Re: [O] Include sections of org document in tangled files

[Charles C. Berry]

On Fri, 2 Dec 2016, David Dynerman wrote:

> Dear list,
>
> Is it possible to include sections of an org document while tangling.
>
> I have in mind something like the following:
>
> * Some section

[David's version deleted]

#+NAME: doc
#+BEGIN_SRC org :exports results :results replace
  This is an introduction. We're going to write some code that
  implements (a finite version of) the formula

  \[
  f(x) = 1 + x + \frac{x^2}{2} + \frac{x^3}{6} + \ldots +
  \frac{x^n}{n!} + \ldots
  \]

  Here's some background about the exponential function.

#+END_SRC

#+header: :noweb (unless org-export-current-backend "yes")
#+BEGIN_SRC python :tangle myfunction.py
  from math import factorial

  def f(x,n):
      """
      <<doc>>
      """

      y = 0
      for i in range(n+1):
          y = y + x**i/factorial(i)

      return y
#+END_SRC


> The idea would be that when I export this to HTML, I get a nice literate
> programming math jax'd section introduction that explains what the
> function is doing.

Right. The above does that.

You need `org' as a babel language. Eval'ing `(require 'ob-org)' is good 
enough for just trying to export this, but customizing 
`org-babel-load-languages' to include `org' is better if you use this 
regularly.


> Then, when I tangle to generate the python file, the
> org section introduction would be included as the python docstring of
> the function.

And it does that.

---

There is an issue you might want to address if you use this approach. 
First, the first triple quotes must not be on the same line as the 
included src block reference. That is because """<src-blk-ref>>""" will 
prepend the quotes to every line in `src-blk-ref'.

If you do not want the newlines between the quotes and the docstring, I 
think there is a post-tangle hook you can use to clean the tangled version 
by removing those newlines.

Also, you can use an export filter to remove the quotes and the noweb 
reference for a cleaner looking exported doc.

Note that you need to use a unique name for each src-block.

HTH,

Chuck