Re: Tangling without clutter?

[Jos'h Fuller <Jos'h.Fuller@arcproductions.com>]

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?

Thanks!

Jos'h