<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On Nov 21, 2017, at 6:02 PM, David Hart <<a href="mailto:david@hartbit.com" class="">david@hartbit.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">Can somebody explain to me what are </div><div style="font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""> nominal and structural types and why Optional should really be a structural type?</div></div></blockquote></div><br class=""><div class="">Nominal types are structs, enums, protocols and classes. They have declarations in source and are uniquely identified by their name. Structural types are functions, meta types, protocol compositions, and tuples.</div><div class=""><br class=""></div><div class="">The distinction is not as clear as you might think because as Chris said, you can imagine tuple being implemented as ‘struct Tuple<T…>’, similarly functions and meta types could also be written as such. It is mostly a syntactic distinction in the language, but it has far-reaching consequences in internal representations, which is why for now it would be tricky to have structural types conform to protocols.</div><div class=""><br class=""></div><div class="">Slava</div></body></html>