Re: [O] org-babel -- Improper syntax error in session mode?

[Thomas S. Dye]

Aloha Herb,

I think a note to that effect belongs here:
http://orgmode.org/manual/session.html#session

Perhaps the behavior related to session persistence could be described
there, as well.

Examples are probably best left to the language-specific documentation,
such as it is, at http://orgmode.org/worg/org-contrib/babel/languages/

Note that there is no language-specific documentation for Python yet.

Is it the case that the Ruby and Perl interpreters won't run code that
does run in non-session mode?

All the best,
Tom

Herbert Sitz <address@hidden> writes:

> Thomas S. Dye <tsd <at> tsdye.com> writes:
>> 
>> Aloha Herbert,
>> 
>> I think you're right about the potential to improve the documentation.
>> That's an on-going process.  Could you suggest some specific changes?
>> 
>> All the best,
>> Tom
>
> Tom -- 
>
> I would suggest just adding specific warnings that session-based evaluation 
> may
> throw syntax errors with valid code.
>
> Here's what Org manual says regarding :session evaluation with :results 
> output':
>
> "The code is passed to the interpreter running as an interactive Emacs 
> inferior
> process. The result returned is the concaOrg tenation of the sequence of 
> (text)
> output from the interactive interpreter. Notice that this is not necessarily 
> the
> same as what would be sent to STDOUT if the same code were passed to a
> non-interactive interpreter running as an external process. . . ."
> [http://orgmode.org/manual/Results-of-evaluation.html#Results-of-evaluation]
>
> All that needs to be added is a warning:
>
> "IMPORTANT:  Note that Org provides only a thin wrapper around a language's
> interactive shell, so valid code that executes properly in non-session mode 
> may
> fail in :session mode.  This is because Org feeds the lines in a :session 
> block
> to the interactive interpreter exactly as written.  In come cases the lines 
> may
> require special formatting in the source block to be executed properly in the
> interactive shell.  For example: . . . "
>
> I think the above issue should be moot for some of the main interpreted
> languages (viz., Python, Perl, Ruby) where there are various ways to execute a
> block of code non-interactively despite being in the interactive shell.  (One 
> of
> those methods is the example I gave in previous message.)  In that case
> identical code will run the same whether it's in an interactive-interpreter
> session or not.  It seems to me that switching to that approach for languages
> that support it should both (1) simplify the Org Babel code, and (2) provide 
> Org
> users with more flexibility and power.
>
> Also, it seems the real power of :session evaluation is to share state between
> Org/Babel source code blocks, not merely to act as a kind of Org-internal
> scratchpad.  As a user trying to take advantage of that state-sharing power I
> would generally want my Org document exports to start from fresh sessions.  
> That
> is, I would write my :session blocks so that they depended on results of code
> run in previous :session blocks, BUT I would want the first :session block to
> start with a fresh session,with a known state.   So on export I would 
> generally
> want any existing named session to be closed and restarted anew for an 
> Org export.
>
> I hope that all makes sense.  I should say I'm not a big Babel user, and I 
> could
> easily be misunderstanding something.  But it seems this is the way the
> :session-based stuff should work, when possible.
>
> -- Herb
>
>
>

-- 
Thomas S. Dye
http://www.tsdye.com