Re: Babel: tangling questions

[Jarmo Hurri <jarmo.hurri@iki.fi>]

Greetings Diego.

Diego Zamboni <diego@zzamboni.org> writes:

>> 1. I want to tangle to the default filename (derived from name of org
>>    file and programming language). However, the :tangle header argument
>>    only takes either "yes" or "filename." If the value is "yes", then
>>    the filename is deduced automatically. How can I specify a tangling
>>    directory and still have the default filename?
>
> You can specify a full path as the value of :tangle, but I don't know
> of a way to specify only the directory.

For my purposes this would be a nice new feature. Specifying a directory
would imply the default filename.

> As a workaround, you can also use emacs-lisp code as the value for
> :tangle, so you could do something like this:
>
>  :tangle (concat "/some/dir/" (file-name-base (file-name-sans-extension
> (buffer-file-name))) ".ext")

Nice! For this to be practical, I need two additional features.

1. Ability to set "/some/dir/" on a per-file basis.
2. Ability to infer ".ext" from the source block.

I was actually extend your suggestion to a solution with both of these
properties. In my emacs init file I define:

(defun org-default-tangle-file-with-dir-from-property ()
  (concat (or (org-entry-get nil "ORG_TANGLE_DIRECTORY" t) ".")
          "/"
          (file-name-base (file-name-sans-extension (buffer-file-name)))
          "."
          (let ((lang (car (org-babel-get-src-block-info t))))
            (or (cdr (assoc lang org-babel-tangle-lang-exts)) lang))))

Then I set on the top of my org file, for example

#+property: ORG_TANGLE_DIRECTORY ../docs

After this the following works like a charm (at least so far):

:tangle (org-default-tangle-file-with-dir-from-property)

>> 3. Is it possible to tangle automatically on (every) export? I always
>>    export, but I might forget to tangle, in which case export and tangle
>>    would be out of sync.
>>
>
> I use the following hook to tangle on every save. I find it indispensable :)
>
>   (add-hook 'org-mode-hook (lambda () (add-hook 'after-save-hook
> 'org-babel-tangle
>                                    'run-at-end 'only-in-org-mode)))

Good idea, I will explore this.

> Also, check out my free book "Literate Config", where I discuss some
> more tips about Literate Programming:
> https://leanpub.com/lit-config/read

Will do.

> Hope this helps,

Sure did. Thanks!

Jarmo