Re: [Maxima-discuss] Construct sequence of identifiers

[Richard F. <fa...@gm...>]

Hi Wolfgang:

 think this FDM program is somewhat counter to the way programs are
usually written in a "functional" style .  FDM
appears to do nothing but
set up global values for h, x(k), y, yn, yp(k) and ypp(k), Y [distinct from
y] and Eqs.

 The text then shows how to use the program BVP, on this data, which
appears to work only for the case n=8, which is hard-coded into FDM.

It seems plausible to recode using subscripted names as   a[1], a[2], ....,
rather than
a1,a2, ... as Robert suggests.   (using concat would not be so terrible,
either. e.g.  a[i]:=concat(a,i)  would do it)

It would be traditional to encode a DE using  'diff(y,t),  'diff(y,t,2) .
Presumably one would introduce the discretization yp, and ypp as part of
the solution procedure.

Maybe this works as given on exactly this example, but I think that
if it were to be included in some library it deserves a little work to be
generalized. Perhaps by you?












On Thu, Jul 20, 2023 at 9:50 AM Dr. Wolfgang Lindner <
dr....@gm...> wrote:

> Dear David, dear Robert,
>
> Thank you all for your advice.
> The problem is attached, it shows up only in Maxima_online - I suspect an
> old version of Maxima running behind the scene.
>
> HTH Wolfgang
>
>
>
> Am 20.07.2023 um 18:34 schrieb Robert Dodier <rob...@gm...>:
>
> On Thu, Jul 20, 2023 at 4:21 AM Dr. Wolfgang Lindner
> <dr....@gm...> wrote:
>
> Is it possible to construct y =[y0, y1, y2, y3, y4]  i.e.
>
>       y  :  makelist (concat (y,i), i,0, 4);
>
> without reference/using to  concat ?
>
>
> Maybe you can say more about what you need to accomplish. Without
> knowing more, my advice is to avoid constructed symbols, and work with
> subscripted symbols (y[0], etc) instead.
>
> best,
>
> Robert
>
>
>
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