[GiNaC-devel] New in GiNaC: step function

[Chris Dams]

Dear Vladimir,

On Fri, 2006-03-10 at 10:33 +0000, Vladimir Kisil wrote:

> CD> maybe the best thing to do would be to have step(0)=1/2 and not to do a
> CD> simplification step(x)^2 -> step(x). 
> CD> Can everybody live with that?
> 
> Since it is consistent no reasons to object.  

OK.

> CD> After all, if desired, such a
> CD> simplification could also be done by the user. (S)he could do
> CD> .subs(step(wild())*step(wild())==step(wild()), subs_options::algebraic).
> 
> In heavy calculations it is important that some simplifications are made
> automatically on intermediate cases. To this end we may have (in the
> core GiNaC or user-defined) another function (say "jump") which have the
> property jump^2(t) -> jump(t).

I would prefer not to have such a function in GiNaC itself. The
difference between "jump" and "step" would be too small to justify
introducing another object IMO. I did not follow the discussion on the
new function system that Jens seems to be building, but what would be
ideal is if the user could implement "jump" by deriving from "step" and
simply add the automatic simplification jump^2 -> jump. I would think
that the number of users that needs this simplification to be done in
the midst of a calculation is not so large as to justify adding the
function "jump" to the library.

Best,
Chris