What would the semantics of subtraction be for this? I'm assuming there would be a `Num` instance for `Natural`.
Richard
On Nov 11, 2014, at 4:35 AM, Herbert Valerio Riedel
Hello CLC et al.,
I hereby suggest to add a type for encoding term-level naturals
data Natural =
deriving (...the usual standard classes...) to `base:Data.Word` module
Motivation ==========
- GHC 7.10 is planned to ship with integer-gmp2[2] as its default `Integer` lib, whose low-level primitives are based on *unsigned* BigNums. And 'Natural' type for integer-gmp2 can be implemented directly w/o the overhead of wrapping an `Integer` via
data Natural = NatS# Word# | NatJ# !PrimBigNat#
as well as having a twice as large domain handled via the small-word constructor and thus avoiding FFI calls into GMP.
- GHC/`base` already provides type-level naturals, but no term-level naturals
- Remove the asymmetry of having an unbounded signed `Integer` but no unbounded /unsigned/ integral type.
Also, `Data.Word` has been carrying the following note[1] for some time now:
It would be very natural to add a type Natural providing an unbounded size unsigned integer, just as Integer provides unbounded size signed integers. We do not do that yet since there is no demand for it.
Discussion period: ~10 days (GHC 7.10 RC freeze is scheduled for Nov 21st)
Cheers, hvr
[1]: http://hackage.haskell.org/package/base-4.7.0.1/docs/Data-Word.html#g:3
[2]: https://phabricator.haskell.org/D82 https://ghc.haskell.org/trac/ghc/wiki/Design/IntegerGmp2 _______________________________________________ Libraries mailing list Libraries@haskell.org http://www.haskell.org/mailman/listinfo/libraries