computeDifference(new PatchGraph() {
protected Label copyVertexWithPrefix(String prefix, Label origLabel)
{
Label result = null;
if (origLabel instanceof StringLabel)
result = new StringLabel(prefix+origLabel);
else
if (origLabel instanceof ErlangLabel)
{
ErlangLabel oErl = (ErlangLabel)origLabel;
result = new ErlangLabel(oErl.function,prefix+oErl.callName,