c 11 – std :: array成员函数empty(),max_size() – 没用但是为

例如：

std::array<int,4> array1;  // size of 4 (but no elements initialized)
std::array<int,0> array2;  // size of zero.

array1.empty();  // false - not empty even though no elements are initialized
array2.empty();  // true - empty and no way to add elements

array1.size();      // room for four now
array1.max_size();  // room for four forever

array2.size();      // no room for anything now
array2.max_size();  // ... or ever

this question的答案处理零“大小”参数和sizeof()的非零返回,即,即使在空的情况下也会占用空间.但那不是我要问的.