 class="special">::</span><span class="identifier">half_pi</span><span class="special">&lt;</span><span class="keyword">double</span><span class="special">&gt;())</span> <span class="special">+</span> <span class="identifier">pow</span><span class="special">(</span><span class="identifier">crossover</span><span class="special">,</span> <span class="number">1</span> <span class="special">-</span> <span class="identifier">p</span><span class="special">)</span> <span class="special">/</span> <span class="speci