Dear Diego,

Gracias!

I slightly modified your solution.

I added the #+INCLUDE line to the end of #+LATEX_HEADER, because then it will overwrite any previous \printanswers and \noprintanswers defined in the HEADER.

#+TITLE:...

...

#+LATEX_HEADER: \usepackage{hyperref}
#+INCLUDE: ./latex-exam-printanswers-switch.org

I used the file name latex-exam-printanswers-switch.org, instead of printanswers.org, because it gives a better indication of what it does.

I used your function as it was, except that I changed the function name and updated the switch org file.

(defun org-latex-export-to-pdf-exam ()
  (interactive)
  (write-region "#+LATEX_HEADER: \\printanswers" nil "latex-exam-printanswers-switch.org")
  (org-latex-export-to-pdf)
  (rename-file (org-export-output-file-name ".pdf") (org-export-output-file-name "-with_answers.pdf"))
  (write-region "" nil "latex-exam-printanswers-switch.org")
  (org-latex-export-to-pdf)
)

It works very fine!

Have a nice Easter!

Yours sincerely,

Xianwen

On 2021-03-24 13:16, Diego Zamboni wrote:

Hi Xianwen,

 

I think the easiest way to conditionally include text in the preamble of the document would be by including a file which can be empty sometimes, and contain the appropriate text when needed. For example, you could have something like this in your Org file:

 

#+include: ./printanswers.org

#+TITLE: Test

...

 

Then the following function will automatically export the file twice, one with the \printanswers command inserted then rename the resulting file, and export again without:

 

(defun org-latex-export-exams ()

  (interactive)

  (write-region "#+latex_header: \\printanswers" nil "printanswers.org")

  (org-latex-export-to-pdf)

  (rename-file (org-export-output-file-name ".pdf") (org-export-output-file-name "-with_answers.pdf"))

  (write-region "" nil "printanswers.org")

  (org-latex-export-to-pdf))

 

You can then run M-x org-latex-export-exams to generate both files.

 

Hope this helps,

--Diego

 

On Wed, Mar 24, 2021 at 11:21 AM Xianwen Chen (陈贤文) <xianwen.chen@gmail.com> wrote:

Dear Christine (and CC list),

Thank you!

 

On 2021-03-19 10:13, Christine Köhn wrote:

Here is one way to do the latex part. You could pass a jobname to latex.

I have this

\IfEndWith*{\jobname}{withsolution}{%
  \usepackage{todonotes}
  \printanswers
}{\usepackage[disable]{todonotes}}

in a myexam.sty file to switch between modes (with or without solutions
and todo notes) and use it in the latex file with

\usepackage{myexam}

You could add your own latex class to org-latex-classes and add this
line there.

The jobname has to be passed to latex with something like -jobname
withsolution if you want it to be with solutions. I use a Makefile for
this purpose which calls latexmk

latexmk -pdf -pdflatex="pdflatex --interaction=errorstopmode" -use-make

and adds -jobname=$(basename $@) if asked to create a pdf ending with
withsolution.pdf. I can send you the Makefile if you're interested.

 

That's very interesting way to solve the problem using LaTeX. Thank you for sharing this. At the moment I'm leaning more towards solving it using emacs lisp.

 

To use the jobname from within orgmode, you'll have to change
org-latex-pdf-process to use the jobname if needed. I think one way to
achieve this is to add a new export backend which is derived from latex
(see org-export-define-derived-backend) and which sets
org-latex-pdf-process accordingly (and resets it afterwards).

 

Thank you again. I'm thinking of a function like following. I'm using comments to express the programming detail that I don't know how to do yet.

 

(deffun org-latex-export-to-pdf-exam ()

  (interactive)

  # do some emacs lisp to add \printanswers to the end of org document header, i.e., adding a line of #+LATEX_HEADER: \printanswers

  (org-latex-export-to-pdf)

  # do some emacs lips to move the foo.pdf to foo-with_solutions.pdf

  # do some emacs lisp to add \noprintanswers to the end of org document header, i.e., removing the line of #+LATEX_HEADER: \printanswers and adding a line of #+LATEX_HEADER: \noprintanswers

  (org-latex-export-to-pdf)

  # remove the line of #+LATEX_HEADER: \noprintanswers

)

 

I don't know enough emacs lisp to fill in the details here for now. However, I think this would be a way to do it within emacs. So each time I call org-latex-export-to-pdf-exam, it would export two PDF files, one with solutions and one without.

 

What do you think?

 

Yours sincerely,

Xianwen