<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="">Hi Joe,<div class=""><br class=""></div><div class="">to just fuzzy compare 2 floating point numbers,</div><div class="">the solution you describe uses</div><div class="">- 2 functions, with therein 6 calls to frexp, abs, max and scalb...</div><div class="">isn’t that overkill ? </div><div class=""><br class=""></div><div class="">I still think a compiler directive embedded in sources at desired locations as e.g.</div><div class=""><br class=""></div><div class="">@setFLoatingPointTolerance: 0.0001 </div><div class=""> . </div><div class=""> if a == b </div><div class=""> ...</div><div class="">@setFloatingPointToleranceOff</div><div class=""> …</div><div class="">@setFLoatingPointTolerance: 0.04 </div><div class=""> . </div><div class=""> if temperature == roomTemperature </div><div class=""> ...</div><div class="">@setFloatingPointToleranceOff</div><div class=""><br class=""></div><div class="">So every floating point compare in source between these directives will be </div><div class="">will be compiled differently.</div><div class="">Leave it to the compiler, so no special functions/ parameters are needed,</div><div class="">and would be far more efficient I think.</div><div class=""><br class=""></div><div class="">Kind Regards</div><div class="">TedvG</div><div class=""><br class=""><div class="">
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<br class=""><div><blockquote type="cite" class=""><div class="">On 02.03.2016, at 22:28, Joe Groff <<a href="mailto:jgroff@apple.com" class="">jgroff@apple.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: 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=""><blockquote type="cite" class=""><div class=""><br class="Apple-interchange-newline">On Mar 2, 2016, at 1:23 PM, Tino Heth 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=""><div class="">I hope that I'll finally have the time to write a pitch for "inheritance for structs" this weekend — this looks like another good use case for a "newtype" feature:<br class=""><br class="">struct Length: Double {<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>static let tolerance: Double = 0.001<br class="">}<br class=""><br class="">override func ==(a: Length, b: Length) -> Bool {<br class=""><span class="Apple-tab-span" style="white-space: pre;"> </span>return (a - b).abs() < Length.tolerance<br class="">}<br class=""><br class="">Of course, this example leaves many questions, but I hope the principle is clear.<br class=""></div></div></blockquote></div><br class="" style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: 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;"><div class="" style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: 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;">This is also a place where function partial application might be interesting:</div><div class="" style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: 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;"><br class=""></div><blockquote class="" style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: 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; margin: 0px 0px 0px 40px; border: none; padding: 0px;"><div class="">func equalityWithTolerance(tolerance: Double) -> (Double, Double) -> Bool {</div><div class=""> return {</div><div class=""> var exp0 = 0, exp1 = 0</div><div class=""> frexp($0, &exp0)</div><div class=""> frexp($1, &exp1)</div><div class=""> return abs($0 - $1) < scalb(tolerance, max(exp0, exp1))</div><div class=""> }</div><div class="">}</div></blockquote><div class="" style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: 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;"><br class=""></div><div class="" style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: 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;">If you could locally bind operators, you could then do this:</div><div class="" style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: 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;"><br class=""></div><blockquote class="" style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: 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; margin: 0px 0px 0px 40px; border: none; padding: 0px;"><div class="">func compareLengths(x: Double, y: Double) -> Bool {</div><div class=""> let (==) = equalityWithTolerance(0x1p-44)</div><div class=""> return x == y // Uses local (==)</div><div class="">}</div><div class=""><br class=""></div></blockquote><span style="font-family: Helvetica; font-size: 14px; font-style: normal; font-variant: 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="">-Joe</span></div></blockquote></div><br class=""></div></body></html>