GiNaC

• Clean, clear to understand code
  
• responsive developers
• fast!

http://www.ginac.de

• class hierarchy
• internal representation
• symbolic functions

What changed

• CLN -> python
• printing order
• creating functions at runtime
• archiving -> pickling
• infinity, exp

To get started:

http://wiki.sagemath.org/pynac/start

What next?

• easy access to structure & traversal
  • operands - __getitem__
  • pre - post order traversal?
  • visitors
• indexed objects
• to_polynomial, to_rational
• arithmetic for symbolic functions (sage.symbolic.function.Function)
• printing
• matrices
• gcd

Symbolic functions (sage.symbolic.function)

• Function (SageObject)
  
  • BuiltinFunction
    • GinacFunction
  • SymbolicFunction

Function - support setting custom fuctionality (eval, evalf, derivative, conjugate, etc.) and registering with the database

BuiltinFunction -

• pickling is easy, just store function name and arguments, since guaranteed to be in the library
• arguments converted back to original type automatically

GinacFunction - not added to the registry

SymbolicFunction

• can set arbitrary attributes (has a __dict__)
• knows how to pickle custom functionality (these have to be python functions)