Re: [ghc-steering-committee] Precedence of r.x

When I first picked up Haskell professionally, I was told “we don’t write f.g, we write f . g, because when someone manages to add the record syntax, the former will be record selection”. So I’ve always considered f.g to be forbidden syntax. Morally a syntax error, if you will, that the parser accidentally didn’t catch. So, while it is true that *today* f r.x parses as (f r).x (that is, (B)). I see no objection for (A), which does make more visual sense to me. On Thu, Dec 12, 2019 at 10:49 AM Simon Marlow wrote:

Definitely (A).

On Thu, 12 Dec 2019 at 09:44, Simon Peyton Jones via ghc-steering-committee wrote:

...

A question for the committee.

What does f r.x mean, where there is no white space on either side of the dot?

A. The proposal says it means (f (r.x)) B. Joachim wants it to mean ((f r).x)

In trying to guide the discussion to a conclusion I proposed to fix on (A). I don't think it was controversial in the public discussion, it's compatible with qualified names, and forcing `f (r.x)` looks horribly clumsy to me.

Partly it's a question of whether your starting point is (a) "." is fundamentally an operator, albeit with some special extra rules, or (b) R.x, r.x, and .x are new syntactic forms, unrelated to the infix operator (.) I'm definitely thinking of it in the latter way.

I don't really want to re-open this question, and I'm not sure if the authors of the proposal could live with (B). However, if the committee wants to reopen the question, then that is what we should do. Can you express a view on this narrow question?

Simon _______________________________________________ ghc-steering-committee mailing list ghc-steering-committee@haskell.org https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee

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