char *complement (char *set) {
  int limit = 255;
  char *table = (char *) malloc((1+limit) * sizeof(char));  /* FIXED */
  int i;

  /* populate table with all non-null characters */
  for (i = 0; i < limit; i++) table[i] = i+1;
  table[limit] = 0;

  /* for characters in 'set',
     make their value in the table NULL */
  while (*set) table[*set++ - 1] = 0;

  /* now, swap NULLs in the table with the last element
     in the table, to condense the table */
  for (i = 0; i < limit; i++)
    if (! table[i])
      table[i] = table[--limit], table[limit] = 0;

  return table;
}