for (Set<String> variables : spec.getVariables()) {
if (variables.size() > 1) {
throw new UnsupportedOperationException("Can't encode interactions yet");
}
if (variables.size() == 0) {
throw new ImpossibleStateError("No variables!");
}
final String var = variables.iterator().next();
if ("1".equals(var)) {
constantEncoder.addToVector((byte[]) null, r);
} else {