Re: [O] :noweb header argument

[Eric Schulte]

>>> As I recall this was originally implemented and then later removed because
>>> it was causing more confusion and problems than it was worth. I hope it
>>> hasn't crossed the line of existence more than once. At some point it
>>> should be placed behind a user-customizable variable, preferably something
>>> like `org-babel-export-code-format' which defaults to something like
>>> "%code" but could be augmented to something like "Block Name: *%name*\n
>>> %code". It is not immediately clear if such a variable should have
>>> different values for different export backends or (likely preferable)
>>> should expand into Org-mode text *before* export.
>>
>> I think you're right about getting this done early in the process. I've been
>> thinking only about LaTeX export because that is my immediate goal--not a
>> good design perspective.
>>

I've just pushed up a minor code change which makes customization of the
format of exported code blocks possible.  I've added a new customization
variable named `org-babel-exp-code-template' which can be used to
specify the text which replaces code block bodies during export.  The
default value of this variable specifies the existing export behavior.
The attached Org-mode file demonstrates this variable in action.

#+Title: Custom code block export formats

- Example code block
  #+Name: foo
  #+BEGIN_SRC sh :bar baz
    echo qux
  #+END_SRC

- Evaluate this block to export (shows the export of the name).
  #+Name: do-export-name
  #+BEGIN_SRC emacs-lisp :results silent
    (let ((org-babel-exp-code-template
           "\n=%name=:\n#+BEGIN_SRC %lang%flags\n%body\n#+END_SRC"))
      (org-export-as-html nil))
  #+END_SRC

- Evaluate this block to export (shows the export of header arguments).
  #+Name: do-export-header-arguments
  #+BEGIN_SRC emacs-lisp :results silent
    (let ((org-babel-exp-code-template
           "Header arguments for =%name=.
    | header  | value    |
    |---------+----------|
    | bar     | %bar     |
    | results | %results |\n#+BEGIN_SRC %lang%flags\n%body\n#+END_SRC"))
      (org-export-as-html nil))
  #+END_SRC

I imagine that this variable would likely be customized on a
file-by-file basis using "file local variables".

>>
>> Perhaps I could help by specifying what I'm trying to do? I'd like to write
>> an article or book about particular statistical analyses. I want this also
>> to be a piece of reproducible research so readers of the book can follow
>> along and perhaps analyze data of their own. I'd like to write a code block
>> once and then use it in the following ways: 1) evaluate and return the
>> results of analyses; 2) export as a floating listing so I can refer to it in
>> discussions of implementation; and 3) tangle to a source code file that can
>> be used as the basis for a package that can be used outside of Org mode.
>>

Sounds like a very cool project.  If this will be public I would love to
link to it from [1] when it is complete.

>>
>> 1) is easy with #+call: With the :wrap header argument that we've
>> partially implemented, I can mark the results off in whatever environment I
>> like, which is a wonderful bit of flexibility. Different kinds of results
>> can be presented distinctively.
>>
>> 2) is partially there--the code itself is handled nicely by minted and
>> I'm able to make it look as good as I want. What I'm lacking now is an easy
>> way to identify the code block. Seb's suggestion that the header lines be
>> included is one way, though Eric F.'s point about the special characters
>> tripping up LaTeX is well taken. It might be some work to get an
>> intermediate representation that can be exported to all the targets. My
>> alternate idea, which is to wrap the code block in an environment to which I
>> can attach a caption and a label, is the LaTeX approach and might not work
>> as well for other export targets.

This new solution replaces the code block with Org-mode text before
export.  This should be the most flexible as arbitrary #+HTML and
#+LATEX lines can be used in Org-mode.

Best,

Footnotes: 
[1]  http://orgmode.org/worg/org-contrib/babel/uses.html

-- 
Eric Schulte
http://cs.unm.edu/~eschulte/