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Re: Odd (to me) Context issue with Packages?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg115523] Re: Odd (to me) Context issue with Packages?
  • From: Jason Ledbetter <jasonbrent at gmail.com>
  • Date: Thu, 13 Jan 2011 03:28:44 -0500 (EST)

I received a reply off-line that provided a resolution.

In summary, it seems that ToExpression is apparently running outside of the
BeginPackage/EndPackage defined Context and as a result the variables I'm
trying to reference (from String) via ToExpression are getting set in the
Global` context.

A potential workaround was: ToExpression["PackageName`Private`"~~variable]
vs. just ToExpression@variable

In making the suggested change, I was able to get this code (and my first
version which is worlds apart from the mess below) to work as I'd expected.

I'm not sure if this is a bug in/around ToExpression or not...

-jbl

On Sun, Jan 9, 2011 at 2:20 AM, Jason Ledbetter <jasonbrent at gmail.com>wrote:

> Folk,
>
> I have two (small, ~20KB and ~17KB) notebooks at the following URIs that
> are
> working demonstrate my current Mathematica 8 frustrations.
>
> 1) http://forever.broked.net/~jason/demo_fail2.nb<http://forever.broked.net/%7Ejason/demo_fail2.nb>
>
> This notebook is the same code from the next example with a package and
> exported function wrapper around in. In this example, there are two input
> cells that need to be executed in order for the failure to appear.
>
> After "genInfo2[]" is executed in the second cell, a simple manipulate
> appears and both of the functions Covariance and Correlation fail because
> some of the variables are apparently in a different Context than I expect.
> e.g., they "cpu" variable that is shown in the output cell from the
> Manipulate appears to be in Global` instead of Huh`Private` as I'd expect.
>
> There *IS* a Huh`Private`cpu variable that gets created here, but
> apparently
> it isn't what is getting passed through the Manipulate and into the
> Covariance and Correlation functions.
>
> (Execute Remove["Huh`*"] to clean up what this adds to your M environment)
>
> 2) http://forever.broked.net/~jason/demo_fail.nb<http://forever.broked.net/%7Ejason/demo_fail.nb>
>
> This is the same code as in demo_fail2.nb, but without the package wrapper
> around it. THIS code works exactly as I'm expecting.
>
> I've been beating my head against #1 for too many hours now.
>
> Can someone shed some light into what is going on here and how to fix this
> apparent context failure?
>
> Note: If you execute demo_fail.nb before demo_fail2.nb, the failure will
> not
> occur. This appears to be because demo_fail2.nb's requirements are
> satisfied
> by variables in Global` context at that point.
>
> -jbl
>
>


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