[isabelle-dev] Safe approach to hypothesis substitution

[Thomas Sewell]

I'm pretty sure this one is a bug. Try typing this into your favourite 
Isabelle session:

lemma foo:
   "fwrap f = (%v. f v) ==> P f"
   apply clarify

And note the system hangs. I think this is a pretty good argument to 
support the case that it doesn't occur in any existing Isabelle scripts.

Just to be safe, though, I can test this change in isolation against all 
the HOL libraries and the AFP thisevening when my machine has spare CPU 
time. I guess I should test against Isabelle 2009-2 rather than a 
development snapshot since the AFP will be known to build?

Yours,
     Thomas.

On 26/08/10 02:49, Makarius wrote:
> On Wed, 25 Aug 2010, Thomas Sewell wrote:
>
>    
>> Finally, the change to inspect_pair is indeed just a bugfix. I don't
>> this check is needed for the simplifier driven version of hyp_subst
>> anyway, so the bug shouldn't often be seen.
>>      
> Often it is hard to tell what is a bug or an obscure feature required like
> that by some other tool.
>
> Anyway, I recommend to try that tiny bit of the change on all existing
> Isabelle + AFP theories.  Then we can apply it independently, with a more
> informative log message that "fixed bug", though.
>
>
>   	Makarius
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