/**
* Gets the ID of the given scope.
*
* @param scp scope
* @return id if existing, {@code null} otherwise
*/
private int id(final Scope scp) {
if (ids != null) {
final Integer id = ids.get(scp);
return id == null ? -1 : id;
}
final int ss = scopes.size();
for (int s = 0; s < ss; s++) if (scopes.get(s) == scp) return s;
return -1;
}
