How to add valid key without specifying value to a std::map?

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不知归路 2021-02-20 05:10

I have a std::map, and I would like to add a valid key to iterate over it later, but without giving any value (it will be given later on in the course of the iterations).

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星月不相逢 (楼主)

2021-02-20 05:24
I suppose something that could help you out is Boost.Optional.
```
#include 
#include 

class CantConstructMe
{
    CantConstructMe() {}
};

int main()
{
    std::map > m;
    m[0];
}
```
The lack of available default constructor is not an issue, by default optional will be empty.
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