Application scenarios of C++ function pointers

The function pointer in C refers to the variable pointing to the memory address of the function. It is often used in scenarios such as callback functions, dynamic binding, and event processing. For example, in the sorting algorithm, we can use function pointers to implement different comparison functions to flexibly choose the sorting algorithm.

C Application scenarios of function pointers

What is a function pointer?

In C, a function pointer is a pointer to a function. It is a variable pointing to the memory address of the function.

Declaration of function pointer

The declaration of function pointer is very similar to the declaration of ordinary function, except that an asterisk (*) is added in front of the function name:

typedef int (*FuncPtr)(int, int);

The above declaration defines a function pointer named FuncPtr, which points to a function that accepts two parameters of type int and returns an int type The function.

Usage of function pointers

Function pointers can be used in the following scenarios:

• Callback function:Convert the function Passed as an argument to other functions to be called later.
• Dynamic binding: Associate function pointers with actual functions at runtime, thereby achieving polymorphism.
• Event handling: Define a handler function for a specific event (such as a button click) and store it in a function pointer.

Practical case: Sorting algorithm

We can use function pointers to implement different sorting algorithms. Here is a sort function using a comparison function using a function pointer:

#include <algorithm>

bool Ascending(int a, int b) {
  return a < b;
}

bool Descending(int a, int b) {
  return a > b;
}

void Sort(int* arr, int size, bool (*CompareFunc)(int, int)) {
  std::sort(arr, arr + size, CompareFunc);
}

int main() {
  int arr[] = {5, 3, 1, 2, 4};
  int size = sizeof(arr) / sizeof(arr[0]);

  // 使用升序比较函数进行排序
  Sort(arr, size, Ascending);

  // 使用降序比较函数进行排序
  Sort(arr, size, Descending);

  return 0;
}

In the above code, CompareFunc is a function pointer to a function that accepts two int type parameters and returns a bool type comparison function. We define two comparison functions Ascending and Descending, which compare two numbers in ascending and descending order. The

Sort function sorts the array arr using the comparison function passed in. By using function pointers, we can flexibly choose different comparison functions to implement different sorting algorithms.

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