gamma~0 in p.mu*gamma~mu should be p.0 but is returned as 0
- using coeff(), tcoeff(), lcoeff() or collect() on elements of
noncommutative products might return wrong or surprising results
-* Likewise, subs() can be used to substitute functions, tensors and indexed
- expressions.
+* subs() no longer only substitutes symbols and indices but performs a more
+ general "syntactic substitution", i.e. it substitutes whole objects in sub-
+ expressions. You can subs((a+b)^2,a+b==3) and get 9, but subs(a+b+c,a+b==3)
+ doesn't do anything.
+ Limitations:
+ - substituting numerics (subs(expr, 2==4)) will not replace then in all
+ occurences; in general, you shouldn't substitute numerics, though
* Added preliminary (re)implementations of color and clifford classes.
* simplify_indexed(): contraction of symmetric and antisymmetric tensors
is zero.