RULES USED BY THE MAH-JONG PROGRAMS

The game currently implemented is a version of the classical Chinese
game. The most convenient and comprehensive set of rules is that
provided by A. D. Millington, "The Complete Book of Mah-Jongg", 
Weidenfield & Nicolson (1993), ISBN 0 297 81340 4.
In the following, M 103 denotes item 103 of the rules laid out in Chapter 3 
of that book. I here describe only the differences from these
rules, some of which differences are consequences of using computers,
and some of which are points where my house rules differ from
Millington's version. In due course, all variations (of Chinese
classical) will be accommodated, if there is sufficient desire.

Classification of tiles (M 1-8): the tiles are a standard Chinese set.
The tiles do not have Arabic numerals, except for the flowers and
seasons, where the identifying Chinese characters are too small to be
legible. A numbered set is included in the distribution and can be
used via the Tileset display preference.
The flowers and seasons may be removed from the tile set by unsetting
the  Flowers  game option.

Preliminary (M 9-10): nothing to say.

Duration of the game (M 11-14): standard rules. In particular, the
title of East does not pass after a wash-out.

Selection of seats (M 15): the players are seated in the
order they connect to the server, or randomly, according to the option 
given to the server.

The deal etc. (M 16-27): There is no attempt to simulate the usual
dealing ritual (M 16-20, 23-26); the wall is built randomly by the
server. The dead wall is also maintained by the server.
The existence of a dead wall is controlled by the  DeadWall  game
option; normally there is a dead wall.
The deal wall is either 14 tiles and kept at 13 or 14 during play (as
in most authors), or is 16 tiles, not extended during play (per
Millington (M 22)), according to the  DeadWall16  game option.
Replacement tiles for kongs are always taken from the loose tiles,
but replacements for bonus tiles may be drawn from the live wall (M 31),
or from the loose tiles, according to the  FlowersLoose  game option.

Object of game (M 28-31): all winning hands must comprise four sets
and a pair, with the exception of the Thirteen Unique Wonders.
If the  SevenPairs  game option is set, then a hand of any seven
pairs is also allowed as a winning hand.

Bonus tiles (M 31): M requires that bonus tiles must be declared in
the turn in which they are drawn; otherwise the player may not
exchange or score them (and thus they cannot go out). We do not make
this restriction, as it is (a) pointless (b) unenforceable in real
life. Bonus tiles may be declared at any time after drawing from the
wall. (Obviously, there is no reason not to declare them immediately.)

Commencement of the Game (M 32-33): standard.

Playing procedure (M 34-38): standard.
In particular, the other players have to give permission for
east to start playing (M 34).
The display of discards cannot be controlled by the server; the
current X client displays them in an organized fashion, rather than
the random layout required by M 35.

Chow (M 39-42): standard.

Pung (M 43-45): standard.

Kongs (M 46-52): M distinguishes three types of kong: concealed,
claimed (by Kong), and annexed (formed by adding a discard to an
exposed pung), and allows claimed kongs to be counted as concealed for 
the purposes of doubling combinations. I have not seen this anywhere
else; normally, a claimed kong is treated as exposed for all purposes.
We follow the normal convention; however, the game option
KongHas3Types can be set to implement M's rules. In this case, the xmj
program will distinguish claimed kongs by displaying them with the
last tile face down, whereas annexed kongs are all face up.
Players may declare a concealed kong, or add to a pung,
only when they have just drawn a tile from the wall (live or dead);
not just after a claiming a discard. (A silly restriction in my view,
but one that all rule sets seem to have (M 51).)

Calling and Mah Jong (M 53-54): standard. (I.e. there is no "Calling"
declaration.)

NOTE: M permits players to change their mind about making a claim 
(M 69); we do not, and all claims are irrevocable. Question: should we 
allow revocation?

Original Call (M 55): the Original Call declaration must be made
simultaneously with the first discard, rather than afterwards.
NOTE: the server does *not* check that the declarer does indeed
have a calling hand, as a mistaken original call does not damage the
other players or the progress of the game. The server does, however,
thereafter prevent the declarer from changing their hand; therefore a
mistaken original call will make it impossible to go out. (Note: in M, 
an Original Caller may change their hand, but will thereby lose the
ability to go out (M 55(b)); is this a better way to treat it?)
Note also: as per M, an original call can be made even if another
player has claimed a discard before, unlike the Japanese version.

Robbing a Kong (M 57-60): Robbing a kong is implemented. However, as
with discards, we require that kongs are robbed before anything else
happens, and in particular before the konger draws a replacement tile.
Therefore, after a kong, all other players must either claim Mah Jong
or pass. (The provided programs will pass automatically if robbing is
not possible.) As for discards, there is a time limit.

Precedence of claims for discard (M 61-65):
Many rules allow a discard to be claimed up until the time the next
discard is made. M does this, with elaborate rules for the precise
specification.
For ease of implementation, we do not allow this: instead, all players 
are required to make a claim or pass, and once all players have
claimed, the successful claim is implemented irrevocably.
The server imposes a time limit; players that do not claim within
the limit are deemed to have passed. This defaults to 15 seconds,
but can be changed or disabled by the  Timeout  game option.

Irregularities in Play (M 66-81): the server does not permit unlawful
moves, and so no irregularities can arise.

False Declaration of Mah Jong (M 82-83): such declarations are not
permitted by the server.

False Naming of Discards (M 84-88): this also cannot happen.

Incorrect Hands (M 89): cannot happen.

Letting Off a Cannon (M 90-96): as in M. However, if a player makes
a dangerous discard, but has no choice, the server will determine
this; it is not necessary to plead "no choice" explicitly, and neither 
is the player's hand revealed to the other players.

Wash-Out (M 97-99): standard.

Points of Etiquette (M 100-102): not applicable.

Displaying the Hand (M 103-106):
The format of display is a matter for the client program, and cannot
be controlled by the server.
After Mah Jong, the players are responsible for declaring concealed
sets in whatever way they wish. The winner, of course, is required to
declare a complete hand; but the losers may declare as they wish.
Once a set is declared, it cannot be revoked. Note that the losers may 
declare multiple scoring pairs.

Procedure in Settlement (M 107-111):
The settlement is classical: that is, the winner gets the value of
their hand from all players; the losers pay one another the
differences between their scores; except all payments to or from East
are doubled; and if players let off a cannon, they pay everybody's debt.
Unlike normal play (M 110), all hands are scored by the server, rather 
than by the players. Settlement is also computed by the server.
Some variations in settlement are provided: if the LosersSettle game
option is set to false, there are no payments between losers; if the
EastDoubles game option is set to false, payments to or from East are
not doubled; if the DiscDoubles game option is set to true, then the
discarder of the tile that gave Mah-Jong will pay double to the
winner, and a self-draw is paid double by everybody.

Method of Scoring (M 112-122):
The method is standard (M 112), viz calculate points obtained from
sets and bonuses, and then apply doubles.

The following points are given for tiles:

  Bonus tiles:
    4 each (M 114(a))

  Pungs:
    2 for exposed minor tiles; 4 for exposed major or concealed minor;
    8 for concealed major. (M 114(b))

  Kongs:
    8 for exposed minor; 16 for exposed major or concealed minor;
    32 for concealed major. (M 114(c))

  Chows:
    no score. (M 114(d))

  Pair:
    2 for a pair of Dragons, Own Wind, or Prevailing Wind.
    A pair that is both Own and Prevailing Wind scores 4. (M 114(e))
    Non-winning hands may score more than one pair.

  Basic points:
    the winner gets 20 points for going Mah Jong.
    This can be changed by the  MahJongScore  game option 
    (M 115(a) has 10 points).

  Seven Pairs hand:
    If Seven Pairs hands are allowed, they receive an additional score of
    20 points, changed by the  SevenPairsVal  game option.

  Winning from wall:
    if the final tile is drawn from the wall, 2 points
    are added (M 115(b)). 

  Filling the only place:
    if the final tile is the only denomination
    that could have completed the hand, 2 points are added (M 115(c)).
    NOTE: As in M, if all four copies of a tile are exposed on the table,
    it does not count as available for completing the hand.

  Fishing the eyes:
    a player who completes by obtaining a pair gets 2
    points if the pair is minor, or 4 if major (M 115(d)).
    Note: to obtain these points for a discard, the player must actually
    claim the discard for a pair: e.g. if waiting on 5677, and 7 is
    discarded, the player must claim for the pair, not the chow.

The following doubles apply to all hands.
All possible clauses apply unless stated otherwise.

  Having own flower or own season.
    No extra score. Changed by the  FlowersOwnEach  game option.

  Having own flower AND own season,
    1 double. (M 116(a)). Changed by the  FlowersOwnBoth  game option.

  Having all four flowers,
    1 double. (M 116(b)). Changed by the  FlowersBouquet  game option.

  Having all four seasons,
    1 double. (M 116(b)). Changed by the  FlowersBouquet  game option.
    

  Each set of dragons,
    1 double. (M 116(d))

  A set of the player's own wind,
    1 double. (M 116(e))

  A set of the prevailing wind,
    1 double. (M 116(f))

  "Little Three Dragons": two sets and a pair of dragons.
    1 double. (M 116(g))

  "Big Three Dragons": three sets of dragons.
    2 doubles. (M 116(h))

  "Little Four Winds": three sets and a pair of winds.
    1 double. (M 116(i))

  "Big Four Winds": four sets of winds.
    2 doubles. (M 116(j))
    
    (Note: the definitions of these last four doubles when applied to
    non-winning hands are subject to wide variations. Possibly there
    should be options to allow other possibilities.)

  Three concealed pungs:
    1 double. (M 116(k))
    (Note: if the KongHas3Types game option is set, a claimed kong counts
    as concealed for this hand; see the note above under "Kongs".)

The following doubles apply to the winning hand only:

  No score hand: four chows and a non-scoring pair.
    1 double. (M 117(a))
    (Note: like M, we allow any of the extra points (Fishing the Eyes,
    etc) to go with this double. Some rules say that the extra points
    invalidate this hand. Possibly there should be an option for this.)

  No chows:
    1 double. (M 117(b))

  Concealed hand:
    1 double (M 117(c)), changeable with the  ConcealedFully  game
    option. (Note: this means a hand that is fully concealed after going
    out. Another common value for this is 3 doubles, in which case 1
    double is usually given for a semi-concealed hand (see below).)
    (Note: if the KongHas3Types game option is set, a claimed kong counts
    as concealed for this hand; see the note above under "Kongs".)

The following doubles normally apply to the winning hand only;
however, the  LosersPurity  game option can be set to allow
losing hands to score them (this is a highly deprecated American
feature, but has been requested by a user).

  Semi-concealed hand:
    no doubles, changeable with the  ConcealedAlmost  game
    option. (Not in M)
    (Note: this means a winning hand that is concealed up to the point of
    going out, or, if enabled, a concealed losing hand. According to a
    discussion on rec.games.mahjong, a winning semi-concealed hand is
    classically awarded one double (with three given for fully concealed).
    One book in my possession (U.S.A., early 1920s) awards this double
    only to a hand that is concealed except for the pair.)
    (Note: if the KongHas3Types game option is set, a claimed kong counts
    as concealed for this hand; see the note above under "Kongs".)

  One suit with honours:
    1 double. (M 117(d))

  One suit only:
    3 doubles. (M 117(e))

  All majors:
    1 double. (M 117(f))

  All honours (in an unlimited game):
    2 doubles. (M 117(g)) 
    (Note: such a hand will also score the double for all majors.)

  All terminals (in an unlimited game):
    2 doubles. (Not in M)
    (Note: such a hand will also score the double for all majors.)

The following doubles apply only to the winning hand:

  Winning with loose tile:
    1 double. (M 117(h))
    (Note: with the default settings, replacements for bonus tiles come from
    the live wall. Hence this double applies only to winning after Kong.)

  Winning from the bottom of the sea (winning with last tile),
    1 double. (M 117(i))

  Catching a fish from the bottom of the sea (winning with last discard),
    1 double. (M 117(j))

  Robbing a kong,
    1 double. (M 117(k))

  Completing Original Call,
    1 double. (M 117(l))

Limit (M 118-120): the limit is 1000 by default, and can be changed by 
the  ScoreLimit  game option. The  NoLimit  game option can be 
used to play a game "with the roof off".


The following hands are limit hands:

  Heaven's Blessing: East wins with dealt hand. (M 122(a))

  Earth's Blessing: player wins with East's first discard. (M 122(b))

  Gathering Plum Blossom from the Roof: winning with 5 Circles from the
    loose wall. (M 122(c))

  Catching the Moon from the Bottom of the Sea: winning with 1 Circle as 
    the last tile. (M 122(d))
    (Note: M says that the tile must be drawn. It seems more reasonable
    also to allow it to be the last discard, which is what we
    do. Objections?)

  Scratching a Carrying Pole: robbing a kong of 2 Bamboos. (M 122(e))

  (Note: these last three limits are rather arbitrary, but of the
    arbitrary limits they are apparently the most common. There should be
    options to disable them.)

  Kong upon Kong: making a Kong, making another Kong with the loose
    tile, and with the second loose tile obtaining Mah Jong. (Also, of
    course, with three or four successive kongs.) (M 122(f))

  Four Kongs. (M 122(g))

  Buried Treasure: all concealed and no chows. (M 122(h))

  The Three Great Scholars: three sets of dragons and no chows. (M 122(i))
    (Note: in most rules I have seen, there is no restriction to a no chow 
    hand. Since in M's rules, three sets and a chow scores at least
    (10 (M has 10 for Mah Jong) + 12 (at least 3 pungs))
    times 8 (2 for each set of dragons) times 4 (for Big Three Dragons)
    = 704, this is significant with the default limit. For us, with 20 for
    going out, Big Three Dragons is over the default limit anyway.)

  Four Blessings o'er the Door: four sets of winds and a pair. (M 122(j))

  All Honours. (M 122(k))

  Heads and Tails: all terminals. (M 122(l))

  Imperial Jade: contains only Green Dragon and 2,3,4,6,8 Bamboo. (M 122(m))
    (Note: another rather arbitrary hand, but widely adopted.)

  Nine Gates: calling on 1-1-1-2-3-4-5-6-7-8-9-9-9 of one suit. (M 122(n)).

  Wriggling Snake: 1-1-1-2-3-4-5-6-7-8-9-9-9 plus 2, 5 or 8 of 
    one suit (M 122(o)).
    (Note: another rather arbitrary hand.)

  Concealed Clear Suit: one suit only and all concealed. (M 122(p))

  Thirteen Unique Wonders: one of each major tile, and a match to any of 
    them. (M 122(q))

  East's 13th consecutive Mah-Jong. (M 122(r))


General note: there are many other doubles and limits kicking
around. I welcome opinions on which should be possible options; and
also on which of the above I should eject from the default set.
I dislike Imperial Jade, Wriggling Snake, and the ones depending on a
specific tile (Gathering Plum Blossom, Catching the Moon, Scratching a 
Carrying Pole): which of these are so commonly adopted that they
should be in even a fairly minimalist default set?


GAME OPTIONS
------------

This section describes the options that can be set in the
game. Whether an option can be used, depends on the version of the
programs. This is described by a "protocol version number"; this is
not strictly speaking a version just of the communication protocol,
but a version number reflecting the combination of protocol and
programs. When playing by oneself, this does not matter, but in the
case of a networked game, players might have different versions of the 
software, in which case the game is played according to the lowest
version of any player.

Game options can be controlled in two ways: the  --option-file 
argument to the  mj-server  program gives options to be applied to 
the game, or options can be set by the players, using the interface
described in the manual section for  xmj .

In the user interface, the options are referred to by a one line
description, but each option also has a short name, given here.

Options are of several types:

  bool 
    boolean, or on/off, options.

  int 
    integer options

  nat 
    non-negative integer options

  string 
    is a miscellaneous type, whose values are strings of at most 127
    characters which must not contain white space

  score 
    is the type used for options that give the score of some combination
    or feature in a hand. A score is either a limit (or a half-limit; the
    underlying protocol supports percentages of limits, but the current
    user programs only support limits and half limits); or a number of
    doubles to be awarded; or a number of points to be added. It is
    possible (though never needed) to have both points and doubles. If
    points/doubles are specified as well as a limit, they will be used in
    a no-limit game. (The server implements a hard limit of 100000000
    on all scores to avoid arithmetic overflow, but that's unlikely to
    worry anybody.)
    
Currently supported options
---------------------------

The following options are implemented in the versions of the program
with which this document is distributed. If playing against people
with older versions of the software, some options may not be
available. The list gives for each option the short name, type, and
short description, followed by a detailed explanation.

  Timeout  ( nat ) time limit for claims
    This is the time in seconds allowed to claim a discard, or to rob a
    kong. If set to zero, there is no timeout. The default is 15 seconds.
    
  TimeoutGrace  ( nat ) grace period when clients handle timeouts
    This period (in seconds) is added to the Timeout above before the
    server actually forces a timeout. This is for when clients handle
    timeouts locally, and allows for network lags. If this option is zero,
    clients are not permitted to handle timeouts locally. The current
    server also only allows players to handle timeouts locally if all of
    them wish to do so.
    
  ScoreLimit  ( nat ) limit on hand score
    This is the limit for the score of a hand. In a no-limit game, it is
    the notional value of a "limit" hand. The default is 1000.
    
  NoLimit  ( bool ) no-limit game
    If this option is set, the game has no limit on hand scores. The
    default is unset.
    
  MahJongScore  ( score ) base score for going out
    This is the number of points for obtaining Mah-Jong. 
    The default is 20.
    
  SevenPairs  ( bool ) seven pairs hand allowed
    If this option is set, then Mah-Jong hands of seven pairs (any seven
    pairs) are allowed. The default is unset.
    
  SevenPairsVal  ( score ) score for a seven pair hand
    This gives the score (in addition to the base Mah-Jong score) for a
    seven pairs hand. The default is 20.
    
  Flowers  ( bool ) play using flowers and seasons
    If this option is set, the deal includes four flowers and four seasons 
    in the Chinese Classical style. If unset, only the 136 standard tiles
    are used. The default is set.
    
  FlowersLoose  ( bool ) flowers replaced by loose tiles
    If playing with flowers, this option determines whether flowers and
    seasons are replaced from the live wall (unset), or by loose tiles
    (set). The default is unset.
    
  FlowersOwnEach  ( score ) score for each own flower or season
    This option gives the score for having one's own flower or season.
    If one has both, this score will be given twice. The default is no
    score.
    
  FlowersOwnBoth  ( score ) score for own flower and own season
    This is the score for having both one's own flower and one's own
    season. Note that this is awarded in addition to twice the previous
    score. The default is 1 double.
    
  FlowersBouquet  ( score ) score for all four flowers or all four seasons
    This is the score for having all four flowers or all four seasons.
    The default is 1 double.
    
  DeadWall  ( bool ) there is a dead wall
    This determines whether there is a dead wall, so that play ends when
    it is reached (set), or whether all tiles may be drawn (unset).
    The default is set.
    
  DeadWall16  ( bool ) dead wall is 16 tiles, unreplenished
    If this option is set, then the dead wall initially has 16 tiles,
    and does not have any more tiles added to it (this is the set-up
    described by Millington). If the option is unset, then the dead wall
    initially  has 14 tiles, and after two loose tiles have been taken,
    two tiles are moved from the live wall to the dead wall (this is the
    set-up described by almost everyone else). The default is unset in
    versions 1.1 onwards, and set previously. (To be precise, the protocol 
    level default is set, but all servers from 1.1 onwards will change
    this to unset.)
    
  ConcealedFully  ( score ) score for fully concealed hand
    This is the score for a winning hand with no open sets.
    The default is 1 double.
    
  ConcealedAlmost  ( score ) score for almost concealed hand
    This is the score for a hand that is concealed up to the point of
    going out.
    The default is no additional score.
    
  LosersPurity  ( bool ) losing hands score doubles for pure, concealed etc.
    If this option is set, losing hands will score various doubles for one
    suit, almost concealed, etc. See the rules for details. This option is
    an (Anglo-)Americanism alien to Chinese Classical (see Foster for a
    spirited but faulty argument in its favour, and Millington for the rejoinder).
    The default is unset.
    
  KongHas3Types  ( bool ) claimed kongs count as concealed for doubling
    If this option is set, claimed kongs count as concealed for various
    doubling combinations, although they score as exposed for basic
    points. See the note above under "Kongs".
    The default is unset.
    
  LosersSettle  ( bool ) losers pay each other
    If this option is set, the losers pay each other the difference
    between their scores. If it unset, they pay only the winner.
    The default is set.
    
  EastDoubles  ( bool ) east pays and receives double
    If this option is set, payments to and from East Wind are doubled,
    as in the Chinese Classical game.
    The default is set.
    
  DiscDoubles  ( bool ) the discarder pays double
    If this option is set, the settlement procedure is changed to a style
    common in Singapore. That is, if the winning player wins off a
    discard, the discarder pays double the hand value, and the other
    players pay the hand value. If the winner wins from the wall, then all
    other players pay double the hand value.
    The default is unset.
    Note: EastDoubles and DiscDoubles can be set together, but nobody
    plays such a rule.
    
  ShowOnWashout  ( bool ) reveal tiles on washout
    If this option is set, the players' hands will be revealed in the 
    event of a washout.
    
  NumRounds  ( nat ) number of rounds to play
    This option says how many rounds to play in the game. For aesthetic
    reasons, the possible values are 1, 2, or a multiple of 4. In the 2
    round case, the East and South rounds will be played. It defaults to
    the usual 4 rounds.
    
Option file format
------------------

Both in the option file and in the  .xmjrc  file, options are
recorded in the format used by the server protocol. This is a line of
the form

GameOption 0  NAME TYPE MINPROT ENABLED VALUE DESC

The meanings of the elements are:

  GameOption  0
    identifies this as a game option line (the 0 is an irrelevant field
    from the protocol).

  NAME
    is the name of the option.

  TYPE
    is the type of the option.

  MINPROT
    is the minimum protocol version with which the option can be used
    (which is not necessarily the version at which it was introduced).

  ENABLED
    will always be 1.

  VALUE
    is the value: a decimal (signed) integer for  nat  and  int ;
    0 or 1 for  bool ; the string for  string ; and for
    score , if the score is C centi-limits, D doubles and 
    P points, the value is C*1000000 + D*10000 + P.

  DESC
    is a short description of the option, which is not required but is
    usually copied in from the server.