In what scenarios are C++ lambda expressions particularly useful?

C++ Lambda Expressions: Powerful Tools for Specific Scenarios

Introduction

Lambda An expression is an anonymous function introduced in C++ that allows you to create short, inline function objects. They're great for handling simple tasks that don't require declarations or separate naming.

Lambda syntax

Lambda expressions adopt the following syntax:

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

• capture-list: Specify to capture Variables.
• parameters: Specify the parameters of the function.
• return-type: Specifies the return type of the function.
• body: Define the behavior of the function.

Uses

Lambda expressions are particularly useful in the following scenarios:

• Function object callbacks:Passed to other functions or objects as callback functions.
• STL algorithms: Passed as arguments to standard library algorithms, such as std::sort and std::find.
• Event handling: Respond to user input or system events (for example, in a GUI framework).
• Closures: Capture variables to create closures that persist in the scope outside the function.

Practical case

1. As a callback function

The following code uses lambda expressions to convert strings For uppercase:

#include <iostream>
#include <string>

using namespace std;

int main() {
  string str = "hello";
  transform(str.begin(), str.end(), str.begin(), [](char c) { return toupper(c); });
  cout << str << endl;  // 输出：HELLO

  return 0;
}

2. As STL algorithm parameter

The following code uses lambda expression to find the first number greater than 5:

#include <iostream>
#include <vector>

using namespace std;

int main() {
  vector<int> nums = {1, 3, 5, 7, 9};
  auto it = find_if(nums.begin(), nums.end(), [](int n) { return n > 5; });
  if (it != nums.end()) {
    cout << "找到了第一个大于 5 的数字：" << *it << endl;  // 输出：7
  } else {
    cout << "没有找到大于 5 的数字" << endl;
  }

  return 0;
}

3. As a closure

The following code demonstrates how to create a closure using a lambda expression:

#include <iostream>

using namespace std;

int main() {
  int x = 10;
  auto f = [x](int y) { return x + y; };
  cout << f(5) << endl;  // 输出：15

  return 0;
}

Note: Compare to named functions , Lambda expressions have the following limitations:

• They do not have independent namespaces.
• They cannot be overloaded.
• They cannot have default parameters.

When using lambda expressions, carefully weigh their advantages and limitations to determine whether they are the best choice for a specific scenario.

The above is the detailed content of In what scenarios are C++ lambda expressions particularly useful?. For more information, please follow other related articles on the PHP Chinese website!