<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div>Why not have them return a `Bool?`? If both arguments are non-nil, it can return the results of the comparison, otherwise it can return nil.<br><br>- Dave Sweeris</div><div><br>On Jul 7, 2016, at 16:37, Jacob Bandes-Storch via swift-evolution <<a href="mailto:swift-evolution@swift.org">swift-evolution@swift.org</a>> wrote:<br><br></div><blockquote type="cite"><div><div dir="ltr"><div>These operators cause some potential for confusion:</div><div><br></div><div><div> public func <<T : Comparable>(lhs: T?, rhs: T?) -> Bool</div><div> public func ><T : Comparable>(lhs: T?, rhs: T?) -> Bool<br></div><div> public func <=<T : Comparable>(lhs: T?, rhs: T?) -> Bool<br></div><div> public func >=<T : Comparable>(lhs: T?, rhs: T?) -> Bool</div><div><br></div><div>1. The meaning of T? < T? is not immediately obvious (Why is nil < .some(x) for any x? Personally, my intuition says that Optional should only provide a partial order, with .none not being ordered w.r.t. .some(x).)</div><div><br></div><div>2. Even if the meaning is understood, it can be surprising when the (T?, T?) -> Bool version is used instead of (T, T) -> Bool.</div><div><br></div><div>Prior discussion:</div><div>- <a href="http://thread.gmane.org/gmane.comp.lang.swift.devel/2089">http://thread.gmane.org/gmane.comp.lang.swift.devel/2089</a><br></div><div>- <a href="http://thread.gmane.org/gmane.comp.lang.swift.evolution/10095">http://thread.gmane.org/gmane.comp.lang.swift.evolution/10095</a></div></div><div><span style="font-size:12.8px">- <a href="rdar://">rdar://</a></span><span style="font-size:12.8px">16966712&</span><span style="font-size:12.8px">22833869</span></div><div><span style="font-size:12.8px">- Replies to <a href="https://twitter.com/jtbandes/status/646914031433871364">https://twitter.com/jtbandes/status/646914031433871364</a></span></div><div><span style="font-size:12.8px"><br></span></div><div><span style="font-size:12.8px">In the swift-dev thread from May, Chris said:</span></div><div><span style="font-size:12.8px"><br></span></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><span style="font-size:12.8px">One of the ideas that Joe Pamer has been discussing is whether the implicit promotion from T to T? should be disabled when in an operator context. Doing so would fix problems like this, but making the code invalid.</span></blockquote><div style="font-size:12.8px"><br></div></blockquote><div><br></div><div>A change like this would be source-breaking, so if the core team has recommendations for how to handle these issues, now is probably the time to get it done.</div><br clear="all"><div><div class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div>Jacob<br></div></div></div></div>
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