From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Charles C. Berry" <ccberry@ucsd.edu>
Subject: Re: Dynamic tangle target?
Date: Wed, 21 Sep 2016 18:06:42 -0700
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To: Philip Hudson <phil.hudson@iname.com>
Cc: emacs orgmode-mailinglist <emacs-orgmode@gnu.org>

On Wed, 21 Sep 2016, Philip Hudson wrote:

> AFAICT :tangle takes only "yes", "no", or a literal pathname.

Stuff like

    :tangle (my-lisp-function arg1 arg2)

will work.

> How
> might I dynamically generate a pathname for :tangle? I suppose what I
> want is some kind of escape syntax for eval'ing a Lisp form, like
> maybe:
>
>    :tangle %(my-dynamic-filename-generator)

Try this:

#+BEGIN_SRC R :tangle (concat "my-" "file" ".R")
abs <- def
#+END_SRC

just as an example.

BTW, org-babel-view-src-block-info (C-c C-v C-i) will show you what header 
args evaluate as without the need to eval or tangle them.

HTH,

Chuck