c++ STL中一些常用函数/模板

std::floor         //-->向下取整数
std::ceil          // -->向上取整数：
std::llround     //最接近的整数
std::numeric_limits<double>::epsilon() //最小双精度小数
std::numeric_limits<int>::max()           //最大值
std::numeric_limits<int>::min()           //最大值

std::ref           //用于std::bind 通过引用传递
std::cref        //用于std::bind 通过常引用传递

void foo(int& a) {
    a = 10;
}

void run_func(std::function<void(void)> fun) {
    if (fun) {
        fun();
    }
}
int a = 0;
run_func(std::bind(foo, std::ref(a));

std::vector<int> a = {1,2,3,4,5,6};
std::sort(a.begin(), a.end(), std::greater<int>());//内置类型的由大到小排序
std::sort(a.begin(), a.end(), std::less<int>());   //内置类型的由小到大排序

#define BIT_SET(a,b) ((a) |= (1ULL<<(b)))
#define BIT_CLEAR(a,b) ((a) &= ~(1ULL<<(b)))
#define BIT_FLIP(a,b) ((a) ^= (1ULL<<(b)))
#define BIT_CHECK(a,b) (!!((a) & (1ULL<<(b)))) 


/* 将vector src的内存空洞清除 */
void vector_swap() {
    std::vector<int> src = {4,5,6,7,1,2,3};

    LOG(INFO) << "v size = "<< src.capacity(); //7
    src.erase(src.begin());
    LOG(INFO) << "v size = "<< src.capacity(); //7

    std::vector<int>(src).swap(src);
    LOG(INFO) << "v size = "<< src.capacity(); //6
}

/* 清空vector的内存*/
void vector_del() {
    std::vector<int> src = {4,5,6,7,1,2,3};

    LOG(INFO) << "v size = "<< src.capacity(); //7
    
    std::vector<int>().swap(src);
    
    LOG(INFO) << "v size = "<< src.capacity(); //0
}

std::typeid(double) //变量类型