C++ – How to check if array of unsigned int is empty or not

I have this:

std::uint32_t data[6];
std::map<std::string, std::variant<int, float, std::string, std::uint32_t> map_;

map_["data0"] = data[0] ? data[0] : 0;
map_["data1"] = data[1] ? data[1] : 0;
map_["data2"] = data[2] ? data[2] : 0;
map_["data3"] = data[3] ? data[3] : 0;
map_["data4"] = data[4] ? data[4] : 0;
map_["data5"] = data[5] ? data[5] : 0;

The idea of map_["data0"] = data[0] ? data[0] : 0; is to see if there is any value already set in data[0]if not to set 0.

However this does not work properly. Even if data[0] is not set it does not return ‘0’.

Any idea how can I check the array at specific index if the std::uint32_t is "initilized" or set ?

>Solution :

It is not possible to check if an integer type is initialized or not. An integer is not a pointer, and it is not pointer-like, it is not nullable. An uninitialized integer has an indeterminate value which cannot be inspected and which is distinct from the concept of null.

You need to track whether or not each element has a value yourself somehow.

Possible solutions include :

• Using a sentinel value. For example, you could decide that the
  maximum representable value means "no value" and initialized all
  elements to that value.

• Using flags. You could create another array of bool or a
  std::bitset to track which element has a value.

• Using a different type which can encode more information, such as
  std::optional<std::uint32_t> data[6];.