title: Pointer type compile-time error in GSL ODE solution
body: <p>I'm working with the code on the GSL examples page to try to solve a system of four differential equations. I've been wrestling with passing five parameters to the ODE system, and have arrived at one final (I hope!) compile-time error. A snippet follows, giving me the error</p>
  
  <pre><code>114:57: error: invalid conversion from ‘int (*)(double, const double*, 
  double*, double**, void*)’ to ‘int (*)(double, const double*, double*, 
  double*, void*)’ [-fpermissive]
  </code></pre>
  
  <p>which corresponds to the line starting with <code>gsl_odeiv2_system</code>:</p>
  
  <pre><code>int main()
  {
    double t = 0.0;
    double y[4] = { 0.0, 0.0, 1.0, 1.0 };
    int i, s;
  
    struct pendula_params * info;
    info-&gt;m2 = 1.0;
    info-&gt;m1 = 1.0;
    info-&gt;l1 = 1.0;
    info-&gt;l2 = 1.0;
    info-&gt;g  = 1.0;
  
    gsl_odeiv2_system sys = { pendula, jacobian, 4, &amp;info };
  
    gsl_odeiv2_driver *d =
      gsl_odeiv2_driver_alloc_y_new (&amp;sys, gsl_odeiv2_step_msadams,
                                     1e-3, 1e-8, 1e-8);
  </code></pre>
  
  <p>Any thoughts on what might be going on?</p>
  
  <p>Many thanks,</p>
  
  <p>Mark C.</p>