Subject: "depends" problem of variables with subscripts
From: Evan
Date: Wed, 11 Jul 2007 01:10:15 +0800
On 7/10/07, Richard Fateman <fateman at cs.berkeley.edu> wrote:
> Ways in which subsup variables differ from the mathematical (possible):
>
> The index names are part of the object and not separable, at least after the
> object is created.
> For example, if you create subsup x n 3, and subsequently change the value
> of n, that has no effect on subsup x n 3.
> You cannot differentiate with respect to n.
> If your intention is to have a sub/super script denote an order of
> differentiation, or an iterative application of a function e.g. F^(3)(x)
> is F(F(F(x))), then the semantics will not be obvious.
What I care more now is that the difference between operating an array
element and scalar element, for example if I refer subsup x n 3 by
x[n,3], to assign a value to it, I have to using x[n,3]::10 instead of
x[n,3]:3. So I prefer something that a subscripted/superscripted
variable behaves the same as a usual variable without
subscript/superscript at all cases except displaying
>
> In answer to your particular question, x and x[1] generally can coexist
> separately.
> Though if there is no evidence that you have in mind any array named x,
> and x is set to a list like x:[a,b,c], then x[1] evaluates to a.
>
> Mathematical notation conventions generally frown on what you suggest. If
> you have a need for both x and x[1],
> perhaps you should be using X or bold_X or Xi ... as in
> X=[x[1],x[2],x[3]].
Thank you for the explanation
>
> If you use x[1], x[2] and x[3], and that is all, and you don't iterate as
> for i:1 thru 3 do ....x[i]..., then you are probably much better off using
> x1, x2, x3. As for the fact that you might like the appearance of
> subscripts, If that is the biggest problem you encounter using Maxima, that
> would be GREAT.
Maxima IS great, I'm trying to using it to replace pencils and papers
>
> There are lots of parts of the display that you have relatively little
> control over. For example, getting terms to be ordered exactly the right
> way, a+b or b+a, is something quite simple..
>
I think that's the major obstacle to abandon pencils and papers totally
>
>
> RJF
>
>
> > -----Original Message-----
> > From: maxima-bounces at math.utexas.edu
> > [mailto:maxima-bounces at math.utexas.edu] On Behalf Of Evan
> > Sent: Monday, July 09, 2007 7:03 PM
> > To: fateman at cs.berkeley.edu
> > Cc: maxima at math.utexas.edu
> > Subject: Re: [Maxima] "depends" problem of variables with subscripts
> >
> > I know nothing of programming in lisp, so all I can do now is
> > requesting, sorry
> >
> > the code works for displaying, but variables introduced in this way
> > will have some different behaviors as usual variables. maybe some more
> > hacks are needed. It's ok for me to wait for these features to be
> > included in a new release.
> >
> > another question, will it cause problems if I introduce x and x[1] at
> > the same time in derivations as independent variables, for x is
> > actually the array name of the element x[1]?
> >
> > On 7/10/07, Richard Fateman <fateman at cs.berkeley.edu> wrote:
> > > See http://www.cs.berkeley.edu/~fateman/temp/subsuper.lisp
> > >
> > > For a solution to this problem using nformat.
> > > It could be installed by you, or by one of the CVS owners.
> > >
> > > It makes atoms of the form subsup x 1 2 display with sub
> > and super
> > > scripts.
> > > It also shows how to make them.
> > >
> > > RJF
> > >
> > >
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> >
>
>