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gnus: Group Info

 
 11.7.6 Group Info
 -----------------
 
 Gnus stores all permanent info on groups in a “group info” list.  This
 list is from three to six elements (or more) long and exhaustively
 describes the group.
 
    Here are two example group infos; one is a very simple group while
 the second is a more complex one:
 
      ("no.group" 5 ((1 . 54324)))
 
      ("nnml:my.mail" 3 ((1 . 5) 9 (20 . 55))
                      ((tick (15 . 19)) (replied 3 6 (19 . 3)))
                      (nnml "")
                      ((auto-expire . t) (to-address . "ding@gnus.org")))
 
    The first element is the “group name”—as Gnus knows the group,
 anyway.  The second element is the “subscription level”, which normally
 is a small integer.  (It can also be the “rank”, which is a cons cell
 where the ‘car’ is the level and the ‘cdr’ is the score.)  The third
 element is a list of ranges of read articles.  The fourth element is a
 list of lists of article marks of various kinds.  The fifth element is
 the select method (or virtual server, if you like).  The sixth element
 is a list of “group parameters”, which is what this section is about.
 
    Any of the last three elements may be missing if they are not
 required.  In fact, the vast majority of groups will normally only have
 the first three elements, which saves quite a lot of cons cells.
 
    Here’s a BNF definition of the group info format:
 
      info          = "(" group space ralevel space read
                      [ "" / [ space marks-list [ "" / [ space method [ "" /
                      space parameters ] ] ] ] ] ")"
      group         = quote <string> quote
      ralevel       = rank / level
      level         = <integer in the range of 1 to inf>
      rank          = "(" level "." score ")"
      score         = <integer in the range of 1 to inf>
      read          = range
      marks-lists   = nil / "(" *marks ")"
      marks         = "(" <string> range ")"
      method        = "(" <string> *elisp-forms ")"
      parameters    = "(" *elisp-forms ")"
 
    Actually that ‘marks’ rule is a fib.  A ‘marks’ is a ‘<string>’
 consed on to a ‘range’, but that’s a bitch to say in pseudo-BNF.
 
    If you have a Gnus info and want to access the elements, Gnus offers
 a series of macros for getting/setting these elements.
 
 ‘gnus-info-group’
 ‘gnus-info-set-group’
      Get/set the group name.
 
 ‘gnus-info-rank’
 ‘gnus-info-set-rank’
      Get/set the group rank (Group Score).
 
 ‘gnus-info-level’
 ‘gnus-info-set-level’
      Get/set the group level.
 
 ‘gnus-info-score’
 ‘gnus-info-set-score’
      Get/set the group score (Group Score).
 
 ‘gnus-info-read’
 ‘gnus-info-set-read’
      Get/set the ranges of read articles.
 
 ‘gnus-info-marks’
 ‘gnus-info-set-marks’
      Get/set the lists of ranges of marked articles.
 
 ‘gnus-info-method’
 ‘gnus-info-set-method’
      Get/set the group select method.
 
 ‘gnus-info-params’
 ‘gnus-info-set-params’
      Get/set the group parameters.
 
    All the getter functions take one parameter—the info list.  The
 setter functions take two parameters—the info list and the new value.
 
    The last three elements in the group info aren’t mandatory, so it may
 be necessary to extend the group info before setting the element.  If
 this is necessary, you can just pass on a non-‘nil’ third parameter to
 the three final setter functions to have this happen automatically.
 

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