How to replace function pointer with C++ lambda expression?

Replacing function pointers with lambda expressions improves readability, reduces boilerplate code, and increases reusability. Specifically, lambda expressions use the following syntax: [capture list](parameter list) -> return type {body}, and can be used in practical cases such as vector sorting to improve code simplicity and maintainability.

Replace function pointers with C Lambda expressions

Lambda expressions were introduced in C++11, providing a simple Method to define anonymous functions or function pointers. Replacing function pointers with lambda expressions has many benefits, including:

• Better readability
• Reduce boilerplate code
• Improve code reusability

Syntax

The syntax of lambda expression is as follows:

[capture list](parameter list) -> return type { body }

• capture list: A comma within parentheses A delimited list of variables that will be captured from the scope of the lambda expression.
• parameter list: A comma-separated parameter list within parentheses.
• return type: The return value type of the function (optional).
• body: The body of the function, enclosed in curly braces.

Example

The following is an example of replacing a function pointer with a lambda expression:

// 函数指针方式
int compare(int a, int b) { return a - b; }

// Lambda 表达式方式
auto compare = [](int a, int b) { return a - b; };

Practical case: sorting vectors

We can see the advantages of lambda expressions in a practical case:

#include <vector>
#include <algorithm>

int main() {
  std::vector<int> v = { 1, 5, 3, 2, 4 };

  // 用 lambda 表达式对向量进行排序
  std::sort(v.begin(), v.end(), [](int a, int b) { return a < b; });

  // 打印排序后的向量
  for (int x : v) {
    std::cout << x << " ";
  }

  return 0;
}

In this case, lambda expressions are used to define a comparison function that is used to Sort vectors. There is no need to define separate functions, and the code is simpler and easier to understand.

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