c++ decltypeÓ÷¨_c++ typedef struct

ʹÓ÷½Ê½1 ÀàËÆauto

std::vector<int> v;

    typedef decltype(v.begin()) it;

    for (it i = v.begin(); i != v.end(); i++)
    {

    }

//»òÕß

for (auto i = v.begin(); i != v.end(); i++)
    { }

ʹÓ÷½Ê½2 iºÍjµÄÀàÐÍÏàͬ

int i = 1;
    decltype(i) j = i * 2;

ʹÓ÷½Ê½3 ·µ»ØÀàÐͺóÖÃ

template<typename T, typename U>
    auto add(T t, U u) -> decltype(t + u)
    {
        return t + u;
    }

    auto t = add(1.1, 2.2);