C++ function types and characteristics

C functions have the following types: simple functions, const functions, static functions, and virtual functions; features include: inline functions, default parameters, reference returns, and overloaded functions. For example, the calculateArea function uses π to calculate the area of ​​a circle of a given radius and returns it as output.

#Types and Properties of C Functions

A function in C is a reusable block of code that receives input and produces output. Functions have an explicit name, parameter list, and return value type.

Function type

Simple function: The simplest function type without any prefix or suffix modifiers.

void myFunction();  // 返回 void，不接收参数

const Function: The function does not modify the data it accesses.

const int &myFunction(const int &x);  // 返回常引用，接收常引用

Static function: The function does not depend on the class object and can only access static data members.

static void myFunction();  // 静态函数，不接收参数

Virtual function: Function used for polymorphism, allowing derived classes and parent classes to have functions with the same name, but different behaviors.

virtual void myFunction() = 0;  // 纯虚函数，必须在派生类中重写

Function features

Inline function: Inline the function code directly into the calling function to improve performance.

inline int myFunction(int x) { return x * x; }  // 内联函数，接收一个整型参数，返回平方的值

Default parameters: Allow function parameters to specify default values ​​when called.

int myFunction(int x, int y = 10);  // 默认参数为 10

Reference return: The function can return a reference to the data, allowing the caller to directly modify the original data.

int &myFunction(int &x);  // 返回对整型变量的引用

Overloaded functions: Functions with the same name but different parameter lists.

int myFunction(int x);  // 一个参数
double myFunction(double x);  // 一个 double 参数

Practical case

Consider a function that calculates the area of ​​a circle:

#include <cmath>

double calculateArea(double radius) {
  return M_PI * radius * radius;  // 返回圆的面积
}

int main() {
  double radius = 5.0;
  double area = calculateArea(radius);
  cout << "半径为 " << radius << " 的圆的面积为 " << area << endl;
  return 0;
}

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