Re: [isabelle] size_changes raises Option and Bind



Hi Andreas,

On 04/27/2012 11:33 AM, Andreas Lochbihler wrote:
In Isabelle 2011-1, size_change raises the exception Option (line 81 in
general/basics.ML) and Bind (line 277 of termination.ML) for the
following function definitions. The NOT operator seems to cause the
trouble, because size_change (and lexicographic_order) work perfectly
well when I unfold NOT i = -i - 1.

This either seems like a bug in termination or some bad setup for NOT.

Thanks for reporting this. It is a bug in size_change (more precisely, the dependency graph construction). Embarrasingly, the edges in the graph seem to have the wrong direction, which got unnoticed several years. This shows that size_change still isn't used/tested much.

I am preparing a fix.

Alex





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