[GiNaC-list] A bad idea: GiNaC as the symbolic manipulation engine in Sage

[Jens Vollinga]

Hi,

Alexei Sheplyakov schrieb:
> GiNaC is a special purpose symbolic manipulation library. The purpose of
> GiNaC is to do "simple" manipulations with "large" expressions using a common
> programming language (as opposed to ill designed, unstable ones as offered

well, I don't quite agree but maybe I am misinterpreting the quotation 
marks ;-). If you want to handle large expression, then use FORM. And 
what a simple manipulation is depends on whom you ask. Maybe for a 
mathematician symbolic integration for example is a very simple 
manipulation ...

GiNaC's raison d'etre is to help doing physics calculations. And it 
might be that even some not so simple symbolic manipulation are needed 
for that end.

> by most of CASes). So, I don't think GiNaC is a good choice for Sage
> (which attempts to be a general purpose _interactive_ CAS).

They would use ginac via a python wrapper, so I don't see any problems here.

> The order of expressions (in particular, symbols) is not stable. This is
> a price for a fast comparison of expressions. 

Additional nitpicking: that is not quite true. There is a difference 
between a stable order and a human-friendly order. I mentioned the 
reasons for non-stability in my last email. It has nothing to do with 
speed. Speed of comparison has only an effect on the human-friendliness. 
In a GUI system with mostly short expressions an additional reordering 
for the output is feasible and could be done outside ginac by the python 
code.

Regards,
Jens