/* 
   
   Copyright (C) Bernard Piette 
                 University of Durham (UK) 
                 Department of Mathematical Sciences
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
   
   You can modify or use any part of the source code but only under the  
   condition that this Copyright notice is kept in the resulting source file.
*/
#ifndef PDE_H
#define PDE_H
#include <grf_pde.h>
#include <cmath>
#include <fstream>
#include <cstdio>

class pde { 
public:
         // constructors and destructors
  pde(double xmin,double xmax,int nx);
  virtual ~pde();

         // Method to Override for specific equation
  virtual void Eqn(double &F)=0;           // Equations to solve
  virtual void Init(double x,double &F)=0; // Initial value
  void init_grf(grf_pde *grfp) { grfp_ = grfp; };
  void set_dt(double dt) { dt_ = dt;}

  double xmin() { return(Xmin_);}
  double xmax() { return(Xmax_);}
  double dx() { return(dx_);}
  int    nx() { return(nx_);}

  virtual void set_neighbour_fcts(double *f,int i);
  virtual void eval_derivatives();

         // integration method overriden by sub-classes
  virtual void initial_value();   
  void write_grf();       // Output one graph
  virtual double integrate_1step() {return(0.0);}; // to override   

         // Calls integrate_1step() several times
  virtual double integrate_until(double t);
  virtual double integrate_grf_until(double tmax,double grf_dt);

protected:
  double dt_;
  double t_;
  double Xmin_;
  double Xmax_;
  double dx_;

  int nx_;

  double *f_,*fl_,*fll_,*fr_,*frr_; // fcts pointers
  double x_;                 // local value of x = Xmin_+i_*dx_ 
  int i_;                    // local value of grid index 

         // allocate arrays for the fcts and densities
  double *Fcts_;     // A vector of size nx    

  double Force_;       // The evaluated equation 
  double fx_,fxx_,fxxx_,fxxxx_;

  // Graphic variables
  grf_pde *grfp_;
  int grf_index_;
};
#endif