[GiNaC-devel] About a (poor) parity in expressions.

[Sergei Steshenko]

--- On Sun, 10/17/10, Vladimir V. Kisil <kisilv at maths.leeds.ac.uk> wrote:

> From: Vladimir V. Kisil <kisilv at maths.leeds.ac.uk>
> Subject: Re: [GiNaC-devel] About a (poor) parity in expressions.
> To: "GiNaC development list" <ginac-devel at ginac.de>, "Sergei Steshenko" <sergstesh at yahoo.com>
> Date: Sunday, October 17, 2010, 2:59 PM
>        
> Dear Sergei,
> 
> >>>>> On Sun, 17 Oct 2010 13:40:19 -0700
> (PDT), Sergei Steshenko <sergstesh at yahoo.com>
> said:
>     SS> To me it looks like two missing
> rewriting rules.
> 
>     Yes, it is so. But if they added to
> GiNaC core this can break
>   something in a different place, see the example with
> my own suggestion
>   to "add a rewriting rule":
> 
> http://www.ginac.de/pipermail/ginac-devel/2009-October/001678.html
> 
>   A hundred of rewriting rules in the core GiNaC will
> make it slow and
>   can cause other problems. A couple of rewriting
> rules added in the user's
>   code to address a specific issue at the right place
> are much more
>   manageable. This what I am doing in my own
> programmes right now.
> 
>   Best wishes,
>   Vladimir  
> -- 
> Vladimir V. Kisil     email: kisilv at maths.leeds.ac.uk
> --               
>       www: http://www.maths.leeds.ac.uk/~kisilv/
> 


So what ? I.e. exp(x) * exp(-x) == exp(x - x) == exp(0) == 1.

So, yet another rewriting rule is missing ?

Thanks,
  Sergei.