<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=""><div class="">I agree the second is much nicer, and a lot clearer on what each of the options does; fitImage: true is pretty clear, but fitImage: false is not, but the ad-hoc enum is clear on both counts. That said, the questions of interoperability are a big issue for ad-hoc enums, as either they’re too strict which becomes inconvenient (a .Fit | .Fill working with one method but not another) or too relaxed to be safe. Of course, in the latter case you’re replacing a Bool, which couldn’t be more relaxed in terms of where it accepts values from.</div><div class=""><br class=""></div><div class="">Still, I think in this case it would be better to fully-define an enum, as it gives you total control over compatibility and reusability of the type, which you can’t really with the ad-hoc form without making it overly complex.</div><div class=""><br class=""></div><div class="">The main type of ad-hoc enum I want to see is a union-type like so:</div><div class=""><br class=""></div><div class=""><font face="Monaco" class=""><span class="Apple-tab-span" style="white-space:pre"> </span>func someMethod(value:(Int | String)) { … }</font></div><div class=""><br class=""></div><div class="">This would basically be an ad-hoc enum where each case identifies one of the possible types, and the value bound as that type. This works however because there’s no ambiguity in the meaning; an (Int | String) is the same wherever you use it, whereas a general-purpose ad-hoc enum is less clear, as an other method might also take .Fit and .Fill values, but these may have a slightly different meaning.</div><div class=""><br class=""></div><div class="">So yeah, I like the idea in principle, but I think in practice it has too many headaches to overcome for it to be as simple as it first appears =(</div><br class=""><div><blockquote type="cite" class=""><div class="">On 31 May 2016, at 17:16, Erica Sadun 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=us-ascii" class=""><div style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Here's a function signature from some code from today:<div class=""><br class=""></div><div class=""><table class="highlight js-file-line-container tab-size" data-tab-size="8" style="box-sizing: border-box; border-spacing: 0px; border-collapse: collapse; tab-size: 8; color: rgb(51, 51, 51); font-family: Helvetica, arial, nimbussansl, liberationsans, freesans, clean, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 13px;"><tbody style="box-sizing: border-box;" class=""><tr style="box-sizing: border-box;" class=""><td id="file-scalecrop-swift-LC6" class="js-file-line blob-code-inner blob-code" style="box-sizing: border-box; padding: 0px 10px; position: relative; vertical-align: top; overflow: visible; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 12px; word-wrap: normal; white-space: pre;"><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">scaleAndCropImage</span>(</td></tr><tr style="box-sizing: border-box;" class=""><td id="file-scalecrop-swift-L7" class="blob-num js-line-number" data-line-number="7" style="box-sizing: border-box; padding: 0px 10px; width: 50px; min-width: 50px; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 12px; line-height: 18px; text-align: right; white-space: nowrap; vertical-align: top; cursor: pointer; -webkit-user-select: none; border-style: solid; border-color: rgb(238, 238, 238); border-width: 0px 1px 0px 0px;"></td><td id="file-scalecrop-swift-LC7" class="js-file-line blob-code-inner blob-code" style="box-sizing: border-box; padding: 0px 10px; position: relative; vertical-align: top; overflow: visible; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 12px; word-wrap: normal; white-space: pre;"> image: UIImage,</td></tr><tr style="box-sizing: border-box;" class=""><td id="file-scalecrop-swift-L8" class="blob-num js-line-number" data-line-number="8" style="box-sizing: border-box; padding: 0px 10px; width: 50px; min-width: 50px; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 12px; line-height: 18px; text-align: right; white-space: nowrap; vertical-align: top; cursor: pointer; -webkit-user-select: none; border-style: solid; border-color: rgb(238, 238, 238); border-width: 0px 1px 0px 0px;"></td><td id="file-scalecrop-swift-LC8" class="js-file-line blob-code-inner blob-code" style="box-sizing: border-box; padding: 0px 10px; position: relative; vertical-align: top; overflow: visible; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 12px; word-wrap: normal; white-space: pre;"> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">toSize</span> <span class="pl-smi" style="box-sizing: border-box;">size</span>: CGSize,</td></tr><tr style="box-sizing: border-box;" class=""><td id="file-scalecrop-swift-L9" class="blob-num js-line-number" data-line-number="9" style="box-sizing: border-box; padding: 0px 10px; width: 50px; min-width: 50px; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 12px; line-height: 18px; text-align: right; white-space: nowrap; vertical-align: top; cursor: pointer; -webkit-user-select: none; border-style: solid; border-color: rgb(238, 238, 238); border-width: 0px 1px 0px 0px;"></td><td id="file-scalecrop-swift-LC9" class="js-file-line blob-code-inner blob-code" style="box-sizing: border-box; padding: 0px 10px; position: relative; vertical-align: top; overflow: visible; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 12px; word-wrap: normal; white-space: pre;"> <b class="">fitImage: <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">Bool</span> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">=</span> <span class="pl-c1" style="box-sizing: border-box; color: rgb(0, 134, 179);">true</span></b></td></tr><tr style="box-sizing: border-box;" class=""><td id="file-scalecrop-swift-L10" class="blob-num js-line-number" data-line-number="10" style="box-sizing: border-box; padding: 0px 10px; width: 50px; min-width: 50px; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 12px; line-height: 18px; text-align: right; white-space: nowrap; vertical-align: top; cursor: pointer; -webkit-user-select: none; border-style: solid; border-color: rgb(238, 238, 238); border-width: 0px 1px 0px 0px;"></td><td id="file-scalecrop-swift-LC10" class="js-file-line blob-code-inner blob-code" style="box-sizing: border-box; padding: 0px 10px; position: relative; vertical-align: top; overflow: visible; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 12px; word-wrap: normal; white-space: pre;"> ) <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">-></span> UIImage {</td></tr></tbody></table><div class=""><br class=""></div><div class=""><br class=""></div><div class="">And here's what I want the function signature to actually look like:</div></div><div class=""><br class=""></div><div class=""><table class="highlight js-file-line-container tab-size" data-tab-size="8" style="box-sizing: border-box; border-spacing: 0px; border-collapse: collapse; tab-size: 8; color: rgb(51, 51, 51); font-family: Helvetica, arial, nimbussansl, liberationsans, freesans, clean, sans-serif, 'Apple Color Emoji', 'Segoe UI Emoji', 'Segoe UI Symbol'; font-size: 13px;"><tbody style="box-sizing: border-box;" class=""><tr style="box-sizing: border-box;" class=""><td id="file-scalecrop-swift-LC6" class="js-file-line blob-code-inner blob-code" style="box-sizing: border-box; padding: 0px 10px; position: relative; vertical-align: top; overflow: visible; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 12px; word-wrap: normal; white-space: pre;"><span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">func</span> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">scaleAndCropImage</span>(</td></tr><tr style="box-sizing: border-box;" class=""><td id="file-scalecrop-swift-L7" class="blob-num js-line-number" data-line-number="7" style="box-sizing: border-box; padding: 0px 10px; width: 50px; min-width: 50px; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 12px; line-height: 18px; text-align: right; white-space: nowrap; vertical-align: top; cursor: pointer; -webkit-user-select: none; border-style: solid; border-color: rgb(238, 238, 238); border-width: 0px 1px 0px 0px;"></td><td id="file-scalecrop-swift-LC7" class="js-file-line blob-code-inner blob-code" style="box-sizing: border-box; padding: 0px 10px; position: relative; vertical-align: top; overflow: visible; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 12px; word-wrap: normal; white-space: pre;"> image: UIImage,</td></tr><tr style="box-sizing: border-box;" class=""><td id="file-scalecrop-swift-L8" class="blob-num js-line-number" data-line-number="8" style="box-sizing: border-box; padding: 0px 10px; width: 50px; min-width: 50px; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 12px; line-height: 18px; text-align: right; white-space: nowrap; vertical-align: top; cursor: pointer; -webkit-user-select: none; border-style: solid; border-color: rgb(238, 238, 238); border-width: 0px 1px 0px 0px;"></td><td id="file-scalecrop-swift-LC8" class="js-file-line blob-code-inner blob-code" style="box-sizing: border-box; padding: 0px 10px; position: relative; vertical-align: top; overflow: visible; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 12px; word-wrap: normal; white-space: pre;"> <span class="pl-en" style="box-sizing: border-box; color: rgb(121, 93, 163);">toSize</span> <span class="pl-smi" style="box-sizing: border-box;">size</span>: CGSize,</td></tr><tr style="box-sizing: border-box;" class=""><td id="file-scalecrop-swift-L9" class="blob-num js-line-number" data-line-number="9" style="box-sizing: border-box; padding: 0px 10px; width: 50px; min-width: 50px; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 12px; line-height: 18px; text-align: right; white-space: nowrap; vertical-align: top; cursor: pointer; -webkit-user-select: none; border-style: solid; border-color: rgb(238, 238, 238); border-width: 0px 1px 0px 0px;"></td><td id="file-scalecrop-swift-LC9" class="js-file-line blob-code-inner blob-code" style="box-sizing: border-box; padding: 0px 10px; position: relative; vertical-align: top; overflow: visible; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 12px; word-wrap: normal; white-space: pre;"> <b class="">operation: <font color="#0086b3" class="">(.Fit | .Fill)</font> <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">=</span> .<font color="#0086b3" class="">Fit</font></b></td></tr><tr style="box-sizing: border-box;" class=""><td id="file-scalecrop-swift-L10" class="blob-num js-line-number" data-line-number="10" style="box-sizing: border-box; padding: 0px 10px; width: 50px; min-width: 50px; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 12px; line-height: 18px; text-align: right; white-space: nowrap; vertical-align: top; cursor: pointer; -webkit-user-select: none; border-style: solid; border-color: rgb(238, 238, 238); border-width: 0px 1px 0px 0px;"></td><td id="file-scalecrop-swift-LC10" class="js-file-line blob-code-inner blob-code" style="box-sizing: border-box; padding: 0px 10px; position: relative; vertical-align: top; overflow: visible; font-family: Consolas, 'Liberation Mono', Menlo, Courier, monospace; font-size: 12px; word-wrap: normal; white-space: pre;"> ) <span class="pl-k" style="box-sizing: border-box; color: rgb(167, 29, 93);">-></span> UIImage {</td></tr></tbody></table><div class=""><br class=""></div></div><div class=""><br class=""></div><div class="">where I don't have to establish a separate enumeration to include ad-hoc enumeration-like semantics for the call. A while back, Yong hee Lee introduced anonymous enumerations (and the possibility of anonymous option flags) but the discussion rather died.</div><div class=""><br class=""></div><div class="">I'm bringing it up again to see whether there is any general interest in pursuing this further as I think the second example is more readable, appropriate, and Swifty than the first, provides better semantics, and is more self documenting.</div><div class=""><br class=""></div><div class="">Thanks for your feedback,</div><div class=""><br class=""></div><div class="">-- Erica</div><div class=""><br class=""></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="">https://lists.swift.org/mailman/listinfo/swift-evolution<br class=""></div></blockquote></div><br class=""></body></html>