<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">On Apr 20, 2016, at 12:31 PM, David Owens II via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:<div><blockquote type="cite" class=""><div class=""><meta http-equiv="Content-Type" content="text/html charset=us-ascii" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">This is similar to another concern I raised with functions and being able to essentially erase the function argument names and apply two different named parameters just because their types match.<div class=""><br class=""></div><div class="">It seems reasonable to me that you can go from (x: Int, y: Int) => (Int, Int). However, going from (x: Int, y: Int) => (a: Int, b: Int) feels somewhat odd. Yes, the types can obviously slot in there fine, but how much importance do the labels for the types bring to the table?</div><div class=""><br class=""></div><div class="">Similarly, should this (Int, Int) => (x: Int, y: Int) be allowed through an implicit means? If so, then it's really just an intermediate step for (x: Int, y: Int) => (a: Int, b: Int) working.</div></div></div></blockquote><div><br class=""></div><div>I completely agree, I think it makes sense to convert from unlabeled to labeled (or back) but not from “labeled" to "differently labeled”.</div><div><br class=""></div><blockquote type="cite" class=""><div class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class="">So what matters more, type signatures or label names?</div><div class=""><br class=""></div><div class="">Here's an example:</div><div class=""><br class=""></div><blockquote style="margin: 0 0 0 40px; border: none; padding: 0px;" class=""><div class=""><font face="Menlo" class="">typealias Functor = (left: Int, right: Int) -> Int</font></div><div class=""><font face="Menlo" class=""><br class=""></font></div><div class=""><font face="Menlo" class="">func hi(x: Int, y: Int, fn: Functor) -> Int {</font></div><div class=""><font face="Menlo" class=""> return fn(left: x, right: y)</font></div><div class=""><font face="Menlo" class="">}</font></div><div class=""><font face="Menlo" class=""><br class=""></font></div><div class=""><font face="Menlo" class="">hi(1, y: 2, fn: +)</font></div><div class=""><font face="Menlo" class="">hi(1, y: 2, fn: *)</font></div></blockquote><div class=""><br class=""></div><div class="">If we say that the parameter names are indeed vital, then the above code cannot work as the operators that match the type signature are defined as: </div><div class=""><br class=""></div><blockquote style="margin: 0 0 0 40px; border: none; padding: 0px;" class=""><div class=""><font face="Menlo" class="">public func +(lhs: Int, rhs: Int) -> Int</font></div></blockquote><div class=""><br class=""></div><div class="">Obviously, given a name to the parameter brings clarity and can be self documenting, but if we want the above to work while making names just as vital as the type signature, then we need to declare `Functor` as such:</div><div class=""><br class=""></div><blockquote style="margin: 0 0 0 40px; border: none; padding: 0px;" class=""><div class=""><div class=""><font face="Menlo" class="">typealias Functor = (_ left: Int, _ right: Int) -> Int</font></div></div></blockquote><div class=""><br class=""></div><div class="">However, that's not even legal code today, and even if it were, is that really better?</div></div></div></blockquote></div><br class=""><div class="">I don’t think this follows, since operator parameters are always unlabeled. I suspect we don’t reject it, but I’d be in favor of rejecting:</div><div class=""><br class=""></div><div class="">func +(lhs <b class="">xyz</b>: Int, rhs <b class="">abc</b>: Int) -> Int { }</div><div class=""><br class=""></div><div class="">-Chris</div></body></html>