calculator1.h

合理运用栈

#include"stack.h"

#include<iostream>
#include<cstdlib>
#include<cmath>
#include<cstring>
using namespace std;

enum Boolean{False,True};

class Calculator
{
private:
	Stack <double> Num;           //操作数栈
	Stack <char>   Op;  
	void EnterNum(double num);     //将操作数num压入数栈
	void EnterOp(char op);         //将操作符op压入符号栈
	Boolean GetTwoOperands(double &oper1,double &oper2);   //从数栈中提取两个操作数。
	int Judge(char op);      //判断优先级
	Boolean Compare(char &op1,char &op2) ; //比较优先级
	void Compute(char c);    //执行运算
public:
	Calculator(void);
	void Run(void);         //运行
	void Clear(void);       //清理栈
};


Calculator::Calculator()
{}
void Calculator::EnterNum(double num)
{	Num.Push(num);} 

void Calculator::EnterOp(char op)
{	Op.Push(op);  }

Boolean Calculator::GetTwoOperands(double &oper1,double &oper2)
{
	if(Num.StackEmpty())
	{
		cerr<<"error:stack empty!"<<endl;
		Clear();
	}
	else
	{oper1=Num.Pop();}

	if(Num.StackEmpty())
	{
		cerr<<"error:stack empty!"<<endl;
		Clear();
		return False;
	}
	else
	{
		oper2=Num.Pop();
		return True;
	}
}
int Calculator::Judge(char op)    //优先级越高，返回值越大
{
	if(op!='('&&op!=')'&&op!='^'&&op!='*'&&op!='/'&&op!='+'&&op!='-')
	{
		cerr<<"error: Judge input error!"<<endl;
		Clear();
		exit(1);
	}
	else
	{
		int m;
		switch(op)
		{
		case '(':  m=5;break;
		case '^':  m=4;break;
		case '*':  m=3;break;
		case '/':  m=3;break;
		case '+':  m=2;break;
		case '-':  m=2;break;
		case ')':  m=1;break;
		}
        return m;
	}
}
Boolean Calculator::Compare(char &op1,char &op2)
{
	if( Judge(op1)>=Judge(op2)) //当op1的优先级比op2的优先级高或相等时返回true
		return True;
	else
	    return False;
} 
void Calculator::Compute(char c)
{
	Boolean result;
	double operand1,operand2 ;
	result=GetTwoOperands(operand1,operand2);
	if(result==True)
	{
        switch(c)
		{
		case '^': Num.Push(pow(operand2,operand1));break;
		case '*': Num.Push(operand2*operand1);break;
		case '/': if(operand1==0)
				  {
					  cerr<<"error: divide by 0 !"<<endl;
					  Clear();
					  exit(1);
				  }
		          else
				  {Num.Push(operand2/operand1);break;}
		case '+': Num.Push(operand2+operand1);break;
		case '-': Num.Push(operand2-operand1);break;
		}
	}
	else
		Clear();
}
void Calculator::Run(void)
{
	Clear();
	char b;
	double data;

	while(cin>>b, b!='=')
	{
		if(b >= '0' && b <= '9')
		{ // ch为数值
			cin.putback(b);// 将ch放回输入流中 
            cin>>data;// 按double型方式，重新读入操作数
			EnterNum(data);//  将操作数放入栈中
		}
		else if (b=='^'||b == '+' || b == '-' || b == '*' || b == '/'||b=='('||b==')')  // b是运算符
		{
			if(Op.StackFull())
			{
				cerr<<"error: stack full!"<<endl;
				exit(1);
			}
			if(Op.StackEmpty())
			{  Op.Push(b);}
			else
			{
				char Top;
				if(b==')')
				{
					while(Op.peek()!='('  )
					{
						char ch;
						ch=Op.Pop();
						Compute(ch);
						if(Op.StackEmpty())
						{
                            cerr<<"error: missing char '(' "<<endl;
							exit(1);
						}
					}
					if(Op.peek()=='(')
					{
						Op.Pop();
					}					
				}
				else   //b!=')'
				{
					Top=Op.peek();		    				
                    while( True==Compare(Top,b)&& Top!='(' )  //如果站定元素的优先级比读进操作高或相等
					{
						Compute(Top);
						Op.Pop();   //运算符被执行，不能再应用
                        //cout<<Num.peek()<<endl;
						if(Op.StackEmpty())
							break;
					    Top=Op.peek();
					}
					Op.Push(b);  //						
				}
			}
		}				
	}
	while(1)
	{
	    if(Op.StackEmpty()) 
			break;
		Compute(Op.Pop());	
	}
    cout<<Num.peek()<<endl;
}
void Calculator::Clear()
{
	Num.ClearStack();
	Op .ClearStack();
}