帮看下这个问题

[xiaofang3100]

#include<stdlib.h>
#include<iostream>
#include<string>
using namespace std;

class Counter
{
public:
int operand;
static double total;
Counter(int a=0):operand(a){}
Counter& operator+(Counter &t);
Counter& operator-(Counter &t);
Counter& operator*(Counter &t);
Counter& operator/(Counter &t);
friend istream& operator>>(istream &input,Counter &s);
friend istream& operator<<(ostream &output,Counter &s);
};

double Counter::total=0;

Counter& Counter::operator +(Counter &t)
{
operand=operand+t.operand;
total+=operand;
return *this;
}

Counter& Counter::operator-(Counter &t)
{
operand=operand-t.operand;
total+=operand;
return *this;
}

Counter& Counter::operator*(Counter &t)
{
operand=operand*t.operand;
total+=operand;
return *this;
}

Counter& Counter::operator/(Counter &t)
{
if(t.operand==0)
abort();
operand=double(operand)/double(t.operand);
return *this;
}

istream& operator>>(istream &input,Counter &s)
{
input>>s.operand;
return input;
}

ostream& operator<<(ostream &output,Counter &s)
{
output<<"total="<<s.total<<endl;
return output;
}

void main()
{
char opera;
string s;
cin>>s;//我输入的是1+2
Counter a(s[0]),b(s[2]);
opera=s[1];
switch(opera)
{
case '+':
a=a+b;break;
}
cout<<Counter::total<<endl;//输出的是99
}
帮忙看下这个程序我输入1+2怎么结果输出99,而不是输出3,帮我找下哪里出错了,谢谢了.

[p0303230]

s是字符串
s[0] s[2]是'1' '2'
明白了吧

[独孤过儿]

a在count类里面，仅仅是一个函数的参数，而不是一个成员变量，你需要额外的添加a的声明！

[jieao111]

编译都通不过，，不知道你怎么运行的。。friend istream& operator < <(ostream &output,Counter &s);

[taodm]

是一群马甲，还是都是用的同样的垃圾书啊
friend istream& operator < <(ostream &output,Counter &s);
连续出现了。

[jieao111]

以下是常用的ASCII码对照表：

十进制 十六进制 字符
9 9 TAB(制表符)

49 31 1
50 32 2
51 33 3
52 34 4
53 35 5
54 36 6
55 37 7
56 38 8
57 39 9


49＋50＝99

[就呆在云上]

正常
程序用的是1和2的字符对应的十进制数
相加就是99

[就呆在云上]

程序本身有一个编译错误
修改了：

#include <stdlib.h> 
#include <iostream> 
#include <string> 

using namespace std;

class Counter 
{ 
public: 
	int operand; 
	static double total; 
	Counter(int a=0):operand(a){} 
	Counter(char a){
		operand = int(a) - 48;
	} 
	Counter& operator+(Counter &t); 
	Counter& operator-(Counter &t); 
	Counter& operator*(Counter &t); 
	Counter& operator/(Counter &t); 
	friend istream& operator >>(istream &input,Counter &s); 
	friend ostream& operator <<(ostream &output,Counter &s); 
}; 

double Counter::total=0; 

Counter& Counter::operator +(Counter &t) 
{ 
	operand=operand+t.operand; 
	total+=operand; 
	return *this; 
} 

Counter& Counter::operator-(Counter &t) 
{ 
	operand=operand-t.operand; 
	total+=operand; 
	return *this; 
} 

Counter& Counter::operator*(Counter &t) 
{ 
	operand=operand*t.operand; 
	total+=operand; 
	return *this; 
} 

Counter& Counter::operator/(Counter &t) 
{ 
	if(t.operand==0) 
	abort(); 
	operand=double(operand)/double(t.operand); 
	return *this; 
} 

istream& operator >>(istream &input,Counter &s) 
{ 
	input>>s.operand; 
	return input; 
} 

ostream& operator << (ostream &output,Counter &s) 
{ 
	output << "total=" << s.total <<endl; 
	return output; 
} 

void main() 
{ 
	char opera; 
	string s; 
	cin>>s;//我输入的是1+2 
	Counter a(s[0]),b(s[2]); 
	opera=s[1]; 
	switch(opera) 
	{ 
		case '+': 
		a=a+b;break; 
	} 
	cout <<Counter::total <<endl;//输出的是99 
} 

[OenAuth.Core]

添加一个构造函数吧（我只留下加法运算，方便理解）：
#include <stdlib.h>
#include <iostream>
#include <string>
using namespace std;

class Counter
{
public:
int operand;
static double total;
Counter(int a=0):operand(a){}
Counter(char a){
switch(a){
case '1':
operand=1;
break;
case '2':
operand=2;
break;
//自己加CASE语句，一直到9，不过这只能实现10以内的计算。
}
}
Counter& operator+(Counter &t);
friend ostream& operator<<(ostream &output,Counter &s);
};

double Counter::total=0;

Counter& Counter::operator +(Counter &t)
{
operand=operand+t.operand;
total+=operand;
return *this;
}
ostream& operator<<(ostream &output,Counter &s)
{
output <<"total=" <<s.total <<endl;
return output;
}

void main()
{
char opera;
string s;
cin>>s;//我输入的是1+2
Counter a(s[0]),b(s[2]);
opera=s[1];
switch(opera)
{
case '+':
a=a+b;break;
}
cout <<Counter::total <<endl;//输出的是99
}

[OenAuth.Core]

还有friend istream& operator < <(ostream &output,Counter &s); 改成：
friend 0stream& operator < <(ostream &output,Counter &s);