如何比较类中的两个对象(调用对象和参数)? [英] How to compare two objects (the calling object and the parameter) in a class?
问题描述
我为一个作业写了一个Date类,我在执行一个函数时遇到麻烦。
这是类的头文件。
{
public:
Date(); //没有参数的构造函数
Date(int m,int d,int y); //带参数的构造函数。
//访问器
int GetMonth(); //返回钻石的大小
int GetDay();
int GetYear();
// mutators
bool Set(int m,int d,int y);
bool SetFormat(char f);
//标准输入和输出例程
void Input();
void Show();
void Increment(int numDays = 1);
int比较(const Date& d);
private:
int month,//月变量
day,//日变量
年; //年变量
char格式;
};
我想要的成员函数是int Compare(const Date& d)函数。我需要这个函数来比较两个Date对象(调用对象和
参数),并且应该返回:-1如果调用对象先到达
按时间顺序,0如果对象是相同的日期,如果参数对象
按时间先后顺序排列。
我试过用==运算符做一个简单的if语句,但我得到错误。
if(d1 == d2)
cout< 日期是一样的;
return(0);
创建对象后,函数应该像这样调用d1.Compare p>
提前谢谢!
int Date :: Compare(const Date& d){
if(year< d.year){
return -1;
}
else if(year> d.year){
return 1;
}
else if(month< d.month){
return -1;
}
else if(month> d.month){
return 1;
}
//一天一样
return 0;
}
通常,您还需要提供重载的比较运算符,例如也在类定义内):
bool operator ==(const Date& d)const {
return!Compare (d)。
}
bool operator< (const Date& d)const {
return Compare(d)< 0;
}
... //考虑使用boost :: operators
PS:有更聪明的实现 Compare()
- 只是检查其他答案。这个很简单易读,但完全符合你的规格。
I am writing a "Date" class for an assignment and I am having trouble doing one the of the functions.
This is the header file for the class.
class Date
{
public:
Date(); // Constructor without parameters
Date(int m, int d, int y); // Constructor with parameters.
// accessors
int GetMonth(); // returns the size of the diamond
int GetDay();
int GetYear();
// mutators
bool Set(int m, int d, int y);
bool SetFormat(char f);
// standard input and output routines
void Input();
void Show();
void Increment(int numDays = 1);
int Compare(const Date& d);
private:
int month, // month variables
day, // day variable
year; // year variable
char format;
};
The member function I am trying to make is the int Compare(const Date& d) function. I need this function to compare two Date objects (the calling object and the parameter), and should return: -1 if the calling object comes first chronologically, 0 if the objects are the same date, and 1 if the parameter object comes first chronologically.
I have tried doing a simple if statement with the == operator but I get errors.
if (d1 == d2)
cout << "The dates are the same";
return (0);
After the objects are created, the function should be called like this d1.Compare(d2)
Thank you in advance!
int Date :: Compare (const Date& d) {
if (year<d.year) {
return -1;
}
else if (year>d.year) {
return 1;
}
else if (month<d.month) {
return -1;
}
else if (month>d.month) {
return 1;
}
// same for day
return 0;
}
Usually, you'lll also want to provide overloaded comparison operators, for example (also within the class definition):
bool operator == (const Date& d) const {
return !Compare(d);
}
bool operator < (const Date& d) const {
return Compare(d)<0;
}
... // consider using boost::operators
PS: There are smarter implementations of Compare()
- just check the other answers. This one is pretty straightforward and readable, but conforms exactly to your specification.
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