C++ symbolic expression tools?

[Eric Tiedemann]

Greetings lispers!

I'm looking for C++ tools for i/o and representation of symbolic
expressions.  Since this topic has been discussed in the past on this list,
I thought I'd ask here.

Salient points:

a) Either Scheme or Common Lisp sexprs would be useful.

b) I can't just use a generic Lisp-in-C library since I'm using this for
realtime purposes and can't afford an intrusive garbage collection pause.

c) GPLed code would be useful, but a somewhat more liberal license would be
preferred.

d) The ideal library would integrate seamlessly with C++ generic arithmetic.

e) I'm already using a (GLPLed) version that I cobbled together, so if
nothing turns up, I can share/develop it with others. :)

Best Regards,

E