[isabelle-dev] Relations vs. Predicates

[Florian Haftmann]

Hi Christian,

> by the way, I noticed that sometimes [to_pred] yields undesirable
> results (containing case-expressions), e.g.,
> 
> thm trancl_power[to_pred]
> 
> results in
> 
> (case ?p of (x, xa) ⇒ ?R^++ x xa) =
> (∃n>0. case ?p of (x, xa) ⇒ (?R ^^ n) x xa)
> 
> is this an inherent problem or could this be "repaired" by adding
> appropriate [pred_set_conv] (I do not know how this workds in detail).

I do not know whether this is inherent (Stefan could know).

There are (at least) two solutions:
* [unfold prod_case_unfold]
* [of "(a, b)", unfold <some suitable rule>]

Note that internally prod_case is also used as »uncurry« combinator.

Hope this helps,
	Florian

-- 

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http://home.informatik.tu-muenchen.de/haftmann/pgp/florian_haftmann_at_informatik_tu_muenchen_de

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