automatic differentiation and change expression ordering

5 Nov 2003

      Hello,

I have two questions:

1. is it possible to prevent automatic differentiation of some 
expression? For example, when I do (with ginac 1.1.4):

DECLARE_FUNCTION_1P( intensity )
static ex intensity_eval( const ex & r ) { return intensity(r).hold(); }
// here i tried to hold it :-)
REGISTER_FUNCTION( intensity, eval_func(intensity_eval) )
int main()
{
   symbol r("r");
   ex der1  = mul( diff( intensity(r), r ), r ).hold();
   ex deriv = der1.diff(r);
   cout << deriv << endl;
   return 0;
}

I get the following output:
D[0,0](intensity)(r)*r+D[0](intensity)(r)

But I would like to get something like this:

D[0]( D[0](intensity)(r)*r )(r)

Is it possible with ginac?

2. What is the simplest way to change the order in multiplication so 
that the differential operators print after all other terms:
r*D[0,0](intensity)(r)
instead of
D[0,0](intensity)(r)*r

And the third one ;-)
Is there maybe some work done to output fderivative in latex style?

Thanks in advance

Andrius

automatic differentiation and change expression ordering

Andrius Kurtinaitis