[Proposal] Renaming (:=:) to (==)

Conal Elliott conal at conal.net
Mon Sep 30 18:25:41 UTC 2013


I'm hoping we don't get more deeply invested in the syntactic change in GHC
7.6 that removed the possibility of symbolic type variables ("~>", "*",
"+", etc). I had a new job and wasn't paying attention when SPJ polled the
community. From my perspective, the loss has much greater scope than the
gain for type level naturals. I'd like to keep the door open to the
possibility of bringing back the old notation with the help of a language
pragma. It would take a few of us to draft a proposal addressing details.

Not at all meaning to start a syntax debate on this thread. Just an
explanation of my -1 for the topic at hand.

- Conal

-- Conal

On Sat, Sep 28, 2013 at 9:57 PM, Edward Kmett <ekmett at gmail.com> wrote:

> As part of the discussion about Typeable, GHC 7.8 is going to include a
> Data.Type.Equality module that provides a polykinded type equality data
> type.
> I'd like to propose that we rename this type to (==) rather than the (:=:)
> it was developed under.
> We are already using (+), (-), (*), etc. at the type level in type-nats,
> so it would seem to fit the surrounding convention.
> I've done the work of preparing a patch, visible here:
> https://github.com/ekmett/packages-base/commit/fb47f8368ad3d40fdd79bdeec334c0554fb17110
> Thoughts?
> Normally, I'd let this run the usual 2 week course, but we're getting down
> to the wire for 7.8's release. Once 7.8 ships, we'd basically be stuck with
> the current name forever.
> Discussion Period: 1 week
> -Edward Kmett
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