!7

sclass ApplySF {
  S name;
  int pos;
  L args;
  
  *() {}
  *(S *name, int *pos, O... args) { this.args = asList(args); }
  
  O call(O o) {
    L args = cloneList(this.args);
    args.add(pos, o);
    ret makeAndCall(name, toObjectArray(args));
  }
}

sclass Operation {
  ApplySF op;
  Data result;
  
  *() {}
  *(ApplySF *op) {}
}

sclass Data {
  O data;
  bool error;
  new L<Operation> operations;
  
  *() {}
  *(O *data) {}
}

static Data initial;

p-tt {
  S input = loadSnippet(#1008462);
  initial = new Data(input);
  doOp(initial, new ApplySF("findSubstringsEnclosedBy_inner", 0, '<', '>'));
  printTree("", initial);
}

svoid printTree(Data data) {
  if (data == null) { print("-"); ret; }
  if (data.error) print("Error");
  else print("Data: " + shorten(struct(data.data)));
  print_threadIndentPlus();
  try {
    int i = 0;
    for (Operation op : data.operations) {
      print("Op " + (++i) + ": " + struct(op.op));
      printTree(op.result);
    }
  } finally {
    print_threadIndentMinus();
  }
}

svoid doOp(Data data, ApplySF theOp) {
  Operation op = new Operation(theOp);
  data.operations.add(op);
  try {
    op.result = new Data(op.op.call(data.data));
  } catch {
    op.result = nu(Data, error := true);
  }
}