11 namespace ActsFatras {
 
   16 class SimulatorErrorCategory final : 
public std::error_category {
 
   18   const char* 
name() const noexcept final { 
return "SimulatorError"; }
 
   19   std::string 
message(
int c) 
const final {
 
   20     switch (static_cast<SimulatorError>(
c)) {
 
   21       case SimulatorError::eInvalidInputParticleId:
 
   22         return "Input particle id with non-zero generation or sub-particle";
 
   29 const SimulatorErrorCategory s_simulatorErrorCategory;
 
   34   return {
static_cast<int>(
e), s_simulatorErrorCategory};