# [GiNaC-list] Problem simplifying exponents in polynomials

Gerry Boland gerboland at gmail.com
Tue Jun 5 11:46:37 CEST 2007

Dear Chris,
you've given me exactly what I needed! Many thanks
-Gerry

On 01/06/07, Chris.Dams at mi.infn.it <Chris.Dams at mi.infn.it> wrote:
>
> Dear Gerry,
>
> > I've not managed to make the expand() & collect() functions do this, it
> > seems to not want to perform something like:
> >
> > e^t*e^(1-t)=e^1
>
> Yes, this is not included in the automatic simplifications, so you will
> have to do it yourself. In cases like this I usually use a function that I
> call simplify and that is defined as
>
> ex simplify(const ex&x,const exmap &m)
> {  if (is_a<mul>(x))
>    {  ex y=x;
>       ex xprev;
>       do
>       {  xprev = y;
>          y = y.subs(m, subs_options::subs_algebraic).expand();
>       } while(xprev != y);
>       return y;
>    }
>    {  exvector ev;
>       for(size_t i=0;i<x.nops();++i)
>          ev.push_back(simplify(x.op(i), m));
>
>    }
>    return x;
> }
>
> This can be used by doing
> exmap m;
> m[power(e,wild(0))*power(e,wild(1))] = power(e, wild(0)+wild(1));
> f = simplify(f, m)
>
> Good luck,
> Chris
>
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