//! Function to add a participant to the participant group, while checking that its ID is not already in use.
void addParticipant(Participant &p)
{
if(_participants.find(p.getID())!=_participants.end())
throw std::runtime_error("Duplicate participant ID!");
_participants[p.getID()] = p;
}
//! Function to add the specified participant in the list of impossible recipients for this participant.
void addImpossibleRecipient(const Participant &p)
{
_impossible_recipients.push_back(p.getID());
}