[isabelle-dev] NEWS: 'subgoal' command
daniel.matichuk at nicta.com.au
Fri Jul 3 04:02:28 CEST 2015
I like the dots notation, it resolves the issue of having to always think about the parameters in reverse order.
I've found a few small issues related to clashing/fresh names.
First, It looks like the suffix naming doesn't quite work if there are clashing existing goal params.
lemma "⋀x y. A x y"
subgoal for … x
Results in "x" being named "xa" instead of x. This works as expected in prefix naming, however.
Additionally, fresh names are chosen for any free variables that appear in the subgoal
lemma "⋀x y. A x y"
subgoal for A
Results in "x" being named "Aa". In this case I would expect either an error ("Free name clash") or for the new fixed term to shadow the free A.
The second choice is a bit strange, however, because you end up with two different coloured "A"s in the goal.
Finally, duplicate for-fixes should be disallowed. Currently this results in fresh names being chosen for the duplicates.
This was as of Isabelle/22830a64358f.
From: isabelle-dev [isabelle-dev-bounces at mailbroy.informatik.tu-muenchen.de] on behalf of Makarius [makarius at sketis.net]
Sent: Thursday, July 02, 2015 10:30 PM
To: isabelle-dev at in.tum.de
Subject: [isabelle-dev] NEWS: 'subgoal' command
* Command 'subgoal' allows to impose some structure on backward
refinements, to avoid proof scripts degenerating into long of 'apply'
sequences. Further explanations and examples are given in the isar-ref
This refers to Isabelle/441fdbfbb2d3, which also contains the
documentation and examples.
Practical experience will show what are the full consequences. E.g. how
close do we get to a situation without the need for rule_tac, case_tac
etc. with their implicit access to hidden goal paramaters.
It should also solve certain indentation problems in long apply scripts.
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