On Apr 14, 2016, at 10:21 PM, John McCall <rjmcc...@apple.com> wrote: > >> On Apr 14, 2016, at 9:57 PM, Chris Lattner via swift-evolution >> <swift-evolution@swift.org> wrote: >> >> We currently accept function type syntax without parentheses, like:
> To me, the unparenthesized style suggests that the input and output are > peers, which feels more natural for the sort of value-to-value > transform/predicate where this most commonly occurs. Parenthesizing the > input feels fussier, which contributes to a sense that the argument is just > one component to producing the result. > The parentheses are grammatically unnecessary in most cases (by frequency of > use in higher-use programming, not by feature count). I agree with your point that many simple higher order programming examples (e.g. map, filter, etc) take a single argument. That said, I don’t agree that this means that we should syntactically privilege this special case. In many places in the Swift grammar we aim for consistency, even if it means a bit more punctuation in specific cases. > Our grammar generally allows grammatically-unnecessary parentheses to be > omitted (except the C-style for loop, until we killed it) — I guess you could > count function call syntax, but we had strong reasons there that don't seem > to apply here. We notably chose to deviate from C statement grammar > specifically to allow unnecessary parentheses to be omitted. This would feel > weirdly inconsistent with that. We allow parens to be omitted from control flow expressions, where they are redundant with paren exprs. I don’t see how that translates to our type grammar. > I guess the flip side is that call and declaration syntax both require > parentheses (unless the only argument is a trailing closure), but again, we > had strong justifications for that: declarations would always be ambiguous > without parens, and calls would have serious problems (and the style-wars > factor would be much larger, especially now with mandatory keyword arguments > by default). Right, but regardless of *why* we always require parens on Decls and ApplyExprs, we really do (and that isn’t going to change). Being consistent between func decls and function types is quite important IMO. -Chris _______________________________________________ swift-evolution mailing list swift-evolution@swift.org https://lists.swift.org/mailman/listinfo/swift-evolution
