docs/SGF Spec/backgammon.html

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   7 <H1>Backgammon (GM[6])</H1>
   8
   9 For more information contact Gary Wong (author of
  10 <A HREF="http://www.gnu.org/software/gnubg/gnubg.html">Gnu Backgammon</A>)
  11 at <A HREF="mailto:gary@cs.arizona.edu">gary@cs.arizona.edu</A>.
  12
  13 <H2><A NAME="types">Point & Stone type</A></H2>
  14
  15 In Backgammon, the Stone becomes Point, and is a single lower case letter.
  16 <P>
  17 <IMG src="images/bgpoint.png" ALT="[coordinates (bgpoint.png)]">
  18 Coordinate system for points and moves
  19 <P>
  20 `a' is the 1 point for white (and the 24 point for black), through to
  21 `x' which is the 24 point for white (and the 1 point for black).  `y'
  22 is the bar, and `z' is the bearoff tray.
  23
  24 <H2><A NAME="moves">Move type</A></H2>
  25
  26 Normal moves specify the dice roll (as a pair of digits from 1 to 6)
  27 followed by 0 to 4 source/destination pairs.  Moves which hit are not
  28 recorded differently.
  29 <P>
  30 Other legal moves include `double', `take' and `drop' for cube action
  31 (where `double' includes initial and subsequent doubles, as well as
  32 beavers).
  33 <P>
  34 Examples of legal moves include:
  35 <DL>
  36 <DT>W[31hefe]
  37 <DD>White playing an opening 31 as 8/5 6/5.
  38 <DT>B[61yg]
  39 <DD>Black entering with bar/18.
  40 <DT>B[66]
  41 <DD>Black failing to enter with 66.
  42 <DT>W[66fzezdzcz]
  43 <DD>White rolling 66 and playing 6/off 5/off 4/off 3/off.
  44 <DT>W[double];B[double];W[take];W[66fzfzfzfz]
  45 <DD>White doubles, black beavers, white accepts the beaver and rolls 66 to
  46 play 6/off(4).
  47 </DL>
  48
  49 <H3><A NAME="colours">Colours</A></H3>
  50 The specification describes players as "black" and "white"; if an
  51 implementation uses alternate names, then the following defaults are
  52 recommended for consistency:
  53 <P>
  54 <PRE>
  55  White = O = 0
  56  Black = X = 1
  57 </PRE>
  58
  59 <H2><A NAME="properties">Properties</A></H2>
  60
  61 <PRE>
  62 <A NAME="CO"><B>Property:</B>   CO</A>
  63 <B>Propvalue:</B>       <A HREF="sgf4.html#types">simpletext</A>
  64 <B>Propertytype:</B>    setup
  65 <B>Function:</B>        Set the position of the doubling cube.  The value
  66                 should be `b' (black), `w' (white), `c' (centred), or `n'
  67                 (none -- for cubeless or Crawford games).
  68 <B>Related:</B> <A HREF="#CV">CV</A>
  69
  70 <A NAME="CV"><B>Property:</B>   CV</A>
  71 <B>Propvalue:</B>       <A HREF="sgf4.html#types">number</A>
  72 <B>Propertytype:</B>    setup
  73 <B>Function:</B>        Set the value of the doubling cube.  This value
  74                 defaults to 1 at the beginning of the game, but a CV property
  75                 should be added when setting up a position where a double has
  76                 been made, or at the beginning of a money game if automatic
  77                 doubles occur.
  78 <B>Related:</B> <A HREF="#CP">CP</A>
  79
  80 <A NAME="DI"><B>Property:</B>   DI</A>
  81 <B>Propvalue:</B>       <A HREF="sgf4.html#types">number</A>
  82 <B>Propertytype:</B>    setup
  83 <B>Function:</B>        Set the dice without moving (this could be useful for
  84                 creating problem positions, e.g. DI[31])
  85 <B>Related:</B> <A HREF="#CO">CO</A>
  86
  87 <A NAME="MI"><B>Property:</B>   MI</A>
  88 <B>Propvalue:</B>       list of composed <A HREF="sgf4.html#types">simpletext</A> ':' <A HREF="sgf4.html#types">simpletext</A>
  89 <B>Propertytype:</B>    game-info
  90 <B>Function:</B>        Specifies information about the match the game belongs to.
  91                 This property should specify a list of tag/value pairs, where
  92                 the allowable tags are case-insensitive, and include:
  93
  94                   length - the match length (number of points); value should
  95                            be a <A HREF="sgf4.html#types">number</A>
  96                   game   - the number of this game within the match (the
  97                            first game is 1); value should be a <A HREF="sgf4.html#types">number</A>
  98                   bs     - the score for Black at the start of the game;
  99                            value should be a <A HREF="sgf4.html#types">number</A>
 100                   ws     - the score for White at the start of the game;
 101                            value should be a <A HREF="sgf4.html#types">number</A>
 102
 103                 Unknown tags should be ignored (a warning may be produced).
 104                 The order of tags in the list is not significant.  An example
 105                 MI property is:
 106                                   MI[length:7][game:3][ws:2][bs:1]
 107 <B>Related:</B> <A HREF="properties.html#EV">EV</A>, <A HREF="properties.html#GN">GN</A>, <A HREF="#RE">RE</A>, <A HREF="properties.html#RO">RO</A>
 108
 109 <A NAME="RE"><B>Property:</B>   RE</A>
 110 <B>Propvalue:</B>       <A HREF="sgf4.html#types">simpletext</A>
 111 <B>Propertytype:</B>    game-info
 112 <B>Function:</B>        The <A HREF="properties.html#RE">general RE property</A> has the following
 113                 modification in backgammon games: in the case of a
 114                 resignation, the value should also specify the number of
 115                 points before the R(esign).  Here are three example RE
 116                 properties:
 117
 118                         RE[B+6R]      -- White resigns a backgammon on a 2
 119                                          cube (worth 6 points).
 120                         RE[W+2Resign] -- Black resigns a gammon on a 1 cube
 121                                          (worth 2 points).
 122                         RE[W+4]       -- Black drops a redouble to 8 (note
 123                                          this is considered a normal loss, not
 124                                          a resignation).
 125 <B>Related:</B> <A HREF="properties.html#RE">RE</A>
 126
 127 <A NAME="RU"><B>Property:</B>   RU</A>
 128 <B>Propvalue:</B>       <A HREF="sgf4.html#types">simpletext</A>
 129 <B>Propertytype:</B>    game-info
 130 <B>Function:</B>        Backgammon-specific values for the <A HREF="properties.html#RU">general RU property</A>
 131                 include the following:
 132
 133                   [Crawford] -- the Crawford rule is being used in this match,
 134                     although this is not the Crawford game.
 135                   [Crawford:CrawfordGame] -- this IS the Crawford game.
 136                   [Jacoby] -- the Jacoby rule is in use for this game.
 137 <B>Related:</B> <A HREF="properties.html#RU">RU</A>
 138 </PRE>
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