[isabelle-dev] Reviving an old thread: [isabelle] structured induction: mutual definitions and "arbitrary" in inductions?

Makarius makarius at sketis.net
Wed Oct 12 16:01:52 CEST 2011

On Wed, 12 Oct 2011, Brian Huffman wrote:

> After implementing the warning, I dug through the revision history and
> was surprised to find that my "new" feature actually used to exist! It
> was removed in January 2006:
> http://isabelle.in.tum.de/repos/isabelle/rev/ca56111fe69c
> I don't understand why the warning message was ever removed. The
> commit message "fix_tac: no warning" is unhelpful.

This needs some further investigation.  My log message from 2006 is an 
example of how not to do it -- just parroting the change without any 
explanation.  (2006 was a bad year in Isabelle development.)

Does your own change do anything different from the old version?

BTW, that one was originating from here: 


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