
Friends I'd like to move our record-syntax discussion forward. Link to proposal discussionhttps://github.com/ghc-proposals/ghc-proposals/pull/282, and December GHC steering committee debateshttps://mail.haskell.org/pipermail/ghc-steering-committee/2019-December/thre.... No-space arguments I believe have agreed that f r.x (with no spaces around the dot, and no parens around r.x) means f (r.x) That is, treat it consistently with qualified names. I asked everyone to express a view; Iavor, Eric, Arnaud, Joachim, and Richard all said it was at least acceptable; others expressed no view. So let's take that as a decision, at least for now. Naked selectors Next question: how should we treat a "naked selector", namely .x where there is no space after the dot, but there is a space before. I think there are three viable choices: 1. It's simply illegal. This defers the choice; perhaps later we will have more experience to go on. 2. It's a postfix operator, binding less tightly than function application, but more tightly than any infix operator. So then (r .x) means r.x, and (r .x .y) means r.x.y. But (f r .x) means (f r).x. This choice naturally supports chaining (nice to have, but not essential). We can write f .map double .filter isEven meaning (f.map double).filter isEven 1. It's a postfix operator, binding more tightly than function application, just as record update does. So then (f r .x) means (f r.x), and (f r .x .y s .z) means (f r.x.y s.z). This choice allows us to regard our decision about (f r.x) as what naturally happens if we parse it as three lexemes: f, r, and .x. But it also breaks the "function application binds more tightly than anything else" rule, just as (f r {x=3}) sadly does already. It does not permit chaining, at least not without stacked-up parens. In all three cases we allow (.x), meaning (\r. r.x). For (2) and (3) we can regard it as a "section", like infix operators only simpler because there is no argument. I think this is the last major question we have to answer. What are your views? Personally I lean towards (2), but I could certainly live with (1). I'm a bit reluctant to adopt (3). Simon