text: #ifndef MASS_EQUATION_HPP
  #define MASS_EQUATION_HPP
  
  /*!
      Calculates the pressure coefficients.
      
      Those coefficients are related to the mass conservation equation and 
      generates a linear system which the pressure is the main variable.
  */
  void calculate_pressure_coefficients(
      int nv,
      double dx,
      double dy,
      double rho,
      double **u_hat,
      double **v_hat,
      double **Ap_u,
      double **Ap_v,
      double **Ap_p,
      double **Ae_p,
      double **Aw_p,
      double **As_p,
      double **An_p,
      double **B_p
  );
  
  #endif
  