From mboxrd@z Thu Jan  1 00:00:00 1970
From: Eric Schulte <schulte.eric@gmail.com>
Subject: Re: Using cat() with R prints R session prompt (>) in results block
Date: Sat, 23 Mar 2013 16:20:31 -0600
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To: John Hendy <jw.hendy@gmail.com>
Cc: emacs-orgmode <emacs-orgmode@gnu.org>

[...]
> I'm getting the > prompt from my R session output
> with the cat() command. For example:
>
> #+name: test
> #+begin_src R :session r :results output raw :exports results
>
> cat(paste("#+end_center"))
> cat("\n")
>
> #+end_src
>
> #+RESULTS: test
> #+end_center>
>
> How do I stop that?
>
> As a side note... if I remove cat("\n"), nothing gets put into the
> #+results block -- it's just empty. I don't understand why.
>

Hi John,

This seems to be related to newlines and the parsing of session output.
Results aren't noticed without a newline, and when intermediately
printed results do not end in a newline, the prompt is pasted along with
the results.

If we look at the R session buffer, the cause of this bad behavior can
be seen.

    ,----[ESS buffer]
    | > cat(paste("#+end_center"))
    | cat("\n")
    | 'org_babel_R_eoe'
    | cat(paste("#+end_center"))
    | #+end_center> cat("\n")
    | 
    | 
    | > 'org_babel_R_eoe'
    | [1] "org_babel_R_eoe"
    `----

I'm not sure that we can (robustly and reasonably) distinguish the R
prompt from R process output when the prompt does not appear at the
start of a line.  Perhaps ESS could mark R prompts with a special text
property which would make this much easier from the Org-mode side?

Is it possible simply to ensure that code block output lines end in
newlines?

Cheers,

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