How do function pointers work in C++?

In C++, a function pointer is a variable pointing to a function, which can dynamically pass or store the function as a parameter. The syntax is: type name * function name. When allocating, use the function pointer address and dereference it when calling. For example, when calculating the maximum value using a function pointer, the calculation is performed by allocating the function pointer and calling it.

How function pointers work in C++

In C++, a function pointer is a variable that points to a function. It allows us to dynamically pass functions as parameters or store them in data structures.

Syntax

The function pointer is declared like a regular function, but the type name is followed by an asterisk (*):

typedef void (*FunctionPointer)(int);

Assignment

We can do it like Assign a function address to a function pointer like an ordinary pointer:

FunctionPointer fp = &myFunction;

Call

We can call it by dereferencing the function pointer:

fp(10);

Practical case

Let's consider a program that uses function pointers to calculate the maximum of two numbers:

#include <iostream>

using namespace std;

// 最大值函数
int max(int a, int b) {
  return a > b ? a : b;
}

// 函数指针比较函数
int compare(int a, int b, int (*fp)(int, int)) {
  return fp(a, b);
}

int main() {
  // 分配函数指针并调用它来计算两数的最大值
  int (*fp)(int, int) = &max;
  int result = compare(5, 10, fp);

  // 打印结果
  cout << "最大值：" << result << endl;

  return 0;
}

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