documentation update

[ginac.git] / NEWS

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 This file records noteworthy changes.
 
+0.8.2 (<date>)
+* degree(), ldegree(), coeff(), lcoeff(), tcoeff() and collect() work with
+  non-symbols as the second argument in ginsh.
+* the argument to collect() can be a list of objects in which case the
+  result is either a recursively collected polynomial, or a polynomial in
+  a distributed form with terms like coeff*x1^e1*...*xn^en, as specified by
+  the second argument to collect().
+
+0.8.1 (16 April 2001)
+* degree(), ldegree(), coeff(), lcoeff(), tcoeff() and collect() can now
+  be used with constants, functions and indexed expressions as well, so you
+  can use it to collect by powers of Pi or sin(x), or to find the coefficient
+  of gamma~0.
+  Limitations:
+   - it only works with symbols, constants, functions and indexed expressions,
+     trying to find the coefficient of, e.g., "x^2" or "x+y" won't work;
+   - it does not know about dummy index summations; the coefficient of
+     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.
+* 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.
+* Replaced the various print*() member functions by a single print() that
+  takes a print_context object that determines the output formatting. This
+  should make it easier to add more output types, such as LaTeX output,
+  which is based on work by Stefan Weinzierl.
+* Added functions to retrieve the properties stored in archive objects
+  outside of unarchive() (for printing or debugging purposes).
+* Some bugfixes (indexed objects, archive writing).
+* .collect() on non-polynomials is now algebraically correct.
+
 0.8.0 (24 March 2001)
 * Complete revamp of indexed objects. Instead of multiple classes for
   indexed things and their indices there is now only one "indexed" class