Modern C++ 语法糖

1. if/switch 初始化语句
// before
auto* tmp = praseExpression();
if (tmp != nullptr) {
	doSomething;
}

// after
if (auto* tmp = praseExpression(); tmp != nullptr) {
	doSomething();
}

2.结构化绑定
std::tuple<int, string> nexToken() {
	return {4, "fallthrogh"};
}

//before 
int main() {
	auto token = nexToken();
	std::cout << std::get<0>(token) << ", " << std::get<1>(token);
	return 0;
}

//after
int main() {
	auto[tokentype, lexeme] = nexToken();
	std::cout << tokentype << ", " << lexeme << endl;
	return 0;
}

3. std::string_view
//before
void isKeyword(const std::string & lit) {
	work();
}

//after
void isKeyword(std::string_view lit) {
	work();
}

4.内联变量
inline int k = 10; //不需要为一个简单的变量分一个.cpp 写定义了

5.折叠表达式和泛型lambda
//before
if(x == 'X' || x = 'x' || x = '.') {
	work();
}
// after
static auto anyone = [](auto&& k, auto&& ...arge)->bool{return ((args == k) || ...); };
if (anyone(x, 'x', 'X', '.') {
	work();
}

6. 继承构造函数
struct Base {
	Base(int a, char b, double c, string d) : a(a), b(b), c(c), d(std::move(d)) {}
	int a;
	char b;
	double c;
	string d;
};

//before
struct Derive: public Base{
	Derive(int a, char b, double c, string d):Base(a, b, c, d){}
}

//after
struct Derive: public Base {
	using Base::Base;
};

知乎 @racljk