// find out which input to the match the solution set is
MatchNode mn = (MatchNode) successor;
if (mn.getFirstPredecessorNode() == solutionSetNode) {
mn.makeJoinWithSolutionSet(0);
} else if (mn.getSecondPredecessorNode() == solutionSetNode) {
mn.makeJoinWithSolutionSet(1);
} else {
throw new CompilerException();
}
}
else if (successor.getClass() == CoGroupNode.class) {