On Mon, Jan 11, 2016 at 12:29 PM, M Farkas-Dyck
I have seen these redefined many times now. Examples: https://hackage.haskell.org/package/numericpeano-0.2.0.0/docs/Numeric-Peano.... https://hackage.haskell.org/package/numeric-prelude-0.4.2/docs/Number-Peano.... https://hackage.haskell.org/package/type-fun-0.0.1/docs/TypeFun-Data-Peano.h... https://hackage.haskell.org/package/number-0.1.1.0/docs/Data-Number-Peano.ht... https://hackage.haskell.org/package/Peano-0.0.4/docs/Data-Peano.html#t:Peano
I often see them used as DataKinds. Too, operations on them can be lazy, which is sometimes useful.
I filed a ticket: https://ghc.haskell.org/trac/ghc/ticket/11402
I'm a fan of blessing some particular implementation in order to minimize the code redundancy. Though I'd prolly suggest making it a Platform package rather than rolling it into base itself (unless there's some reason why it needs to be in base itself). Wherever it ends up, I really like that the patch names the type Peano rather than Nat. I often use Nat as a newtype of Int (and Natural as a newtype of Integer) for when I need efficient implementations of natural numbers, so it's nice to give the lazy unary representation a different name. -- Live well, ~wren