[isabelle-dev] Default simprules for division in fields

[Tobias Nipkow]

I set up field_simps to yield a decision procedure for field equality, provided
all denominators can be proved to be 0. Hence I am sceptical if adding new rules
to it is a good idea. Florian, can you give an example where previously
field_simps was too weak but with the two additional rules it works?

Tobias

On 04/04/2014 17:37, Lawrence Paulson wrote:
> A very good idea, which reduces the impact of the change on existing proofs. I am trying it out now.
> 
> Seeing no objections, I am quite likely to push this change later today.
> 
> Larry
> 
> On 4 Apr 2014, at 15:08, Florian Haftmann <florian.haftmann at informatik.tu-muenchen.de> wrote:
> 
>>> lemma divide_minus_left [simp]: "(-a) / b = - (a / b)"
>>> lemma divide_minus_right [simp]: "a / - b = - (a / b)”
>>>
>>> It would be a mistake to reorient the simprules, but I am suggesting that they should not be declared as simprules with either orientation.
>>
>> Maybe
>>> lemma divide_minus_left [field_simps]: "(-a) / b = - (a / b)"
>>> lemma divide_minus_right [field_simps]: "a / - b = - (a / b)”
>> instead?
>>
>> 	Florian
>>
>> -- 
>>
>> PGP available:
>> http://home.informatik.tu-muenchen.de/haftmann/pgp/florian_haftmann_at_informatik_tu_muenchen_de
>>
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