Re: [babel] Bugs for Emacs Lisp code blocks

["Sebastien Vauban" <wxhgmqzgwmuf-geNee64TY+gS+FvcfC7Uqw@public.gmane.org>]

Hi Eric,

"Sebastien Vauban" wrote:
> Eric Schulte wrote:
>> "Sebastien Vauban" <wxhgmqzgwmuf-geNee64TY+gS+FvcfC7Uqw@public.gmane.org> writes:
>>> Eric Schulte wrote:
>>>> Emacs Lisp is an exception in terms of colname processing, it has default
>>>> header arguments set to pass column names through to the code block,
>>>> where the processing may be done trivially in Emacs Lisp.
>>>
>>> OK, but I don't understand the precedence of header arguments. I thought
>>> that a header argument given on the code block preempted all the other
>>> values (system-wide default for all languages, language defaults,
>>> file-wide arguments, and subtree arguments).
>>>
>>> Why isn't this true here as well?
>>
>> That is what is happening here, although combinations of :hlines and
>> :colnames can be tricky. Especially weird, is that if you want to *unset* a
>> header argument which is set at a higher level, you need to set it to '(),
>> as in ":colnames '()".
>
> #+name: unset-colnames-example-input
> | a | b |
> |---+---|
> | 1 | 2 |
> | 3 | 4 |
>
> ** Having no =:colnames= header argument (case 1)
>
> I understand that the following example does have =:colnames= set to =yes=:
> it is neither unset nor changed on the code block specification.
>
> #+begin_src emacs-lisp :var data=unset-colnames-example-input
>   data
> #+end_src
>
> #+results:
> | a | b |
> |---+---|
> | 1 | 2 |
> | 3 | 4 |
>
> Hence, this result is what is expected.
>
> ** Using =:colnames no= header argument (case 2)
>
> #+begin_src emacs-lisp :var data=unset-colnames-example-input :colnames no
>   data
> #+end_src
>
> #+results:
> | a | b |
> |---+---|
> | 1 | 2 |
> | 3 | 4 |
>
> Here, I still don't understand why I do see the table header line: I did
> change the default =:colnames yes= specification to =:colnames no= on the
> code block. I did override the default value. Why is the =no= argument not
> respected?

This still escapes me.

> ** Using =:colnames ()= header argument (case 6)
>
> As you told me, to "unset" the =:colnames yes= header argument, we must use:
>
> #+begin_src emacs-lisp :var data=unset-colnames-example-input :colnames ()
>   data
> #+end_src
>
> #+results:
> | 1 | 2 |
> | 3 | 4 |
>
> That does work.
>
> What is still unclear to me as well, is why =()= and =nil= aren't the same
> from Babel's point of view?

However, I think I understood this one: it is because nil is interpreted as a
string, not as the empty list; right?

That's because strings aren't quoted, right?

Best regards,
  Seb

-- 
Sebastien Vauban