Re: [Maxima-discuss] bug in ic1

[Gunter K. <gu...@pe...>]

If it is different constants I would prefer it to have a different name. %k67 is therefore fine to me even though I know that this means my code has to be prepared that a change at the beginning of the file might make it a %k68.

Am 27. Februar 2021 17:41:32 MEZ schrieb Robert Dodier <rob...@gm...>:
>On Sun, Feb 21, 2021 at 11:34 AM Dimiter Prodanov <dim...@gm...> wrote:
>
>> ic1(z(x)=%c1-'integrate((z(u607)^2*(x-u607))/u607,u607,x,M),x=M,z(x)=0);
>> crashes
>
>> however
>> ic1(z(x)=%c-'integrate((z(u607)^2*(x-u607))/u607,u607,x,M),x=M,z(x)=0);
>>
>> returns
>> z(x)=z(M)-integrate((z(u607)^2*x-u607*z(u607)^2)/u607,u607,x,M)
>>
>> So in my view, the symbol %c should not be hardcoded in ic1.
>
>Hi Dimiter, by the way, from where did %c1 appear?
>
>I've looked at this problem for a bit, and what I'm seeing is that the
>ode2 code assumes throughout that constants are only named %c, %k1, or
>%k2. It wouldn't be too hard to change that to numbered constants;
>there is already a mechanism (integration_constant and
>integration_constant_counter) to generate numbered constants in the
>integration code.
>
>There are at least two problems introduced by that. The smaller one is
>that the presence of numbered constants would probably make it harder
>to check results automatically. OK, that can be fixed up without much
>trouble.
>
>The larger one is that the results might seem messy to users. After a
>while you'll get stuff like %k67*sin(x) + %k68*cos(x) and if you want
>"nice" constants you'll have to reset integration_constant_counter.
>That sounds painful.
>
>In some sense creating new constants is the right thing to do. Is it
>sufficiently right to overcome the clumsiness of it? What does anyone
>think about any of this stuff?
>
>best,
>
>Robert Dodier
>
>
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