[isabelle-dev] Obsolete numeral experiments?
florian.haftmann at informatik.tu-muenchen.de
Wed May 29 22:32:52 CEST 2013
>> Can we delete that, and keep the history inside the history? Or are there
>> remaining aspects that are not in the official numeral implementation (and
>> reform) by Brian Huffman?
> Numeral_Representation.thy defines a couple of type classes for
> subtraction that were never added to the main libraries:
> semiring_minus and semiring_1_minus. (I believe these were Florian's
> work.) They would let us generalize some rules that are currently
> specific to nat. We should discuss whether these (or some variation)
> would be appropriate to add to Groups.thy before we delete
I have some plans in the drawer to introduce / refine type classes for
»confined subtraction« coverting natural numbers and multisets. There I
will reconsider semiring_minus and semiring_1_minus. The remainder of
the theory indeed is obsolete. I guess there are subtle and not so
subtle differences between that concept and the now existing
implementation, but I do not worry much about that, since the
implementation resolves the ancient central problem of signed numerals
and is just working.
-------------- next part --------------
A non-text attachment was scrubbed...
Size: 261 bytes
Desc: OpenPGP digital signature
More information about the isabelle-dev