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MathGroup Archive 1997

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Re: package impasse?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg6219] Re: [mg6213] package impasse?
  • From: David Withoff <withoff>
  • Date: Fri, 28 Feb 1997 03:21:37 -0500
  • Sender: owner-wri-mathgroup at wolfram.com

> In previous postings, I described in more or less detail a problem I
> have with implementing a package.  Please tell me if my conclusion
> about this is correct.
> 
> A user defines a certain function f, which in turn may reference other
> user-defined objects g and c.  These _other_ names are unknown to the package
> designer (me)!
> 
> The package doesn't export anything.  What it does do is evaluate the
> user's f at certain arguments supplied within the package.
> 
> Since the user-defined objects upon which f depends have names unknown
> to the package, the StartPackage expression must be of the form
> 
>    StartPackage["thepackage`", "Global`"]
> 
> Hence (and this is what I'm asking about):  there is NO WAY to prevent
> name clashes between objects created within the package and objects
> created by the user -- other than the package's trying to use very
> cryptic and obscure names, of course.
> 
> If the user's f was self-contained, or depended only upon objects
> whose names were known in advance to the package designer, then of
> course there's no problem: avoid including "Global`" in StartPackage
> and instead refer to f within the package as Global`f.  But that's not
> the realistic situation here.
> 
> If I am correct, then this seems a fatal shortcoming of Mathematica's
> implementation of namespaces via contexts.
> 
> If I am incorrect, then I anxiously await a solution!
> 
> --
>   Murray Eisenberg                       Internet:  murray at math.umass.edu
>   Mathematics & Statistics Dept.            Voice:  413-545-2859 (W)
>   University of Massachusetts                       413-549-1020 (H)
>   Amherst, MA 01003                           Fax:  413-545-1801

=======================================================================

I'd afraid that I don't understand the question.  I gave it a good
effort, reading your message a couple of times and everything, and
I still wasn't able to figure it out.

Perhaps the following question will help to illustrate my lack of
understanding:  If the function f is self-contained, then why does
the package designer care about symbols that are used within the
definition of f?

The context system certainly isn't perfect, but I'm not aware of
anything that might qualify as a "fatal shortcoming", or of any
situations where I can't get what I want by using some variant of
package design or through manipulation of the context search path.
One discussion of this (including an alternate package design) can
be found in "Mathematica: A Practical Approach" by Nancy Blachman.  

Dave Withoff
Wolfram Research


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