please include function shorten.

static Symbol shortenSymbol(Symbol s) { ret shortenSymbol(s, shorten_default); }

static Symbol shortenSymbol(Symbol s, int max) {
  ret shortenSymbol(s, max, "...");
}

static Symbol shortenSymbol(Symbol s, int max, S shortener) {
  if (s == null) ret emptySymbol();
  if (max < 0) ret s;
  return s.length() <= max ? s : symbol(substring(str(s), 0, min(s.length(), max-l(shortener))) + shortener);
}

static Symbol shortenSymbol(int max, Symbol s) { ret shortenSymbol(s, max); }