\input texinfo @c -*-texinfo-*- @setfilename chess.info @documentencoding UTF-8 @documentlanguage en @settitle Emacs Chess: chess.el @copying Copyright @copyright{} 2001, 2002, 2004, 2014 Free Software Foundation, @abbr{Inc.} @quotation Permission is granted to copy, distribute and/or modify this document under the terms of the @acronym{GNU} Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, with the Front-Cover Texts being ``A @acronym{GNU} Manual,'' and with the Back-Cover Texts as in (a) below. A copy of the license is included in the section entitled ``@acronym{GNU} Free Documentation License.'' (a) The @acronym{FSF}'s Back-Cover Text is: ``You have the freedom to copy and modify this @acronym{GNU} manual.'' @end quotation @end copying @dircategory Emacs @direntry * Chess: (chess). Chess.el is an Emacs chess client. @end direntry @setchapternewpage on @ifinfo @insertcopying @end ifinfo @synindex vr fn @c The titlepage section does not appear in the Info file. @titlepage @sp 4 @c The title is printed in a large font. @center @titlefont{User's Guide} @sp 1 @center @titlefont{to} @sp 1 @center @titlefont{Emacs Chess: chess.el} @ignore @sp 2 @center release 2.0 @c -release- @end ignore @sp 3 @center John Wiegley and Mario Lang @c -date- @c The following two commands start the copyright page for the printed @c manual. This will not appear in the Info file. @page @vskip 0pt plus 1filll @insertcopying @end titlepage @contents @c ================================================================ @c The real text starts here @c ================================================================ @ifnottex @node Top, The chess.el library @top Emacs Chess: chess.el @file{Chess.el} is an Emacs chess client and library, designed to be used for writing chess-related programs, or for playing games of chess against various chess engines, including Internet servers. The library can be used for analyzing variations, browsing historical games, or a multitude of other purposes. The purpose of this manual is to help you understand how @file{chess.el} is structured for use as a library, and also how to use it as a client. @end ifnottex @menu * The chess.el library:: Basic objects required to deal with Chess * Modules:: The module-system explained * Chessboard displays:: Different types of chessboards in a buffer * Engines:: Internal and external chess-playing engines * Chess Session:: Tying it all together * Internet Chess Servers:: Playing chess with other people * GNU Free Documentation License:: * Concept Index:: * Function and Variable Index:: * Key Index:: @end menu @node The chess.el library @chapter The @file{chess.el} library @cindex library This chapter documents the low-level aspects of @file{chess.el}, mostly targeting developers interested in understanding the underlying @acronym{API}s@. @xref{Chessboard displays}, and the chapters following it, if you are interested in the more user-visible aspects of @file{chess.el}. @menu * Positions:: * Plies:: * Variations:: * Games:: * Collections:: * Chess Opening Books:: @end menu @node Positions @section Positions @cindex position A chess @dfn{position} is a given layout of pieces on a chess board, also reflecting which @dfn{side} (i.e., player) is next to move, and what privileges are currently available to each side (castling short or long, en passant capture, etc). A position may be represented in @acronym{ASCII} using @acronym{FEN} (or EPD), or graphically by displaying a chess board. It is rather inconvenient to render them verbally. The position can be represented on a remote terminal using X windows, or by transmitting the @acronym{FEN} string via a network connection or clipboard, to another chess board rendering tool. It may of course also be represented physically, by setting up the pieces to match the @acronym{FEN} specification. Chess puzzles are most often provided as a set of positions. @menu * Creating positions:: * Position coordinates:: * Position details:: * Annotations:: * FEN notation:: * EPD notation:: @end menu @node Creating positions @subsection Creating positions @cindex creating positions @cindex position, creating @defun chess-pos-create &optional blank Create a new chess position, set at the starting position. If @var{blank} is non-@code{nil}, all of the squares will be empty. The current side-to-move is always white. @end defun @defun chess-pos-copy position Copy the given chess @var{position}. If there are annotations or @acronym{EPD} opcodes set, these lists are copied as well, so that the two positions do not share the same lists. @end defun @defvar chess-starting-position Starting position of a chess game. @end defvar @defun chess-fischer-random-position Generate a Fischer Random style position. @end defun @node Position coordinates @subsection Position coordinates @cindex coordinates @cindex position coordinates First of all, position coordinates use a coordinate system of octal indices, where the index @samp{?\044} signifies rank 4 file 4 (i.e., "e4"). Rank is numbered 0 to 7, top to bottom, and file is 0 to 7, left to right. @defun chess-index-rank index Return the rank component of the given @var{index}. @end defun @defun chess-index-file index Return the file component of the given @var{index}. @end defun @defun chess-rf-to-index rank file Convert @var{rank} and @var{file} coordinates into an octal index. @end defun For those who wish to use @acronym{ASCII} coordinates, such as "e4", there are two conversion functions: @defun chess-coord-to-index coord Convert a @var{coord} string into an index value. @end defun @defun chess-index-to-coord index Convert the chess position @var{index} into a coord string. @end defun For fast manipulation of chess position indices, the following constants and functions are provided: @cindex queen @cindex rook For queens and rooks: @cindex north @defvr Constant chess-direction-north Signify one step north, as seen from the perspective of the white player. @end defvr @cindex east @defvr Constant chess-direction-east Signify one step east, as seen from the perspective of the white player. @end defvr @cindex south @defvr Constant chess-direction-south Signify one step south, as seen from the perspective of the white player. @end defvr @cindex west @defvr Constant chess-direction-west Signify one step west, as seen from the perspective of the white player. @end defvr @cindex queen @cindex bishop For queens and bishops: @cindex northeast @defvr Constant chess-direction-northeast Signify one step northeast, as seen from the perspective of the white player. @end defvr @cindex southeast @defvr Constant chess-direction-southeast Signify one step southeast, as seen from the perspective of the white player. @end defvr @cindex southwest @defvr Constant chess-direction-southwest Signify one step southwest, as seen from the perspective of the white player. @end defvr @cindex northwest @defvr Constant chess-direction-northwest Signify one step northwest, as seen from the perspective of the white player. @end defvr @defun chess-next-index index direction Create a new @var{index} from an old one, by advancing it into @var{direction}. If the resulting index is not valid (outside the board), @code{nil} is returned. @end defun Due to the underlying technique used to efficiently detect off-board squares, a direction specifier should at most do two steps in any direction. Directions can be combined, so that @code{(* chess-direction-north 2)} will give a typical initial white pawn push. @node Position details @subsection Position details Given an octal index value, you can look up what's on a particular square, or set that square's value: @defun chess-pos-piece position index Return the piece on @var{position} at @var{index}. @end defun @defun chess-pos-piece-p position index piece-or-color Return non-@code{nil} if the given @var{piece-or-color} is at @var{position}/@var{index}. If @var{piece-or-color} is @code{t} for white or @code{nil} for black, any piece of that color will do. @end defun @defun chess-pos-set-piece position index piece Set the piece on @var{position} at @var{index} to @var{piece}. @var{piece} must be one of @code{?K}, @code{?Q}, @code{?N}, @code{?B}, @code{?R}, or @code{?P} for white pieces, or one of the corresponding lowercase letters for black pieces. @end defun @defun chess-pos-search position piece-or-color Look anywhere on @var{position} for @var{piece-or-color}, returning all coordinates. If @var{piece-or-color} is @code{t} for white or @code{nil} for black, any piece of that color will do. @end defun @defun chess-pos-search* position &rest pieces Look on @var{position} for any of @var{pieces}. The result is an alist where each element looks like @w{@code{(@var{piece} . @var{indices})}}. Pieces which did not appear in @var{position} will be present in the resulting alist, but the @code{cdr} of their entries will be @code{nil}. @end defun @defun chess-search-position position target piece &optional check-only no-castling Look on @var{position} from @var{target} for a @var{piece} that can move there. This routine looks along valid paths of movement for @var{piece}. It differs from @code{chess-pos-search}, which is a more basic function that doesn't take piece movement into account. If @var{piece} is @code{t} or @code{nil}, valid piece movements for any piece of that color will be considered (@code{t} for white, @code{nil} for black). Otherwise, the letter-case of the @var{piece} determines color. The return value is a list of candidates, which means a list of indices that indicate where a piece may have moved from. If @var{check-only} is non-@code{nil} and @var{piece} is either @code{t} or @code{nil}, only consider pieces which can give check (not the opponent's king). If @var{no-castling} is non-@code{nil}, do not consider castling moves. @end defun @defun chess-pos-can-castle position side Return whether the king on @var{position} can castle on @var{side}. The @var{side} argument must be either @samp{?K} for the king side, or @samp{?Q} for the queen side (use lowercase to query if black can castle). @end defun @defun chess-pos-set-can-castle position side value Set whether the king can castle on the given @var{position} on @var{side}. See @code{chess-pos-can-castle}. It is only necessary to call this function if setting up a position manually. Note that all newly created positions have full castling privileges set, unless the position is created blank, in which case castling privileges are unset. See @code{chess-pos-create}. @end defun @defun chess-pos-en-passant position Return the index of any pawn on @var{position} that can be captured en passant. Returns @code{nil} if en passant is unavailable. @end defun @defun chess-pos-set-en-passant position index Set the index of any pawn on @var{position} that can be captured en passant. @end defun @defun chess-pos-status position Return whether the side to move in the @var{position} is in a special state. Return @code{nil} if not, otherwise one of the keywords: @code{:check}, @code{:checkmate} or @code{:stalemate}. @end defun @defun chess-pos-set-status position value Set whether the side to move in @var{position} is in a special state. The @var{value} should either be @code{nil}, to indicate that the @var{position} is normal, or one of the symbols: @code{check}, @code{checkmate}, @code{stalemate}. @end defun @defun chess-pos-side-to-move position Return the color whose move it is in @var{position}. @end defun @defun chess-pos-set-side-to-move position color Set the color whose move it is in @var{position}. @end defun @defun chess-pos-passed-pawns position color &optional pawn-indices If @var{color} has Passed Pawns in @var{position}, return a list of their indices. Optionally, if @var{indices} is non-@code{nil}, those indices are considered as candidates. A Pawn whose advance to the eighth rank is not blocked by an opposing Pawn in the same file and who does not have to pass one on an adjoining file is called a passed Pawn. @end defun @defvar chess-pos-always-white When set, it is assumed that white is always on move. This is really only useful when setting up training positions. This variable automatically becomes buffer-local when changed. @end defvar @defun chess-pos-move position &rest changes Move a piece on the @var{position} directly, using the indices in @var{changes}. This function does not check any rules, it only makes sure you are not trying to move a blank square. @end defun @node Annotations @subsection Annotations @cindex annotations @defun chess-pos-annotations position Return the list of annotations for this position. @end defun @defun chess-pos-add-annotation position annotation Add an annotation for this position. @end defun @node FEN notation @subsection FEN notation @cindex FEN notation @acronym{@dfn{FEN}, Forsyth-Edwards Notation} encodes a chess position using a simple string. The format is: @example @var{position} @var{side} @var{castling} @var{en-passant} @end example The @var{position} gives all eight ranks, by specifying a letter for each piece in the position, and a number for any intervening spaces; ranks are separated by slashes. Trailing spaces need not be counted. Uppercase letters signify white pieces, and lowercase black. For example, if your position only had a black king on d8, your @var{position} string would be: @example 3k//////// @end example @noindent for the three spaces (a, b and c file), the black king, and then all the remaining ranks (which are all empty, so their spaces can be ignored). The @var{side} is @samp{w} or @samp{b}, to indicate whose move it is. The @var{castling} can contain @samp{K}, @samp{Q}, @samp{k} or @samp{q}, to signify whether the white or black king can still castle on the king or queen side. If neither color can castle on any side, @samp{-} should be provided. The @var{en-passant} signifies the target square of an en passant capture, such as @samp{e3} or @samp{a6}. @defun chess-fen-to-pos fen Convert the @acronym{FEN} string @var{fen} to a chess position. @end defun @defun chess-pos-to-fen position &optional full Convert a chess @var{position} to a @acronym{FEN} string. If @var{full} is non-@code{nil}, represent trailing spaces as well. @end defun This is how the starting position looks like: @vindex chess-starting-position @lisp (chess-pos-to-fen chess-starting-position) @result{} "rnbqkbnr/pppppppp/////PPPPPPPP/RNBQKBNR w KQkq -" @end lisp Some external programs might have problems parsing terse @acronym{FEN} strings. If you are unsure, use the more verbose form: @lisp (chess-pos-to-fen chess-starting-position t) @result{} "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq -" @end lisp @node EPD notation @subsection EPD notation @cindex EPD notation @acronym{@dfn{EPD}, Extended Position Description} is a standard for describing chess positions along with an extended set of structured attribute values using the @acronym{ASCII} character set. It is intended for data and command interchange among chess-playing programs. It is also intended for the representation of portable opening library repositories. A single @acronym{EPD} uses one text line of variable length composed of four data fields, followed by zero or more operations. The four fields of the @acronym{EPD} specification are the same as the first four fields of the @acronym{FEN} specification (@pxref{FEN notation}). A text file composed exclusively of @acronym{EPD} data records should have a file name with the @file{.epd} extension. @defun chess-epd-to-pos &optional string Convert extended position description @var{string} to a chess position. If @var{string} is not specified, look for an @acronym{EPD} string in the current buffer, and advance point after the correctly parsed position. @end defun @defun chess-pos-to-epd position Convert a chess @var{position} to a string representation in extended position description format. @end defun @defun chess-epd-read-file file Return a list of positions contained in @var{file}. @end defun @menu * Operations:: * Opcode "acd" analysis count depth:: * Opcode "acn" analysis count nodes:: * Opcode "acs" analysis count seconds:: * Opcode "am" avoid move(s):: * Opcode "bm" best move(s):: @end menu @node Operations @subsubsection Operations @cindex EPD operations @cindex opcodes An @acronym{EPD} operation is composed of an opcode followed by zero or more operands, and terminated by a semicolon. Multiple operations are separated by a single space character. If there is at least one operation present in an @acronym{EPD} record, it is separated from the last (fourth) data field by a single space character. Some opcodes that allow for more than one operand may have special ordering requirements for the operands. For example, the @samp{pv} (predicted variation) opcode requires its operands (moves) to appear in the order in which they would be played. All other opcodes that allow for more than one operand should have operands appearing in @acronym{ASCII} order. An example of the latter set is the @samp{bm} (best move[s]) opcode; its operands are moves that are all immediately playable from the current position. @node Opcode "acd" analysis count depth @subsubsection Opcode @samp{acd} analysis count depth @cindex @samp{acd} opcode The opcode @samp{acd} takes a single non-negative integer operand. It is used to represent the depth of the ply (@pxref{Plies}) examined in an analysis. @node Opcode "acn" analysis count nodes @subsubsection Opcode @samp{acn} analysis count nodes @cindex @samp{acn} opcode The opcode @samp{acn} takes a single non-negative integer operand. It is used to represent the number of nodes examined in an analysis. Note that the value may be quite large for some extended searches, and so use of (at least) a long (four byte) representation is suggested. @node Opcode "acs" analysis count seconds @subsubsection Opcode @samp{acs} analysis count seconds @cindex @samp{acs} opcode The opcode @samp{acs} takes a single non-negative integer operand. It is used to represent the number of seconds used for an analysis. Note that the value may be quite large for some extended searches, and so use of (at least) a long (four byte) representation is suggested. @node Opcode "am" avoid move(s) @subsubsection Opcode @samp{am} avoid move(s) @cindex @samp{am} opcode The opcode @samp{am} indicates a set of zero or more moves, all immediately playable from the current position, that are to be avoided in the opinion of the @acronym{EPD} writer. Each operand is a @acronym{SAN} move; they appear in @acronym{ASCII} order. @node Opcode "bm" best move(s) @subsubsection Opcode @samp{bm} best move(s) @cindex @samp{bm} opcode The opcode @samp{bm} indicates a set of zero or more moves, all immediately playable from the current position, that are judged to the best available by the @acronym{EPD} writer. Each operand is a @acronym{SAN} move; they appear in @acronym{ASCII} order. @node Plies @section Plies @cindex ply A @dfn{ply} is the differential between two positions. In other words, it is the coordinate transformations applied to one position in order to arrive at the following position. It is also informally called "a move". A ply may be represented in @acronym{ASCII} by printing the @acronym{FEN} string of the base position, and then printing the positional transformation in algebraic notation. Since the starting position is usually known, the @acronym{FEN} string is optional. A ply may be represented graphically by moving the chess piece(s) involved. It may be rendered verbally by voicing which piece is to move, where it will move to, and what will happen a result of the move (piece capture, check, etc). Plies may be sent over network connections, postal mail, e-mail, @abbr{etc.}, so long as the current position is maintained at both sides. Transmitting the base position's @acronym{FEN} string along with the ply offers a form of confirmation during the course of a game. @menu * Creating plies:: * Ply details:: * The "next" position:: * Algebraic notation:: @end menu @node Creating plies @subsection Creating plies @cindex creating plies @cindex ply, creating @defun chess-ply-create position &optional valid-p &rest changes Create a ply from the given @var{position} by applying the supplied @var{changes}. This function will guarantee the resulting ply is valid, and will also annotate the ply with @code{:check} or other modifiers as necessary. It will also extend castling, and will prompt for a promotion piece. Note: Do not pass in the rook move if @var{changes} represents a castling maneuver. @end defun @defun chess-legal-plies position &rest keywords Return a list of all valid plies in @var{position}. The allowed @var{keywords} are: @table @code @item :any Return @code{t} if any piece can move at all. @item :color @var{boolean} If @var{boolean} is @code{t}, return plies for white, if @code{nil}, return plies for black. @item :piece @var{character} Return plies for a specific piece designated by @var{character}. @item :file @var{file} Given a @var{file}, a number (0-7), return plies for any piece or color present on that @var{file}. @code{:piece} or @code{:color} must be present. @item :index @var{index} Return plies for the piece at @var{index}. @item :target @var{index} Return plies that go to a specific coordinate specified by @var{index}. @item :candidates @var{index}@enddots{} If provided, only consider the source coordinates specified by the indices. @end table These will constrain the plies generated to those matching the above criteria. NOTE: All of the returned plies will reference the same copy of the position object passed in. @end defun @node Ply details @subsection Ply details @cindex ply details @defun chess-ply-pos ply Return the base position associated with @var{ply}. @end defun @defun chess-ply-set-pos ply position Set the base position of @var{ply}. @end defun @defun chess-ply-changes Return the coordinate transformations and keywords associated with this @var{ply}. Value is a list made of a pair of indices (or two pairs, in case of castling) followed by optional keywords. @end defun @defun chess-ply-set-changes Set the coordinate transformations and keywords associated with this @var{ply}. @end defun @defun chess-ply-source ply Return the source square index value of @var{ply}. @end defun @defun chess-ply-target ply Return the target square index value of @var{ply}. @end defun For example, here is how to find the source square of a freshly created ply: @lisp (chess-ply-source (chess-ply-create chess-starting-position nil (chess-coord-to-index "e2") (chess-coord-to-index "e4"))) @result{} 52 @end lisp @node The "next" position @subsection The ``next'' position @defun chess-ply-next-pos ply Return the position that results from executing @var{ply}. @end defun @defun chess-ply-final-p ply Return non-@code{nil} if this is the last ply of a game/variation. @end defun @node Algebraic notation @subsection Algebraic notation @cindex algebraic notation A thing to deal with in chess is algebraic move notation, such as @samp{Nxf3+}. This notation is a shorthand way of representing where a piece is moving from and to, by specifying the piece involved, where it's going, and whether or not a capture or check is involved. You can convert from algebraic notation to a ply using the following function: @defun chess-algebraic-to-ply position move &optional trust Convert the algebraic notation @var{move} for @var{position} to a ply. If optional argument @var{trust} is non-@code{nil}, accept check or checkmate symbols (@samp{+} and @samp{#}) as given. @end defun The function also checks if a move is valid, and will raise an error if not. To convert from a ply to algebraic notation, use: @cindex standard algebraic notation @cindex short algebraic notation @cindex long algebraic notation @cindex figurine algebraic notation @cindex numeric notation @defun chess-ply-to-algebraic ply &optional type Convert the given @var{ply} to algebraic notation (a string). Optional argument @var{type} specifies the kind of algebraic notation to generate: @table @code @item :san Generate short (or standard) algebraic notation. This is the default. @item :lan Generate long algebraic notation (like @samp{Nb1-c3}). @item :fan Generate figurine algebraic notation (uppercase letters will be replaced by Unicode chess figures). @item :numeric Generate ICCF numeric notation as used in correspondence chess (like @samp{2133}). @end table @end defun Lastly, there is a regexp for quickly checking if a string is in algebraic notation or not, or searching out algebraic strings in a buffer: @defvar chess-algebraic-regexp A regular expression that matches all possible algebraic moves. This regexp handles short, long and figurine algebraic notation. @end defvar @node Variations @section Variations @cindex variation A @dfn{variation} is a sequence of plies that occur after some starting position. If the starting position represents the initial setup of a chess board, and if the final ply results in completion of the game, it is called ``the main variation''. Otherwise, variations typically represented interesting tangents during a game---but not actually played---as envisioned by the player, an annotator, or someone studying the game. Variations may be represented in @acronym{ASCII} by stating the @acronym{FEN} string for starting position, followed by the list of plies that follow that position. They are difficult to represent graphically, except for showing each position in turn with a slight pause between---or by allowing the user to navigate each of the subsequent positions in turn. They may be represented verbally by announcing each of the plies in turn, as mentioned above. @menu * Creating variations:: * Variation positions:: * Variation plies:: * Making a move in a variation:: @end menu @node Creating variations @subsection Creating variations @cindex creating variations @cindex variation, creating @c lispfun chess-var-create @defun chess-var-create &optional position Create a new chess variation object. Optionally, use the given starting @var{position}. @end defun @node Variation positions @subsection Variation positions @cindex variation positions @defun chess-var-pos variation &optional index Return the position related to @var{variation}'s @var{index} ply. @end defun @defun chess-var-index variation Return the @var{variation}'s current position index. @end defun @defun chess-var-seq variation Return the current @var{variation} sequence. @end defun @defun chess-var-side-to-move variation &optional index Return the color whose move it is in @var{variation} at @var{index} (or at the last position of @var{variation} if @var{index} is @code{nil}). @end defun @node Variation plies @subsection Variation plies @cindex variation plies @defun chess-var-ply variation &optional index Return @var{variation}'s @var{index}th ply. @end defun @defun chess-var-plies variation Return the plies of @var{variation}. @end defun @defun chess-var-to-algebraic variation &optional long Reveal the plies of @var{variation} by converting them to algebraic notation. @end defun @node Making a move in a variation @subsection Making a move in a variation @cindex variation, make a move @defun chess-var-move variation ply Make a move in the current @var{variation} by applying the changes of @var{ply}. This creates a new position and adds it to the main variation. The @samp{changes} of the last ply reflect whether the var is currently in progress (@code{nil}), if it is drawn, resigned, mate, etc. @end defun @defun chess-var-add-ply variation ply Add the given @var{ply} to @var{variation}. @end defun @node Games @section Games @cindex game A @dfn{game} includes its main variation, incidental information about the game (who played it, where, when, who won, etc.), and any sub-variations of interest to those studying the game afterwards. @dfn{Game tags} is an alist that associates arbitrary English tag names to their values. A game may be represented in @acronym{ASCII} using @acronym{@dfn{PGN}, Portable Game Notation}. Representing them graphically or verbally is similar to what is done for variations (@pxref{Variations}). @defun chess-game-add-hook game function &optional data prepend Add to @var{game} an event hook @var{function}. @end defun @defun chess-game-add-ply game ply Add @var{ply} to the main variation of @var{game}. @end defun @defun chess-game-hooks game Return the event hooks associated with @var{game}. @end defun @defun chess-game-plies game Return the main variation of @var{game} as a list of plies. @end defun @defun chess-game-remove-hook game function &optional data Remove from @var{game} all event hooks that match @var{function}. If @var{data} is specified, only remove hooks with matching associated data. @end defun @defun chess-game-run-hooks game &rest args Run the event hooks of @var{game} and pass it @var{args}. @end defun @defun chess-game-set-hooks game hooks Set the event hooks associated with @var{game}. @end defun @defun chess-game-set-plies game plies Set the list of plies which represents the main variation of @var{game}. @end defun @menu * Creating games:: * Game tags:: * Game positions:: * Game plies:: * Making a move:: * PGN notation:: @end menu @node Creating games @subsection Creating games @cindex creating games @cindex game, creating @defun chess-game-create &optional position tags Create a new chess game object. Optionally use the given starting @var{position}. @var{tags} is the starting set of game tags (which can always be changed later using the various tag-related methods). @end defun @node Game tags @subsection Game tags @cindex game tags @cindex tags @defun chess-game-tags game Return the tags alist associated with @var{game}. @end defun @defun chess-game-set-tags game tags Set the tags alist associated with @var{game}. After the @var{tags} alist was set the @samp{set-tags} event is triggered. @end defun @defun chess-game-tag game tag Return the value for @var{tag} in @var{game}. @end defun @defun chess-game-set-tag game tag value Set the @var{tag} for @var{game} to @var{value}. @end defun @defun chess-game-del-tag game tag Delete the specified @var{tag} from @var{game}. @end defun @node Game positions @subsection Game positions @cindex game positions @defun chess-game-pos game &optional index Return the current position of @var{game} or a position of a given @var{index}. @end defun @defun chess-game-index game Return the @var{game}'s current position index. @end defun @defun chess-game-seq game Return the current @var{game} sequence number. @end defun @defun chess-game-side-to-move game &optional index Return the side, specified as color, whose move it is in @var{game} at @var{index} (or at the last position if @var{index} is @code{nil}). Value is @code{t} for white and @code{nil} for black. @end defun @node Game plies @subsection Game plies @cindex game plies @defun chess-game-ply game &optional index Return a ply of @var{game}. If @var{index} is non-@code{nil}, the last played ply is returned. @end defun @node Making a move @subsection Making a move @defun chess-game-move game ply Make a move in the current @var{game} using @var{ply}. This creates a new position and adds it to the main variation. The @samp{changes} of the last ply reflect whether the game is currently in progress (@code{nil}), if it is drawn, resigned, mate, etc. @end defun @node PGN notation @subsection PGN notation @cindex PGN notation @defun chess-pgn-to-game &optional string Convert the @acronym{PGN} notation at point into a chess game. Optionally use the supplied @var{string} instead of the current buffer. @end defun @defun chess-game-to-pgn game &optional indented to-string Convert a chess @var{game} to @acronym{PGN} notation. If @var{indented} is non-@code{nil}, indent the move texts. If @var{to-string} is non-@code{nil}, return a string instead of inserting the resulting @acronym{PGN} text. @end defun @defun chess-pgn-insert-plies game index plies &optional for-black indented no-annotations @emph{NYI}: Still have to implement the @var{indented} argument. @end defun @menu * PGN mode:: @end menu @node PGN mode @subsubsection PGN mode @cindex PGN mode @defun chess-pgn-visualize Visualize the move for the @acronym{PGN} game under point. This does not require that the buffer be in PGN mode. @end defun @node Collections @section Collections @cindex collection A @dfn{collection} is a set of games archived for later perusal. A set of games conceptually represents a large tree of branching variations, and can be used for studying current theory, examining Master preferences, etc. @file{Chess.el} itself does not attempt to provide library services, nor does it ever represent library collections in memory. Instead, it interacts with a chess database engine for the purpose of storing and retrieving games from the library, or performing library-wide analyses and searches. @menu * Opening Databases:: * Querying Databases:: * Modifying Databases:: * Finalizing Databases:: * Database Modules:: @end menu @node Opening Databases @subsection Opening Databases @cindex opening database @cindex collection database @cindex database, opening @defvar chess-database-modules List of database modules to try when @code{chess-database-open} is called. @end defvar @defun chess-database-open file &optional module Open a game database specified by @var{file}. You can optionally specify the database @var{module} to use. Returns the opened database object, or nil. @end defun @node Querying Databases @subsection Querying Databases @cindex querying databases @defun chess-database-filename database Return the filename of an already opened @var{database}. @end defun @c lispfun chess-database-count @defun chess-database-read database index Return from @var{database} the chess game object at @var{index}. @end defun @defun chess-database-query database &rest terms Run a query on @var{database}. The @var{terms} are partly dependent on the chess-database module in use. For the @samp{chess-scid} module, using @code{tree-search @var{game}} means perform a tree search on the last position of @var{game}. @end defun @node Modifying Databases @subsection Modifying Databases @cindex modifying databases @cindex database, modifying @defun chess-database-read-only-p database Return non-@code{nil} if @var{database} is read only. @end defun @c lispfun chess-database-write @c lispfun chess-database-replace @node Finalizing Databases @subsection Finalizing Databases @c lispfun chess-database-save @c lispfun chess-database-close @node Database Modules @subsection Database Modules @cindex database modules Currently, there are two subclasses of the above defined database base-class: @menu * chess-file:: * chess-scid:: @end menu @node chess-file @subsubsection chess-file @cindex chess-file module This module does not use an external chess database program to store and retrieve games. It uses the @acronym{PGN} of @acronym{EPD} format parsing routines provided in @file{chess-pgn.el} and @file{chess-epd.el} to implement collections for ordinary @acronym{PGN} and @acronym{EPD} files. @acronym{EPD} file collections are represented as a collection of games originating at the given position. One might argue that conceptually, they represent a collection of positions, but it is more convenient to merge all collections into one uniform concept. @node chess-scid @subsubsection chess-scid @cindex chess-scid module This module implements basic reading and writing functionality for @acronym{@dfn{SCID}, Shane's Chess Information Database} files. @node Chess Opening Books @section Chess Opening Books @cindex chess opening books modules There are two different modules/libraries provided for looking up chess positions in opening books. @menu * ECO Classification:: * Polyglot opening book format support:: @end menu @node ECO Classification @subsection ECO Classification @cindex ECO classification @cindex chess-eco module @vindex chess-default-modules Module @code{chess-eco} provides a database of well known names for chess opening positions. If this module is activated (see variable @code{chess-default-modules}), known chess opening positions will be announced in the minibuffer during a game. @node Polyglot opening book format support @subsection Polyglot opening book format support @cindex polyglot opening book format The popular and freely documented Polyglot opening book format is supported. There is a default polyglot book file shipped with @file{chess.el} to support engines which do not have built-in support for looking up positions in opening books (such as some @acronym{UCI} protocol based engines). @defopt chess-polyglot-book-file Path to default polyglot book file. @end defopt @defvar chess-polyglot-book If non-@code{nil}, the buffer holding the currently loaded polyglot book data. This is used by @acronym{UCI} based engine modules as well as the internal AI. @end defvar @defun chess-polyglot-book-open file Open a polyglot book @var{file}. Returns a buffer object which contains the binary data. @end defun @findex chess-ply-keyword @defun chess-polyglot-book-plies book position Return a list of plies found in @var{book} for @var{position}. The resulting list is ordered, most interesting plies come first. The @code{:polyglot-book-weight} ply keyword is used to store the actual move weights. Use @code{chess-ply-keyword} on elements of the returned list to retrieve them. @end defun @vindex chess-polyglot-book-strength @defun chess-polyglot-book-ply book position &optional strength If non-@code{nil}, a (randomly picked) ply from @var{book} for @var{position}. Random distribution is defined by the relative weights of the found plies. If non-@code{nil}, @var{strength} defines the bias towards better moves. A value below 1.0 will penalize known good moves while a value above 1.0 will prefer known good moves. The default is the value of @code{chess-polyglot-book-strength}. A strength value of 0.0 will completely ignore move weights, and evenly distribute the probability that a move gets picked. @end defun @node Modules @chapter Modules @cindex modules Positions, plies and variations are typically accessed in reference to a game object, which has a main variation containing the plies and positions that represent the number of moves made within that game up to the final position. Another thing that the game object does is to manage events that occur within that game. If a move is made from the final position, for example, it will cause a new ply to be created, adding it to the end of the main variation. Then, a @samp{move} event is triggered within the game and passed to any chess modules which are currently associated with that game. The concept of modules allows far more complex aspects of chess playing to be dealt with, while allowing the library itself to still operate solely in terms of the game object. For example, although the plies of a game object contain all the information the computer needs to follow the game, a user needs much more. He wants to see the pieces move. To support this, a display module (@pxref{Chessboard displays}) can be created, and linked to the game. The first effect of this association will be to create a chess board display and show the game's final position on it. Now whenever plies are added to the game, the chess board will be updated to show the effect of that move on the board. The display module realizes that a move has been made by receiving the @samp{move} event which is passed to all modules associated with the game object. There may be any number of modules associated with a chess game, and they may do anything you like. Basically, for a module called @samp{chess-sample}, a function must exist called @code{chess-sample-handler}. This takes two or more arguments: a game object, the event symbol, and whatever other arguments were passed along with the event symbol. When an event is triggered on a game object (this may happen as a byproduct of manipulating the game, or events may be manually generated), every associated module, in order, is called with that event and whatever arguments were passed along with the event. The game object is passed also, so that the module knows which game this event has occurred in reference to. Once called, the module can do whatever it likes. Some events expect certain values to be returned, to indicate success or failure in processing the event. There are many different events, each depicting something specific that might happen in the context of playing or manipulating a chess game. Some events relate only to the chess game itself, some are triggered by the various chess engines that might be associated with that game. Modules may even trigger events in response to event. The game itself remains unaware of events, except for the fact that it will pass them along to every module associated with that game. This is how displays get updated, for example, because once a @samp{move} event is triggered, each display knows that it must now look at the new final position and update its display. It may even trigger new events special to displays, to cause a refresh to happen after update calculations have been performed, for example. All such details are left to the module, and the game does not interfere with such intra-module messaging. Looked at as an object-oriented design, these are typical polymorphic events. Certain generic situations frequently occur, such as moves, which trigger events so that everyone concerned with the game can be updated as to the move that occurred. This way, no one need to actively query the game to find out if something new has happened. The game will notify every listening module by sending an event. The core library, which consists of code to manipulate games, does not define any modules. The rest of the @file{chess.el} library is strictly a set of module implementations, of various types. Display modules react to moves, and may modify the game based on user input; engine modules react to moves by notifying the engine of the move; network client modules react to moves by sending the move text over the network. Engine and network modules may also trigger new events when the engine or network player has decided on their move, and this move is then applied to the game object. At the moment, no negotiation is done to determine which module may modify the game object. All modules have equal privilege. This means it is the programmer's duty not to associate conflicting modules with a single game object. If two artificial intelligence engines were linked, for example, they would quickly start stepping on each other's toes. But it is perfectly fine to have one artificial intelligence engine, and another passive engine whose only purpose is to relay the moves to a networked observer on another computer. The possibilities are endless. Modules are very easy to write, although engines and displays are rather different from each other in their principles. There is a base engine, and a base display, which receive the same events as any other module. But then there are derived engines and derived displays which trigger a whole family of events specific to those module types. If you suspect a bug in your module, put a breakpoint in your handler function, and wait for the offending event to come through. Then you can watch what your module does in response to that event. If it leaves the game object alone, it should be easy to locate the problem, since it will always be within the module itself. But if your module also modifies the game object in response to certain events, you may induce a feedback loop that is much more difficult to sort out. Test often and keep in mind that @emph{many} events might end up coming through as a result of the game changes your module makes! That, in essence, is how the module system works. From the game object's perspective, it is a very simple mechanism, much like a function ring or a hook. The hook is called at certain points, so that any listener can react to changes in the game. But from each module's perspective, it is a rich way to allow inter-operation between both passive and reactive modules, all of them acting together to enrich the context of play involving the central game object. The only other rule to be mentioned is that each module instance should be associated with only one game object at a time, although a game object may have unlimited modules of any type linked to it. Otherwise, trying to update a chess board based on input from two different games would get impossible to sort out. Better to create a new board for every game---the way ordinary humans would do it in the real world. @node Chessboard displays @chapter Chessboard displays @cindex chessboard display @cindex display The previous chapter described all the objects found in chess---positions, plies, variations, games and collections. However, these objects can only be manipulated programmatically using the functions given so far. In order to present them in a meaningful fashion to a human reader, it is necessary to create and use a display object. @menu * Generic display manipulation functions:: * Chess display mode:: * Plain ASCII diagram displays:: * ICS1 style ASCII displays:: * Graphical displays:: @end menu @node Generic display manipulation functions @section Generic display manipulation functions @cindex display manipulation functions @defun chess-display-create game style perspective Create a chess display, for displaying chess objects. The @var{game} is the chess game object to use, @var{style} should be the display type to use (a symbol), and @var{perspective} determines the viewpoint of the board: if non-@code{nil}, the board is viewed from White's perspective. @end defun @c lispfun chess-display-destroy @defun chess-display-active-p Return non-@code{nil} if the displayed chessboard reflects an active game. Basically, it means we are playing, not editing or reviewing. @end defun @defun chess-display-clear-board Setup the current board for editing. @end defun @c lispfun chess-display-game @defun chess-display-highlight display &rest args Highlight in @var{display} the squares given in @var{args} on the current position. The @var{args} is a list of highlighting modes and position coordinates. The default highlighting mode is @code{:selected} which is supported by most displays. @end defun @c lispfun chess-display-index @defun chess-display-invert Invert the perspective of the current chess board. @end defun @defun chess-display-move display ply Move a piece on @var{display}, by applying the given @var{ply}. The position of @var{ply} must match the currently displayed position. @end defun @c lispfun chess-display-move-backward @c lispfun chess-display-move-first @c lispfun chess-display-move-forward @c lispfun chess-display-move-last @defun chess-display-perspective display Return the current perspective of @var{display}. @end defun @c lispfun chess-display-ply @defun chess-display-position display Return the position currently viewed on @var{display}. @end defun @defun chess-display-quit Quit the game associated with the current display. @end defun @defun chess-display-set-game display game &optional index Set the given @var{display} to display the @var{game} object, optionally at @var{index}. This is the function to call to cause a display to view a game. It will also update all of the listening engines and other displays to also view the same game. @end defun @c lispfun chess-display-set-index @defun chess-display-set-perspective display perspective Set @var{perspective} of @var{display}. @end defun @c lispfun chess-display-set-ply @c lispfun chess-display-set-position @defun chess-display-set-position display &optional position my-color Set the game associated with @var{display} to use @var{position} and @var{my-color}. @end defun @c lispfun chess-display-set-variation @defun chess-display-set-variation display variation &optional index Set @var{display} @var{variation}. If @var{index} is not specified, this will cause the first ply in the variation to be displayed, with the user able to scroll back and forth through the moves in the variation. Any moves made on the board will extend/change the variation that was passed in. @end defun @c lispfun chess-display-update @defun chess-display-update display &optional popup Update the chessboard @var{display}. If @var{popup} is non-@code{nil}, make sure it is visible. @end defun @c lispfun chess-display-variation @node Chess display mode @section Chess display mode @cindex chess display mode @dfn{Chess display mode} is a special major mode (@pxref{Major Modes, , , emacs}) that allows to select pieces to move with the mouse or by moving point to the desired square/piece. Additionally, you can enter moves in a variant of algebraic notation via the keyboard. All the chessboard displays described in following sub-sections share the basic behavior provided by chess display mode. They basically only differ in appearance of the various chessboards. @defopt chess-display-highlight-legal If non-nil, highlight valid target squares when a piece is selected. @end defopt @menu * Basic operations:: * Selecting pieces with the keyboard:: * Selecting pieces with the mouse:: * Entering moves with algebraic notation:: @end menu @node Basic operations @subsection Basic operations @table @kbd @kindex C-i @kindex TAB @item C-i @itemx @key{TAB} @findex chess-display-invert Invert the perspective of the current chess board (@code{chess-display-invert}). @kindex , @item , @findex chess-display-move-backward Show the previous move in the current game (@code{chess-display-move-backward}). @cindex algebraic notation, searching moves @kindex C-r @item C-r @findex chess-display-search-backward Find previous move which algebraic notation matches a regular expression (@code{chess-display-search-backward}). @kindex C-s @item C-s @findex chess-display-search-forward Find next move which algebraic notation matches a regular expression (@code{chess-display-search-forward}). @kindex . @item . @findex chess-display-move-forward Show the next move in the current game (@code{chess-display-move-forward}). @kindex < @item < @findex chess-display-move-first Move to the initial position of the current game (@code{chess-display-move-first}). @kindex > @item > @findex chess-display-move-last Move to the last position of the current game (@code{chess-display-move-last}). @kindex C-c C-d @item C-c C-d @findex chess-display-draw Offer to draw the current game (@code{chess-display-draw}). @kindex C-c C-r @item C-c C-r @findex chess-display-resign Resign the current game (@code{chess-display-resign}). @kindex M-w @kindex C-u M-w @item M-w @itemx C-u M-w @findex chess-display-kill-board Copy the currently displayed position to the kill ring as a @acronym{FEN} string (@code{chess-display-kill-board}). With prefix argument, copy the current game in @acronym{PGN} to the kill ring. @kindex C-y @item C-y @findex chess-display-yank-board Set the current display position via a @acronym{FEN} string from the kill ring (@code{chess-display-yank-board}). This is useful to copy positions from one chessboard display to another, as well as quickly setting up a position from a @acronym{FEN} string previously added to the kill ring from somewhere else. @kindex X @item X @findex chess-display-quit Quit this chessboard display (@code{chess-display-quit}). This destroys the session (and all related modules) associated with this chessboard display. @end table @node Selecting pieces with the keyboard @subsection Selecting pieces with the keyboard In character based chessboard displays, point can be moved around in the buffer as usual. You can indicate the initial square/piece and the target square/piece by moving point to the desired position and pressing @kbd{@key{RET}}. @table @kbd @kindex RET @item @key{RET} @findex chess-display-select-piece Select the piece/square currently indicated by point (@code{chess-display-select-piece}) to move from/to. @end table @node Selecting pieces with the mouse @subsection Selecting pieces with the mouse Similarly, you can also use the mouse (if available) to indicate the source and target square of your move. @table @kbd @kindex down-mouse-1 @kindex down-mouse-2 @kindex drag-mouse-1 @kindex drag-mouse-2 @item down-mouse-1 @itemx down-mouse-2 @itemx drag-mouse-1 @itemx drag-mouse-2 @findex chess-display-select-piece Select the piece/square currently indicated by the mouse pointer (@code{chess-display-select-piece}) to move from/to. @end table @node Entering moves with algebraic notation @subsection Entering moves with algebraic notation @cindex algebraic notation, entering moves with @table @asis @kindex a @kindex b @kindex c @kindex d @kindex e @kindex f @kindex g @kindex h @kindex 1 @kindex 2 @kindex 3 @kindex 4 @kindex 5 @kindex 6 @kindex 7 @kindex 8 @kindex N @kindex B @kindex R @kindex Q @kindex K @kindex x @kindex = @item @kbd{a} @dots{} @kbd{h} @itemx @kbd{1} @dots{} @kbd{8} @itemx @kbd{N} @itemx @kbd{B} @itemx @kbd{R} @itemx @kbd{Q} @itemx @kbd{K} @itemx @kbd{x} @itemx @kbd{=} @findex chess-input-shortcut Enter move in algebraic notation. The move will be accepted as soon as it is unambiguous. So in most situations, you do not need to type the complete algebraic move string. For instance, if there is only one piece which can be taken by one of your knights, typing @kbd{N x} is sufficient to select that move. Additionally, the characters @kbd{x} and @kbd{=} are optional, as there is no difference between @kbd{N x e 4} and @kbd{N e 4}. @kindex backspace @item @key{backspace} @findex chess-input-shortcut-delete Delete the last entered chess move character (@code{chess-input-shortcut-delete}). This is useful if you have accidentally typed a wrong character, and the move was not unambiguous yet. @end table @node Plain ASCII diagram displays @section Plain ASCII diagram displays @cindex ASCII diagram display The simplest display style available is @code{chess-plain}, a very customizable @acronym{ASCII} board diagram display. This is how the starting position looks in its default configuration: @example +---------------+ 8|r n b q k b n r| 7|p p p p p p p p| 6|. . . . . . . .| 5|. . . . . . . .| 4|. . . . . . . .| 3|. . . . . . . .| 2|P P P P P P P P| 1|R N B Q K B N R| +---------------+ a b c d e f g h @end example @defopt chess-plain-separate-frame If non-@code{nil}, display the chessboard in its own frame. @end defopt @defopt chess-plain-border-style If non-@code{nil}, a vector of Characters used to draw borders. Otherwise, omit to draw any border around the chessboard diagram. @end defopt @defopt chess-plain-black-square-char Character used to indicate empty black squares. @end defopt @defopt chess-plain-white-square-char Character used to indicate black white squares. @end defopt @defopt chess-plain-piece-chars Alist of pieces and their corresponding characters. @end defopt @defopt chess-plain-upcase-indicates Defines what an upcase char should indicate. The default is @code{'color}, meaning a upcase char is a white piece, a lowercase char a black piece. Possible values: @code{'color} (default), @code{'square-color}. If set to @code{'square-color}, an uppercase character indicates a piece on a black square. (Note that you also need to modify @code{chess-plain-piece-chars} to avoid real confusion.) @end defopt @defopt chess-plain-spacing Number of spaces between files. @end defopt @kindex M-x customize-group RET chess-plain RET @cindex customize chess-plain display To customize options of @code{chess-plain}, use @kbd{M-x customize-group @key{RET} chess-plain @key{RET}}. @node ICS1 style ASCII displays @section ICS1 style ASCII displays @cindex ICS1 display The @code{chess-ics1} module is a more verbose @acronym{ASCII} chessboard display. This is how the starting position looks with this chessboard display: @example +---+---+---+---+---+---+---+---+ 8 | r | n | b | q | k | b | n | r | +---+---+---+---+---+---+---+---+ 7 | p | p | p | p | p | p | p | p | +---+---+---+---+---+---+---+---+ 6 | | | | | | | | | +---+---+---+---+---+---+---+---+ 5 | | | | | | | | | +---+---+---+---+---+---+---+---+ 4 | | | | | | | | | +---+---+---+---+---+---+---+---+ 3 | | | | | | | | | +---+---+---+---+---+---+---+---+ 2 | P | P | P | P | P | P | P | P | +---+---+---+---+---+---+---+---+ 1 | R | N | B | Q | K | B | N | R | +---+---+---+---+---+---+---+---+ a b c d e f g h @end example @defopt chess-ics1-separate-frame If non-@code{nil}, display the chessboard in its own frame. @end defopt @kindex M-x customize-group RET chess-ics1 RET @cindex customize ics1 display To customize options of @code{chess-ics1}, use @kbd{M-x customize-group @key{RET} chess-ics1 @key{RET}}. @node Graphical displays @section Graphical displays @cindex graphical display @cindex chess-images module The graphical chessboard display (@code{chess-images}) uses image files to create a visually appealing chessboard in a buffer. @defopt chess-images-directory A directory which contains images in @acronym{XPM} format. If you want to draw your own images, each image file must be named @file{@var{color}-@var{piece}.xpm}, where @var{color} is either black or white, and @var{piece} is one of rook, knight, bishop, queen, king or pawn. The only image format currently supported is @acronym{XPM}. @end defopt @defopt chess-images-separate-frame If non-@code{nil}, display the chessboard in its own frame. @end defopt @kindex M-x customize-group RET chess-images RET @cindex customize chess-images display For all customization options of @code{chess-images}, use @kbd{M-x customize-group @key{RET} chess-images @key{RET}}. @node Engines @chapter Engines @cindex engines @dfn{Engines} represent opponents in Chess. The main type of engine interfaces with an external chess program. However, there can be other uses for engine objects, such as providing networked engined for playing with opponent over different types of transports. @menu * Common functions:: * The Null Engine:: * AI:: * Crafty:: * Fruit:: * Glaurung:: * GNU Chess:: * Phalanx:: * Sjeng:: * Stockfish:: @end menu @node Common functions @section Common functions @cindex engines, common functions @defun chess-engine-create module game &optional response-handler &rest handler-ctor-args Create a new chess engine @var{module} (a symbol) associated with @var{game}. Optionally supply a new @var{response-handler}. @end defun @defun chess-engine-set-option engine option value Set @var{engine} @var{option} to @var{value} by invoking its handler with the @samp{set-option} event. @end defun @c lispfun chess-engine-destroy @c lispfun chess-engine-set-position @c lispfun chess-engine-position @defun chess-engine-position engine Return the current position of the game associated with @var{engine}. @end defun @c lispfun chess-engine-set-game @c lispfun chess-engine-game @c lispfun chess-engine-index @c lispfun chess-engine-move @c lispfun chess-engine-command @defun chess-engine-command engine event &rest args Call the handler of @var{engine} with @var{event} (a symbol) and @var{args}. @end defun @c lispfun chess-engine-send @defun chess-engine-send engine string Send the given @var{string} to @var{engine}. If @code{chess-engine-process} is a valid process object, use @code{process-send-string} to submit the data. Otherwise, the @samp{send} event is triggered and the engine event handler can take care of the data. @end defun @node The Null Engine @section The Null Engine @cindex null engine @cindex chess-none The most basic engine module is @code{chess-none}, a stub module that does nothing. This is useful for a game of chess against another human, where both use the same computer to enter moves and display the current chess position. It can also be useful for creating @acronym{FEN} strings of specific positions. @kindex C-u M-x chess RET none RET To bring up a chessboard with no active engine attached, use @kbd{C-u M-x chess @key{RET} none @key{RET}}. @node AI @section AI @cindex AI engine The @acronym{AI} engine module defines a pure Emacs Lisp implementation of an opponent. Contrary to all other engine modules mentioned later on, it does not require any external programs to be installed. @kindex C-u M-x chess RET ai RET To explicitly select this engine as an opponent, use @kbd{C-u M-x chess @key{RET} ai @key{RET}}. @defopt chess-ai-depth Defines the default search depth for this engine. @end defopt @defopt chess-ai-quiescence-depth Defines the number of plies to search for a quiet position. This is in addition to @code{chess-ai-depth}. @end defopt If you'd like to employ the search and evaluation functions provided by this module programmatically, the following function is the top-level entry point. @defun chess-ai-best-move position &optional depth eval-fn Find the supposedly best move (ply) for @var{position}. @var{depth} defaults to the value of @code{chess-ai-depth}. @end defun @node Crafty @section Crafty @cindex crafty @dfn{Crafty} is a chess program written by Michael Byrne, UAB professor Dr.@ Robert Hyatt, Tracy Riegle, Peter Skinner and Ted Langreck. It is directly derived from Cray Blitz, winner of the 1983 and 1986 World Computer Chess Championships. If the @command{crafty} program is installed and can be found in the program search path (@code{exec-path}), the @code{chess-crafty} engine module will automatically detect it. @vindex chess-crafty-path If @command{crafty} is installed in a non-standard location, variable @code{chess-crafty-path} can be set to point to its executable file. @kindex C-u M-x chess RET crafty RET If you have multiple engines installed you can explicitly select to play against Crafty by invoking @kbd{C-u M-x chess @key{RET} crafty @key{RET}}. @node Fruit @section Fruit @cindex fruit @dfn{Fruit} is a chess engine developed by Fabien Letouzey. It was commercially available from September 2005 until July 2007. Now it is freeware and you can download it for free from @uref{http://www.fruitchess.com/}. The development on Fruit by Fabien Letouzey has ceded and it is unlikely to continue. Fruit was vice world computer chess champion 2005. If the @command{fruit} command is installed and can be found in the program search path (@code{exec-path}), the @code{chess-fruit} engine module will automatically detect it. @vindex chess-fruit-path If Fruit is installed in a non-standard location, variable @code{chess-fruit-path} can be set to point to its executable file. @kindex C-u M-x chess RET fruit RET If you have multiple engines installed you can explicitly select to play against Fruit by invoking @kbd{C-u M-x chess @key{RET} fruit @key{RET}}. @node Glaurung @section Glaurung @cindex glaurung @dfn{Glaurung} is another freely distributed strong computer chess engine. If the @command{glaurung} program is installed and can be found in the program search path (@code{exec-path}), the @code{chess-glaurung} engine module will automatically detect it. @vindex chess-glaurung-path If Glaurung is installed in a non-standard location, variable @code{chess-glaurung-path} can be set to point to its executable file. @kindex C-u M-x chess RET glaurung RET If you have multiple engines installed you can explicitly select to play against Glaurung by invoking @kbd{C-u M-x chess @key{RET} glaurung @key{RET}}. @node GNU Chess @section GNU Chess @cindex gnuchess @uref{http://gnu.org/software/chess/, @dfn{@acronym{GNU} Chess}} is free software, licensed under the terms of the @acronym{GNU} General Public License, and is maintained by collaborating developers. As one of the earliest computer chess programs with full source code available, it's one of the oldest for Unix-based systems and has since been ported to many other platforms. If the @command{gnuchess} program is installed and can be found in the program search path (@code{exec-path}), the @code{chess-gnuchess} engine module will automatically detect it. @vindex chess-gnuchess-path If @acronym{GNU} Chess is installed in a non-standard location, variable @code{chess-gnuchess-path} can be set to point to its executable file. @kindex C-u M-x chess RET gnuchess RET If you have multiple engines installed you can explicitly select to play against @acronym{GNU} Chess by invoking @kbd{C-u M-x chess @key{RET} gnuchess @key{RET}}. @node Phalanx @section Phalanx @cindex phalanx @dfn{Phalanx} is an old, popular chess engine, with an interesting history. If the @command{phalanx} program is installed and can be found in the program search path (@code{exec-path}), the @code{chess-phalanx} engine module will automatically detect it. @vindex chess-phalanx-path If Phalanx is installed in a non-standard location, variable @code{chess-phalanx-path} can be set to point to its executable file. @kindex C-u M-x chess RET phalanx RET If you have multiple engines installed you can explicitly select to play against Phalanx by invoking @kbd{C-u M-x chess @key{RET} phalanx @key{RET}}. @node Sjeng @section Sjeng @cindex sjeng @uref{http://sjeng.org/, @dfn{Sjeng}} is a championship-winner automated chess engine developed by Gian-Carlo Pascutto from Belgium. While its original version was free, recent developments are for sale. If the @command{sjeng} program is installed and can be found in the program search path (@code{exec-path}), the @code{chess-sjeng} engine module will automatically detect it. @vindex chess-sjeng-path If Sjeng is installed in a non-standard location, variable @code{chess-sjeng-path} can be set to point to its executable file. @kindex C-u M-x chess RET sjeng RET If you have multiple engines installed you can explicitly select to play against Sjeng by invoking @kbd{C-u M-x chess @key{RET} sjeng @key{RET}}. @node Stockfish @section Stockfish @cindex stockfish @uref{http://www.stockfishchess.org/, @dfn{Stockfish}} is one of the strongest chess engines in the world, appearing near or at the top of most chess engine rating lists. Stockfish is also free software, licensed under the terms of the @acronym{GNU} General Public License. If the @command{stockfish} program is installed and can be found in the program search path (@code{exec-path}), the @code{chess-stockfish} engine module will automatically detect it. @vindex chess-stockfish-path If Stockfish is installed in a non-standard location, variable @code{chess-stockfish-path} can be set to point to its executable file. @kindex C-u M-x chess RET stockfish RET If you have multiple engines installed you can explicitly select to play against Stockfish by invoking @kbd{C-u M-x chess @key{RET} stockfish @key{RET}}. @node Chess Session @chapter Chess Session @cindex chess session A @dfn{chess session} assembles all modules mentioned in previous chapters into a working system to interact with. A session typically consists of at least one display module, one engine module, and possibly a number of optional modules. All these modules share a common game object which is used to keep track of the currently active game. @defun chess engine disable-popup engine-response-handler &rest engine-ctor-args Play a game against @var{engine}. This function constructs all the necessary modules required for a chess session. In particular, it will start @var{engine} and create a chess display as configured in @code{chess-default-display}. This is the main entry-point for interactively launching a chessboard display with associated engine. If you want to launch a chess session as part of your own code, the probably more expressive alias @code{chess-session} might be interesting to use. @end defun You can have several active chess sessions. In fact, some features later described in this manual make use of this, @pxref{Internet Chess Servers}. @kindex M-x chess RET @vindex chess-default-display @vindex chess-default-engine To interactively start a chess session, invoke @kbd{M-x chess @key{RET}}. This uses @code{chess-default-display} to determine the chessboard display to use, and @code{chess-default-engine} to determine an opponent. @kindex C-u M-x chess RET If you want to play against a specific engine, provide a prefix argument as in @kbd{C-u M-x chess @key{RET}}, which will prompt for an engine module. The module name has the common prefix @samp{chess-} stripped. So you enter @kbd{gnuchess} to indicate you'd like to play against the @code{chess-gnuchess} module. @node Internet Chess Servers @chapter Internet Chess Servers @cindex internet chess servers Based on the services provided above, there is also a special mode for communication with Internet Chess Servers. On an Internet Chess Server you can seek to play against other human or computer players, observe other games being played or examined, play tournaments, chat with fellow chess players, participate in team games, or do various other interesting chess related things. A default set of well known servers is defined in the following variable: @defvar chess-ics-server-list A list of servers to connect to. The format of each entry is: (@var{server} @var{port} [@var{handle}] [@var{password-or-filename}] [@var{helper}] [@var{helper args}@enddots{}]) @end defvar Internet Chess Servers based on @uref{http://www.freechess.org/, @acronym{FICS, Free Internet Chess Server}} and @uref{http://www.chessclub.com/, @acronym{ICC, Internet Chess Club}} are currently supported. @menu * Connecting to a server:: * Chess ICS Mode:: * Command History:: * Seeking an opponent for a new game:: * The sought game display:: * Watching other games:: @end menu @node Connecting to a server @section Connecting to a server @cindex connecting to internet chess server To open a new connection to an Internet Chess Server, use: @c lispfun chess-ics @defun chess-ics server port &optional handle password-or-filename helper &rest helper-args Connect to an Internet Chess Server. If called interactively, you will be prompted to enter a server (from @code{chess-ics-server-list} and possibly identification credentials. @end defun @node Chess ICS Mode @section Chess ICS Mode @cindex Chess ICS mode @cindex mode, ICS The major mode for ICS buffers is Chess ICS mode. Many of its special commands are bound to the @kbd{C-c} prefix. Here is a list of ICS mode commands: @table @kbd @item @key{RET} @kindex RET @findex comint-send-input Send the current line as input to the server (@code{comint-send-input}). Any prompt at the beginning of the line is omitted. If point is at the end of buffer, this is like submitting the command line in an ordinary interactive shell. However, you can also invoke @key{RET} elsewhere in the ICS buffer to submit the current line as input. @item C-d @kindex C-d @findex comint-delchar-or-maybe-eof Either delete a character or send @acronym{EOF, End Of File} (@code{comint-delchar-or-maybe-eof}). Typed at the end of the ICS buffer, this sends @acronym{EOF} to the server and terminates the connection. Typed at any other position in the buffer, this deletes the character at point, as usual. @item C-c C-a @kindex C-c C-a @findex comint-bol-or-process-mark Move to the beginning of the line, but after the prompt if any (@code{comint-bol-or-process-mark}). If you repeat this command twice in a row, the second time it moves back to the process mark, which is the beginning of the input that you have not yet sent to the server. (Normally that is the same place---the end of the prompt on this line---but after @kbd{C-c @key{SPC}} the process mark may be in a previous line.) @item C-c @key{SPC} @kindex C-c SPC @findex comint-accumulate Accumulate multiple lines of input, then send them together (@code{comint-accumulate}). This command inserts a newline before point, but does not send the preceding text as input to the server---at least, not yet. Both lines, the one before this newline and the one after, will be sent together (along with the newline that separates them), when you type @key{RET}. @item C-c C-u @kindex C-c C-u @findex comint-kill-input Kill all text pending at end of buffer to be sent as input (@code{comint-kill-input}). If point is not at end of buffer, this only kills the part of this text that precedes point. @item C-c C-w @kindex C-c C-w @findex backward-kill-word Kill a word before point (@code{backward-kill-word}). @item C-c C-o @kindex C-c C-o @findex comint-delete-output Delete the last batch of output from an ICS server command (@code{comint-delete-output}). This is useful if a server command spews out lots of output that just gets in the way. @item C-c C-s @kindex C-c C-s @findex comint-write-output Write the last batch of output from an ICS server command to a file (@code{comint-write-output}). With a prefix argument, the file is appended to instead. Any prompt at the end of the output is not written. @item C-c C-r @itemx C-M-l @kindex C-c C-r @kindex C-M-l @findex comint-show-output Scroll to display the beginning of the last batch of output at the top of the window; also move the cursor there (@code{comint-show-output}). @item C-c C-e @kindex C-c C-e @findex comint-show-maximum-output Scroll to put the end of the buffer at the bottom of the window (@code{comint-show-maximum-output}). @item M-x comint-truncate-buffer @findex comint-truncate-buffer @vindex comint-buffer-maximum-size This command truncates the ICS buffer to a certain maximum number of lines, specified by the variable @code{comint-buffer-maximum-size}. Here's how to do this automatically each time you get output from the server: @example (add-hook 'comint-output-filter-functions 'comint-truncate-buffer) @end example @end table @cindex Comint mode @cindex mode, Comint ICS mode is a derivative of Comint mode, a general-purpose mode for communicating with interactive subprocesses. Most of the features of ICS mode actually come from Comint mode, as you can see from the command names listed above. @node Command History @section ICS Command History @cindex command history ICS buffers support two ways of repeating earlier commands. You can use keys like those used for the minibuffer history; these work much as they do in the minibuffer, inserting text from prior commands while point remains always at the end of the buffer. You can move through the buffer to previous inputs in their original place, then resubmit them or copy them to the end. @menu * ICS Command Ring:: * ICS History Copying:: @end menu @node ICS Command Ring @subsection ICS Command History Ring @cindex command history ring @table @kbd @findex comint-previous-input @kindex M-p @item M-p @itemx C-@key{UP} Fetch the next earlier old ICS command (@code{comint-previous-input}). @kindex M-n @findex comint-next-input @item M-n @itemx C-@key{DOWN} Fetch the next later old ICS command (@code{comint-next-input}). @kindex M-r @findex comint-history-isearch-backward-regexp @item M-r Begin an incremental regexp search of old ICS commands (@code{comint-history-isearch-backward-regexp}). @item C-c C-x @kindex C-c C-x @findex comint-get-next-from-history Fetch the next subsequent command from the history (@code{comint-get-next-from-history}). @item C-c . @kindex C-c . @findex comint-input-previous-argument Fetch one argument from an old ICS command (@code{comint-input-previous-argument}). @item C-c C-l @kindex C-c C-l @findex comint-dynamic-list-input-ring Display the buffer's history of ICS commands in another window (@code{comint-dynamic-list-input-ring}). @end table ICS buffers provide a history of previously entered commands. To reuse commands from the history, use the editing commands @kbd{M-p}, @kbd{M-n}, @kbd{M-r} and @kbd{M-s}. These work just like the minibuffer history commands (@pxref{Minibuffer History, , , emacs}), except that they operate within the ICS buffer rather than the minibuffer. @kbd{M-p} fetches an earlier ICS command to the end of the ICS buffer. Successive use of @kbd{M-p} fetches successively earlier commands, each replacing any text that was already present as potential input. @kbd{M-n} does likewise except that it finds successively more recent ICS commands from the buffer. @kbd{C-@key{UP}} works like @kbd{M-p}, and @kbd{C-@key{DOWN}} like @kbd{M-n}. The history search command @kbd{M-r} begins an incremental regular expression search of previous ICS commands. After typing @kbd{M-r}, start typing the desired string or regular expression; the last matching ICS command will be displayed in the current line. Incremental search commands have their usual effects---for instance, @kbd{C-s} and @kbd{C-r} search forward and backward for the next match (@pxref{Incremental Search, , , emacs}). When you find the desired input, type @key{RET} to terminate the search. This puts the input in the command line. Any partial input you were composing before navigating the history list is restored when you go to the beginning or end of the history ring. Often it is useful to reexecute several successive ICS commands that were previously executed in sequence. To do this, first find and reexecute the first command of the sequence. Then type @kbd{C-c C-x}; that will fetch the following command---the one that follows the command you just repeated. Then type @key{RET} to reexecute this command. You can reexecute several successive commands by typing @w{@kbd{C-c C-x @key{RET}}} over and over. The command @kbd{C-c .}@: (@code{comint-input-previous-argument}) copies an individual argument from a previous command, like @kbd{@key{ESC} .}@: in Bash. The simplest use copies the last argument from the previous ICS command. With a prefix argument @var{n}, it copies the @var{n}th argument instead. Repeating @kbd{C-c .}@: copies from an earlier ICS command instead, always using the same value of @var{n} (don't give a prefix argument when you repeat the @kbd{C-c .}@: command). These commands get the text of previous ICS commands from a special history list, not from the ICS buffer itself. Thus, editing the ICS buffer, or even killing large parts of it, does not affect the history that these commands access. @node ICS History Copying @subsection ICS History Copying @cindex history copying @cindex copying command history @table @kbd @kindex C-c C-p @findex comint-previous-prompt @item C-c C-p Move point to the previous prompt (@code{comint-previous-prompt}). @kindex C-c C-n @findex comint-next-prompt @item C-c C-n Move point to the following prompt (@code{comint-next-prompt}). @kindex C-c RET @findex comint-copy-old-input @item C-c @key{RET} Copy the input command at point, inserting the copy at the end of the buffer (@code{comint-copy-old-input}). This is useful if you move point back to a previous command. After you copy the command, you can submit the copy as input with @key{RET}. If you wish, you can edit the copy before resubmitting it. If you use this command on an output line, it copies that line to the end of the buffer. @item Mouse-2 If @code{comint-use-prompt-regexp} is @code{nil} (the default), copy the old input command that you click on, inserting the copy at the end of the buffer (@code{comint-insert-input}). If @code{comint-use-prompt-regexp} is non-@code{nil}, or if the click is not over old input, just yank as usual. @end table Moving to a previous input and then copying it with @w{@kbd{C-c @key{RET}}} or @kbd{Mouse-2} produces the same results---the same buffer contents---that you would get by using @kbd{M-p} enough times to fetch that previous input from the history list. However, @w{@kbd{C-c @key{RET}}} copies the text from the buffer, which can be different from what is in the history list if you edit the input text in the buffer after it has been sent. @node Seeking an opponent for a new game @section Seeking an opponent for a new game @cindex seeking opponents After you connected to a server, one of the first things you will want to do is find an opponent for a new game. You can use the ICS command @samp{seek} to announce your availability for a chess game to interested people. For example: @example fics% seek 10 10 rated @end example This will announce your availability to play a rated game with 10 minutes initial time-control for each player, and 10 seconds added for every move made. @node The sought game display @section The sought game display @cindex sought game display @cindex seek advertisements There is a special mode for displaying games sought by other users on an Internet Chess Server. Provided you didn't turn off seek advertisements manually (for instance by setting the seek variable to 0 (off) on the ICS server by issuing "set seek 0"), the first seek advertisement automatically pops up a new window which is in @code{chess-ics-ads-mode}, a derivative of @code{tabulated-list-mode}. @c lispfun chess-ics-ads-mode @defun chess-ics-ads-mode A mode for displaying ICS game seek advertisements. This mode runs the hook @code{chess-ics-ads-mode-hook}, as the final step during initialization. key binding --- ------- ? describe-mode @var{ret} chess-ics-sought-accept chess-ics-sought-accept @end defun @kindex RET In this buffer, use @kbd{mouse-2} or @kbd{@key{RET}} on a line to accept that particular game and play it. @node Watching other games @section Watching other games @cindex watching other games You can also watch other games currently being played on @acronym{ICS}. Even services like @samp{LectureBot} from @acronym{FICS} can be used. @example fics% observe lecturebot You are now observing game 5. Game 5: LectureBot (0) LectureBot (0) unrated untimed 0 0 LectureBot(TD)(----)[5] kibitzes: (Note: A passed pawn is a pawn that does not have enemy pawns blocking the path either on the same or adjacent files). LectureBot(TD)(----)[5] kibitzes: Connected passed pawns are a pain to have to deal with. They are usually a winning advantage if they cannot be blockaded. The blockading piece has to give up duties elsewhere. It's almost like being a piece up. fics% unobserv lecturebot Removing game 5 from observation list. fics% @end example Once you start to observe a particular game or player, the current position will pop up in a chessboard display. As you are an observer, you will not be able to enter new moves. However, you should be able to navigate back and forth in the history of the game. If a new move is made by any party in the game and you are currently displaying the last position in the game, the chessboard display will automatically update to reflect the new position and show the last move in the mode line. @node GNU Free Documentation License @appendix GNU Free Documentation License @include fdl.texi @node Concept Index @unnumbered Concept Index @printindex cp @node Function and Variable Index @unnumbered Function and Variable Index @printindex fn @node Key Index @unnumbered Key Index @printindex ky @bye