C++/Overload/Compare
Содержание
Define
<source lang="cpp">
- include <iostream>
- include <vector>
- include <algorithm>
- include <string>
using namespace std; class Employee {
string name; unsigned number;
public:
Employee() { name = ""; number = 0; }
Employee(string n, unsigned num) {
name = n;
number = num;
}
string get_name() { return name; }
unsigned get_number() { return number; }
}; void show(vector<Employee> vect) {
vector<Employee>::iterator itr; for(itr=vect.begin(); itr != vect.end(); ++itr) cout << itr->get_number() << " " << itr->get_name() << endl;;
} bool operator<(Employee a, Employee b){
return a.get_number() < b.get_number();
} int main() {
vector<Employee> employeeList;
employeeList.push_back(Employee("A", 9));
employeeList.push_back(Employee("B", 8));
employeeList.push_back(Employee("C", 6));
employeeList.push_back(Employee("D", 1));
show(employeeList);
sort(employeeList.begin(), employeeList.end());
show(employeeList);
return 0;
}
</source>
overloaded "==" operator compares strings
<source lang="cpp">
- include <iostream>
using namespace std;
- include <string.h>
class String{
private:
enum { SZ = 80 };
char str[SZ];
public:
String(){ strcpy(str, ""); }
String( char s[] ){ strcpy(str, s); }
void display() const{ cout << str; }
void getstr(){ cin.get(str, SZ); }
bool operator == (String ss) const{
return ( strcmp(str, ss.str)==0 ) ? true : false;
}
};
int main(){
String s1 = "yes";
String s2 = "no";
String s3;
cout << "\nEnter "yes" or "no": ";
s3.getstr();
if(s3==s1)
cout << "You typed yes\n";
else if(s3==s2)
cout << "You typed no\n";
else
cout << "You didn"t follow instructions\n";
return 0;
}
</source>
overloaded "
<source lang="cpp">
- include <iostream>
using namespace std; class Distance
{
private:
int feet;
float inches;
public:
Distance() : feet(0), inches(0.0){ }
Distance(int ft, float in) : feet(ft), inches(in) { }
void getdist(){
cout << "\nEnter feet: "; cin >> feet;
cout << "Enter inches: "; cin >> inches;
}
void showdist() const{
cout << feet << "\"-" << inches << "\"";
}
bool operator < (Distance) const;
}; bool Distance::operator < (Distance d2) const{
float bf1 = feet + inches/12; float bf2 = d2.feet + d2.inches/12; return (bf1 < bf2) ? true : false;
} int main(){
Distance dist1;
dist1.getdist();
Distance dist2(6, 2.5);
cout << "\ndist1 = "; dist1.showdist();
cout << "\ndist2 = "; dist2.showdist();
if( dist1 < dist2 )
cout << "\ndist1 is less than dist2";
else
cout << "\ndist1 is greater than (or equal to) dist2";
cout << endl;
return 0;
}
</source>
Overloading Equality and Inequality Operators
<source lang="cpp">
- include <iostream>
using namespace std; class CDate { private:
int m_nDay; int m_nMonth; int m_nYear; void AddDays (int nDaysToAdd); void AddMonths (int nMonthsToAdd); void AddYears (int m_nYearsToAdd);
public:
CDate (int nDay, int nMonth, int nYear)
: m_nDay (nDay), m_nMonth (nMonth), m_nYear (nYear) {};
void DisplayDate ()
{
cout << m_nDay << " / " << m_nMonth << " / " << m_nYear << endl;
}
// integer conversion operator
operator int();
// equality operator that helps with: if (mDate1 == mDate2)...
bool operator == (const CDate& mDateObj);
// overloaded equality operator that helps with: if (mDate == nInteger)
bool operator == (int nDateNumber);
// inequality operator
bool operator != (const CDate& mDateObj);
// overloaded inequality operator for integer types
bool operator != (int nDateNumber);
}; CDate::operator int() {
return ((m_nYear * 10000) + (m_nMonth * 100) + m_nDay);
} // equality operator that helps with if (mDate1 == mDate2)... bool CDate::operator == (const CDate& mDateObj) {
return ( (mDateObj.m_nYear == m_nYear)
&& (mDateObj.m_nMonth == m_nMonth)
&& (mDateObj.m_nDay == m_nDay) );
} bool CDate::operator == (int nDateNumber) {
return nDateNumber == (int)*this;
} // inequality operator bool CDate::operator != (const CDate& mDateObj) {
return !(this->operator== (mDateObj));
} bool CDate::operator != (int nDateNumber) {
return !(this->operator == (nDateNumber));
} void CDate::AddDays (int nDaysToAdd) {
m_nDay += nDaysToAdd;
if (m_nDay > 30)
{
AddMonths (m_nDay / 30);
m_nDay %= 30; // rollover 30th -> 1st
}
} void CDate::AddMonths (int nMonthsToAdd) {
m_nMonth += nMonthsToAdd;
if (m_nMonth > 12)
{
AddYears (m_nMonth / 12);
m_nMonth %= 12; // rollover dec -> jan
}
} void CDate::AddYears (int m_nYearsToAdd) {
m_nYear += m_nYearsToAdd;
} int main () {
CDate mDate1 (25, 6, 2008);
mDate1.DisplayDate ();
CDate mDate2 (23, 5, 2009);
mDate2.DisplayDate ();
if (mDate2 != mDate1)
cout << "The two dates are not equal... As expected!" << endl;
CDate mDate3 (23, 5, 2009);
mDate3.DisplayDate ();
if (mDate3 == mDate2)
cout << "mDate3 and mDate2 are evaluated as equals" << endl;
// Get the integer equivalent of mDate3 using operator int()
int nIntegerDate3 = mDate3;
cout << nIntegerDate3<< endl;
// Use overloaded operator== (for int comparison)
if (mDate3 == nIntegerDate3)
cout << "The integer and mDate3 are equivalent" << endl;
// Use overloaded operator != that accepts integers
if (mDate1 != nIntegerDate3)
cout << "The mDate1 is inequal to mDate3";
return 0;
}
</source>
Overload the < and >
" src="http://www.java2s.com/Code/CppImages/Overloadtheand.PNG">
<source lang="cpp">
- include <iostream>
using namespace std; class MyClass {
int x, y;
public:
MyClass() {
x=0;
y=0;
}
MyClass(int i, int j) {
x=i;
y=j;
}
void getXY(int &i, int &j) {
i=x;
j=y;
}
int operator<(MyClass object2);
int operator>(MyClass object2);
}; int MyClass::operator<(MyClass object2) {
return x<object2.x && y<object2.y;
} int MyClass::operator>(MyClass object2) {
return x>object2.x && y>object2.y;
}
int main() {
MyClass object1(10, 10), object2(5, 3); if(object1>object2) cout << "object1 > object2\n"; else cout << "object1 <= object2 \n"; if(object1<object2) cout << "object1 < object2\n"; else cout << "object1 >= object2\n"; return 0;
}
</source>
