path: root/chess.texi

\input texinfo  @c -*-texinfo-*-

@c Documentation for Chess.el.
@c Copyright (C) 2001, 2002 John Wiegley.

@c This file is free software; you can redistribute it and/or modify it
@c under the terms of the GNU General Public License as published by the
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@c %**start of header
@setfilename chess.info
@settitle Emacs Chess: chess.el
@c %**end of header

@dircategory Emacs
@direntry
* Chess: (chess).     Chess.el is an Emacs chess client.
@end direntry
@setchapternewpage on

@ifinfo
Copyright @copyright{} 2001, 2002 John Wiegley.

Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1 or
any later version published by the Free Software Foundation.
@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
@center @titlefont{to}
@sp
@center @titlefont{Emacs Chess: chess.el}
@ignore
@sp 2
@center release 2.0
@c -release-
@end ignore
@sp 3
@center John Wiegley
@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
Copyright @copyright{} 2001, 2002 John Wiegley.

Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1 or
any later version published by the Free Software Foundation.
@end titlepage

@contents

@c ================================================================
@c                   The real text starts here
@c ================================================================

@ifinfo
@node Top, Emacs Chess: chess.el, (dir), (dir)
@top Emacs Chess: chess.el

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 Chess.el is
structured for use as a library, and also how to use it as a client.
@end ifinfo

@chapter The chess.el library
@cindex library

@section Positions

A chess @dfn{position} is a given layout of pieces on a chess board,
also reflecting which side 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 ASCII using FEN (or EPD) notation, 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 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 FEN
notation.

Chess puzzles are most often provided as a set of positions.

@subsection Creating positions

@c lispfun chess-pos-create

@c lispfun chess-pos-copy

@defvar chess-starting-position
Starting position of a chess game.
@end defvar

@c lispfun chess-fischer-random-position

@subsection Position coordinates

First of all, a coordinate system of octal indices is
used, where ?\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.

@c lispfun chess-index-rank

@c lispfun chess-index-file

@c lispfun chess-rf-to-index

For those who wish to use ASCII coordinates, such as "e4", there
are two conversion functions:

@c lispfun chess-coord-to-index

@c lispfun chess-index-to-coord

There is also one helper function for iterative changes of an index:

@c lispfun chess-incr-index

@subsection Position details

With an octal index value, you can look up what's on a particular
square, or set that square's value:

@c lispfun chess-pos-piece

@c lispfun chess-pos-piece-p

@c lispfun chess-pos-set-piece

@c lispfun chess-pos-search

@c lispfun chess-search-position

@c lispfun chess-pos-can-castle

@c lispfun chess-pos-set-can-castle

@c lispfun chess-pos-en-passant

@c lispfun chess-pos-set-en-passant

@c lispfun chess-pos-status

@c lispfun chess-pos-set-status

@c lispfun chess-pos-side-to-move

@c lispfun chess-pos-set-side-to-move

@c lispfun chess-pos-passed-pawns

@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

@c lispfun chess-pos-move

@subsection Annotations

@c lispfun chess-pos-annotations

@c lispfun chess-pos-add-annotation

@subsection FEN notation

FEN notation encodes a chess position using a simple string.  The
format is:

   POSITION SIDE CASTLING EN-PASSANT

The POSITION gives all eight ranks, by specifying a letter for each
piece on the position, and a number for any intervening spaces.
Trailing spaces need not be counted.  Uppercase letters signify
white, and lowercase black.  For example, if your position only had
a black king on d8, your POSITION string would be:

  3k////////

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 SIDE is w or b, to indicate whose move it is.

CASTLING can contain K, Q, k or q, to signify whether the white or
black king can still castle on the king or queen side.  EN-PASSANT
signifies the target sqaure of an en passant capture, such as "e3" or "a6".

The starting chess position always looks like this:

  rnbqkbnr/pppppppp/////PPPPPPPP/RNBQKBNR/ w KQkq -

And in "full" mode (where all spaces are accounted for):

  rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq -

@c lispfun chess-fen-to-pos

@c lispfun chess-pos-to-fen

@subsection EPD notation

EPD is "Extended Position Description"; it is a standard for describing chess
positions along with an extended set of structured attribute values using the
ASCII character set.  It is intended for data and command interchange among
chessplaying programs.  It is also intended for the representation of portable
opening library repositories.

A single EPD uses one text line of variable length composed of four data field
followed by zero or more operations.  The four fields of the EPD specification
are the same as the first four fields of the FEN specification.

A text file composed exclusively of EPD data records should have a file name
with the suffix ".epd".

@c lispfun chess-epd-to-pos

@c lispfun chess-pos-to-epd

@c lispfun chess-epd-read-file

@subsubsection Operations

An EPD operation is composed of an opcode followed by zero or more operands and
is concluded by a semicolon.

Multiple operations are separated by a single space character.  If there is at
least one operation present in an EPD line, 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 "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 ASCII order.  An example of the latter set is the "bm"
(best move[s]) opcode; its operands are moves that are all immediately playable
from the current position.

@subsubsection Opcode "acd" analysis count depth

The opcode "acd" takes a single non-negative integer operand.  It is used to
represent the ply depth examined in an analysis.

@subsubsection Opcode "acn" analysis count nodes

The opcode "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.

@subsubsection Opcode "acs" analysis count seconds

The opcode "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.

@subsubsection Opcode "am" avoid move(s)

The opcode "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 EPD
writer.  Each operand is a SAN move; they appear in ASCII order.

@subsubsection Opcode "bm" best move(s)

The opcode "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 EPD
writer.  Each operand is a SAN move; they appear in ASCII order.

@section Plies

A @dfn{ply} is the differential between two positions.  Or, 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 ASCII by printing the FEN string of the base
position, and then printing the positional transformation in algebraic
notation.  Since the starting position is usually known, the 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, etc.,
so long as the current position is maintained at both sides.
Transmitting the base position's FEN string along with the ply offers a
form of confirmation during the course of a game.

@subsection Creating plies

@c lispfun chess-ply-create

@c lispfun chess-legal-plies

@subsection Ply details

@c lispfun chess-ply-pos

@c lispfun chess-ply-set-pos

@c lispfun chess-ply-changes

@c lispfun chess-ply-set-changes

@c lispfun chess-ply-source

@c lispfun chess-ply-target

@subsection The "next" position

@c lispfun chess-ply-next-pos

@c lispfun chess-ply-final-p

@subsection Algebraic notation

A thing to deal with in chess is algebraic move notation, such as
Nxf3+.  (I leave description of this notation to better manuals
than this).  This notation is a shorthand way of representing where
a piece is moving from and to, by specifying the piece is involved,
where it's going, and whether or not a capture or check is
involved.

You can convert from algebraic notation to a ply (one pair in most
cases, but two for a castle) using the following function (NOTE:
POSITION determines which side is on move (by calling
`chess-pos-side-to-move')):

@c lispfun chess-algebraic-to-ply

The function also checks if a move is legal, and will raise an
error if not.

To convert from a ply to algebraic notation, use:

@c lispfun chess-ply-to-algebraic

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 both long and short form.
@end defvar

@section Variations

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 ASCII by stating the 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.

@subsection Creating variations

@c lispfun chess-var-create

@subsection Variation positions

@c lispfun chess-var-pos

@c lispfun chess-var-index

@c lispfun chess-var-seq

@c lispfun chess-var-side-to-move

@subsection Varation plies

@c lispfun chess-var-ply

@c lispfun chess-var-plies

@c lispfun chess-var-to-algebraic

@subsection Making a move in a variation

@c lispfun chess-var-move

@c lispfun chess-var-add-ply

@section Games

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.

Where TAGS is an alist that associates arbitrary English tag names to
their values.

A game may be represented in ASCII using standard PGN notation.
Representing them graphically or verbally is similar to what is done
for variations.

@c lispfun chess-game-add-hook

@c lispfun chess-game-add-ply

@c lispfun chess-game-hooks

@c lispfun chess-game-plies

@c lispfun chess-game-remove-hook

@c lispfun chess-game-run-hooks

@c lispfun chess-game-set-hooks

@c lispfun chess-game-set-plies

@subsection Creating games

@c lispfun chess-game-create

@subsection Game tags

@c lispfun chess-game-tags

@c lispfun chess-game-set-tags

@c lispfun chess-game-tag

@c lispfun chess-game-set-tag

@c lispfun chess-game-del-tag

@subsection Game positions

@c lispfun chess-game-pos

@c lispfun chess-game-index

@c lispfun chess-game-seq

@c lispfun chess-game-side-to-move

@subsection Game plies

@c lispfun chess-game-ply

@subsection Making a move

@c lispfun chess-game-move

@subsection PGN notation

@c lispfun chess-pgn-to-game

@c lispfun chess-game-to-pgn

@c lispfun chess-pgn-insert-plies

@subsubsection PGN mode

@c lispfun chess-pgn-visualize

@section Collections

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.

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.

@subsection Opening Databases

@defvar chess-database-modules
List of database modules to try when `chess-database-open' is called.
@end defvar

@c lispfun chess-database-open

@subsection Querying Databases

@c lispfun chess-database-filename

@c lispfun chess-database-count

@c lispfun chess-database-read

@c lispfun chess-database-query

@subsection Modifying Databases

@c lispfun chess-database-read-only-p

@c lispfun chess-database-write

@c lispfun chess-database-replace

@subsection Finalising Databases

@c lispfun chess-database-save

@c lispfun chess-database-close

@subsection Database Modules

Currently, there are two subclasses of the above defined
database base-class:

@subsubsection chess-file

This module does not use an external chess database program
to store and retrieve games.  It uses the PGN of EPD format parsing
routines provided in `chess-pgn.el' and `chess-epd.el' to implement Collections
for ordinary PGN and EPD files.

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.

@subsubsection chess-scid

This modules implement basic reading and writing functionality
for SCID (Shane's Chess Information Database) files.

@chapter 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 `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 (see next chapter) 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 `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
chess-sample, a function must exist called `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 (and 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 '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 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 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 *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.

@chapter Chessboard displays

The previous chapter described all the objects found in
chess---positions, plies, variations, games and collections.  However,
these objects can only be manipulated programmitically 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.

@section Generic display manipulation functions

@c lispfun chess-display-create

@c lispfun chess-display-destroy

@c lispfun chess-display-active-p

@c lispfun chess-display-clear-board

@c lispfun chess-display-game

@c lispfun chess-display-highlight

@c lispfun chess-display-index

@c lispfun chess-display-invert

@c lispfun chess-display-move

@c lispfun chess-display-move-backward

@c lispfun chess-display-move-first

@c lispfun chess-display-move-forward

@c lispfun chess-display-move-last

@c lispfun chess-display-perspective

@c lispfun chess-display-ply

@c lispfun chess-display-position

@c lispfun chess-display-quit

@c lispfun chess-display-set-game

@c lispfun chess-display-set-index

@c lispfun chess-display-set-perspective

@c lispfun chess-display-set-ply

@c lispfun chess-display-set-position

@c lispfun chess-display-set-variation

@c lispfun chess-display-update

@c lispfun chess-display-variation

@section Plain ASCII diagram displays

The simplest display style available is chess-plain, a very customisable
ASCII board diagram display.

@defvar chess-plain-separate-frame
If non-nil, display the chessboard in its own frame.
@end defvar

@defvar chess-plain-draw-border
Non-nil if a border should be drawn (using `chess-plain-border-chars').
@end defvar

@defvar chess-plain-border-chars
A list of Characters used to draw borders.
@end defvar

@defvar chess-plain-black-square-char
Character used to indicate empty black squares.
@end defvar

@defvar chess-plain-white-square-char
Character used to indicate black white squares.
@end defvar

@defvar chess-plain-piece-chars
Alist of pieces and their corresponding characters.
@end defvar

@defvar chess-plain-upcase-indicates
Defines what a upcase char should indicate.
The default is 'color, meaning a upcase char is a white piece, a
lowercase char a black piece.  Possible values: 'color (default),
'square-color.  If set to 'square-color, a uppercase character
indicates a piece on a black square. (Note that you also need to
modify `chess-plain-piece-chars' to avoid real confusion.)
@end defvar

@defvar chess-plain-spacing
Number of spaces between files.
@end defvar

@section ICS1 style ASCII displays

@defvar chess-ics1-separate-frame
If non-nil, display the chessboard in its own frame.
@end defvar

@section Graphical displays

@chapter Engines

Engines are the representation of an opponent 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.

@section Common functions

@c lispfun chess-engine-create

@c lispfun chess-engine-set-option

@c lispfun chess-engine-destroy

@c lispfun chess-engine-set-position

@c lispfun chess-engine-position

@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

@c lispfun chess-engine-send

@section Crafty

@section Gnu Chess

@section Phalanx

@section Sjeng

@chapter Internet Chess Servers

Based on the services provided above, there is also a speical 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 player or examined,
play tournaments, chat with fellow chess players, participate in a team game,
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:

  (SERVER PORT [HANDLE] [PASSWORD-OR-FILENAME] [HELPER] [HELPER ARGS...])
@end defvar

@section Connecting to a server

To open a new connection to an Internet Chess Server, use:

@c lispfun chess-ics

@section Seeking an opponent for a new game

After you connected to a server, one of the first things you will
want to do is find an oponent for a new game.  You can use the
ICS command "seek" to announce your availability for a chess game
to interested people.

@section The sought game display

There is a special mode for displaying games sought by other users
on an Internet Chess Server.  Provided you didn't turn off seek ads
manually (for instance by setting the seek variable to 0 (off) on the
ICS server by issueing "set seek 0"), the first seek advertisment
automatically pops up a new window which is in `chess-ics-sought-mode'.

@c lispfun chess-ics-sought-mode

In this buffer, use mouse-2 or @kbd{RET} on a line to accept that
particular game and play it.

@unnumbered Concept Index

@printindex cp

@unnumbered Function and Variable Index

@printindex fn

@unnumbered Key Index

@printindex ky
@bye