https://svn.boost.org/trac10/ticket/13202 <p> I think the documentation for <code>adjacent_filtered</code>'s postcondition, ie: </p> <blockquote class="citation"> <p> For all adjacent elements <code>[x,y]</code> in the returned range, <code>bi_pred(x,y)</code> is <code>true</code>. </p> </blockquote> <p> …isn't quite right. For example, this: </p> <div class="wiki-code"><div class="code"><pre><span class="cp">#include</span> <span class="cpf">&lt;boost/range/adaptor/adjacent_filtered.hpp&gt;</span><span class="cp"></span> <span class="cp">#include</span> <span class="cpf">&lt;iostream&gt;</span><span class="cp"></span> <span class="cp">#include</span> <span class="cpf">&lt;vector&gt;</span><span class="cp"></span> <span class="kt">int</span> <span class="nf">main</span><span class="p">()</span> <span class="p">{</span> <span class="k">const</span> <span class="n">std</span><span class="o">::</span><span class="n">vector</span><span class="o">&lt;</span><span class="kt">int</span><span class="o">&gt;</span> <span class="n">a</span> <span class="o">=</span> <span class="p">{</span> <span class="mi">0</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="mi">3</span><span class="p">,</span> <span class="mi">4</span><span class="p">,</span> <span class="mi">5</span><span class="p">,</span> <span class="mi">6</span> <span class="p">};</span> <span class="k">const</span> <span class="k">auto</span> <span class="n">b</span> <span class="o">=</span> <span class="n">a</span> <span class="o">|</span> <span class="n">boost</span><span class="o">::</span><span class="n">adaptors</span><span class="o">::</span><span class="n">adjacent_filtered</span><span class="p">(</span> <span class="p">[]</span> <span class="p">(</span><span class="k">const</span> <span class="kt">int</span> <span class="o">&amp;</span><span class="n">x</span><span class="p">,</span> <span class="k">const</span> <span class="kt">int</span> <span class="o">&amp;</span><span class="n">y</span><span class="p">)</span> <span class="p">{</span> <span class="k">return</span> <span class="p">(</span> <span class="n">y</span> <span class="o">%</span> <span class="mi">2</span> <span class="o">==</span> <span class="mi">1</span> <span class="p">)</span> <span class="o">&amp;&amp;</span> <span class="p">(</span> <span class="n">y</span> <span class="o">==</span> <span class="n">x</span> <span class="o">+</span> <span class="mi">1</span> <span class="p">);</span> <span class="p">}</span> <span class="p">);</span> <span class="k">for</span> <span class="p">(</span><span class="k">const</span> <span class="k">auto</span> <span class="o">&amp;</span><span class="nl">x</span> <span class="p">:</span> <span class="n">b</span><span class="p">)</span> <span class="p">{</span> <span class="n">std</span><span class="o">::</span><span class="n">cerr</span> <span class="o">&lt;&lt;</span> <span class="n">x</span> <span class="o">&lt;&lt;</span> <span class="s">&quot;</span><span class="se">\n</span><span class="s">&quot;</span><span class="p">;</span> <span class="p">}</span> <span class="p">}</span> </pre></div></div><p> …outputs: </p> <pre class="wiki">0 1 3 5 </pre><p> Yet two of the pairs of adjacent elements <code>[x,y]</code> in this range fail <code>bi_pred(x,y)</code> (because they differ by 2, not 1). </p> <p> I think it's more like: <code>bi_pred</code> is true on each element in the returned range preceded by the element that preceded it in the <em>original</em> range (not in the <em>returned</em> range). </p> en-us /htdocs/site/boost.png https://svn.boost.org/trac10/ticket/13202 Trac 1.4.3