differential operators

[Kai Ludwig]

Christian Bauer wrote:
> Hi!
> 
> On Tue, Nov 18, 2003 at 06:20:30PM +0100, Kai Ludwig wrote:
> 
>>dF/du = du/du * du/dx + u * d/du du/dx
>>
>>thus, formally
>>
>>dF/du = du/dx + u * d/dx
> 
> 
> Here's something hacked together that achieves the desired effect for
> GiNaC 1.2 (treating the dx like a function):
> 
> const unsigned TINFO_differential = 0x42420001U;
>                                                                                 
> DECLARE_FUNCTION_1P(dx)
> 
> // this is ad-hockery...
> static ex dx_deriv(const ex & a, unsigned diff_param) { return dx(1); }
> 
> REGISTER_FUNCTION(dx,
>   derivative_func(dx_deriv).
>   set_return_type(return_types::noncommutative, TINFO_differential))
> 
> int main()
> {
>     symbol u("u", return_types::noncommutative, TINFO_differential);
>     ex F = u * dx(u);
> 
>     cout << F << endl;
>      // "u*dx(u)"
>     cout << F.diff(u) << endl;
>      // "u*dx(1)+dx(u)"
> }
> 
> But I don't know if that's general enough for what you have in mind.
> 
> Bye,
> Christian
> 
Danke ;-)

I plan to use GiNaC in a few months within our project...
Maybe then I can send you results/questions_hope_not

Kai