[isabelle-dev] NEWS

Florian Haftmann florian.haftmann at informatik.tu-muenchen.de
Wed Jan 4 21:18:52 CET 2012

>> 'set' is now a proper type constructor.  Definitions mem_def and
>> Collect_def have disappeared.  INCOMPATIBILITY, rephrase sets S used as
>> predicates by `%x. x : S` and predicates P used as sets by `{x. P x}`.
>> For typical proofs, it is often sufficent to prune any tinkering with
>> former theorems mem_def and Collect_def.
> The NEWS entry looks a bit too optimistic.  The majority of users after
> Isabelle2008 will have to change their theories, and need some more
> explicit instructions how to do it sucessfully (e.g. port forwards by
> eliminating mem_def/Collect_def before making the actual jump into the
> new version).

Good question how such explicit instructions could look like.
Eliminating mem_def/Collect_def in a first pass is usually not feasible,
because the set/pred-ignorant versions of Isabelle tended to move back
and forth between both worlds by their automation setup.  The migration
strategy had always been to adjust terms to respect the set/pred
distinction, and then adjust the proofs accordingly.  No trick behind it.




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