1.2.0 (<insert date>)
* Added a structure<T> template class for the easy creation of user-defined
algebraic classes.
-* <visitors>
+* Added support for (acyclic) visitors, to allow cleaner implementations of
+ algebraic algorithms.
* <iterators>
-* <new-style printing>
-* <noncommutative symbols>
+* Completely revamped the implementation of expression output. It is now
+ possible to add new output formats, to change the behavior of predefined
+ formats at run-time, and to have different output styles for algebraic
+ functions.
+* Symbols can be made non-commutative.
* Improved the speed of subs(), normal(), to_rational() and to_polynomial()
by the use of maps instead of lists. The old forms
subs(const lst & ls, const lst & lr, unsigned options)