[GiNaC-list] Covariant derivative(its long..)

[Sheplyakov Alexei]

On Sun, Apr 03, 2005 at 11:47:47PM -0300, mdias at ift.unesp.br wrote:
> 
> I tried this very confuse code, and I am happy if somebody could help-me. I
> tried to make covariant derivative derivated from a indexed. Use it like:
> D(indexed(A,mu),nu)
>  But the fatal errors in this code (among millions..):
> i) simplify_indexed() crashs or doesnt work !!
> II) get_free_indexes not work, so D^\alpha(A_beta)A^\beta A_\alpha
> -D^\beta(A_alpha)A^\beta A_\alpha is not zero
>  In the last post , Christian Bauer suggests "override is eval_indexed() (for
> automatic evaluation) and
> contract_with()/add_indexed()/scalar_mul_indexed() (for manual evaluation,
> AKA simplify_indexed())" and showed the way: look color.cpp source.
> 

[snip]

>   protected:
> 	void do_print(const print_context & c, unsigned level) const;
>         ex symtree, arg,index; 
>   lst seq;

You have re-defined `seq' member. Class indexed already has one (of
type std::vector<GiNaC::ex> type). This looks like asking for trouble,
unless you *exaclty* know what are you doing.

[Huge snip] 

You haven't implemented codiff::eval_indexed(), codiff::add_indexed(),
etc. So simplify_indexed() can't do something useful with your class. 

> ex covdiff::subs(const exmap & m, unsigned options) const

Do you really need to re-implement subs?

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