```
//
// Equation.h define the equation class to be solved.
//
#ifndef EQUATION_H
#define EQUATION_H
#include "Mesh.h"
#include"Variable.h"
#include"Media.h"
#include"Simulation.h"
#include <string>
#include<vector>
#include <assert.h>
#include <iostream>
using namespace std;
class Equation
{
protected:
// the equation name it should be the same with the variaible name
string name;
// the equation residual
double residual;
// a pointer to the Mesh
Mesh* pMesh;
// a pointer to the varible soved in the equation
Variable* pVariable;
// a pointer to the simulation
Simulation* pSimulation;
// a pointer to the media
Media* pMedia;
// the matrix A that contain the discretised equation Ax=source
vector<double> csrA;
// the source contain the discretised equation source term
vector<double> source;
public:
// the default constructor with no parameter
Equation() { pVariable=new Variable(); int size=pMesh->getNbCells(); pVariable->setSize(size); source.resize(size); csrA.resize(pMesh->getNbNoneZero() );}
// the constructor with one parameter name
Equation(const string& aName) { name=aName; pVariable=new Variable();int size=pMesh->getNbCells(); pVariable->setSize(size);source.resize(size); csrA.resize(pMesh->getNbNoneZero() );}
~Equation(){pVariable->clear();delete pVariable;}
};
#endif
```

When i compile use the vs2008 , it gives me the following errror

```
1>------ Build started: Project: FlowingHeat, Configuration: Debug Win32 ------
1>Compiling...
1>main.cpp
1>g:\computation\c++cfd\flowingheat\flowingheat\equation.h(36) : error C2143: syntax error : missing ';' before '*'
1>g:\computation\c++cfd\flowingheat\flowingheat\equation.h(36) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
1>g:\computation\c++cfd\flowingheat\flowingheat\equation.h(36) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
1>g:\computation\c++cfd\flowingheat\flowingheat\equation.h(65) : error C2061: syntax error : identifier 'Simulation'
1>g:\computation\c++cfd\flowingheat\flowingheat\equation.h(65) : error C2065: 'pSimulation' : undeclared identifier
1>g:\computation\c++cfd\flowingheat\flowingheat\equation.h(65) : error C2065: 'apSimulation' : undeclared identifier
```

it seems it can not use the class Simlation, but i have include the header file"Simulation.h".

Could you please tell me how to resolve this problem.

Regards