/* 
   
   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.
*/
#include <pde_euler.h>
#include <iostream>

using namespace std;

// Constructor for Euler pde 
// Allocated 2 extra arrays     
//******************************
pde_euler::pde_euler(double xmin,double xmax,int nx) 
   : pde(xmin,xmax,nx)
{ tmp1_ = new double[nx_];    
}

// Destructor
//***********
pde_euler::~pde_euler()
{ delete [] tmp1_;
}

// Perform a single euler integration step on the grid 
// Update the time t_                                  
// pde : pde parameters                                
// Eqn(Force) : computes the right hand side of        
//     the equation.                                   
//       uses f_,fl_,fr_: local fct pointer          
//       Force : Reference to a double for the result.     
//       i_    : lattice index                         
// Return : the updated time                           
//*****************************************************
double pde_euler::integrate_1step()
{ int i;  

      // Scan the whole grid 
  for(i=0; i < nx_; i++)
  {     // set f_, fl_, fr_, x_ and i_
    set_neighbour_fcts(Fcts_,i);

        // Computes the force for point i and  
        // stores it in Force                  
    Eqn(Force_); 

    // Update each fct using Force : f(n+1) = f(n) + Force*dt 
    // tmp1 is used to store the fct temporarily              

    tmp1_[i] = f_[0]  + dt_*Force_;  
  }

  /* Update Fct with the new fct */
  for(i=0; i < nx_; i++)
  { Fcts_[i] = tmp1_[i];
  }
  t_ += dt_;  // Udate the integration time 
  return(t_);
}