rt-thread/components/rtgui/utils/perfect_hash/doc/parameters.txt

    string  |  expands to
    --------+--------------------------------
      $NS   |  the length of S1 and S2
      $S1   |  array of integers S1
      $S2   |  array of integers S2
      $NG   |  length of array G
      $G    |  array of integers G
      $NK   |  the number of keys, i.e. length of array K and H
      $K    |  array with the quoted keys
      $H    |  array of integer hash values
      $$    |  $ (a literal dollar sign)