# [isabelle] Beta-contraction

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?
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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