Proposal: Add Peano numbers to base

wren romano wren at
Mon Jan 11 23:16:12 UTC 2016

On Mon, Jan 11, 2016 at 12:29 PM, M Farkas-Dyck <m.farkasdyck at> wrote:
> I have seen these redefined many times now. Examples:
> I often see them used as DataKinds. Too, operations on them can be
> lazy, which is sometimes useful.
> I filed a ticket:

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,

More information about the Libraries mailing list