Re: Extract source code /with/ captions

[James Harkins <jamshark70@gmail.com>]

On Monday, January 13, 2014 1:19:28 AM HKT, John Kitchin wrote:
> I think I have done something like that before. What I did was make it so
> each code block would be written out to a file, e.g.
> course-notes/script-%d.py and a link would be put in the exported pdf 
right
> after that block. I do not know how you could get the captions though.

Thanks for the suggestion. I think it might be overkill for my case. One 
thing is, I don't need links in the LaTeX output -- hence, no need to tie 
it to LaTeX export.

So, after a night's sleep, I remembered something about org-element and 
took a look at some docstrings. A clever comment about "The (almost) 
almighty `org-element-map'" attracted particular attention :)  and indeed, 
it turns out that it does almost all the hard work.

Some progress, then:

(defun hjh-print-src-blocks ()
  "Iterate src blocks from org-element and print them to *Messages*."
  (interactive)
  (let ((tree (org-element-parse-buffer)))
    (org-element-map tree 'src-block
      (lambda (element)
	(message "\n\n\nELEMENT:")
	(print (plist-get (car (cdr element)) :caption))))))

I pulled one frame with two src blocks out of the presentation, put it in a 
separate file, and running this function from the buffer produces this in 
the messages buffer (omitting some blank lines, which I had inserted while 
running this under edebug):

ELEMENT:
(((#("25% coin toss in SmallTalk" 0 26 (:parent #2)))))

ELEMENT:
(((#("25% coin toss in SuperCollider" 0 30 (:parent #2)))))

This is correct, and I also see that I can use (plist-get ... :value) to 
get the code string.

Here, I'm hung up on some (large?) gaps in my elisp knowledge. I have no 
idea what #(...) signifies, or what functions I can use to get the string 
out of it. "#" Is not an especially useful search term in google, bing 
etc...

Can anyone help with my next step?

Also, big thanks to Nicolas for org-element. The fact that an elisp novice 
can extract captions for source blocks in about half an hour of tinkering 
is nothing short of criminally easy. Spectacular.

hjh