What are some practical examples of using C++ lambda expressions for data filtering and transformation?

In C, lambda expressions can be used to easily filter and transform data. For example, you can use lambda expressions to filter odd elements in a container, transform elements in a container, filter and transform associative containers, use lambda expressions in algorithms, and pass lambda expressions as function arguments. These methods can make data processing tasks simpler and more efficient.

A practical case of using C lambda expressions for data filtering and transformation

Lambda expressions are very useful in C, especially It's when filtering and transforming data. Here are some examples of practical applications:

1. Filter elements in a container

std::vector<int> numbers = {1, 2, 3, 4, 5, 6, 7, 8, 9};

// 使用 lambda 表达式过滤奇数
std::vector<int> odd_numbers = std::filter(numbers.begin(), numbers.end(), [](int n) { return n % 2 != 0; });

2. Transform elements in a container

std::vector<double> squares = std::transform(numbers.begin(), numbers.end(), [](int n) { return n * n; });

3. Filter and transform associated containers

std::map<int, std::string> name_age = {
    {1, "John"},
    {2, "Mary"},
    {3, "Bob"},
    {4, "Alice"}
};

// 过滤年龄大于 2 的人
auto filtered_name_age = std::map<int, std::string>(name_age.begin(), name_age.end(), [](const std::pair<int, std::string>& p) { return p.second.size() > 2; });

4. Use lambda expressions in algorithms

std::sort(numbers.begin(), numbers.end(), [](int a, int b) { return a > b; }); // 从大到小排序

5. Passing lambda expressions as function parameters

void process_data(std::vector<int>& data, std::function<void(int)> callback) {
    for (int& element : data) {
        callback(element);
    }
}

process_data(numbers, [](int n) { std::cout << n << " "; }); // 打印出容器中的每个元素

These are just some of the ways in C to use lambda expressions for data filtering and transformation. By leveraging lambda expressions, you can write concise and powerful code to handle various data manipulation tasks.

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