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<body><div>We already don't have a .last on CollectionType and nobody's been complaining about that. Besides, sequences don't necessarily even terminate.<br></div>
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<div>-Kevin Ballard</div>
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<div>On Wed, Dec 30, 2015, at 04:01 PM, Daniel Duan wrote:<br></div>
<blockquote type="cite"><div>Users who don’t get the single-pass nature of SequenceType may expect a .last as well.<br></div>
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<div><div><blockquote type="cite"><div>On Dec 30, 2015, at 3:57 PM, Kevin Ballard via swift-evolution <<a href="mailto:swift-evolution@swift.org">swift-evolution@swift.org</a>> wrote:<br></div>
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<div><div><div>It's sometimes useful to get the first element of a sequence. To that end I'd like to propose<br></div>
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<div><div style="margin-top:0px;margin-bottom:0px;font-size:11px;line-height:normal;font-family:Menlo;color:rgb(112, 61, 170);"><span class="colour" style="color:rgb(187, 44, 162)">extension</span><span style=""></span>SequenceType<span style=""> {</span><br></div>
<div style="margin-top:0px;margin-bottom:0px;font-size:11px;line-height:normal;font-family:Menlo;color:rgb(144, 45, 208);"><span style=""></span>/// Returns the first element of `self`, or `nil` if `self` is empty.<br></div>
<div style="margin-top:0px;margin-bottom:0px;font-size:11px;line-height:normal;font-family:Menlo;color:rgb(144, 45, 208);"><span style=""></span>/// - Complexity: O(1)<br></div>
<div style="margin-top:0px;margin-bottom:0px;font-size:11px;line-height:normal;font-family:Menlo;color:rgb(112, 61, 170);"><span style=""></span><span class="colour" style="color:rgb(187, 44, 162)">var</span><span style=""> first: </span>Self<span style="">.</span>Generator<span style="">.</span>Element<span style="">? {</span><br></div>
<div style="margin-top:0px;margin-bottom:0px;font-size:11px;line-height:normal;font-family:Menlo;"><span class="colour" style="color:rgb(187, 44, 162)">var</span> gen = <span class="colour" style="color:rgb(61, 29, 129)">generate</span>()<br></div>
<div style="margin-top:0px;margin-bottom:0px;font-size:11px;line-height:normal;font-family:Menlo;"><span class="colour" style="color:rgb(187, 44, 162)">return</span> gen.<span class="colour" style="color:rgb(61, 29, 129)">next</span>()<br></div>
<div style="margin-top:0px;margin-bottom:0px;font-size:11px;line-height:normal;font-family:Menlo;"> }<br></div>
<div style="margin-top:0px;margin-bottom:0px;font-size:11px;line-height:normal;font-family:Menlo;">}<br></div>
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<div>I think it makes sense to add this property to the definition of SequenceType as well, so various sequences can override it to avoid constructing a generator.<br></div>
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<div>With this added to SequenceType, we can remove it from CollectionType, as the behavior will be the same.<br></div>
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<div>-Kevin Ballard<br></div>
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