[isabelle-dev] NEWS: Rat in Isabelle/ML

[Makarius]

*** ML ***

* Structure Rat for rational numbers is now an integral part of
Isabelle/ML, with special notation @int/nat or @int for numerals (an
abbreviation for antiquotation @{Pure.rat argument}) and ML pretty
printing. Standard operations on type Rat.rat are provided via ad-hoc
overloading of + - * / < <= > >= ~ abs. INCOMPATIBILITY, need to
use + instead of +/ etc. Moreover, exception Rat.DIVZERO has been
superseded by General.Div.


This refers to Isabelle/c7de5b311909, which also contains the updated
documentation.

The antiquotation syntax @int/nat for @{Pure.rat argument} is stretching
the existing syntax very little, see 921a5be54132. Further changesets in
the vicinity clean up rat.ML is various repects -- it is surprising how
many details can be missing in such a small module.

I have compared it with the MyRat implementation by Manuel Eberl
https://lists.cam.ac.uk/mailman/htdig/cl-isabelle-users/2016-April/msg00002.html
as well as rat.ML in https://bitbucket.org/lcpaulson/metitarski
b11e8139b880 (where a comment says that it goes back to John Harrison).


Further comments? Anything missing?


	Makarius