[ghc-steering-committee] DH quantifiers (#102), Recommendation: accept

[Joachim Breitner]

Dear Committee,

this is your secretary speaking:

Dependent Haskell quantifiers were proposed, by Richard.
https://github.com/ghc-proposals/ghc-proposals/pull/102
rendered at
https://github.com/goldfirere/ghc-proposals/blob/pi/proposals/0000-pi.rst

I’ll shepherd that myself.

This proposal defines and reserves the syntax for the quantifiers that
eventually Dependent Haskell will need, and allows their use where it
makes sense already (e.g. in Kinds). The quantifier are:

forall a.
forall a '.
forall a ->
forall a '->
foreach a.
foreach a '.
foreach a ->
foreach a '->
ty =>
ty '=>
ty ->
ty '->


It addresses the interaction with warning (e.g. -Wcompat). It looks
well-thought-through, one might infer that the authors wrote a thesis
about this stuff.

There is some syntactic bikeshedding possible; for example the proposal
proposes "foreach" instead of "pi" (the latter would make "pi" a
keyword, which would be unfortunate for those who deal with circles).

If someone has better ideas, in particular about the use of ' to denote
matchable arrows, we still have time to suggest them.

I recommend to accept this proposal in the current form or with further
refinements to the syntax, if we can come up with them.


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