scope dropPunctuation3.

static LS #keep = ll("*", "<", ">");
static SS #cache = defaultSizeMRUCache();

static LS dropPunctuation3(LS tok) {
  tok = new ArrayList<S>(tok);
  for (int i = 1; i < tok.size(); i += 2) {
    S t = tok.get(i);
    if (t.length() == 1 && !Character.isLetter(t.charAt(0)) && !Character.isDigit(t.charAt(0)) && !dropPunctuation3_keep.contains(t)) {
      // merge spacing and make sure it's not completely empty
      tok.set(i-1, or2(tok.get(i-1) + tok.get(i+1), " "));
      tok.remove(i);
      tok.remove(i);
      i -= 2;
    }
  }
  return tok;
}

sS dropPunctuation3(S s) {
  ret getOrCreate_f0(cache, s,
    () -> join(dropPunctuation3(javaTokNoQuotes(s)));
}

end scope

Began life as a copy of #1000814