sS dropTrailingNumberFromAngleBracketCategory(S s) {
  if (!isAngleBracketed(s)) ret s;
  int i = l(s)-1;
  while (i > 1 && isDigit(s.charAt(i-1))) --i;
  if (i == l(s)-1) ret s;
  ret substring(s, 0, i) + ">";
}