Help with recursive assignment

[Gerard]

Maple 9.3:

When I try
> x := x[0] + t^2;
I get "Error, recusive assignment", but when I try
> x := t -> x[0] + t^2;
x(t);
x(0);
I get the outputs
x := t -> x_0 + t^2
x_0 + t^2
x_0

So the latter method doesn't mind the possible recursion.
But it also does not give me what I want. Is there some way
to force maple to create a variable x that has x[0] in its value?

I could of course use x0 in stead of x[0] but that is not what
we want.

I already tried subs, but that did not work either:
> x := k + t^2;
subs( k=x[0], x );
produces
x := k + t^2
(k+t^2)_0 + t^2

HELP!

TIA and regards,
G.

[A N Niel]

In article <ek4v51$igt$1...@aioe.server.aioe.org>, Gerard
<no....@no.where> wrote:

> > x := x[0] + t^2;

So this would mean
x[0] + t^2 = (x[0] + t^2)[0] + t^2
= ((x[0] + t^2)[0] + t^2)[0] + t^2
and so on.

If that is really what you want, then Maple cannot do this.

If it is NOT what you want, you need to explain...

[Robert Israel]

In article <ek4v51$igt$1...@aioe.server.aioe.org>,
Gerard <no....@no.where> wrote:

>Maple 9.3:
>
>When I try
> > x := x[0] + t^2;
>I get "Error, recusive assignment", but when I try
> > x := t -> x[0] + t^2;
> x(t);
> x(0);
>I get the outputs
> x := t -> x_0 + t^2
> x_0 + t^2
> x_0
>
>So the latter method doesn't mind the possible recursion.
>But it also does not give me what I want. Is there some way
>to force maple to create a variable x that has x[0] in its value?

Actually, I suspect you want a variable x that has something that
_looks_ like x_0 as its value. Try

> x:= `tools/rename`(x)[0];

Robert Israel isr...@math.ubc.ca
Department of Mathematics http://www.math.ubc.ca/~israel
University of British Columbia Vancouver, BC, Canada

[Gerard]

"Robert Israel" <isr...@math.ubc.ca> wrote in message news:ek5hka$3t6$1...@nntp.itservices.ubc.ca...

> In article <ek4v51$igt$1...@aioe.server.aioe.org>,
> Gerard <no....@no.where> wrote:
>>Maple 9.3:
>>
>>When I try
>> > x := x[0] + t^2;
>>I get "Error, recusive assignment", but when I try
>> > x := t -> x[0] + t^2;
>> x(t);
>> x(0);
>>I get the outputs
>> x := t -> x_0 + t^2
>> x_0 + t^2
>> x_0
>>
>>So the latter method doesn't mind the possible recursion.
>>But it also does not give me what I want. Is there some way
>>to force maple to create a variable x that has x[0] in its value?
>
> Actually, I suspect you want a variable x that has something that
> _looks_ like x_0 as its value. Try
>
> > x:= `tools/rename`(x)[0];

You probably mean
> x0 := `tools/rename`(x)[0];
which gives the correct output.
Also the definition
> x := x0 + t^2
gives
x := x_0 + t^2 (with subscript)
which looks okay.

But it is not really okay. There seems to be no way to give x[0] a
value now.
When I try
> x[0] := 3; t := 6; x;
I get the output
x_0 := 3 (with subscript, of course)
t := 6
x (the x I just defined is dead)

So I can't use this.

It looks like Maple does not treat an indexed name like x[0] on an
equal footing as the names x and x0. It is clear that x and x0 are
fully independent variables, but x[0] is something that cannot really
be used as a variable - unless you take care never to use x as
a variable in the same context.
Indeed, I just tried this:
> restart;
> x := t^2;
x := t^2
> x;
t^2
> x[1] := 12;
x_1 := 12
> x;
x (dead)

We have to create an HTML formatted article with proper subscript
notation, like x_0 ("x subscript 0") as opposed to the ugly x0.
This is just one example. The article has many functions (f) and
subscripted variables (f_i).
It seems we won't be able to use Maple for this.
Or does someone know a secret workaround?

Thanks,
G.

[Gerard]

"A N Niel" <ann...@nym.alias.net.invalid> wrote in message news:231120061824215313%ann...@nym.alias.net.invalid...

It is not what I want.
I explained in my answer to Robert Israel.
Thanks and regards,
G.

[Walter Roberson]

In article <ek79io$lsg$1...@aioe.server.aioe.org>,

Gerard <no....@no.where> wrote:
>You probably mean
> > x0 := `tools/rename`(x)[0];
>which gives the correct output.
>Also the definition
> > x := x0 + t^2
>gives
> x := x_0 + t^2 (with subscript)
>which looks okay.

>But it is not really okay. There seems to be no way to give x[0] a
>value now.
>When I try
> > x[0] := 3; t := 6; x;
>I get the output
> x_0 := 3 (with subscript, of course)
> t := 6
> x (the x I just defined is dead)

>So I can't use this.

x0 := `tools/rename`('x')[0];
x := x0 + 't'^2;
assign(eval(x0,1),3);
t := 6;
x;
assign(eval(x0,1),7);
t := 11;
x;
eval(x,1);
--
Okay, buzzwords only. Two syllables, tops. -- Laurie Anderson

[Walter Roberson]

In article <ek7bgv$7jr$1...@canopus.cc.umanitoba.ca>,

Walter Roberson <robe...@ibd.nrc-cnrc.gc.ca> wrote:
>In article <ek79io$lsg$1...@aioe.server.aioe.org>,
>Gerard <no....@no.where> wrote:

>> x := x_0 + t^2 (with subscript)

>x0 := `tools/rename`('x')[0];

>x := x0 + 't'^2;
>assign(eval(x0,1),3);
>t := 6;
>x;
>assign(eval(x0,1),7);
>t := 11;
>x;
>eval(x,1);

More simply,

x := `x[0]` + t^2;
`x[0]` := 3;
t := 6;
x;
`x[0]` := 7;

t := 11;
x;
eval(x,1);

--
"It is important to remember that when it comes to law, computers
never make copies, only human beings make copies. Computers are given
commands, not permission. Only people can be given permission."
-- Brad Templeton

[Gerard]

"Walter Roberson" <robe...@ibd.nrc-cnrc.gc.ca> wrote in message news:ek7bgv$7jr$1...@canopus.cc.umanitoba.ca...

SUPER! That makes two syllables, right?

I have tested this out on the entire project and it does exactly
what we want it to do!

Thanks a big bunch and kind regards,
G.

[isr...@math.ubc.ca]

You could do that if you saved the "new" x under a different name.

> newx:= `tools/rename`(x);
x:= newx[0] + t^2;
assign(newx[0], 6);
x;

> It looks like Maple does not treat an indexed name like x[0] on an
> equal footing as the names x and x0. It is clear that x and x0 are
> fully independent variables, but x[0] is something that cannot really
> be used as a variable - unless you take care never to use x as
> a variable in the same context.
> Indeed, I just tried this:
> > restart;
> > x := t^2;
> x := t^2
> > x;
> t^2
> > x[1] := 12;
> x_1 := 12
> > x;
> x (dead)

When you assign a value to x[1], you implicitly make x into a table
whose entry for
index 1 is that value. If it's a table, it can't have the value t^2.
That's why you need
a different name.

[Gerard]

"Walter Roberson" <robe...@ibd.nrc-cnrc.gc.ca> wrote in message news:ek7br8$829$1...@canopus.cc.umanitoba.ca...

> In article <ek7bgv$7jr$1...@canopus.cc.umanitoba.ca>,
> Walter Roberson <robe...@ibd.nrc-cnrc.gc.ca> wrote:
>>In article <ek79io$lsg$1...@aioe.server.aioe.org>,
>>Gerard <no....@no.where> wrote:
>
>>> x := x_0 + t^2 (with subscript)
>
>>x0 := `tools/rename`('x')[0];
>>x := x0 + 't'^2;
>>assign(eval(x0,1),3);
>>t := 6;
>>x;
>>assign(eval(x0,1),7);
>>t := 11;
>>x;
>>eval(x,1);
>
> More simply,
>
> x := `x[0]` + t^2;
> `x[0]` := 3;
> t := 6;
> x;
> `x[0]` := 7;
> t := 11;
> x;
> eval(x,1);

Yes, but this way there are no subscripts in the output, and
subscripted indices is what we absolutely need.

Thanks again,
G.

[Gerard]

<isr...@math.ubc.ca> wrote in message news:1164395242.0...@l12g2000cwl.googlegroups.com...

Yes, this is similar to Walter Roberson's workaround.

>> It looks like Maple does not treat an indexed name like x[0] on an
>> equal footing as the names x and x0. It is clear that x and x0 are
>> fully independent variables, but x[0] is something that cannot really
>> be used as a variable - unless you take care never to use x as
>> a variable in the same context.
>> Indeed, I just tried this:
>> > restart;
>> > x := t^2;
>> x := t^2
>> > x;
>> t^2
>> > x[1] := 12;
>> x_1 := 12
>> > x;
>> x (dead)
>
> When you assign a value to x[1], you implicitly make x into a table
> whose entry for
> index 1 is that value. If it's a table, it can't have the value t^2.
> That's why you need
> a different name.

I understand now.
I think we can work things out now.

Thanks (a lot!) again and regards,
G.