using boolean_t = BooleanType;
The type used to store JSON booleans.
RFC 8259 implicitly describes a boolean as a type which differentiates the two literals true and false.
To store boolean values in C++, a type is defined by the template parameter BooleanType which chooses the type to use.
With the default values for BooleanType (bool), the default value for boolean_t is bool.
Boolean values are stored directly inside a basic_json type.
Example
The following code shows that boolean_t is by default, a typedef to bool.
#include <iostream>
#include <iomanip>
#include <nlohmann/json.hpp>
using json = nlohmann::json;
int main()
{
std::cout << std::boolalpha << std::is_same<bool, json::boolean_t>::value << std::endl;
}
Output:
true