<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><blockquote type="cite" class=""><div class="">On 19. Apr 2017, at 01:48, Xiaodi Wu <<a href="mailto:xiaodi.wu@gmail.com" class="">xiaodi.wu@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class="">So, as I understand it, `Float.init(exactly: Double.pi) == nil`. I would expect NSNumber to behave similarly (a notion with which Martin disagrees, I guess). I don't see a test that shows whether NSNumber behaves or does not behave in that way.</div></div></blockquote><div><br class=""></div><div class="">At present they behave differently: </div><div class=""><br class=""></div><div class=""><div class=""><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures;" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: rgb(62, 30, 129);" class="">print</span><span style="font-variant-ligatures: no-common-ligatures;" class="">(</span><span style="font-variant-ligatures: no-common-ligatures; color: rgb(112, 61, 170);" class="">Float</span><span style="font-variant-ligatures: no-common-ligatures;" class="">(exactly: </span><span style="font-variant-ligatures: no-common-ligatures; color: rgb(112, 61, 170);" class="">Double</span><span style="font-variant-ligatures: no-common-ligatures;" class="">.</span><span style="font-variant-ligatures: no-common-ligatures; color: rgb(112, 61, 170);" class="">pi</span><span style="font-variant-ligatures: no-common-ligatures;" class="">) </span><span style="font-variant-ligatures: no-common-ligatures; color: rgb(186, 45, 162);" class="">as</span><span style="font-variant-ligatures: no-common-ligatures;" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: rgb(186, 45, 162);" class="">Any</span><span style="font-variant-ligatures: no-common-ligatures;" class="">)</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: rgb(0, 0, 0);" class=""> </span><span style="font-variant-ligatures: no-common-ligatures;" class="">// nil</span></div></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo;" class=""><span style="font-variant-ligatures: no-common-ligatures;" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: rgb(62, 30, 129);" class="">print</span><span style="font-variant-ligatures: no-common-ligatures;" class="">(</span><span style="font-variant-ligatures: no-common-ligatures; color: rgb(112, 61, 170);" class="">Float</span><span style="font-variant-ligatures: no-common-ligatures;" class="">(exactly: </span><span style="font-variant-ligatures: no-common-ligatures; color: rgb(112, 61, 170);" class="">NSNumber</span><span style="font-variant-ligatures: no-common-ligatures;" class="">(value: </span><span style="font-variant-ligatures: no-common-ligatures; color: rgb(112, 61, 170);" class="">Double</span><span style="font-variant-ligatures: no-common-ligatures;" class="">.</span><span style="font-variant-ligatures: no-common-ligatures; color: rgb(112, 61, 170);" class="">pi</span><span style="font-variant-ligatures: no-common-ligatures;" class="">)) </span><span style="font-variant-ligatures: no-common-ligatures; color: rgb(186, 45, 162);" class="">as</span><span style="font-variant-ligatures: no-common-ligatures;" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: rgb(186, 45, 162);" class="">Any</span><span style="font-variant-ligatures: no-common-ligatures;" class="">)</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: rgb(0, 0, 0);" class=""> </span><span style="font-variant-ligatures: no-common-ligatures;" class="">// Optional(3.14159274)</span></div><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures;" class=""><br class=""></span></div><div style="margin: 0px; line-height: normal; color: rgb(0, 132, 0);" class=""><span style="color: rgb(0, 0, 0);" class="">I realize that identical behavior would be logical and least surprising. My only concern was about cases like</span></div></div><div class=""><span style="color: rgb(0, 0, 0);" class=""><br class=""></span></div><div class=""><div style="margin: 0px; line-height: normal;" class=""><div style="font-family: Menlo; font-size: 11px; margin: 0px; line-height: normal; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">let</span><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> num = ... </span><span style="font-variant-ligatures: no-common-ligatures" class="">// some NSNumber from a JSON deserialization</span></div><div style="font-family: Menlo; font-size: 11px; margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""> </span><span style="font-variant-ligatures: no-common-ligatures; color: #ba2da2" class="">let</span><span style="font-variant-ligatures: no-common-ligatures" class=""> fval = </span><span style="font-variant-ligatures: no-common-ligatures; color: #703daa" class="">Float</span><span style="font-variant-ligatures: no-common-ligatures" class="">(exactly: </span><span style="font-variant-ligatures: no-common-ligatures; color: #4f8187" class="">num</span><span style="font-variant-ligatures: no-common-ligatures" class="">)</span></div><div style="font-family: Menlo; font-size: 11px; margin: 0px; line-height: normal;" class=""><span style="font-variant-ligatures: no-common-ligatures" class=""><br class=""></span></div><div style="margin: 0px; line-height: normal;" class="">where one cannot know how the number is represented internally and what precision it needs. But then one could use the truncating conversion or `.floatValue` instead.</div><div style="margin: 0px; line-height: normal;" class=""><br class=""></div></div></div><blockquote type="cite" class=""><div class=""><div dir="ltr" class=""><div class="gmail_extra"><br class=""></div><div class="gmail_extra"><br class=""><div class="gmail_quote">On Tue, Apr 18, 2017 at 11:43 AM, Philippe Hausler <span dir="ltr" class=""><<a href="mailto:phausler@apple.com" target="_blank" class="">phausler@apple.com</a>></span> wrote:<br class=""><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word;line-break:after-white-space" class=""><div class=""><div class="h5"><br class=""><div class=""><blockquote type="cite" class=""><div class="">On Apr 18, 2017, at 9:22 AM, Stephen Canon <<a href="mailto:scanon@apple.com" target="_blank" class="">scanon@apple.com</a>> wrote:</div><br class="m_-6340981287830468260Apple-interchange-newline"><div class=""><blockquote type="cite" 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" class=""><br class="m_-6340981287830468260Apple-interchange-newline">On Apr 18, 2017, at 12:17 PM, Joe Groff <<a href="mailto:jgroff@apple.com" target="_blank" class="">jgroff@apple.com</a>> wrote:<br class=""><br class=""><br class=""><blockquote type="cite" class="">On Apr 17, 2017, at 5:56 PM, Xiaodi Wu via swift-evolution <<a href="mailto:swift-evolution@swift.org" target="_blank" class="">swift-evolution@swift.org</a>> wrote:<br class=""><br class="">It seems Float.init(exactly: NSNumber) has not been updated to behave similarly?<br class=""><br class="">I would have to say, I would naively expect "exactly" to behave exactly as it says, exactly. I don't think it should be a synonym for Float(Double(exactly:)).<br class="">On Mon, Apr 17, 2017 at 19:24 Philippe Hausler via swift-evolution <<a href="mailto:swift-evolution@swift.org" target="_blank" class="">swift-evolution@swift.org</a>> wrote:<br class="">I posted my branch and fixed up the Double case to account for your concerns (with a few inspired unit tests to validate)<br class=""><br class=""><a href="https://github.com/phausler/swift/tree/safe_nsnumber" target="_blank" class="">https://github.com/phausler/<wbr class="">swift/tree/safe_nsnumber</a><br class=""><br class="">There is a builtin assumption here though: it does presume that the swift’s representation of Double and Float are IEEE compliant. However that is a fairly reasonable assumption in the tests.<br class=""></blockquote><br class=""></blockquote></div></blockquote></div></div></div></div></blockquote></div></div></div></div></blockquote><div><br class=""></div><div><br class=""></div><div>Even with the updated code at <a href="https://github.com/phausler/swift/tree/safe_nsnumber" class="">https://github.com/phausler/swift/tree/safe_nsnumber</a><div class=""><br class=""></div><div class=""><span class="" style="font-family: Menlo; font-size: 11px; font-variant-ligatures: no-common-ligatures;"> </span><span class="" style="font-family: Menlo; font-size: 11px; font-variant-ligatures: no-common-ligatures; color: rgb(62, 30, 129);">print</span><span class="" style="font-family: Menlo; font-size: 11px; font-variant-ligatures: no-common-ligatures;">(</span><span class="" style="font-family: Menlo; font-size: 11px; font-variant-ligatures: no-common-ligatures; color: rgb(112, 61, 170);">Double</span><span class="" style="font-family: Menlo; font-size: 11px; font-variant-ligatures: no-common-ligatures;">(exactly: </span><span class="" style="font-family: Menlo; font-size: 11px; font-variant-ligatures: no-common-ligatures; color: rgb(112, 61, 170);">NSNumber</span><span class="" style="font-family: Menlo; font-size: 11px; font-variant-ligatures: no-common-ligatures;">(value: </span><span class="" style="font-family: Menlo; font-size: 11px; font-variant-ligatures: no-common-ligatures; color: rgb(112, 61, 170);">Int64</span><span class="" style="font-family: Menlo; font-size: 11px; font-variant-ligatures: no-common-ligatures;">(</span><span class="" style="font-family: Menlo; font-size: 11px; font-variant-ligatures: no-common-ligatures; color: rgb(39, 42, 216);">9000000000000000001</span><span class="" style="font-family: Menlo; font-size: 11px; font-variant-ligatures: no-common-ligatures;">))) </span><span class="" style="font-family: Menlo; font-size: 11px; font-variant-ligatures: no-common-ligatures; color: rgb(186, 45, 162);">as</span><span class="" style="font-family: Menlo; font-size: 11px; font-variant-ligatures: no-common-ligatures;"> </span><span class="" style="font-family: Menlo; font-size: 11px; font-variant-ligatures: no-common-ligatures; color: rgb(186, 45, 162);">Any</span><span class="" style="font-family: Menlo; font-size: 11px; font-variant-ligatures: no-common-ligatures;">)</span></div><div class=""><div style="margin: 0px; font-size: 11px; line-height: normal; font-family: Menlo; color: rgb(0, 132, 0);" class=""><span style="font-variant-ligatures: no-common-ligatures; color: #000000" class=""> </span><span style="font-variant-ligatures: no-common-ligatures" class="">// Optional(9e+18)</span></div><div class=""><br class=""></div><div class="">still succeeds, however the reason seems to be an error in the `init(exactly value: someIntegerType)` inititializers of Float/Double, I have submitted a bug report: <a href="https://bugs.swift.org/browse/SR-4634" class="">https://bugs.swift.org/browse/SR-4634</a>.</div><div class=""><br class=""></div></div></div><br class=""><blockquote type="cite" class=""><div class=""><div dir="ltr" class=""><div class="gmail_extra"><div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div style="word-wrap:break-word;line-break:after-white-space" class=""><div class=""><div class="h5"><div class=""><blockquote type="cite" class=""><div class=""><blockquote type="cite" 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" class="">(+Steve Canon) What is the behavior of Float.init(exactly: Double)? NSNumber's behavior would ideally be consistent with that.<br class=""></blockquote><br 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" class=""><span 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;float:none;display:inline!important" class="">The implementation is essentially just:</span><br 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" class=""><br 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" class=""><span class="m_-6340981287830468260Apple-tab-span" 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:pre-wrap;word-spacing:0px"> </span><span 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;float:none;display:inline!important" class="">self.init(other)</span><br 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" class=""><span class="m_-6340981287830468260Apple-tab-span" 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:pre-wrap;word-spacing:0px"> </span><span 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;float:none;display:inline!important" class="">guard Double(self) == other else {</span><br 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" class=""><span class="m_-6340981287830468260Apple-tab-span" 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:pre-wrap;word-spacing:0px"> </span><span class="m_-6340981287830468260Apple-tab-span" 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:pre-wrap;word-spacing:0px"> </span><span 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;float:none;display:inline!important" class="">return nil</span><br 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" class=""><span class="m_-6340981287830468260Apple-tab-span" 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:pre-wrap;word-spacing:0px"> </span><span 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;float:none;display:inline!important" class="">}</span><br 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" class=""><br 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" class=""><span 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;float:none;display:inline!important" class="">i.e. if the result is not equal to the source when round-tripped back to double (which is always exact), the result is nil.</span><br 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" class=""><br 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" class=""><span 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;float:none;display:inline!important" class="">– Steve</span></div></blockquote></div><br class=""></div></div><div class="">Pretty much the same trick inside of CFNumber/NSNumber</div></div></blockquote></div><br class=""></div></div>
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