Re: [ghc-steering-committee] Proposal #79 "Add a :kind!! command to ghci" — propose yes

I think this is useful, but I strongly dislike :kind!!. Currently:

:type <expr> gives the type of an expression, without evaluating it :kind <type> gives the kind of a type, without evaluating it <expr> evaluates an expression

Obviously, we can't have

<type> evaluates a type

because that's terribly ambiguous. On the thread, I proposed :eval-type, which got a less-than-lukewarm response. But I'll propose that here, regardless. Really, anything is better than :kind!! for me. (And I think we should remove :kind! too, and use a system like with have with :type +v and :type +d to have an evaluate-this-type command, with options.) Richard

On Mar 20, 2018, at 10:42 PM, Manuel M T Chakravarty wrote:

We need to decide on the Proposal #79 ”Add a :kind!! command to ghci, to expand type families and type synonyms”:

(rendered) https://github.com/alpmestan/ghc-proposals/blob/master/proposals/0000-kind-b... (discussion) https://github.com/ghc-proposals/ghc-proposals/pull/79

I agree that this is useful functionality and it is a simple change to GHCi. There has been some discussion about the naming of this command, but TBH I didn’t find any of the alternatives more convincing than ”:kind!!”, so I’d suggest to stick with that.

I favour accepting this proposal. Are there any dissenting opinions?

Cheers, Manuel

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