用面向对象语言实现一个计算器控制台程序

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#include <iostream>
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using namespace std;
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//Operation 运算类
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class Operation{
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    double m_numberA;
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    double m_numberB;
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public:
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    void SetNumA(double numA) { m_numberA = numA;}
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    void SetNumB(double numB) { m_numberB = numB;}
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    double GetNumA(void) const { return m_numberA;}
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    double GetNumB(void) const { return m_numberB;}
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    virtual double GetResult() = 0;
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};
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class OperationAdd:public Operation{
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public:
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    double GetResult(){
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        return GetNumA() + GetNumB();
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    }
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};
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class OperationSub:public Operation{
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public:
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    double GetResult(){
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        return GetNumA() - GetNumB();
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    }
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};
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class OperationMul:public Operation{
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public:
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    double GetResult(){
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        return GetNumA() * GetNumB();
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    }
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};
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class OperationDiv:public Operation{
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public:
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    double GetResult(){
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        if (GetNumB() == 0)
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            throw "numB cannot be zero!";        
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        return GetNumA() / GetNumB();
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    }
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};
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class OperationFactory{
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public:
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    static Operation* CreateOperate(char oper){
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        Operation *poper = NULL;
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        switch (oper){
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            case '+':
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                poper = new OperationAdd;
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                break;
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            case '-':
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                poper = new OperationSub;
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                break;
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            case '*':
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                poper = new OperationMul;
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                break;
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            case '/':
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                poper = new OperationDiv;
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                break;
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        }
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        return poper;
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    }
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};
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int main()
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{
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    cout<<"input A:";
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    double numA;
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    cin>>numA;    
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    cout<<"input operator:";
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    char oper;
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    cin>>oper;
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    cout<<"input B:";    
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    double numB;
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    cin>>numB;    
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    Operation *poper = OperationFactory::CreateOperate(oper);
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    poper->SetNumA(numA);
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    poper->SetNumB(numB);
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    cout<<poper->GetNumA()<<' '<<oper<<' '<<poper->GetNumB()<<" = "<<poper->GetResult()<<endl; 
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    system("pause");
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    return 0;
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}