<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Long term we'd like to make it so that operators can be methods of their operand types, either instead of or in addition to being globals. That seems like a better way of addressing these concerns.<div class=""><br class=""></div><div class="">-Joe</div><div class=""><br class=""><div><blockquote type="cite" class=""><div class="">On Dec 8, 2015, at 2:01 AM, Richard Fox via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class=""><h3 style="margin-bottom:16px;line-height:1.43;font-size:1.5em;color:rgb(51,51,51);font-family:'Helvetica Neue',Helvetica,'Segoe UI',Arial,freesans,sans-serif,'Apple Color Emoji','Segoe UI Emoji','Segoe UI Symbol';margin-top:0px!important" class=""><span style="font-size:16px;line-height:25.6px;font-weight:normal" class="">Hi all,</span><br class=""></h3><p style="margin-top:0px;margin-bottom:16px;color:rgb(51,51,51);font-family:'Helvetica Neue',Helvetica,'Segoe UI',Arial,freesans,sans-serif,'Apple Color Emoji','Segoe UI Emoji','Segoe UI Symbol';font-size:16px;line-height:25.6px" class="">I would like to propose changing the Equatable protocol to use <code style="font-family:Consolas,'Liberation Mono',Menlo,Courier,monospace;font-size:13.6px;padding:0.2em 0px;margin:0px;border-radius:3px;background-color:rgba(0,0,0,0.0392157)" class="">isEqual(to:Self) -> Bool</code>, defined inside of a type to replace the currently used operator <code style="font-family:Consolas,'Liberation Mono',Menlo,Courier,monospace;font-size:13.6px;padding:0.2em 0px;margin:0px;border-radius:3px;background-color:rgba(0,0,0,0.0392157)" class="">==</code> function, which is defined outside of the type.</p><h3 style="margin-top:1em;margin-bottom:16px;line-height:1.43;font-size:1.5em;color:rgb(51,51,51);font-family:'Helvetica Neue',Helvetica,'Segoe UI',Arial,freesans,sans-serif,'Apple Color Emoji','Segoe UI Emoji','Segoe UI Symbol'" class=""><a id="user-content-reasoning" class="anchor" href="https://gist.github.com/Nadohs/308603afa65cbbfba07c#reasoning" style="color:rgb(64,120,192);text-decoration:none;display:inline-block;padding-right:2px;line-height:1.2;background-color:transparent"><span class="octicon octicon-link" style="font-weight: normal; font-size: 16px; line-height: 1; font-family: octicons; display: inline-block; vertical-align: middle;"></span></a>Reasoning:</h3><ol style="padding:0px 0px 0px 2em;margin-top:0px;margin-bottom:16px;color:rgb(51,51,51);font-family:'Helvetica Neue',Helvetica,'Segoe UI',Arial,freesans,sans-serif,'Apple Color Emoji','Segoe UI Emoji','Segoe UI Symbol';font-size:16px;line-height:25.6px" class=""><li style="box-sizing: border-box;" class="">Having the conforming function defined inside of the type is more intuitive, since in general functions required for conformance are defined within the type. It feels like an unnecesary detail for learners of Swift to have to stumble through.</li></ol><p style="margin-top:0px;margin-bottom:16px;color:rgb(51,51,51);font-family:'Helvetica Neue',Helvetica,'Segoe UI',Arial,freesans,sans-serif,'Apple Color Emoji','Segoe UI Emoji','Segoe UI Symbol';font-size:16px;line-height:25.6px" class="">The implementation for this would look something like this:</p><pre style="overflow:auto;font-family:Consolas,'Liberation Mono',Menlo,Courier,monospace;font-size:13.6px;margin-top:0px;margin-bottom:16px;font-stretch:normal;line-height:1.45;padding:16px;border-radius:3px;word-wrap:normal;color:rgb(51,51,51);background-color:rgb(247,247,247)" class=""><code style="font-family:Consolas,'Liberation Mono',Menlo,Courier,monospace;font-size:13.6px;padding:0px;margin:0px;border-radius:3px;word-break:normal;border:0px;display:inline;max-width:initial;overflow:initial;line-height:inherit;word-wrap:normal;background:transparent" class=""> public protocol Equatable{
....
/// Shortcut for defining `==` function inside type definition.
@warn_unused_result
func isEqual(to:Self) -> Bool
}
@warn_unused_result
public func == <T : Equatable>(lhs: T, rhs: T) -> Bool {
return lhs.isEqual(rhs)
}
</code></pre><h3 style="margin-top:1em;margin-bottom:16px;line-height:1.43;font-size:1.5em;color:rgb(51,51,51);font-family:'Helvetica Neue',Helvetica,'Segoe UI',Arial,freesans,sans-serif,'Apple Color Emoji','Segoe UI Emoji','Segoe UI Symbol'" class=""><a id="user-content-impact-on-existing-code" class="anchor" href="https://gist.github.com/Nadohs/308603afa65cbbfba07c#impact-on-existing-code" style="color:rgb(64,120,192);text-decoration:none;display:inline-block;padding-right:2px;line-height:1.2;background-color:transparent"><span class="octicon octicon-link" style="font-weight: normal; font-size: 16px; line-height: 1; font-family: octicons; display: inline-block; vertical-align: middle;"></span></a>Impact on Existing Code:</h3><p style="margin-top:0px;margin-bottom:16px;color:rgb(51,51,51);font-family:'Helvetica Neue',Helvetica,'Segoe UI',Arial,freesans,sans-serif,'Apple Color Emoji','Segoe UI Emoji','Segoe UI Symbol';font-size:16px;line-height:25.6px" class="">This implementation would break existing code, but could be fixed with a default protocol extension such as:</p><pre style="overflow:auto;font-family:Consolas,'Liberation Mono',Menlo,Courier,monospace;font-size:13.6px;margin-top:0px;margin-bottom:16px;font-stretch:normal;line-height:1.45;padding:16px;border-radius:3px;word-wrap:normal;color:rgb(51,51,51);background-color:rgb(247,247,247)" class=""><code style="font-family:Consolas,'Liberation Mono',Menlo,Courier,monospace;font-size:13.6px;padding:0px;margin:0px;border-radius:3px;word-break:normal;border:0px;display:inline;max-width:initial;overflow:initial;line-height:inherit;word-wrap:normal;background:transparent" class=""> /// Default `isEqual` function to satisfy other types only definiting
/// `==` for equality.
public extension Equatable{
func isEqual(to:Self) -> Bool{
return self == to
}
}
</code></pre><div style="margin-top: 0px; color: rgb(51, 51, 51); font-family: 'Helvetica Neue', Helvetica, 'Segoe UI', Arial, freesans, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 16px; line-height: 25.6px; margin-bottom: 0px !important;" class="">Not adding the default function for <code style="font-family:Consolas,'Liberation Mono',Menlo,Courier,monospace;font-size:13.6px;padding:0.2em 0px;margin:0px;border-radius:3px;background-color:rgba(0,0,0,0.0392157)" class="">isEqual</code> makes more sense to me though, since it would remove any strict requirement for Equatable conformance and leave no warning for the loop you would create by implementing neither <code style="font-family:Consolas,'Liberation Mono',Menlo,Courier,monospace;font-size:13.6px;padding:0.2em 0px;margin:0px;border-radius:3px;background-color:rgba(0,0,0,0.0392157)" class="">isEqual</code> nor <code style="font-family:Consolas,'Liberation Mono',Menlo,Courier,monospace;font-size:13.6px;padding:0.2em 0px;margin:0px;border-radius:3px;background-color:rgba(0,0,0,0.0392157)" class="">==</code>.<br class=""><br class="">Regards,<br class="">Rich Fox</div></div>
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