[GiNaC-devel] Add method ex::symbols for obtaining all symbols appearing in an expression

Hi, You may know the CAS Sage [1] which uses GiNaC. It wraps ginac expressions in Python, and it adds some extra methods of its own. One of those methods is variables(), which returns a list of symbols appearing in the expression. It does so by recursively walking down the expression tree. At one point, that was a bottle neck in my algorithm, and I realized that it would be very easy to cache those variables at construction time from the subexpressions. I think the natural place to implement such a thing would be in GiNaC itself, so that everyone (not only sage users) may benefit. Is this planned and/or would you accept such a patch? Best regards, Timo Kluck [1] www.sagemath.org