keyword">double</span> <span class="special">&gt;</span> <span class="identifier">state_type</span><span class="special">;</span>

<span class="keyword">const</span> <span class="keyword">double</span> <span class="identifier">gam</span> <span class="special">=</span> <span class="number">0.15</span><span class="special">;</span>

<span class="comment">/* The rhs of x' = f(x) */</span>
<span class="keyword">void</span> <span class="identifier">harmonic_oscillator</span><span class="special">(</span> <span c