lamda数据对排序

typedef std::pair<int, double> PAIR_IF;

void CargoPre::SortWithIndex(std::vector <PAIR_IF > &vc, int mode)
{
    switch(mode)
    {
        case 0: /////0 for ording data with first(data num) and decline order
        {
            sort(vc.begin(), vc.end(), [&vc](PAIR_IF a, PAIR_IF b) ->bool{return a.first>b.first;});  ////descending order
            break;
        }
        case 1: /////1 for ording data with second(data) and decline order
        {
            sort(vc.begin(), vc.end(), [&vc](PAIR_IF a, PAIR_IF b) ->bool{return a.second>b.second;});  ////descending order
            break;
        }
        case 2: /////2 for ording data with first(data num) and increasing order
        {
            sort(vc.begin(), vc.end(), [&vc](PAIR_IF a, PAIR_IF b) ->bool{return a.first<b.first;});  ////increasing order
            break;
        }
        case 3://///3 for ording data with second(data) and increasing order
        {
            sort(vc.begin(), vc.end(), [&vc](PAIR_IF a, PAIR_IF b) ->bool{return a.second<b.second;});  ////increasing order
            break;
        }
        default:
        {
            std::cout <<"wrong mode number input" <<std::endl;
            break;
        }
    }
}

这个是我写的一个小排序算法，利用lamda表达式，比如一些数据pair，一个是int型，一个是double型，按照int或者按照double排序，这个一个函数就全包含了