mp-units/HEAD/api_reference/gen/qty.cons.html

<!DOCTYPE html><html lang='en'><head><title>[qty.cons]</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'>5.6</a> Quantity <a class='abbr_ref' href='qty.html#cons'>[qty]</a></h2><h3 ><a class='secnum' style='min-width:80pt'>5.6.5</a> Constructors and assignment <a class='abbr_ref'>[qty.cons]</a></h3><div class='texpara'><div id='lib:quantity,constructor'><div class='itemdecl'><div class='marginalizedparent'><a class='itemDeclLink' href='#lib:quantity,constructor'>🔗</a></div><code class='itemdeclcode'><span class='keyword'>template</span><span class='anglebracket'>&lt;</span><span class='keyword'>typename</span> FwdValue, <a href='qty.ref.concepts.html#concept:Reference' title='5.4.5&emsp;Concepts&emsp;[qty.ref.concepts]'><span id='conceptref:Reference'><span class='texttt'>Reference</span></span></a> R2<span class='anglebracket'>&gt;</span>
  <span class='keyword'>requires</span> <a class='index' id='conceptref:SameValueAs'></a><span class='texttt'><i >SameValueAs</i></span><span class='anglebracket'>&lt;</span>R2<span class='curlybracket'>{</span><span class='curlybracket'>}</span>, R, std<span class='operator'>::</span>remove_cvref_t<span class='anglebracket'>&lt;</span>FwdValue<span class='anglebracket'>&gt;</span>, Rep<span class='anglebracket'>&gt;</span>
<span class='keyword'>constexpr</span> quantity<span class='parenthesis'>(</span>FwdValue<span class='operator'>&amp;</span><span class='operator'>&amp;</span> v, R2<span class='parenthesis'>)</span>;

<span class='keyword'>template</span><span class='anglebracket'>&lt;</span><a class='index' id='conceptref:ValuePreservingTo'></a><span class='texttt'><i >ValuePreservingTo</i></span><span class='anglebracket'>&lt;</span>Rep<span class='anglebracket'>&gt;</span> FwdValue<span class='anglebracket'>&gt;</span>
  <span class='keyword'>requires</span><span class='parenthesis'>(</span>unit <span class='operator'>=</span><span class='operator'>=</span> <span class='operator'>::</span>mp_units<span class='operator'>::</span>one<span class='parenthesis'>)</span>
<span class='keyword'>constexpr</span> quantity<span class='parenthesis'>(</span>FwdValue<span class='operator'>&amp;</span><span class='operator'>&amp;</span> v<span class='parenthesis'>)</span>;
</code></div></div></div><div class='para' id='1'><div class='marginalizedparent'><a class='marginalized' href='#1'>1</a></div><div class='itemdescr'><div class='sourceLinkParent'><a class='sourceLink' href='https://github.com/mpusz/mp-unitse9c5f7236ebfe1b287a5a4a49aaf57fbefa87233/source/quantities.tex#L4517'>#</a></div><div class='texpara'><div id='1.sentence-1' class='sentence'><i >Effects</i>: Initializes <span class='texttt'><i >numerical-value</i></span> with <span class='texttt'>std<span class='operator'>&#x200b;::&#x200b;</span>forward<span class='anglebracket'>&lt;</span>FwdValue<span class='anglebracket'>&gt;</span><span class='parenthesis'>(</span>v<span class='parenthesis'>)</span></span><a class='hidden_link' href='#1.sentence-1'>.</a></div></div></div></div><div class='texpara'><div id='lib:quantity,constructor_'><div class='itemdecl'><div class='marginalizedparent'><a class='itemDeclLink' href='#lib:quantity,constructor_'>🔗</a></div><code class='itemdeclcode'><span class='keyword'>template</span><span class='anglebracket'>&lt;</span><span class='keyword'>typename</span> FwdValue, <a href='qty.ref.concepts.html#concept:Reference' title='5.4.5&emsp;Concepts&emsp;[qty.ref.concepts]'><span id='conceptref:Reference_'><span class='texttt'>Reference</span></span></a> R2, <span class='keyword'>typename</span> Value <span class='operator'>=</span> std<span class='operator'>::</span>remove_cvref_t<span class='anglebracket'>&lt;</span>FwdValue<span class='anglebracket'>&gt;</span><span class='anglebracket'>&gt;</span>
  <span class='keyword'>requires</span><span class='parenthesis'>(</span><span class='operator'>!</span><a class='index' id='conceptref:SameValueAs_'></a><span class='texttt'><i >SameValueAs</i></span><span class='anglebracket'>&lt;</span>R2<span class='curlybracket'>{</span><span class='curlybracket'>}</span>, R, Value, Rep<span class='anglebracket'>&gt;</span><span class='parenthesis'>)</span> <span class='operator'>&amp;</span><span class='operator'>&amp;</span>
          <a class='index' id='conceptref:QuantityConvertibleTo'></a><span class='texttt'><i >QuantityConvertibleTo</i></span><span class='anglebracket'>&lt;</span>quantity<span class='anglebracket'>&lt;</span>R2<span class='curlybracket'>{</span><span class='curlybracket'>}</span>, Value<span class='anglebracket'>&gt;</span>, quantity<span class='anglebracket'>&gt;</span>
<span class='keyword'>constexpr</span> quantity<span class='parenthesis'>(</span>FwdValue<span class='operator'>&amp;</span><span class='operator'>&amp;</span> v, R2<span class='parenthesis'>)</span>;
</code></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#L4531'>#</a></div><div class='texpara'><div id='2.sentence-1' class='sentence'><i >Effects</i>: Equivalent to
<span class='texttt'>quantity<span class='parenthesis'>(</span>quantity<span class='anglebracket'>&lt;</span>R2<span class='curlybracket'>{</span><span class='curlybracket'>}</span>, Value<span class='anglebracket'>&gt;</span><span class='curlybracket'>{</span>std<span class='operator'>&#x200b;::&#x200b;</span>forward<span class='anglebracket'>&lt;</span>FwdValue<span class='anglebracket'>&gt;</span><span class='parenthesis'>(</span>v<span class='parenthesis'>)</span>, R2<span class='curlybracket'>{</span><span class='curlybracket'>}</span><span class='curlybracket'>}</span><span class='parenthesis'>)</span></span><a class='hidden_link' href='#2.sentence-1'>.</a></div></div></div></div><div class='texpara'><div id='lib:quantity,constructor__'><div class='itemdecl'><div class='marginalizedparent'><a class='itemDeclLink' href='#lib:quantity,constructor__'>🔗</a></div><code class='itemdeclcode'><span class='keyword'>template</span><span class='anglebracket'>&lt;</span><a class='index' id='conceptref:QuantityConvertibleTo_'></a><span class='texttt'><i >QuantityConvertibleTo</i></span><span class='anglebracket'>&lt;</span>quantity<span class='anglebracket'>&gt;</span> Q<span class='anglebracket'>&gt;</span>
<span class='keyword'>constexpr</span> <span class='keyword'>explicit</span><span class='parenthesis'>(</span><span class='operator'>!</span>std<span class='operator'>::</span>convertible_to<span class='anglebracket'>&lt;</span><span class='keyword'>typename</span> Q<span class='operator'>::</span>rep, Rep<span class='anglebracket'>&gt;</span><span class='parenthesis'>)</span> quantity<span class='parenthesis'>(</span><span class='keyword'>const</span> Q<span class='operator'>&amp;</span> q<span class='parenthesis'>)</span>;
</code></div></div></div><div class='para' id='3'><div class='marginalizedparent'><a class='marginalized' href='#3'>3</a></div><div class='itemdescr'><div class='sourceLinkParent'><a class='sourceLink' href='https://github.com/mpusz/mp-unitse9c5f7236ebfe1b287a5a4a49aaf57fbefa87233/source/quantities.tex#L4544'>#</a></div><div class='texpara'><div id='3.sentence-1' class='sentence'><i >Effects</i>: Equivalent to <span class='texttt'><span class='texttt'><i >sudo-cast</i></span><span class='anglebracket'>&lt;</span>quantity<span class='anglebracket'>&gt;</span><span class='parenthesis'>(</span>q<span class='parenthesis'>)</span></span> (<a href='qty.non.mem.conv.html' title='5.6.15&emsp;Non-member conversions'>[qty.<span class='shy'></span>non.<span class='shy'></span>mem.<span class='shy'></span>conv]</a>)<a class='hidden_link' href='#3.sentence-1'>.</a></div></div></div></div><div class='texpara'><div id='lib:quantity,constructor___'><div class='itemdecl'><div class='marginalizedparent'><a class='itemDeclLink' href='#lib:quantity,constructor___'>🔗</a></div><code class='itemdeclcode'><span class='keyword'>template</span><span class='anglebracket'>&lt;</span><a href='qty.like.html#concept:QuantityLike' title='5.6.2&emsp;Interoperability&emsp;[qty.like]'><span id='conceptref:QuantityLike'><span class='texttt'>QuantityLike</span></span></a> Q<span class='anglebracket'>&gt;</span>
  <span class='keyword'>requires</span> <a class='index' id='conceptref:QuantityConvertibleTo__'></a><span class='texttt'><i >QuantityConvertibleTo</i></span><span class='anglebracket'>&lt;</span><span class='texttt'><i >quantity-like-type</i></span><span class='anglebracket'>&lt;</span>Q<span class='anglebracket'>&gt;</span>, quantity<span class='anglebracket'>&gt;</span>
<span class='keyword'>constexpr</span> <span class='keyword'>explicit</span><span class='parenthesis'>(</span><i ><span class='texttt'>see below</span></i><span class='parenthesis'>)</span> quantity<span class='parenthesis'>(</span><span class='keyword'>const</span> Q<span class='operator'>&amp;</span> q<span class='parenthesis'>)</span>;
</code></div></div></div><div class='para' id='4'><div class='marginalizedparent'><a class='marginalized' href='#4'>4</a></div><div class='itemdescr'><div class='sourceLinkParent'><a class='sourceLink' href='https://github.com/mpusz/mp-unitse9c5f7236ebfe1b287a5a4a49aaf57fbefa87233/source/quantities.tex#L4557'>#</a></div><div class='texpara'><div id='4.sentence-1' class='sentence'><i >Effects</i>: Equivalent to:
<span class='codeblock'>quantity<span class='parenthesis'>(</span><span class='operator'>::</span>mp_units<span class='operator'>::</span>quantity<span class='curlybracket'>{</span>quantity_like_traits<span class='anglebracket'>&lt;</span>Q<span class='anglebracket'>&gt;</span><span class='operator'>::</span>to_numerical_value<span class='parenthesis'>(</span>q<span class='parenthesis'>)</span>,
                              quantity_like_traits<span class='anglebracket'>&lt;</span>Q<span class='anglebracket'>&gt;</span><span class='operator'>::</span>reference<span class='curlybracket'>}</span><span class='parenthesis'>)</span>
</span></div></div></div></div><div class='para' id='5'><div class='marginalizedparent'><a class='marginalized' href='#5'>5</a></div><div class='itemdescr'><div class='sourceLinkParent'><a class='sourceLink' href='https://github.com/mpusz/mp-unitse9c5f7236ebfe1b287a5a4a49aaf57fbefa87233/source/quantities.tex#L4565'>#</a></div><div class='texpara'><div id='5.sentence-1' class='sentence'><i >Remarks</i>: The expression inside <span class='texttt'><span class='keyword'>explicit</span></span> is equivalent to:
<span class='codeblock'>quantity_like_traits<span class='anglebracket'>&lt;</span>Q<span class='anglebracket'>&gt;</span><span class='operator'>::</span>explicit_import <span class='operator'>|</span><span class='operator'>|</span>
  <span class='operator'>!</span>std<span class='operator'>::</span>convertible_to<span class='anglebracket'>&lt;</span><span class='keyword'>typename</span> quantity_like_traits<span class='anglebracket'>&lt;</span>Q<span class='anglebracket'>&gt;</span><span class='operator'>::</span>rep, Rep<span class='anglebracket'>&gt;</span>
</span></div></div></div></div><div class='texpara'><div id='lib:quantity,operator='><div id='lib:operator=,quantity'><div class='itemdecl'><div class='marginalizedparent'><a class='itemDeclLink' href='#lib:operator=,quantity'>🔗</a></div><code class='itemdeclcode'><span class='keyword'>template</span><span class='anglebracket'>&lt;</span><a class='index' id='conceptref:ValuePreservingTo_'></a><span class='texttt'><i >ValuePreservingTo</i></span><span class='anglebracket'>&lt;</span>Rep<span class='anglebracket'>&gt;</span> FwdValue<span class='anglebracket'>&gt;</span>
  <span class='keyword'>requires</span><span class='parenthesis'>(</span>unit <span class='operator'>=</span><span class='operator'>=</span> <span class='operator'>::</span>mp_units<span class='operator'>::</span>one<span class='parenthesis'>)</span>
<span class='keyword'>constexpr</span> quantity<span class='operator'>&amp;</span> <span class='keyword'>operator</span><span class='operator'>=</span><span class='parenthesis'>(</span>FwdValue<span class='operator'>&amp;</span><span class='operator'>&amp;</span> v<span class='parenthesis'>)</span>;
</code></div></div></div></div><div class='para' id='6'><div class='marginalizedparent'><a class='marginalized' href='#6'>6</a></div><div class='itemdescr'><div class='sourceLinkParent'><a class='sourceLink' href='https://github.com/mpusz/mp-unitse9c5f7236ebfe1b287a5a4a49aaf57fbefa87233/source/quantities.tex#L4582'>#</a></div><div class='texpara'><div id='6.sentence-1' class='sentence'><i >Effects</i>: Equivalent to <span class='texttt'><span class='texttt'><i >numerical-value</i></span> <span class='operator'>=</span> std<span class='operator'>&#x200b;::&#x200b;</span>forward<span class='anglebracket'>&lt;</span>FwdValue<span class='anglebracket'>&gt;</span><span class='parenthesis'>(</span>v<span class='parenthesis'>)</span></span><a class='hidden_link' href='#6.sentence-1'>.</a></div></div></div></div><div class='para' id='7'><div class='marginalizedparent'><a class='marginalized' href='#7'>7</a></div><div class='itemdescr'><div class='sourceLinkParent'><a class='sourceLink' href='https://github.com/mpusz/mp-unitse9c5f7236ebfe1b287a5a4a49aaf57fbefa87233/source/quantities.tex#L4586'>#</a></div><div class='texpara'><div id='7.sentence-1' class='sentence'><i >Returns</i>: <span class='texttt'><span class='operator'>*</span><span class='keyword'>this</span></span><a class='hidden_link' href='#7.sentence-1'>.</a></div></div></div></div></div></body></html>