I have a
typedef std::array<std::byte, 4> CatType;
And I want to initialize a constant of this type. I can do
const CatType mycat = {std::byte{0x00}, std::byte{0x00}, std::byte{0x00}, std::byte{0x00}};
Which works, but I'd like for readability something like
const CatType mycat = 0x001020ff
Which fails with error
conversion from ‘int’ to non-scalar type ‘const CatType’ {aka ‘const std::array<std::byte, 4>’} requested
You can define CatType as a wrapper class instead of a typedef, and define a converting constructor from int:
#include <array>
#include <cstddef>
class CatType {
private:
std::array<std::byte, 4> m_arr;
public:
CatType(int value) :
m_arr {
std::byte((value >> 24) & 255),
std::byte((value >> 16) & 255),
std::byte((value >> 8) & 255),
std::byte(value & 255),
}
{
}
std::byte& operator [](std::size_t index) {
return m_arr[index];
}
std::byte operator [](std::size_t index) const {
return m_arr[index];
}
};
If you do not want to create a wrapper class, a user-defined literal (available since C++11) is the closest you can get:
#include <array>
#include <cstddef>
std::array<std::byte, 4> operator ""_arr(unsigned long long value) {
return std::array<std::byte, 4> {
std::byte((value >> 24) & 255),
std::byte((value >> 16) & 255),
std::byte((value >> 8) & 255),
std::byte(value & 255)
};
}
// Usage:
typedef std::array<std::byte, 4> CatType;
int main() {
const CatType mycat = 0x001020ff_arr;
return 0;
}
