From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Eric Schulte" <schulte.eric@gmail.com>
Subject: Re: [babel] Conditional tangling possible
Date: Tue, 31 Aug 2010 10:19:29 -0600
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To: R.M.Krug@gmail.com
Cc: emacs-orgmode <emacs-orgmode@gnu.org>

Hi Rainer,

Rainer M Krug <r.m.krug@gmail.com> writes:

> On 31/08/10 02:06, Eric Schulte wrote:
>> Hi Rainer,
>> 
>> The easiest way to do this should be,
>> 
>> --8<---------------cut here---------------start------------->8---
>> ** pulling information from tags                                       :blue:
>> 
>> #+begin_src R :var color=(car (org-get-tags-at (point))) :tangle example.R
>>   color
>> #+end_src
>
> OK - that looks good. That solves one problem.
>
> But it is not actually conditional tangling? It is rather the transation
> of a tag into a variable - or am I seeing something wrong?
>

My fault, I misread your original message, something like the following
should work.  You can use the uppermost elisp code block to change the
value of the tangle-tag to whichever tag you wish to be tangled.

--8<---------------cut here---------------start------------->8---
** conditional tangling
#+begin_src emacs-lisp :results silent
  (setq tangle-tag "right")
#+end_src

*** first subheading                                                   :left:
#+begin_src R :tangle (and (equal (car (org-get-tags-at (point))) tangle-tag) "yes")
  "first"
#+end_src

*** second subheading                                                 :right:
#+begin_src R :tangle (and (equal (car (org-get-tags-at (point))) tangle-tag) "yes")
  "second"
#+end_src
--8<---------------cut here---------------end--------------->8---

Cheers -- Eric