Re: Tangling without clutter?

[Eric Schulte <eric.schulte@gmx.com>]

Jos'h Fuller <Jos'h.Fuller@arcproductions.com> writes:

> Hi!
>
>> > It seems like I almost need some variant of the "tangle" argument to
>> > :noweb where syntax references are expanded for evaluation, but not
>> > for anything else.
>> >
>> 
>> Why would you want to tangle out a python src file with an un-expanded
>> noweb reference?  Either way, who am I to judge.  I've just added a new
>> "eval" option to the noweb header argument which will expand noweb
>> references *only* during interactive evaluation.
>
> Please allow me to explain, I think it's a legitimate use case...
>
> I would like to provide a listing of a Python function, then later in
> the document show a demonstration of how it's used. I just did this
> when preparing some documentation for another programmer who is
> porting an application between languages.
>
> So I listed the function, then after a discussion, I had a
> demonstration of how to use the function. I wanted the output from the
> demonstration to be "live", generated from the demonstration
> code. Therefore, I needed to reference the function defined
> above. Unfortunately, the reference was expanded during export so that
> the same block of code appeared /twice/, presenting the reader with
> something like this:
>
> : Here's a function:
> :  def gorking():
> :   return "gork"
> :
> : Here's how to use the function:
> :  def gorking():
> :   return "gork"
> :
> :  print gorking()
> : 
> : Which gives us:
> :  gork
>
> As you can see, it's rather clumsy to have the function in the output
> twice. It's not too bad for this example, but anything more than a few
> lines becomes quite a distraction! This would have been preferable:
>
> : Here's a function:
> :  def gorking():
> :   return "gork"
> :
> : Here's how to use the function:
> :  <<function-gorking>>
> : 
> :  print gorking()
> : 
> : Which gives us:
> :  gork
>
> The original %.org file would look like this:
>
> : Here's a function:
> :  #+name: function-gorking
> :  #+begin_src python :tangle yes
> :  def gorking():
> :   return "gork"
> :  #+end_src
> :
> : Here's how to use the function:
> :  #+name: function-gorking-demo
> :  #+begin_src python :tangle yes
> :  <<function-gorking>>
> :
> :  print gorking()
> :  #+end_src
> : 
> : Which gives us:
> :  #+results: function-gorking-demo
> :  gork
>
> Does that explain it better?
>

Yes, although it seems that the existing "no-export" or "strip-export"
options to the :noweb header argument may better suit your purposes.
These are described in the Org-mode manual, however, they are not
mentioned in the online version of the manual which is out of date.

Cheers,

>
> Thanks!
>
> Jos'h
>
>
>

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