<html aria-label="message body"><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body style="overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;">The forwarded message below from Joseph Myers points out that the range bounds issue addressed by CFP’s N3731 does cover the same issue for complex functions. Here is possible rewording to address the issue for cacos (7.3.5.1). Similar rewording is needed for casin, catan, cacosh, casinh and catanh.<div><br></div><div>+++++</div><div><br></div><div>Change to 7.3.5.1:</div><div><br></div><div>FROM:</div><div><br></div><div><div><b>Description</b></div><div>2 The <font face="Courier New">cacos</font> functions compute the complex arc cosine of <i>z</i>, with branch cuts outside the interval [−1, +1] along the real axis.</div><div><br></div><div><b>Returns</b></div><div>3 The <font face="Courier New">cacos</font> functions return the complex arc cosine value, in the range of a strip mathematically unbounded along the imaginary axis and in the interval [0, <i>pi</i>] along the real axis.</div></div><div><br></div><div>TO:</div><div><br></div><div><b>Description</b></div><div><div>2 The <font face="Courier New">cacos</font> functions compute the branch of the complex arc sine of <i>z</i> whose range is the strip unbounded along the imaginary axis and in the interval [0, <i>pi</i>] along the real axis, with branch cuts outside the interval [-1, +1] along the real axis.</div><div><br></div><div><b>Returns</b></div><div>3 The <font face="Courier New">cacos</font> functions return the complex arc cosine of <i>z</i>.</div><div><br></div><div>4 NOTE The <font face="Courier New">cacos</font> functions, and similarly the <font face="Courier New">casin</font>, <font face="Courier New">catan</font>, <font face="Courier New">cacosh</font>, <font face="Courier New">casinh</font> and <font face="Courier New">catanh</font> functions, can return a value outside the specified branch for the computed mathematical function. Because the branch has boundary points with a coordinate that is not representable as a floating-point number, even correct rounding can yield values outside the branch boundary, depending on the return type and rounding direction.</div><div><br></div><div>+++++</div><div><br></div><div>- Jim Thomas</div><div><br><blockquote type="cite"><div>On Apr 7, 2026, at 8:26 AM, Jim Thomas <jaswthomas@sbcglobal.net> wrote:</div><br class="Apple-interchange-newline"><div><meta http-equiv="content-type" content="text/html; charset=utf-8"><div style="overflow-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;">This regards action item<div><br></div><div><blockquote type="cite"><div style="margin: 0in; font-family: "Times New Roman", serif;"><span style="font-size: 10.5pt; font-family: Calibri, sans-serif;"> Jim: Add agenda item to fix range bounds problem for complex fcns (as done for real functions in N3731).<o:p></o:p></span></div></blockquote></div><div><br></div><div>Following is background for the discussion.</div><div><br></div><div>- Jim Thomas<br id="lineBreakAtBeginningOfMessage"><div><br><blockquote type="cite"><div>Begin forwarded message:</div><br class="Apple-interchange-newline"><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px;"><span style="font-family: -webkit-system-font, "Helvetica Neue", Helvetica, sans-serif;"><b>From: </b></span><span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif;">RAJAN BHAKTA <rbhakta@us.ibm.com><br></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px;"><span style="font-family: -webkit-system-font, "Helvetica Neue", Helvetica, sans-serif;"><b>Subject: </b></span><span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif;"><b>[SC22WG14.35726] N3731 Range bounds for math functions</b><br></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px;"><span style="font-family: -webkit-system-font, "Helvetica Neue", Helvetica, sans-serif;"><b>Date: </b></span><span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif;">March 5, 2026 at 3:19:10 PM PST<br></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px;"><span style="font-family: -webkit-system-font, "Helvetica Neue", Helvetica, sans-serif;"><b>To: </b></span><span style="font-family: -webkit-system-font, Helvetica Neue, Helvetica, sans-serif;">Joseph Myers <josmyers@redhat.com>, "sc22wg14@open-std.org" <sc22wg14@open-std.org><br></span></div><br><div>
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Thanks for the review!</div>
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<span style="text-transform: none;">CFP will look at making similar changes for cacos, casin, catan, cacosh, casinh, catanh in a future paper.</span><br>
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Regards,<br>
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<b>CFP</b></div>
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<b>From: </b>owner-sc22wg14@open-std.org <owner-sc22wg14@open-std.org> on behalf of Joseph Myers <josmyers@redhat.com><br>
<b>Date: </b>Monday, October 20, 2025 at 6:58 PM<br>
<b>To: </b>sc22wg14@open-std.org <sc22wg14@open-std.org><br>
<b>Subject: </b>[EXTERNAL] [SC22WG14.34179] N3731 Range bounds for math functions<br>
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<div class="PlainText" style="font-size: 11pt;">A comment on the N3731 proposal to reword specifications about the range<br>
of values for mathematical functions where correct rounding might produce<br>
a result outside a given interval:<br>
<br>
There's similar wording "in the interval" for various <complex.h><br>
functions, where I'd also expect that it should not be required that the<br>
rounded result actually lies inside that interval and so the wording<br>
should probably have similar changes: cacos, casin, catan, cacosh, casinh,<br>
catanh.<br>
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--<br>
Joseph S. Myers<br>
josmyers@redhat.com<br>
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</div></blockquote></div><br></div></div>_______________________________________________<br>cfp-interest mailing list<br>cfp-interest@oakapple.net<br>http://mailman.oakapple.net/mailman/listinfo/cfp-interest<br></div></blockquote></div><br></div></body></html>