CC++ 中的函数式编程

函数式编程：一种强大的编程范式

cpp
#include 
#include 
#include 
template
std::vector map(const std::vector& input, F func) {
    std::vector result;
    for(const auto& item : input) {
        result.push_back(func(item));
    }
    return result;
}
int main() {
    std::vector numbers = {1, 2, 3, 4, 5};
    auto square = [](int x) { return x * x; };
    std::vector squared_numbers = map(numbers, square);
    for(const auto& number : squared_numbers) {
        std::cout << number << " ";
    }
    return 0;
}

cpp
#include 
int fibonacci(int n) {
    if(n <= 1) {
        return n;
    }
    return fibonacci(n - 1) + fibonacci(n - 2);
}
int main() {
    int n = 10;
    int result = fibonacci(n);
    std::cout << "The " << n << "th Fibonacci number is: " << result << std::endl;
    return 0;
}

cpp
#include 
#include 
template
class LazyList {
public:
    LazyList(std::function generator) : generator(generator) {}
    T operator[](int index) {
        while(elements.size() <= index) {
            elements.push_back(generator());
        }
        return elements[index];
    }
private:
    std::function generator;
    std::vector elements;
};
int main() {
    auto fibonacci = LazyList([&]() {
        static int a = 0, b = 1;
        int result = a;
        a = b;
        b = a + b;
        return result;
    });
    std::cout << fibonacci[10] << std::endl;
    std::cout << fibonacci[20] << std::endl;
    std::cout << fibonacci[30] << std::endl;
    return 0;
}