<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=""><br class=""><div><blockquote type="cite" class=""><div class="">On Feb 16, 2017, at 5:38 PM, Slava Pestov <<a href="mailto:spestov@apple.com" class="">spestov@apple.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><meta http-equiv="Content-Type" content="text/html charset=utf-8" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class=""><div class=""><blockquote type="cite" class=""><div class="">On Feb 16, 2017, at 5:32 PM, David Sweeris 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=""><meta http-equiv="Content-Type" content="text/html charset=utf-8" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><br class=""><div class=""><blockquote type="cite" class=""><div class="">On Feb 16, 2017, at 5:17 PM, Ben Cohen <<a href="mailto:ben_cohen@apple.com" class="">ben_cohen@apple.com</a>> wrote:</div><br class="Apple-interchange-newline"></blockquote><blockquote type="cite" class=""><div class=""><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><div class="">The win with mapping only the values is that the underlying hash table can retain the same physical layout, just with different values in the slots, so it can be done faster.<br class=""><div class=""><blockquote type="cite" class=""></blockquote></div></div></div></div></blockquote></div><br class=""><div class="">Only if the mapped dictionary’s values are the same type (or at least the same size) as in the original dictionary, right? Would the proposed function allow you to mapValues from a [K:V] to a [K:T]?</div></div></div></blockquote><div class=""><br class=""></div>In both cases the key/bucket structure would be the same, I believe.</div><div class=""><br class=""></div></div></div></blockquote><div><br class=""></div><div>Right. Values could be different types, you can still reuse the layout i.e. allocate the same element-count buffer (even if the size of the element differs), then put the pairs in the same places they were per the keys, without going through the whole process of computing hashes, resolving collisions etc.</div><br class=""><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="">Slava</div><div class=""><br class=""><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=""><br class=""></div><div class="">- Dave Sweeris</div></div>_______________________________________________<br class="">swift-evolution mailing list<br class=""><a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a><br class=""><a href="https://lists.swift.org/mailman/listinfo/swift-evolution" class="">https://lists.swift.org/mailman/listinfo/swift-evolution</a><br class=""></div></blockquote></div><br class=""></div></div></blockquote></div><br class=""></body></html>