readme

A very small LISP implementation with several packages and demo programs.

14aug07abu
(c) Software Lab. Alexander Burger


         Pico Lisp Demo Games
         ====================

This directory contains a few simple games. They are neither especially
interesting, nor powerful, but may be useful as programming examples.



'mine' is a simplified version of the minesweeper game. You can start it as:

$ ./p dbg.l games/mine.l -main -go

It will display a 12-by-12 field with 24 (default) hidden mines. You can move
around using the standard 'vi'-keys 'j' (down), 'k' (up), 'l' (right) and 'h'
(left).

Hit ENTER or SPACE to uncover a field, and ESC to terminate the game. In the
latter case (of if a mine exploded), you'll get the Pico Lisp prompt. Then you
can continue the game with

: (go)

possibly after re-initializing it with

: (main)

or exit the Pico Lisp interpreter with ENTER.



'nim' and 'ttt' are only testbeds for the general 'game' alpha-beta search
function (normally, these games are better implemented by directly exploring
their underlying principles and strategies).

Start 'nim' as

$ ./p dbg.l games/nim.l

and then find the optimal move path for, let's say, three heaps of four matches
each:

: (nim 4 4 4)
-> (-100 ((1 . 4) 1 . -4) ((2 . 4) 2 . -4) ((3 . 4) 3 . -4))

This is a winning position (a minimal cost of -100), with three moves (in the
CARs of the move list: Take 4 from heap 1, then 4 from heap 2, and finally 4
from heap 3).



To play Tic-Tac-Toe, enter

$ ./p dbg.l games/ttt.l -main

A three-by-three board is displayed. Enter your moves with the 'go' function:

: (go a 1)
   +---+---+---+
 3 |   |   |   |
   +---+---+---+
 2 |   |   |   |
   +---+---+---+
 1 | T |   |   |
   +---+---+---+
     a   b   c

Your positions are marked with 'T', the computer's with '0'.



The 'chess' game is minimalistic (441 lines of code). Nevertheless, it plays
some slow - though correct - chess. Start it as:

$ ./p dbg.l games/chess.l -main
   +---+---+---+---+---+---+---+---+
 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

The pieces are indicated by the letters 'K'ing, 'Q'ueen, 'R'ook, 'B'ishop,
k'N'ight and 'P'awn, with black pieces in angular brackets.


Alternatively, you can also run it through XBoard (in the X Window System):

$ xboard -fcp games/xchess

This requires the symbolic links in "/usr/lib/" and "/usr/bin/", as recommended
in INSTALL. If this is not an option, please modify the first line ("#!") of
"games/xchess".


Without XBoard, you may enter your moves with the field names (in lower case)
for the "from" and "to" positions:

: (go e2 e4)

Castling may be entered by just specifying the king's move:

: (go e1 g1)

To undo one or several moves, enter

: (go -)

and to redo them

: (go +)

To switch sides (and have the computer play against itself), call 'go' without
arguments:

: (go)

The initial board position can be restored with

: (main)

The global variable '*Depth' holds the maximal depth of the alpha-beta tree
search. It defaults to 5. You may change it to some smaller value for a faster
response, or to a larger value for a deeper search:

: (setq *Depth 7)

The same effect can be achieved by passing the desired depth as the first
argument to 'main':

: (main 7)

The second (optional) argument to 'main' is your color ('NIL' for white and 'T'
for black).

To setup some given board position, call 'main' with a list of triples, with
each describing:

   1. The field
   2. The piece's classes
   3. An optional flag to indicate that the piece did not move yet

: (main 5 NIL
   (quote
      (a2 (+White +Pawn) T)
      (b1 (+White +King))
      (d4 (+Black +King)) ) )
   +---+---+---+---+---+---+---+---+
 8 |   | - |   | - |   | - |   | - |
   +---+---+---+---+---+---+---+---+
 7 | - |   | - |   | - |   | - |   |
   +---+---+---+---+---+---+---+---+
 6 |   | - |   | - |   | - |   | - |
   +---+---+---+---+---+---+---+---+
 5 | - |   | - |   | - |   | - |   |
   +---+---+---+---+---+---+---+---+
 4 |   | - |   |<K>|   | - |   | - |
   +---+---+---+---+---+---+---+---+
 3 | - |   | - |   | - |   | - |   |
   +---+---+---+---+---+---+---+---+
 2 | P | - |   | - |   | - |   | - |
   +---+---+---+---+---+---+---+---+
 1 | - | K | - |   | - |   | - |   |
   +---+---+---+---+---+---+---+---+
     a   b   c   d   e   f   g   h

At any time, you can print the current board position in the above format to a
file with

: (ppos "file")

which later can be restored with

: (load "file")



There is also a plain 'sudoku' solver:

$ ./p dbg.l games/sudoku.l

: (main
   (quote
      (5 3 0 0 7 0 0 0 0)
      (6 0 0 1 9 5 0 0 0)
      (0 9 8 0 0 0 0 6 0)
      (8 0 0 0 6 0 0 0 3)
      (4 0 0 8 0 3 0 0 1)
      (7 0 0 0 2 0 0 0 6)
      (0 6 0 0 0 0 2 8 0)
      (0 0 0 4 1 9 0 0 5)
      (0 0 0 0 8 0 0 7 9) ) )
   +---+---+---+---+---+---+---+---+---+
 9 | 5   3     |     7     |           |
   +   +   +   +   +   +   +   +   +   +
 8 | 6         | 1   9   5 |           |
   +   +   +   +   +   +   +   +   +   +
 7 |     9   8 |           |     6     |
   +---+---+---+---+---+---+---+---+---+
 6 | 8         |     6     |         3 |
   +   +   +   +   +   +   +   +   +   +
 5 | 4         | 8       3 |         1 |
   +   +   +   +   +   +   +   +   +   +
 4 | 7         |     2     |         6 |
   +---+---+---+---+---+---+---+---+---+
 3 |     6     |           | 2   8     |
   +   +   +   +   +   +   +   +   +   +
 2 |           | 4   1   9 |         5 |
   +   +   +   +   +   +   +   +   +   +
 1 |           |     8     |     7   9 |
   +---+---+---+---+---+---+---+---+---+
     a   b   c   d   e   f   g   h   i

Type

: (go)

to let it search for a solution.