[ghc-steering-committee] Proposal: Syntax for visible dependent quantification (#81)
Joachim Breitner
mail at joachim-breitner.de
Fri Jan 5 20:55:43 UTC 2018
Hi,
thanks for the recommendation.
Am Mittwoch, den 20.12.2017, 20:35 +0000 schrieb Roman Leshchinskiy:
> If we decide to discuss just the proposal as is, though, then I'd be
> weakly against the proposed syntax as it is too subtle for my taste
> and abuses familiar mathematical notation somewhat. I'd probably
> prefer something like:
>
> type a -> t
I am not saying that the proposed “forall a ->” syntax is great, but I
think it is still better than “type a -> …”. The reason is that we
already use prefixing “type”, e.g. in export lists (“type Bool”), to
say “this thing is a type” if there is ambiguity. So if anything, then
ifThenElse :: Bool -> a -> a -> a
should be also allowed to be written as
ifThenElse :: type Bool -> a -> a -> a
and hence, in consequence
ifThenElse :: type Bool -> type a -> type a -> a
In other words, “type foo” just clarifies “I mean the _type_ foo”.
Can we get more input?
> Because of this, my recommendation is to strongly encourage the author
> to submit an extended proposal which reserves (but doesn't specify the
> semantics of) the above syntax wholesale.
I’d be on board deciding on that syntax all in one go.
Joachim
--
Joachim Breitner
mail at joachim-breitner.de
http://www.joachim-breitner.de/
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