From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Schulte <schulte.eric@gmail.com>
Subject: Re: [babel] Bugs for Emacs Lisp code blocks
Date: Fri, 12 Apr 2013 16:03:08 -0600
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To: Sebastien Vauban <wxhgmqzgwmuf@spammotel.com>
Cc: emacs-orgmode@gnu.org

>>>
>>> Much clearer, but not yet crystal-clear for me...
>>>
>>> Let me explain. AFAICT, there were 5 possibles values of the ":colnames"
>>> header argument:
>>>
>>> - no header argument :: (default for all languages but Emacs Lisp)
>>> - ":colnames no" :: (default for Emacs Lisp code blocks)
>>> - ":colnames yes" :: Tells Org Babel that your first row contains column
>>>   names.
>>> - ":colnames <LIST>" :: Specifies to use <LIST> as column names.
>>> - ":colnames nil" :: Same as ":colnames yes".
>>>
>>> Right?
>>
>> Almost, values 1 (none) and 5 (nil) are the same.
>
> I don't share your view about this last statement.
>
> ** Input table
>
> #+name: unset-colnames-example-input
> | a | b |
> |---+---|
> | 1 | 2 |
> | 3 | 4 |
>
> ** Having no =3D:colnames=3D header argument (case 1)
>
> Same results for R and sh code blocks (first good news=C2=A0;-)) -- I'm a=
voiding,
> on purpose, testing with Emacs Lisp...
>
> #+begin_src R :var data=3Dunset-colnames-example-input
>   data
> #+end_src
>
> #+results:
> | 1 | 2 |
> | 3 | 4 |
>
> #+begin_src sh :var data=3Dunset-colnames-example-input
>   echo "$data"
> #+end_src
>
> #+results:
> | 1 | 2 |
> | 3 | 4 |
>

Looks good.

>
> ** Using =3D:colnames nil=3D header argument (case 5)
>
> Once again, R and sh blocks do produce the same results...
>
> #+begin_src R :var data=3Dunset-colnames-example-input :colnames nil
>   data
> #+end_src
>
> #+results:
> | a | b |
> |---+---|
> | 1 | 2 |
> | 3 | 4 |
>
> #+begin_src sh :var data=3Dunset-colnames-example-input :colnames nil
>   echo "$data"
> #+end_src
>
> #+results:
> | a | b |
> |---+---|
> | 1 | 2 |
> | 3 | 4 |
>
> ... but they are _not_ equivalent to the "no header argument" (case 1).
>

As I believe I mentioned "nil" on a header argument is not interpreted
as the lisp literal `nil'.  To pass an empty argument to a code block
you should do ":colnames '()", an obscure syntax for an obscure thing.

>
> ** Using =3D:colnames yes=3D header argument (case 3)
>
> On the contrary, case 5 is equivalent to the case 3: same results as
> ":colnames yes".
>
> #+begin_src R :var data=3Dunset-colnames-example-input :colnames yes
>   data
> #+end_src
>
> #+results:
> | a | b |
> |---+---|
> | 1 | 2 |
> | 3 | 4 |
>
> #+begin_src sh :var data=3Dunset-colnames-example-input :colnames yes
>   echo "$data"
> #+end_src
>
> #+results:
> | a | b |
> |---+---|
> | 1 | 2 |
> | 3 | 4 |
>

Because the "nil" you specified above is just treated as a string.  You
get the same thing with.

#+begin_src sh :var data=3Dunset-colnames-example-input :colnames sure
  echo "$data"
#+end_src

#+RESULTS:
| a | b |
|---+---|
| 1 | 2 |
| 3 | 4 |

Cheers,

--=20
Eric Schulte
http://cs.unm.edu/~eschulte