[GHC] #9818: Add `Natural` number type to `base`

[GHC]

#9818: Add `Natural` number type to `base`
-------------------------------------+-------------------------------------
              Reporter:  hvr         |            Owner:  hvr
                  Type:  feature     |           Status:  new
  request                            |        Milestone:  7.10.1
              Priority:  normal      |          Version:
             Component:  Core        |         Keywords:  base natural
  Libraries                          |     Architecture:  Unknown/Multiple
            Resolution:              |       Difficulty:  Unknown
      Operating System:              |       Blocked By:
  Unknown/Multiple                   |  Related Tickets:  #3650
       Type of failure:              |
  None/Unknown                       |
             Test Case:              |
              Blocking:              |
Differential Revisions:  Phab:D473   |
-------------------------------------+-------------------------------------

Comment (by Herbert Valerio Riedel <hvr@…>):

 In [changeset:"4b6537677fa9460ca5febe2eb79a2d9d5bdadba2/ghc"]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="4b6537677fa9460ca5febe2eb79a2d9d5bdadba2"
 Add `isValidNatural` predicate (#9818)

 This predicate function encodes the internal `Natural` invariants, and
 is useful for testsuites or code that directly constructs `Natural`
 values.

 C.f. `integer-gmp2`'s `isValidBigNat#` and `isValidInteger#` predicates
 for testing internal invariants.
 }}}

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9818#comment:3>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler