fier">v</span> <span class="special">=</span> <span class="identifier">x</span> <span class="special">*</span> <span class="number">2</span> <span class="special">/</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">math</span><span class="special">::</span><span class="identifier">constants</span><span class="special">::</span><span class="identifier">pi</span><span class="special">&lt;</span><span class="identifier">mp_type</span><span class="special">&gt;(