例如,有一个使用 double 形参的 square 函数。但是我们还需要一个 square 函数,该函数专门用于整数,并接收一个 int 作为其实参。这两个函数都会做同样的事情:返回其实参的平方值,唯一的区别是参与 *** 作的数据类型。如果在同一程序中使用这两个函数,则可以为每个函数分配唯一的名称。例如,对于使用 int 的函数可以命名为 squarelnt,对于使用 double 的函数可以命名为 squareDouble。
但是,C++ 允许函数重载,这意味着可以为多个函数分配相同的名称,只要它们的形参列表不同即可。下面的程序演示了该功能:
#include <iostream>#include <iomanip>using namespace std;// Function prototypesint square(int);double square(double);int main(){ int userInt; double userReal; // Get an int and a double cout << "Enter an integer and a floating-point value: "; cin >> userInt >> userReal; // display their squares cout << "Here are their squares:"; cout << fixed << showpoint << setprecision(2); cout << square(userInt) << " and " << square(userReal) << endl; return 0;}int square (int number){ return number * number;}double square(double number){ return number * number;}程序输出结果:
Enter an integer and a floating-point value: 12 4.2
Here are their squares: 144 and 17.64
int square(int number)
double square(double number)
square(int)
square(double)
请注意,函数的返回值不是签名的一部分。以下函数无法在同一程序中使用,因为它们的形参列表并无差异。
int square(int number){ return number * number;}double square (int number) //错误!形参列表必须不同{ return number * number;}当有类似函数使用不同数量的形参时,重载也很方便。例如,假设有一个程序包含的函数可以返回整数和。其中一个函数返回 2 个整数的和,另一个返回 3 个整数的和,还有一个返回 4 个整数的和。以下是它们的函数头:
int sum(int num1,int num2)
int sum(int num1,int num2,int num3)
int sum(int num1,int num3,int num4)
#include <iostream>#include <iomanip>using namespace std;//Function prototypeschar getChoice ();double calcWeeklyPay(int,double);double calcWeeklyPay(double);int main(){ char selection; // Menu selection int worked; // Weekly hours worked double rate,// Hourly pay rate yearly; // Annual salary // Set numeric output formatting cout << fixed << showpoint << setprecision(2); //display the menu and get a selection cout << "Do you want to calculate the weekly pay of\n"; cout << "(H) an hourly-wage employee,or \n"; cout << "(S) a salarIEd employee? "; selection = getChoice (); // Process the menu selection switch (selection) { //Hourly employee case 'H': case 'h': cout << "How many hours were worked? "; cin >> worked; cout << "What is the hourly pay rate? "; cin >> rate; cout << "The gross weekly pay is $"; cout << calcWeeklyPay(worked,rate) << endl; break; //SalarIEd employee case 'S' : case 's' : cout << "What is the annual salary? "; cin >> yearly; cout << "The gross weekly pay is $"; cout << calcWeeklyPay(yearly) << endl; } return 0;}char getChoice(){ char letter; // Holds user1s letter choice // Get the user's choice cin >> letter; // ValIDate the choice while (letter != 'H' && letter != 'h' && letter != 'S' && letter != 's') { cout << "Enter H or S:"; cin >> letter; } // Return the choice return letter;}double calcWeeklyPay(int hours,double payRate){ return hours * payRate;}double calcWeeklyPay(double annSalary){ return annSalary / 52.0;}程序输出结果:
Do you want to calculate the weekly pay of
(H) an hourly-wage employee,or
(S) a salarIEd employee? H
How many hours were worked? 40
What is the hourly pay rate? 18.50
The gross weekly pay is $740.00
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