Re: [O] export to latex without labels

[Eric Abrahamsen]

"Salome "Södergran\"" <address@hidden> writes:

> Hello experts,
>
> I've been fiddling around for a while now with the following problem:
>
> When I export something from org to latex I get plenty of \labels that I 
> never refer to. I'd like to get rid of all those labels.
> I found some code [1] that uses a hook that does not work in orgmode anymore. 
> So I tried to adapt that code to the new orgmode way with 
> org-export-filter-final-functions:
>
> (defun ks/org-latex-remove-labels (backend info)
>   "Remove labels generated by org-mode"
>   (when (org-export-derived-backend-p backend 'latex)
>   (let ((case-fold-search nil))
>    (goto-char 1)
>    (replace-regexp "\\\\label{sec-[0-9][^}]*}" "")
>    )))
>
> (eval-after-load 'ox-latex
>   '(add-to-list 'org-export-filter-final-output-functions
>             'ks/org-latex-remove-labels))
>
>
> When I now try to export something from org to latex, I get the following 
> error message:
>  Wrong number of arguments: (lambda (backend) "Remove labels generated by 
> org-mode" (if (org-export-derived-backend-p backend (quote latex)) (progn 
> (let ((case-fold-search nil)) (goto-char 1) (replace-regexp 
> "\\\\label{sec-[0-9][^}]*}" ""))))), 3
>
> I am just an emacs user, not a programmer, and I have no idea what's wrong 
> and what I have to change to make it work. Can anyone give me a hint?
> TIA, Salome

The error message is telling you that the wrong number of arguments were
passed to your filter function. If you look at the doctoring of
org-export-filter-final-output-functions, you'll see that functions in
this filter are passed three arguments (note the 3 at the end of your
error message), but your function only accepts two.

Once you've sorted that out, you'll see that the argument you're missing
is an argument representing the full exported string. That means that
`replace-regexp' is probably the wrong function to be using inside your
function. Actually, if you look at the docstring of replace-regexp, that
was the wrong function to be using anyway :) It recommends using a
combination of re-search-forward and replace-match in lisp functions.

Since you've got a string, try replace-regexp-in-string instead! See the
docstring...

Lastly, it's possible that you could use a more narrowly-targeted filter
for this particular case (rather than filter-final-output, which doesn't
kick in until everything else is done). When exporting to latex, the
element that turns into \label is a target, and that happens in
org-latex-target. The corresponding filter is
org-export-filter-target-functions, so you might consider putting your
function in that variable instead. That could be much simpler: the
function would take three arguments, the second of which is the backend,
as a symbol. You could just check if the symbol was 'latex, and have the
function return an empty string. The function body could be as simple
as:

(defun org-latex-remove-labels (string backend data)
  (if (org-export-derived-backend-p backend 'latex)
      ""
    string))

I haven't tested this for unexpected consequences, mind you...

Really really lastly, does it really matter if there are unused \labels
in the output?

E