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
