[ghc-steering-committee] #477: Unicode ellipsis, recommendation: accept, please vote

[Joachim Breitner]

Dear Commitee!

https://github.com/ghc-proposals/ghc-proposals/pull/477
https://github.com/kindaro/ghc-proposals/blob/unicode-ellipsis/proposals/477-unicode-ellipsis.md

It turns out this simple change isn’t so simple after all. Maybe just
Wadler’s law again… Anyways, it seems all arguments have been brought
before, and it’s up to us to make a decision. A concise summary could
be:

Ignat suggests that under -XUnicodeSyntax, the `…` symbol can be used
instead of `..` (e.g. import Prelude (Maybe(…)), [1…10]). This is
roughly a very reasonable thing to do under -XUnicodeSyntax, at least
for the former use, where `..` clearly is an ellipsised omission.

The wrinkle is the range syntax: Vlad researched that there the two-dot
syntax has historic precendent going back to Knuth and is used in other
languages, and that it is _not_ just a bad ASCII approximation of a
three dot … ellipsis, but really it’s own symbol, and pushed back
because of that. He does not contest the use of … in export/import
statements, though.

A possible rebuttal is that despite the existence of a two-dot-range
notation in some contexts, it is not _that_ universal, and it is still
a form of omission for which an ellipsis (…) is a semantically suitable
symbol.

Pragmatically, I’d argue it would be a bad idea to allow … instead of
.. only in import/export lists, but not range syntax.

So my recommendation is as before (but maybe a bit more weakly): Don’t
let perfect get in the way of good and accept the proposal, despite the
history aspects of the [1..10] syntax, to improve -XUnicodeSyntax for
the Unicode fans out there, and keeping the mapping between Unicode
syntax and ASCII syntax in Haskell one-to-one.

Vlad said on Github he is still opposed, but more weakly. The existence
of this surprisingly long discussion may be an indication that this
feature is not worth it.

To avoid an out-of-proportion discussion (for a change of that relative
now implication), I suggest to simply vote.

I have seen +1 from Arnaud, Richard, and SPJ, and a -1 from Vlad. Let
me know if any of you changed their mind, and the others: let me know
which way you are leaning.

Cheers,
Joachim







-- 
Joachim Breitner
  mail at joachim-breitner.de
  http://www.joachim-breitner.de/