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  <div class="section" id="placeholders">
<h1>placeholders<a class="headerlink" href="#placeholders" title="Permalink to this headline">¶</a></h1>
<div class="section" id="header">
<h2>Header<a class="headerlink" href="#header" title="Permalink to this headline">¶</a></h2>
<div class="highlight-cpp"><div class="highlight"><pre><span class="cp">#include</span> <span class="cpf">&lt;boost/hof/placeholders.hpp&gt;</span><span class="cp"></span>
</pre></div>
</div>
</div>
<div class="section" id="description">
<h2>Description<a class="headerlink" href="#description" title="Permalink to this headline">¶</a></h2>
<p>The placeholders provide <code class="docutils literal"><span class="pre">std::bind</span></code> compatible placeholders that
additionally provide basic C++ operators that creates bind expressions.
Each bind expression supports <code class="docutils literal"><span class="pre">constexpr</span></code> function evaluation.</p>
</div>
<div class="section" id="synopsis">
<h2>Synopsis<a class="headerlink" href="#synopsis" title="Permalink to this headline">¶</a></h2>
<div class="highlight-cpp"><div class="highlight"><pre><span class="k">namespace</span> <span class="n">placeholders</span> <span class="p">{</span>
    <span class="n">placeholder</span><span class="o">&lt;</span><span class="mi">1</span><span class="o">&gt;</span> <span class="n">_1</span> <span class="o">=</span> <span class="p">{};</span>
    <span class="n">placeholder</span><span class="o">&lt;</span><span class="mi">2</span><span class="o">&gt;</span> <span class="n">_2</span> <span class="o">=</span> <span class="p">{};</span>
    <span class="n">placeholder</span><span class="o">&lt;</span><span class="mi">3</span><span class="o">&gt;</span> <span class="n">_3</span> <span class="o">=</span> <span class="p">{};</span>
    <span class="n">placeholder</span><span class="o">&lt;</span><span class="mi">4</span><span class="o">&gt;</span> <span class="n">_4</span> <span class="o">=</span> <span class="p">{};</span>
    <span class="n">placeholder</span><span class="o">&lt;</span><span class="mi">5</span><span class="o">&gt;</span> <span class="n">_5</span> <span class="o">=</span> <span class="p">{};</span>
    <span class="n">placeholder</span><span class="o">&lt;</span><span class="mi">6</span><span class="o">&gt;</span> <span class="n">_6</span> <span class="o">=</span> <span class="p">{};</span>
    <span class="n">placeholder</span><span class="o">&lt;</span><span class="mi">7</span><span class="o">&gt;</span> <span class="n">_7</span> <span class="o">=</span> <span class="p">{};</span>
    <span class="n">placeholder</span><span class="o">&lt;</span><span class="mi">8</span><span class="o">&gt;</span> <span class="n">_8</span> <span class="o">=</span> <span class="p">{};</span>
    <span class="n">placeholder</span><span class="o">&lt;</span><span class="mi">9</span><span class="o">&gt;</span> <span class="n">_9</span> <span class="o">=</span> <span class="p">{};</span>
<span class="p">}</span>
</pre></div>
</div>
</div>
<div class="section" id="operators">
<h2>Operators<a class="headerlink" href="#operators" title="Permalink to this headline">¶</a></h2>
<ul class="simple">
<li>Binary operators: +,-,*,/,%,&gt;&gt;,&lt;&lt;,&gt;,&lt;,&lt;=,&gt;=,==,!=,&amp;,^,|,&amp;&amp;,||</li>
<li>Assign operators: +=,-=,*=,/=,%=,&gt;&gt;=,&lt;&lt;=,&amp;=,|=,^=</li>
<li>Unary operators: !,~,+,-,*,++,&#8211;</li>
</ul>
</div>
<div class="section" id="example">
<h2>Example<a class="headerlink" href="#example" title="Permalink to this headline">¶</a></h2>
<div class="highlight-cpp"><div class="highlight"><pre><span class="cp">#include</span> <span class="cpf">&lt;boost/hof.hpp&gt;</span><span class="cp"></span>
<span class="cp">#include</span> <span class="cpf">&lt;cassert&gt;</span><span class="cp"></span>
<span class="k">using</span> <span class="k">namespace</span> <span class="n">boost</span><span class="o">::</span><span class="n">hof</span><span class="p">;</span>

<span class="kt">int</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span>
    <span class="k">auto</span> <span class="n">sum</span> <span class="o">=</span> <span class="n">_1</span> <span class="o">+</span> <span class="n">_2</span><span class="p">;</span>
    <span class="n">assert</span><span class="p">(</span><span class="mi">3</span> <span class="o">==</span> <span class="n">sum</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">));</span>
<span class="p">}</span>
</pre></div>
</div>
</div>
</div>
<div class="section" id="unamed-placeholder">
<h1>unamed placeholder<a class="headerlink" href="#unamed-placeholder" title="Permalink to this headline">¶</a></h1>
<div class="section" id="id1">
<h2>Header<a class="headerlink" href="#id1" title="Permalink to this headline">¶</a></h2>
<div class="highlight-cpp"><div class="highlight"><pre><span class="cp">#include</span> <span class="cpf">&lt;boost/hof/placeholders.hpp&gt;</span><span class="cp"></span>
</pre></div>
</div>
</div>
<div class="section" id="id2">
<h2>Description<a class="headerlink" href="#id2" title="Permalink to this headline">¶</a></h2>
<p>The unamed placeholder can be used to build simple functions from C++
operators.</p>
<p>Note: The function produced by the unamed placeholder is not a bind expression.</p>
</div>
<div class="section" id="id3">
<h2>Synopsis<a class="headerlink" href="#id3" title="Permalink to this headline">¶</a></h2>
<div class="highlight-cpp"><div class="highlight"><pre><span class="k">namespace</span> <span class="n">placeholders</span> <span class="p">{</span>
    <span class="cm">/* unspecified */</span> <span class="n">_</span> <span class="o">=</span> <span class="p">{};</span>
<span class="p">}</span>
</pre></div>
</div>
</div>
<div class="section" id="id4">
<h2>Example<a class="headerlink" href="#id4" title="Permalink to this headline">¶</a></h2>
<div class="highlight-cpp"><div class="highlight"><pre><span class="cp">#include</span> <span class="cpf">&lt;boost/hof.hpp&gt;</span><span class="cp"></span>
<span class="cp">#include</span> <span class="cpf">&lt;cassert&gt;</span><span class="cp"></span>
<span class="k">using</span> <span class="k">namespace</span> <span class="n">boost</span><span class="o">::</span><span class="n">hof</span><span class="p">;</span>

<span class="kt">int</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span>
    <span class="k">auto</span> <span class="n">sum</span> <span class="o">=</span> <span class="n">_</span> <span class="o">+</span> <span class="n">_</span><span class="p">;</span>
    <span class="n">assert</span><span class="p">(</span><span class="mi">3</span> <span class="o">==</span> <span class="n">sum</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">));</span>
<span class="p">}</span>
</pre></div>
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