<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 Aug 1, 2016, at 7:24 PM, Rick Mann <<a href="mailto:rmann@latencyzero.com" class="">rmann@latencyzero.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><span style="font-family: Alegreya-Regular; font-size: 15px; 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; float: none; display: inline !important;" class="">But my model has implicit reference semantics: multiple instances of a part can share a PartDefinition; it is intended that if the PartDefinition changes, all the referencing instances get the change.</span></div></blockquote></div><br class=""><div class="">Bingo. That’s the very definition of a reference.</div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><br class=""></div><div class=""><blockquote type="cite" class=""><div class="">On Aug 1, 2016, at 7:18 PM, Jack Lawrence <<a href="mailto:jackl@apple.com" class="">jackl@apple.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><span class="" style="font-family: Alegreya-Regular; float: none; display: inline !important;">I’d think that value semantics would be the right choice here. When you do a mutation, you would copy the state of the entire diagram. It should be efficient via COW</span></div></blockquote></div><div class=""><div class=""><span class="" style="font-family: Alegreya-Regular; float: none; display: inline !important;"><br class=""></span></div></div><div class=""><span class="" style="font-family: Alegreya-Regular; float: none; display: inline !important;">It sounds like you’re talking about a <a href="https://en.wikipedia.org/wiki/Persistent_data_structure" class="">persistent data structure</a>, which to me is not the same thing as a value type.</span></div><div class=""><span class="" style="font-family: Alegreya-Regular; float: none; display: inline !important;"><br class=""></span></div><div class=""><span class="" style="font-family: Alegreya-Regular; float: none; display: inline !important;">—Jens</span></div></body></html>