[isabelle-dev] lex_prod changes

Bertram Felgenhauer bertram.felgenhauer at googlemail.com
Thu Aug 20 22:27:57 CEST 2020


I've gotten some emails from Jenkins lately and finally taken a moment
to investigate.

Apparently, R1 <*lex*> R2 was changed to artificially impose
irreflexivity on R1 (checking  a ~= a'  in addition to  a R1 a').

What are the benefits of doing this? There is a (heavy, to me)
downside: It destroys the property that the lexicographic product is
transitive if both input relations are. More fundamentally, while in
the previous formulation, the lexicographic product was a meaningful
and useful operation for quasi-orders, now that use case is closed

Was this change discussed in advance? I may have missed it... in any
case I strongly dislike it.



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