lambda表达式常用用法

#include <iostream> #include <vector> #include <algorithm> // lambda practice int main() { // [] 为存储需要的外部变量， 可分为值获传入与地址传入 // （）函数中的参数列表 // { } 函数体 auto square = [](int x) {return x * x; }; auto is_even = [](int x) {return x % 2 == 0; }; std::cout << "square = " << square(10) << std::endl; std::cout << "is_even = " << is_even(10) << std::endl;; int th = 10; auto bigger = [th](int x) { return x > th; }; auto inc = [&th]() {th++; }; inc(); std::cout << "bigger = " << bigger(20) << std::endl; std::cout << "inc th = " << th << std::endl; int seed = 0; auto gen = [seed]() mutable {return ++seed; }; std::cout << "gen seed = " << gen() << std::endl; std::cout << " seed = " << seed << std::endl; /* * mutable: 对类、结构体中的非静态成员变量有效。 * 作用： 允许某个成员变量在const成员函数中也可以被修改 */ auto add = [](auto a, auto b) { return a + b; }; std::cout << "add float = " << add(1.0, 6.3) << std::endl; std::cout << "add int = " << add(1, 7) << std::endl; // -> double 明确返回值类型 auto safe_div = [](double a, double b) -> double { return (b == 0) ? 0.0 : (a / b); }; std::cout << "safe_div = " << safe_div(1, 0) << std::endl; std::cout << "safe_div = " << safe_div(1, 2) << std::endl; std::vector v = {6, 2, 4, 7, 0, 55, 89, 34}; std::sort(v.begin(), v.end(), [](const auto& a, const auto& b) {return a < b; }); for(const auto& p:v) std::cout << p << std::endl; //transform 按照某种规则映射 std::transform(v.begin(), v.end(), v.begin(), [](int x) {return x * 2; }); for (const auto& p : v) std::cout << p << std::endl; }