fixed bug in the "fast_descrs" optimization;
the bug is that two sets may actually be the same but because of the three-valued logic a different "The" or "Eps" is chosen; e.g. consider the set {1, 2}. If it is approximated in one place as {1, 2?} and in another place as {1?, 2}, then "Eps" would return 1 in the first case and 2 in the second case. This is of course wrong, because both sets potentially represent {1, 2}.
The current fix has a very negative impact on precision.
Subject: Announcing Isabelle2009-2
To: isabelle-users@cl.cam.ac.uk
Isabelle2009-2 is now available.
This release improves upon Isabelle2009-1 in many respects, see the
NEWS file in the distribution for more details. Some notable changes
are:
* Explicit proof terms for type class reasoning.
* Robust treatment of concrete syntax for different logical entities;
mixfix syntax in local proof context.
* Type declarations and notation within local theory context.
* HOL: package for quotient types.
* HOL code generation: simple concept for abstract datatypes obeying
invariants (e.g. red-black trees).
* HOL: new development of the Reals using Cauchy Sequences.
* HOL: reorganization of abstract algebra type class hierarchy.
* HOL: substantial reorganization of main library and related tools.
* HOLCF: reorganization of 'domain' package.
You may get Isabelle2009-2 from the following mirror sites:
Cambridge (UK) http://www.cl.cam.ac.uk/research/hvg/Isabelle/
Munich (Germany) http://isabelle.in.tum.de/
Sydney (Australia) http://mirror.cse.unsw.edu.au/pub/isabelle/