[isabelle-dev] (Re-)introducing set as a type constructor rather than as mere abbreviation

Thomas Sewell Thomas.Sewell at nicta.com.au
Fri Aug 12 02:15:15 CEST 2011

I'm strongly in favour of an explicit set type.

I've been asked for advice by a number of novice Isabelle users and given the same recommendation: go make the development type-check under the old rules. Then the simplifier will start helping you rather than fighting you.

I suppose there might be an alternative strategy involving adapting the simpset or similar to try to standardise blended terms on set operations or function operations. But I don't think this is possible the way Isabelle works - if it were not the default noone then it would not help, and if it were then it would generate years of work in compatibility with the existing proof library.

From: isabelle-dev-bounces at mailbroy.informatik.tu-muenchen.de [isabelle-dev-bounces at mailbroy.informatik.tu-muenchen.de] On Behalf Of Lawrence Paulson [lp15 at cam.ac.uk]
Sent: Thursday, August 11, 2011 11:09 PM
To: Florian Haftmann
Cc: DEV Isabelle Mailinglist
Subject: Re: [isabelle-dev] (Re-)introducing set as a type constructor  rather than as mere abbreviation

I hope that my position on this question is obvious. And if we decide to revert to the former setup, I would be happy to help track down and fix some problems in theories.

On 11 Aug 2011, at 13:43, Florian Haftmann wrote:

> Why (I think) the current state concerning sets is a bad idea:
> * There are two worlds (sets and predicates) which are logically the
> same but syntactically different.  Although the logic construction
> suggests that you can switch easily between both, in practice you can't

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