According to here, explicit:
Specifies constructors and conversion operators (since C++11) that don't allow implicit conversions or copy-initialization.
Thus, are these two techniques identical?
struct Z {
// ...
Z(long long); // can initialize with a long long
Z(long) = delete; // but not anything smaller
};
struct Z {
// ...
explicit Z(long long); // can initialize ONLY with a long long
};
They're not identical.
Z z = 1LL;
The above works with the non-explicit version, but not with the explicit version.
Declaring constructor of Z explicit doesn't prevent conversion of the constructor argument from another type. It prevents the conversion from the argument to Z without calling the constructor explicitly.
Below is an example of explicit constructor call.
Z z = Z(1LL);