计算器.cpp

这是一个计算器的程序

#include<iostream>
#include<conio.h>
using namespace std;

const int maxlen=200;
int &operation(const int &,const int &,const char &);
char expstr[maxlen];
enum Error_code{success=0,downflow,stackempty,overflow}code;

template<class Stack_entry>
class Stack{
public:
	Stack();
	bool isempty() const;
	bool isfull() const;
	void Get_count(int &)const;
	Error_code pop();
	Error_code get(Stack_entry &item)const;
	Error_code push(const Stack_entry &item);
private:
	int count;
	Stack_entry data[maxlen];
};

template<class Stack_entry>
Stack<Stack_entry>::Stack()
{
	count=0;
}

template<class Stack_entry>
bool Stack<Stack_entry>::isempty()const
{
	if(count==0)	return true;
	else return false;
}

template<class Stack_entry>
bool Stack<Stack_entry>::isfull() const
{
	if(count==maxlen) return true;
	else return false;
}

template<class Stack_entry>
void Stack<Stack_entry>::Get_count(int &n)const
{
	n=count;
}

template<class Stack_entry>
Error_code Stack<Stack_entry>::pop()
{
	if(isempty())	return downflow;
	else count--; 
	return success;
}

template<class Stack_entry>
Error_code Stack<Stack_entry>::get(Stack_entry &item)const
{
	if(isempty()) return stackempty;
	else
	item=data[count-1]; 
	return success;
}

template<class Stack_entry>
Error_code Stack<Stack_entry>::push(const Stack_entry &item)
{
	if(isfull()) return overflow;
	else
	data[count]=item;
    count++;
	return success;
}

void Do_command()
{
    Stack<int>S_number;
    Stack<char>S_symbol;
	int getnb1,getnb2,result,i=0,n;
	char  getch;
	while(expstr[i]!='\0')
	{
		switch(expstr[i])
		{
		case '+':
		case '-':
			S_symbol.get(getch);	
			if(S_symbol.isempty()||getch=='(')
				S_symbol.push(expstr[i]);
			else
			{
                S_symbol.get(getch);
                S_symbol.pop();
                S_number.get(getnb1);
                S_number.pop();
                S_number.get(getnb2);
                S_number.pop();
                result=operation(getnb2,getnb1,getch);
				S_number.push(result); ;
				S_symbol.push(expstr[i]);                   
			}
			i++;
			break;
		case '*':
		case '/':
     		S_symbol.get(getch);	
			if(S_symbol.isempty()||getch=='('||getch=='+'||getch=='-')
			{
				S_symbol.push(expstr[i]);
			}
			else
			{
                S_symbol.get(getch);
                S_symbol.pop();
                S_number.get(getnb1);
                S_number.pop();
                S_number.get(getnb2);
                S_number.pop();
                result=operation(getnb2,getnb1,getch);
				S_number.push(result); 
                S_symbol.push(expstr[i]);                       
			}
			i++;
			break;
		case '(': 
			S_symbol.push(expstr[i]);
			i++;
			break;
		case ')':
			S_symbol.get(getch);
			while(getch!='(')
			{
  				S_symbol.pop();
				S_number.get(getnb1);
                S_number.pop();
                S_number.get(getnb2);
                S_number.pop();
                result=operation(getnb2,getnb1,getch);
				S_number.push(result);
				S_symbol.get(getch);
   			}
            S_symbol.pop();
			i++;
			break;
		default:
			int res=0;
			while(expstr[i]>='0'&&expstr[i]<='9')
			{
    			res=res*10+expstr[i]-'0';           
				i++;
			}
			S_number.push(res);                                 
		}
	}
	S_number.Get_count(n);
    while(!S_symbol.isempty()&&n>=2)
	{                                   
        S_symbol.get(getch);
        S_symbol.pop();
		S_number.get(getnb1);
        S_number.pop();
        S_number.get(getnb2);
        S_number.pop();
        result=operation(getnb2,getnb1,getch);
	    S_number.push(result); 
        S_number.Get_count(n);                                                      
   	}
	S_number.get(result);
	cout<<result;
}


int &operation(const int &n1,const int &n2,const char &ch)
{
    static int n;
    switch(ch)
	{    
       	case '+': n=n1+n2; break;
	    case '-': n=n1-n2; break;
		case '*': n=n1*n2; break;
	    case '/': n=n1/n2; break;
	}
	return n;
}
void main()
{
	
	char *introduce="The expression can only contain the number:0~9 and symbol:'+'、'-'、'*'、'/'、'('、')' \n for example: 2+3*(9/3-2)";
	cout<<introduce<<'\n'<<"Enter the expression: ";
	gets(expstr);
    cout<<"expstr="<<expstr<<"="<<flush;
    Do_command();getch();
}