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Classes fail in baffling manner

  • To: mathgroup at
  • Subject: [mg20355] Classes fail in baffling manner
  • From: Joe Strout <joe at>
  • Date: Sat, 16 Oct 1999 00:47:43 -0400
  • Organization: The Salk Institute
  • Sender: owner-wri-mathgroup at

I am completely stumped.  This is the most bizzare result I've gotten
trying to learn a new language in a long time -- it's almost making me
start to like Lisp!

I'm trying to define a class.  It kept working once, then failing the
next time in odd ways, so I started with the Accounts.nb, and very
gradually began to simply rename things in order to make it look more
like my example.  I got this far:

Classes`Class[ Stimulus, Object,
       {mXStart, mYStart},
        {new,      (new[super]; mXStart = #1; mYStart = #2)&},
        {balance,  mXStart&},
        {deposit,  Function[mXStart += #1]},
        {withdraw, Function[mXStart -= #1]},
        {mYStarter,    mYStart&}

Where I've renamed "bal" to "mXStart" (that worked), and then replaced
"Account" with "Stimulus" -- which doesn't work.  It accepts the
definition, but as soon as I try to create an object, I get:

a1 = new[Stimulus, 100, "Roman E. Maeder"]
   Take::"take": "Cannot take positions -6 through -1 in Hold[
      mXStart$67, mYStart$67."

I haven't been able to guess what this might mean.  But it clearly
didn't work, because when I try to call a method, I get results like:

(input) balance[a1]
(output) mXStart$64

If I replace "Stimulus" with "Account" again, it all works again.  I've
tried doing Remove["Stimulus"] and Remove["Classes`Stimulus"] to ensure
that this isn't messing things up, but this same weird behavior occurs
every time.

Somebody please give me a clue!  I am about ready to chuck Mathematica
out the window.

-- Joe

|    Joseph J. Strout           Biocomputing -- The Salk Institute |
|    joe at                 |
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