Re: [isabelle] Beta-contraction



On 04/07/2019 17:28, Peter Lammich wrote:
Hi List,

I have

     ...
     val ctxt = put_simpset HOL_ss ctxt addsimps inline_thms
   in
     Conv.fconv_rule ( Simplifier.rewrite ctxt ) thm


Unfortunately, the resulting theorem is not beta-contracted (it
contains (%x. ...) x ).

However, both inline_thms and thm contain no beta redexes.


Is it expected behaviour of the simplifier to introduce
new beta-redexes, or is this behaviour undesired, and worth
investigating?

I am aware that it can hapen although it is undesired. If you send me a minimal example I can investigate when I find the time.

Tobias

In my application the beta-redexes cause problems in further
conversions, as some operations on Thm seem to silently remove them,
and Thm.equals (used in conversion) cannot match (aconv) the terms any
more.
Of cause, I can quick-fix this by introducing Thm.beta_conv, but I
always thought that expected behaviour of Isabelle functions is not to
produce beta-redexes ?

Thanks for any explanations,
   Peter







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