Rule A13-1-3 (required, implementation, automated)
User defined literals operators shall only perform conversion of passed parameters.
Rationale
It is expected behavior that the user-defined literals operators are only used to convert passed parameters to the type of declared return value. User-defined literals are not supposed to provide any other side-effects.
Example
// $Id: A13-1-3.cpp 289436 2017-10-04 10:45:23Z michal.szczepankiewicz $
#include <cstdint>
#include <iostream>
struct Cube
{
unsigned long long int volume;
constexpr explicit Cube(unsigned long long int v) : volume(v) {}
};
constexpr Cube operator"" _m3(unsigned long long int volume)
{
return Cube(volume); // Compliant
}
struct Temperature
{
unsigned long long int kelvins;
constexpr explicit Temperature(unsigned long long int k) : kelvins(k) {}
};
constexpr Temperature operator"" _K(unsigned long long int kelvins)
{
return Temperature(kelvins); // Compliant
}
static void SumDistances(std::int32_t distance)
{
static std::int32_t overallDistance = 0;
overallDistance += distance;
}
struct Distance
{
long double kilometers;
explicit Distance(long double kms) : kilometers(kms) {}
};
Distance operator"" _m(long double meters)
{
SumDistances(meters); // Non-compliant - function has a side-effect
return Distance(meters / 1000);
}
void operator"" _print(const char* str)
{
std::cout << str << ’\n’; // Non-compliant - user-defined literal operator
// does not perform conversion and has a
// side-effect
}
See also
none