On Wed, Jun 26, 2024 at 08:20:03PM +0800, Qian Yun wrote:
> I found this regression when I was reviewing the reference book.
>
> In chapter 1.16, or 1 page before chapter 2, there's:
>
> f(0) == 1; g(0) == 1
> f(n) == e/2*f(n-1) - x*g(n-1)
> g(n) == -x*f(n-1) + d/3*g(n-1)
> f(3)
>
> Internal Error
> The function * with signature (%, Integer) -> % is missing from
> domain Polynomial(Fraction (Integer))
>
>
>
> If we write "f(n) == f(n-1)*e/2 - x*g(n-1)",
> "g(n) == -x*f(n-1) + g(n-1)*d/3", then there's no problem.
>
> Git bisect (with the help of fricas0-repo) points to commit
> 991f8347 in 2022-Jun-26.
>
> Is this a bug or shall we update this example?
This is a big meta-bug, namely there are functions which are declared
but which are implemented nowhere. In particular, when R is
LinearlyExplicitOver(Integer), then FullyLinearlyExplicitOver(R)
implies RightModule(Integer) and we should implement corresponding
multiplication.
Good fix should implement multiplication in appriopriate place
(or some small number of critical places) so that it is inherited
in other places. However, this has potential for breaking other
things, so I really prefer to delay this after release.
--
Waldek Hebisch
--
You received this message because you are subscribed to the Google Groups
"FriCAS - computer algebra system" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To view this discussion on the web visit
https://groups.google.com/d/msgid/fricas-devel/ZnwePKtwx93s_Blw%40fricas.org.
