Question

这里我有一个异常处理程序，其中我使用了＆amp;＆amp;运营商比较城市名称，我有问题，我有＆amp;＆amp;运营商如果条件但我们知道＆amp;＆amp;只有当这个程序中的所有值都为真时才执行，即使我们输入一个值，这个程序也能正确执行。

为什么＆amp;＆amp;的含义操作员更改此程序？

#include<iostream>  
#include<typeinfo> 
#include<string> 
#include<cstring>

using namespace std;

int main() {
  int i, n, age;  //variable declaration
  double income;
  char city[20];

  cout<<"\n Enter your age:";
  cin>>age;

  try {
    if (age < 18 || age > 55)   
      throw runtime_error("\n Age is not in the range of 18-55");
  } catch(const exception& e) {  //creation of exception object 'e'
    cout<<"EXCEPTION:"<<e.what()<<'\n'; //what()- member funciton of type id
  }

  cout<<"\n Enter your income:";
  cin>>income;
  try {
    if(income<50000||income>100000) 
      throw runtime_error("\n Income is not in the range of 50000-100000");
  } catch(const exception& e)// creation of exception object 'e'
  {
    cout<<"EXCEPTION:"<<e.what()<<'\n'; 
  }
  cout<<"\n In which city do you live?";
  cin>>city;

  try {
    if(strcmp(city, "Pune")
       && strcmp(city, "Banglore")
       && strcmp(city,"Chennai")
       && strcmp(city, "Mumbai"))   
      throw runtime_error("\ncity is not any of these:- Pune/Mumbai/Banglore/Chennai");
  }  catch(const exception& e)// creation of exception object 'e'
  {
    cout<<" EXCEPTION:"<<e.what()<<'\n';
  }

  cout<<"\n Information of person is as follows:";// displpaying all the information accepted
  cout<<"\n Age:"<<age;
  cout<<"\n Income:"<<income;
  cout<<"\n City:"<<city;

  return 0;
}

Answer 1

你知道std :: strcmp（p1，p2）返回整数值，含义如下：

＆LT;如果不匹配的第一个字符的值较低，则为0 p1比p2
0两个字符串的内容相等
＆GT; 0不匹配的第一个字符在p1中的值大于在p2中的值

因此，例如，如果用户输入＆＃34;莫斯科＆＃34;比我们得到的：（1＆amp;＆amp; -1＆amp;＆amp; -1＆amp;＆amp; 1）但它的意思是（真＆amp;＆amp;真＆amp;＆amp;＆amp;＆amp;＆amp;＆amp;＆amp;＆amp;真）和异常将是抛出

相反，您应该只检查相等性，所以只需将代码更改为： ...

if((strcmp(city, "Pune") != 0) && (strcmp(city, "Banglore") != 0) && (strcmp(city,"Chennai") != 0) && (strcmp(city, "Mumbai")!=0))

...

为什么＆amp;＆amp;和经营者正在改变

1 个答案: