Re: [BABEL] [PROPOSAL] Seemless editing of Babel Blocks

From: Dan Davison <davison@stats.ox.ac.uk>
To: Jambunathan K <kjambunathan@gmail.com>
Cc: emacs-orgmode@gnu.org
Subject: Re: [BABEL] [PROPOSAL] Seemless editing of Babel Blocks
Date: Sun, 05 Sep 2010 11:58:35 -0400	[thread overview]
Message-ID: <87wrr0npw4.fsf@stats.ox.ac.uk> (raw)
In-Reply-To: <818w3gv7j7.fsf@gmail.com> (Jambunathan K.'s message of "Sun, 05 Sep 2010 15:25:40 +0530")

Jambunathan K <kjambunathan@gmail.com> writes:

>
> jambu> How about providing user-accessible tapping points within
> jambu> 'org-babel-map-src-blocks' (or a variation thereof) that would
> jambu> enable me have a custom command in my .emacs.
> jambu>
> jambu> For the sake of record, my suggestion is very closely related to
> jambu> what is discussed here.
> jambu>
> jambu> http://eschulte.github.com/babel-dev/PROPOSED-tangle-entire-org-mode-file-in-comments.html
>
> Eric> I've just pushed up an implementation of the functionality
> Eric> described at the link above, see [1] for examples and details.
> Eric>
> Eric> Is this sufficient to satisfy the need you were addressing?  If
> Eric> not how could it be improved?
>
> Eric> Footnotes: 
> Eric> [1]  http://eschulte.github.com/babel-dev/DONE-tangle-entire-org-mode-file-in-comments.html
>
> I am making a request for an API from BABEL core which roughly parallels
> org's org-map-entries.
>
> Using this API a user should be able to 'traverse' babel and non-babel
> blocks within a given scope (region, buffer), examine the local state
> (say a tag or a user-defined property on a subtree), provide a verdict
> on it's inclusion (yes I want it, no skip it) or possibly return a
> transformed custom content (as a list).
>
> 'org-babel-map-src-blocks' has the skeletal structure for this API. All
> it needs is some minimal tinkering to take on a more user-pluggable
> form.

> The proposed API would make UseCase-1 and UseCase-2 possible.
>
> UseCase-1: 
> http://article.gmane.org/gmane.emacs.orgmode/28823
>
> Section-6 provides an illustration.
> Section-5 helps one visualize the essentials of the propsed API.
>
> a) org-to-org-src-view => potential consumer of the proposed API.
> b) beg-org, end-org, beg-babel, end-babel => strategic 'points' of
>    user-interest.
> c) body, body1 => Hooks for user

Hi Jambunathan,

I assume that beg-babel and end-babel are the start and end of the
current code block. What exactly are beg-org and end-org here?

>
> UseCase-2: Tangling with custom pragmas.
> http://article.gmane.org/gmane.emacs.orgmode/29805
>
> Additional Note: Thinking out loud here (aka contrived, over-the-top
> requirement). 
>
> A user might want to override the in-buffer babel-control parameters
> while tangling or execution.
>
> Think of this scenario, I would like to tangle but with comments and
> line nos as a one-off (say for circulating to my colleagues). The
> in-buffer 'static/default' settings suppresses comments. I couldn't be
> bothered to edit the in-buffer settings just for this one-off case. Is
> there a possible way I can achieve this?

Many of the core org-babel functions accept an optional argument named
`info'. This is a data structure which contains all the relevant
settings: language, the body, the header args, etc. If this argument is
provided, then no attempt is made to obtain the settings from the
buffer. So the way to do this is to construct your own info data
structure and then pass it to the org-babel function you are using
(e.g. org-babel-execute-src-block).

Typically, the info structure is created from the buffer using
org-babel-get-src-block-info. See the docstring of that function for a
definition of the data structure.

As an example of on-the-fly construction of an info data structure (and
thus a "virtual" code block that doesn't exist in any buffer), see the
way Eric implemented #+lob calls in `org-babel-lob-execute' (it's quite
clever).

Also note in those functions that there is a useful function
`org-babel-merge-params': In org-babel code, "params" generally means an
association list of header argument (argument, value)
pairs. `org-babel-merge-params' allows you to construct the params alist
from a variety of different sources (the buffer settings, and your own
settings): later arguments have priority over earlier ones. Grepping for
org-babel-merge-params in the code shows some examples of using it to
construct the "params" part of the "info" structure, e.g.:

ob-ref.el:162:	(setq params (org-babel-merge-params params args '((:results . "silent"))))
ob-table.el:119:                      (org-babel-merge-params '((:results . "silent")) params))))

Based on a very quick look, it seems that tangle is gloing to be
slightly different from execute. For tangle, you might want to use a
let-binding to bind a temporary value of org-babel-default-header-args,
constructed using org-babel-merge-params as on line 146 of ob-tangle.el.

Dan

>
> Jambunathan K.
>
>
>
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