[isabelle-dev] (Re-)introducing set as a type constructor rather than as mere abbreviation

[Lawrence Paulson]

I've come across something strange in the file isabelle/afp/devel/thys/DataRefinementIBP/Diagram.thy and was wondering if anybody could think of an explanation.

A proof works only if I insert before it the following:

instance "set" :: (type) complete_boolean_algebra
proof
qed (auto simp add: INF_def SUP_def Inf_set_def Sup_set_def Inf_bool_def Sup_bool_def)

this is strange because this exact text already appears in the file Complete_Lattice.thy (I refer to Florian's version of HOL), which is imported by Main, which is indirectly imported by Diagram. And just in case I was mistaken on this last point, I modified Diagram to import Main explicitly, just to be sure. This instance declaration is still necessary.

I just don't get this. I thought that an instance declaration lasted for ever.

Larry