differential operators

[Christian Bauer]

Hi!

On Fri, Oct 24, 2003 at 12:59:48PM +0200, Kai Ludwig wrote:
> > I'm new to GiNac. Is there a way to execute symbolic differentiation of
> > expressions that includes differential operators ?
> >
> > e.g. suppose an expression
> >
> > ex F = u * dx*u
> >
> > When differentiate that expression F.diff(u)
> > it should result in the expression
> 
> dx*u + u*dx

I'm still not sure what exactly the rules are that are in effect here, but
it seems that "dx" and "u" are noncommutative?

diff() requires a symbol as an argument, so the "u" has to be a symbol.
GiNaC 1.2 (CVS) has the ability to define noncommutative symbols. This might
be a good case for actually testing that feature. :)

The "dx" would probably have to be of a newly defined noncommutative class
with the same return_type_tinfo as the "u", and an overloaded derivative()
member that defines your derivation rules.

Bye,
Christian

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