On Tue, Feb 08, 2022 at 05:48:46PM -0800, Gregory P. Smith wrote:
On Tue, Feb 8, 2022 at 2:41 PM Steven D'Aprano <steve@pearwood.info> wrote:
If the answer to those questions are Yes, that rules out using Unums, posits, sigmoid numbers etc as the builtin float. (The terminology is a bit vague, sorry.) Do we want that?
It does not rule anything else out should they become viable. This is just a statement that to build cpython we require ieee754 support. It does not say anything about how our Python float type is implemented internally.
Posits do not implement IEEE-754. They aren't merely a different internal representation of the IEEE-754 floating point standard, they implement a different numeric system altogether. Things that IEEE-754 require, such as signed zero and signed infinity, are not supported by posits. Posits include a single unsigned zero and a single unsigned infinity. Earlier, I made a mistake: I misremembered that posits support a single NAN, and so I removed Mark's question about requiring NANs from my quoting. I was wrong to do so: posits do not have any NANs. So if we require NANs, or IEEE-754, that rules out posits as the builtin float. -- Steve