!  BestGuess makes the best guess it can out of the match list, assuming that
!  everything in the match list is textually as good as everything else;
!  however it ignores items marked as -1, and so marks anything it chooses.
!  It returns -1 if there are no possible choices.
! ----------------------------------------------------------------------------

[ BestGuess  earliest its_score best i;
    earliest = 0; best = -1;
    for (i=0 : i<number_matched : i++) {
        if (match_list-->i >= 0) {
            its_score = match_scores-->i;
            if (its_score > best) { best = its_score; earliest = i; }
        }
    }
    #Ifdef DEBUG;
    if (parser_trace >= 4)
      if (best < 0) print "   Best guess ran out of choices^";
      else print "   Best guess ", (the) match_list-->earliest, " (", match_list-->earliest, ")^";
    #Endif; ! DEBUG
    if (best < 0) return -1;
    i = match_list-->earliest;
    match_list-->earliest = -1;
    bestguess_score = best;
    return i;
];