title: How could I include this C++ function in my C code
body: <p>I have the following C function that is a part of a code written in C.</p>
  <pre><code>void pusher(int part, int ntime,long double x[3], long double v[3], long double E[3], long double B[3], long double Vth, long double c2, long double x_new[3], long double v_new[3]){
  
     long double x_mid[3];
     long double upart_new[3];
  
      // half time-step for Euler step
       long double dth = 0.5*dt;
      
      // position x_{i+1/2} at time t_{i+1/2} + dt/2 (1st-order Euler scheme)
      for(int i=0;i&lt;3;i++){
          x_mid[i] = x[i] + v[i]*dth;
      }
   
     // TO DO: Get E, B at new position 
  
     /* I want to add the Cpp function at this point in the code. */
     
    // interpolate_fields();
      
  
     // 'Kick' particle (update velocity) based on the chosen integrator
      switch(pusher_name) {
      case 1 :
          Vay(v, E, B, c2, upart_new);
          break;
          
      case 0  :
          Boris_relativ(v, E, B, c2, upart_new);
          break; 
               
      }
  
      long double gL_new = gamma_u(upart_new, c2);
      // full position update at t_{i+1} = t_{i+1/2} + dt/2 = t_i + dt
     for(int i=0;i&lt;3;i++){
          v_new[i]  = upart_new[i]/gL_new; 
          x_new[i]  = x_mid[i] + v_new[i]*dth;
          
     }
  
  }
  </code></pre>
  <p>I also have the following Cpp function that I would like to include at the indicated point in the code. To avoid including the Cpp code in the question, I have uploaded the file here:</p>
  <p><a href="https://www.dropbox.com/s/vbsxme9vozci4tz/ba_interp3.cpp?dl=0" rel="nofollow noreferrer">https://www.dropbox.com/s/vbsxme9vozci4tz/ba_interp3.cpp?dl=0</a></p>
  <p>Is this possible?</p>
  <p>Any suggestions for how I could do this?</p>