mp-units/HEAD/api_reference/gen/qty.get.common.base.html

<!DOCTYPE html><html lang='en'><head><title>[qty.get.common.base]</title><meta charset='UTF-8'/><link rel='stylesheet' type='text/css' href='14882.css'/><link rel='stylesheet' type='text/css' href='https://fonts.googleapis.com/css2?family=Noto+Serif'/><link rel='stylesheet' type='text/css' href='https://fonts.googleapis.com/css2?family=Noto+Sans'/><link rel='stylesheet' type='text/css' href='https://fonts.googleapis.com/css2?family=Noto+Sans+Mono'/><link rel='icon' href='icon.png'/><link rel='stylesheet' type='text/css' href='expanded.css' title='Normal'/><link rel='alternate stylesheet' type='text/css' href='colored.css' title='Notes and examples colored'/><link rel='alternate stylesheet' type='text/css' href='normative-only.css' title='Notes and examples hidden'/></head><body><div class='wrapper'><h1 ><a class='secnum' style='min-width:50pt'>5</a> Quantities and units library <a class='abbr_ref' href='index.html#quantities'>[quantities]</a></h1><h2 ><a class='secnum' style='min-width:65pt'>5.4</a> Reference <a class='abbr_ref' href='qty.ref.html#qty.get.common.base'>[qty.ref]</a></h2><h3 ><a class='secnum' style='min-width:80pt'>5.4.3</a> Quantity specification <a class='abbr_ref' href='qty.spec.html#qty.get.common.base'>[qty.spec]</a></h3><h4 ><a class='secnum' style='min-width:95pt'>5.4.3.6</a> Hierarchy algorithms <a class='abbr_ref' href='qty.spec.hier.algos.html#qty.get.common.base'>[qty.spec.hier.algos]</a></h4><h4 ><a class='secnum' style='min-width:110pt'>5.4.3.6.4</a> Get common base <a class='abbr_ref'>[qty.get.common.base]</a></h4><div class='para' id='1'><div class='marginalizedparent'><a class='marginalized' href='#1'>1</a></div><div class='sourceLinkParent'><a class='sourceLink' href='https://github.com/mpusz/mp-unitse9c5f7236ebfe1b287a5a4a49aaf57fbefa87233/source/quantities.tex#L2216'>#</a></div><div class='texpara'><div id='1.sentence-1' class='sentence'>In this subclause and <a href='qty.is.child.of.html' title='5.4.3.6.5&emsp;Is child of'>[qty.<span class='shy'></span>is.<span class='shy'></span>child.<span class='shy'></span>of]</a>,
let the kind of quantity (<a href="https://www.electropedia.org/iev/iev.nsf/display?openform&ievref=112-01-04">IEC 60050, 112-01-04</a>) hierarchy of <span class='texttt'>q</span> be the tuple
<span class="mjx-chtml"><span class="mjx-math"><span class="mjx-mrow" aria-hidden="true"><span class="mjx-mi"><span class="mjx-char MJXc-TeX-math-I" style="padding-top: 0.446em; padding-bottom: 0.298em;">h</span></span><span class="mjx-mo"><span class="mjx-char MJXc-TeX-main-R" style="padding-top: 0.446em; padding-bottom: 0.593em;">(</span></span><span class="mjx-texatom"><span class="mjx-mrow"><span class="mjx-mtext"><span class="mjx-char MJXc-TeX-type-R" style="padding-top: 0.225em; padding-bottom: 0.519em;">q</span></span></span></span><span class="mjx-mo"><span class="mjx-char MJXc-TeX-main-R" style="padding-top: 0.446em; padding-bottom: 0.593em;">)</span></span><span class="mjx-mo MJXc-space3"><span class="mjx-char MJXc-TeX-main-R" style="padding-top: 0.077em; padding-bottom: 0.298em;">=</span></span><span class="mjx-mo MJXc-space3"><span class="mjx-char MJXc-TeX-main-R" style="padding-top: 0.446em; padding-bottom: 0.593em;">(</span></span><span class="mjx-texatom"><span class="mjx-mrow"><span class="mjx-mtext"><span class="mjx-char MJXc-TeX-type-R" style="padding-top: 0.225em; padding-bottom: 0.519em;">q</span></span></span></span><span class="mjx-mo"><span class="mjx-char MJXc-TeX-main-R" style="margin-top: -0.144em; padding-bottom: 0.519em;">,</span></span><span class="mjx-texatom MJXc-space1"><span class="mjx-mrow"><span class="mjx-mtext"><span class="mjx-char MJXc-TeX-type-R" style="padding-top: 0.225em; padding-bottom: 0.519em;">q<span class='operator'>.</span>par</span></span></span></span><span class="mjx-mo"><span class="mjx-char MJXc-TeX-main-R" style="margin-top: -0.144em; padding-bottom: 0.519em;">,</span></span><span class="mjx-texatom MJXc-space1"><span class="mjx-mrow"><span class="mjx-mtext"><span class="mjx-char MJXc-TeX-type-R" style="padding-top: 0.225em; padding-bottom: 0.519em;">q<span class='operator'>.</span>par<span class='operator'>.</span>par</span></span></span></span><span class="mjx-mo"><span class="mjx-char MJXc-TeX-main-R" style="margin-top: -0.144em; padding-bottom: 0.519em;">,</span></span><span class="mjx-mo MJXc-space1"><span class="mjx-char MJXc-TeX-main-R" style="margin-top: -0.144em; padding-bottom: 0.372em;">…</span></span><span class="mjx-texatom MJXc-space1"><span class="mjx-mrow"></span></span><span class="mjx-mo"><span class="mjx-char MJXc-TeX-main-R" style="padding-top: 0.446em; padding-bottom: 0.593em;">)</span></span></span></span></span>,
where <span class='texttt'>par</span> is <span class='texttt'><i >parent</i></span><a class='hidden_link' href='#1.sentence-1'>.</a></div></div></div><div class='texpara'><div id='lib:get-common-base,QuantitySpec'><div id='lib:QuantitySpec,get-common-base'><div class='itemdecl'><div class='marginalizedparent'><a class='itemDeclLink' href='#lib:QuantitySpec,get-common-base'>🔗</a></div><code class='itemdeclcode'><span class='keyword'>template</span><span class='anglebracket'>&lt;</span><a href='qty.spec.concepts.html#concept:QuantitySpec' title='5.4.3.2&emsp;Concepts&emsp;[qty.spec.concepts]'><span id='conceptref:QuantitySpec'><span class='texttt'>QuantitySpec</span></span></a> <span class='keyword'>auto</span> A, <a href='qty.spec.concepts.html#concept:QuantitySpec' title='5.4.3.2&emsp;Concepts&emsp;[qty.spec.concepts]'><span id='conceptref:QuantitySpec_'><span class='texttt'>QuantitySpec</span></span></a> <span class='keyword'>auto</span> B<span class='anglebracket'>&gt;</span>
<span class='keyword'>consteval</span> <span class='keyword'>auto</span> <span class='texttt'><i >get-common-base</i></span><span class='parenthesis'>(</span><span class='parenthesis'>)</span>;  <span class='comment'>// <i >exposition only</i></span>
</code></div></div></div></div><div class='para' id='2'><div class='marginalizedparent'><a class='marginalized' href='#2'>2</a></div><div class='itemdescr'><div class='sourceLinkParent'><a class='sourceLink' href='https://github.com/mpusz/mp-unitse9c5f7236ebfe1b287a5a4a49aaf57fbefa87233/source/quantities.tex#L2229'>#</a></div><div class='texpara'><div id='2.sentence-1' class='sentence'>Let
<ul class='itemize'><li id='2.1'><div class='marginalizedparent' style='left:-39mm'><a class='marginalized' href='#2.1'>(2.1)</a></div><span class="mjx-chtml"><span class="mjx-math"><span class="mjx-mrow" aria-hidden="true"><span class="mjx-msubsup"><span class="mjx-base"><span class="mjx-mi"><span class="mjx-char MJXc-TeX-math-I" style="padding-top: 0.225em; padding-bottom: 0.298em;">a</span></span></span><span class="mjx-sub" style="font-size: 70.7%; vertical-align: -0.212em; padding-right: 0.071em;"><span class="mjx-mi"><span class="mjx-char MJXc-TeX-math-I" style="padding-top: 0.225em; padding-bottom: 0.298em;">s</span></span></span></span></span></span></span> be the number of elements in <span class='math'><span class='mathalpha'>h</span>(<span class='texttt'>A</span>)</span>,</li><li id='2.2'><div class='marginalizedparent' style='left:-39mm'><a class='marginalized' href='#2.2'>(2.2)</a></div><span class="mjx-chtml"><span class="mjx-math"><span class="mjx-mrow" aria-hidden="true"><span class="mjx-msubsup"><span class="mjx-base"><span class="mjx-mi"><span class="mjx-char MJXc-TeX-math-I" style="padding-top: 0.446em; padding-bottom: 0.298em;">b</span></span></span><span class="mjx-sub" style="font-size: 70.7%; vertical-align: -0.212em; padding-right: 0.071em;"><span class="mjx-mi"><span class="mjx-char MJXc-TeX-math-I" style="padding-top: 0.225em; padding-bottom: 0.298em;">s</span></span></span></span></span></span></span> be the number of elements in <span class='math'><span class='mathalpha'>h</span>(<span class='texttt'>B</span>)</span>,</li><li id='2.3'><div class='marginalizedparent' style='left:-39mm'><a class='marginalized' href='#2.3'>(2.3)</a></div><span class='math'><span class='mathalpha'>s</span></span> be <span class="mjx-chtml"><span class="mjx-math"><span class="mjx-mrow" aria-hidden="true"><span class="mjx-mi"><span class="mjx-char MJXc-TeX-main-R" style="padding-top: 0.372em; padding-bottom: 0.372em;">min</span></span><span class="mjx-mo"><span class="mjx-char"></span></span><span class="mjx-mo"><span class="mjx-char MJXc-TeX-main-R" style="padding-top: 0.446em; padding-bottom: 0.593em;">(</span></span><span class="mjx-msubsup"><span class="mjx-base"><span class="mjx-mi"><span class="mjx-char MJXc-TeX-math-I" style="padding-top: 0.225em; padding-bottom: 0.298em;">a</span></span></span><span class="mjx-sub" style="font-size: 70.7%; vertical-align: -0.212em; padding-right: 0.071em;"><span class="mjx-mi"><span class="mjx-char MJXc-TeX-math-I" style="padding-top: 0.225em; padding-bottom: 0.298em;">s</span></span></span></span><span class="mjx-mo"><span class="mjx-char MJXc-TeX-main-R" style="margin-top: -0.144em; padding-bottom: 0.519em;">,</span></span><span class="mjx-msubsup MJXc-space1"><span class="mjx-base"><span class="mjx-mi"><span class="mjx-char MJXc-TeX-math-I" style="padding-top: 0.446em; padding-bottom: 0.298em;">b</span></span></span><span class="mjx-sub" style="font-size: 70.7%; vertical-align: -0.212em; padding-right: 0.071em;"><span class="mjx-mi"><span class="mjx-char MJXc-TeX-math-I" style="padding-top: 0.225em; padding-bottom: 0.298em;">s</span></span></span></span><span class="mjx-mo"><span class="mjx-char MJXc-TeX-main-R" style="padding-top: 0.446em; padding-bottom: 0.593em;">)</span></span></span></span></span>,</li><li id='2.4'><div class='marginalizedparent' style='left:-39mm'><a class='marginalized' href='#2.4'>(2.4)</a></div><span class='math'><span class='mathalpha'>A</span></span> be a tuple of the last <span class='math'><span class='mathalpha'>s</span></span> elements of <span class='math'><span class='mathalpha'>h</span>(<span class='texttt'>A</span>)</span>, and</li><li id='2.5'><div class='marginalizedparent' style='left:-39mm'><a class='marginalized' href='#2.5'>(2.5)</a></div><span class='math'><span class='mathalpha'>B</span></span> be a tuple of the last <span class='math'><span class='mathalpha'>s</span></span> elements of <span class='math'><span class='mathalpha'>h</span>(<span class='texttt'>B</span>)</span><a class='hidden_link' href='#2.sentence-1'>.</a></li>