static ItIt<S> splitAtSpaceIterator(S s) {
  ret iff_null(new IF0<S> {
    int i = 0, l = l(s);
    
    public S get() {
      // skip space(s)
      
      while (i < l) {
        if (isSpaceEtc(s.charAt(i)))
          ++i;
        else
          break;
      }
      
      if (i >= l)
        null;

      int j = i;
      // scan for non-whitespace
      while (j < l && !isSpaceEtc(s.charAt(j)))
        ++j;
        
      S part = substring(s, i, j);
      i = j;
      ret part;
    }
  });
}

Began life as a copy of #1028697