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Re: functions, packages, and contexts

  • To: mathgroup at
  • Subject: [mg25035] Re: functions, packages, and contexts
  • From: "Allan Hayes" <hay at>
  • Date: Fri, 1 Sep 2000 21:57:41 -0400 (EDT)
  • References: <8one3u$>
  • Sender: owner-wri-mathgroup at

I'm not too clear about what is happening, but here are some suggestions.

Put your packages in the the directory that with Mathematica 4.0 on Windows is
        ...  Wolfram Research\Mathematica\4.0\AddOns\ExtraPackages\MyPackages

Then, if your function MW is in the package "Weight.m" you should give this
package the context "MyPackages`Weight`" via


This package will be loaded by


Then, to be able to use MW  inside the package "MyPackages`React`", you need
to begin the latter's code with

    BeginPackage["MyPackages`React`", "MyPackages`Weight`"]

Here we are telling Mathematica that "MyPackages`Weight`" is a "needed" package (any
number of needed packages may be included) This will cause it to add the
context  "MyPackages`Weight`" to the context search path (given by
$ContextPath) and also evaluate Needs["MyPackages`Weight`" ], this will load
the package if it has not already been loaded.

Allan Hayes
Mathematica Training and Consulting
Leicester UK
hay at
Voice: +44 (0)116 271 4198
Fax: +44 (0)870 164 0565

<Matt.Johnson at> wrote in message
news:8one3u$oh4 at
> Dear All -
> I am new to the package-writing frontier and am running into a problem I
> can't seem to overcome.  The first package I have defines a molecular
> weight (MW) function, which takes a molecule as an argument and returns
> molecular weght.  The molecule must be of the form C1O2, for carbon
> dioxide, for example (each element is followed by the number of atoms of
> that element). The problem I have is that now I am using that package
> within another package.  Because the context has been changed, the
> molecules are sent to the MW function as Global`MyPackages`React`C1O2
> React is the package I am working in.  The MW function has been written to
> pick out elements and numbers, but cannot handle the additional input of
> the context path.   Is there an easy fix for this, i.e. is there a way to
> send the MW function just the molecular notation within the package
> including the context?  Or do I have to define the MW function to pick off
> the C1O2 from the variable for it to work?
> Thanks-
> matt

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