Re: looking for a macro eval workaround (9.1 vs 9.2 and +) for export backend test

[Tim Cross <theophilusx@gmail.com>]

Bruno BEAUFILS <bruno@boulgour.com> writes:

> I have a *lot* of org files with a macro =if-backend= which enables me
> to decide what to export depending on the backend :
>
> #+begin_src org
>   #+macro: if-backend (eval (if (org-export-derived-backend-p org-export-current-backend '$1) "$2"))
> #+end_src
>
> For instance, I use it to include =\hfill= in LaTeX family export
> engines but not in others (html for instance) :
>
> #+begin_src org
>   #+macro: hfill {{{if-backend(latex, \\hfill{} )}}}
> #+end_src
>
> I generally use emacs 26.3 as distributed by Debian bullseyes (which
> offer org-mode version 9.1.9).
>
> On another box I need to work with a more recent org-mode, precisely
> 9.4.
>
> In that environment, due to an incompatible change introduced by
> [[https://orgmode.org/Changes_old.html#outline-container-org003add6][release 9.2]] the same macro has to be written in a different way :
>
> #+begin_src org
>   #+macro: if-backend (eval (if (org-export-derived-backend-p org-export-current-backend (intern $1)) $2))
> #+end_src
>
> And thus I need to change also the macro using it, for instance the
> =hfill= macro has to be written that way :
>
> #+begin_src org
>   #+macro: hfill {{{if-backend(latex, \hfill{} )}}}
> #+end_src
>
> For now I need to work on the same files in these two different environment.
>
> Do anyone have an idea on how to be able whether to define the
> =if-backend= in a way that it can work in both org versions or if
> there is a way to define these macro in different ways depending on
> org version?
>
> I would like to let the definitions in org files and not in emacs init
> files.

Hmm, I just use backend specific blocks for this purpose. e.g.

#+begin_export latex
  \hfil{}
#+end_export

Pretty sure 9.1 supports the same (there was a change, which used
#+EXPORT_LATEX instead of #+begin_export, but I think the old version
still works in 9.4, can't remember which version the change was
introduced). So if 9.1 only supports EXPORT_LATEX, you should still be
able to use it under 9.4

IMO the org #+MACRO is really just a text substitution mechanism (like
C), not a 'real' macro (like elisp has) and as is the case with C, you
really need to keep them pretty simple. Once you start using them to
evaluate code, it isn't hard to find yourself in a mine field.

--
Tim Cross