<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 Jan 26, 2016, at 9:30 AM, Developer via swift-evolution <<a href="mailto:swift-evolution@swift.org" class="">swift-evolution@swift.org</a>> wrote:</div><div class=""><div dir="auto" class=""><div class=""><div class=""><div class=""><div class=""><br class=""><blockquote type="cite" class=""><div class=""><font class=""><span style="background-color: rgba(255, 255, 255, 0);" class="">- occasionally: a rather poorly-named, 2-way sum type (poorly-named b/c its convention won’t generalize to 3-way sums, or 4-ways sums, etc.)</span></font></div></blockquote><div class=""><br class=""></div><div class="">Good thing Either<Either<...>, Either<...>> works.</div></div></div></div></div></div></div></blockquote><br class=""></div><div>This is another example of exactly why Either is terrible in practice. I understand that from a type algebra point of view this is perfectly reasonable and clean and that a 2-way sum is all that is necessary because larger sums are easily created by construction. Type theory-wise it’s lovely.</div><div><br class=""></div><div>But from a literate programming point of view, when will "case let .Left(.Left(a)): case let .Left(.Right(b)): case let .Right(.Left(c)): case let .Right(.Right(d)): “ ever be the most understandable way to express _anything_ in Swift? And why would we want to encourage such things?</div><div><br class=""></div><div><span class="Apple-tab-span" style="white-space:pre"> </span>- Greg</div></body></html>