or; " <br  />
| = P &and; Q <br  />
| \\
| </p>
`----

they are processed by the browser which does nothing special with them,
so they are shown in the output.

Why exactly the last one is parsed as a literal string and not as a line
break, I don't know. Nicolas will probably explain all. The only thing I
can say is that if there is something other than whitespace on the line
before the \\, it gets parsed as a line break; if there is only
whitespace (or nothing), it gets parsed as a string. That's probably a
rough description and not quite right in all particulars, but I hope
it's close enough.

-- 
Nick