请问下面的c++程序我应该怎么改正：

Question

#include "stdafx.h"
#include <iostream>

class COperation //基类
{
public:
int m_nFirst;
int m_nSecond;
virtual double Getresult() = 0;
};

class AddOperation:public COperation //加法
{
public:
virtual double GetResult()
{
return m_nFirst + m_nSecond;
}
};

class SubOperation : public COperation //减法
{
public:
virtual double GetResult()
{
return m_nFirst - m_nSecond;
}
};

class CCalculatorFactory //工厂类
{
public:
static COperation *Create(char cOperator);
};

COperation *CCalculatorFactory::Create(char cOperator) //
{
COperation *oper;
switch(cOperator)
{
case'+':
oper = new AddOperation();
break;
case'-':
oper = new SubOperation();
break;
default:
oper = new AddOperation();
break;
}
return oper;
}

int _tmain(int argc, _TCHAR* argv[])
{
int a , b;
cin>>a>>b;
COperation *op = CCalculatorFactory::Create('-');
op->m_nFrist = a;
op->m_nSecond = b;
cout<<op->GetResult()<<endl;

return 0;
}

运行结果为什么有四条错误：
error C2590: 'Create' : only a constructor can have a base/member initializer list

error C2533: 'CCalculatorFactory' : constructors not allowed a return type

error C2969: syntax error : ';' : expected member function definition to end with '}'

fatal error C1004: unexpected end-of-file found

Answer 1

哈哈，你基类中式Getresult，小写的，后面变成大写了！！！！

Answer 2

少加了命名空间