Games::LMSolve::Base - base class for puzzle solvers.


version 0.12.0


    package MyPuzzle::Solver;

    use Games::LMSolve::Base;

    @ISA = qw(Games::LMSolve::Base);

    # Override these methods:

    sub input_board { ... }
    sub pack_state { ... }
    sub unpack_state { ... }
    sub display_state { ... }
    sub check_if_final_state { ... }
    sub enumerate_moves { ... }
    sub perform_move { ... }

    # Optionally:
    sub render_move { ... }
    sub check_if_unsolvable { ... }

    package main;

    my $self = MyPuzzle::Solver->new();



This class implements a generic solver for single player games. In order to use it, one must inherit from it and implement some abstract methods. Afterwards, its interface functions can be invoked to actually solve the game.


version 0.12.0



The constructor.


Should be inherited to implement the construction.


Actually solve the board based on the arguments in the command line.


input_board($self, $file_spec)

This method is responsible to read the "board" (the permanent parameters) of the puzzle and its initial state. It should place the board in the object's keys, and return the initial state. (in unpacked format).

Note that $file_spec can be either a filename (if it's a string) or a reference to a filehandle, or a reference to the text of the board. input_board() should handle all cases.

You can look at the Games::LMSolve::Input module for methods that facilitate inputting a board.

pack_state($self, $state_vector)

This function accepts a state in unpacked form and should return it in packed format. A state in unpacked form can be any perl scalar (as complex as you like). A state in packed form must be a string.

unpack_state($self, $packed_state)

This function accepts a state in a packed form and should return it in its expanded form.

display_state($self, $packed_state)

Accepts a packed state and should return the user-readable string representation of the state.

check_if_final_state($self, $state_vector)

This function should return 1 if the expanded state $state_vector is a final state, and the game is over.

enumerate_moves($self, $state_vector)

This function accepts an expanded state and should return an array of moves that can be performed on this state.

perform_move($self, $state_vector, $move)

This method accepts an expanded state and a move. It should try to peform the move on the state. If it is successful, it should return the new state. Else, it should return undef, to indicate that the move cannot be performed.

check_if_unsolvable($self, $state_vector) (optional over-riding)

This method returns the verdict if $state_vector cannot be solved. This method defaults to returning 0, and it is usually safe to keep it that way.

render_move($self, $move) (optional overriding)

This function returns the user-readable stringified represtantion of a move.


$self->solve_board($file_spec, %args)

Solves the board specification specified in $file_spec. %args specifies optional arguments. Currently there is one: 'max_iters' that specifies the maximal iterations to run.

Returns whatever run_scan returns.


Continues the current scan. %args may contain the 'max_iters' parameter to specify a maximal iterations limit.

Returns two values. The first is a progress indicator. "solved" means the puzzle was solved. "unsolved" means that all the states were covered and the puzzle was proven to be unsolvable. "interrupted" means that the scan was interrupted in the middle, and could be proved to be either solvable or unsolvable.

The second argument is the final state and is valid only if the progress value is "solved".


Retrieves the current number of iterations.

$self->display_solution($progress_code, $final_state)

If you input this message with the return value of run_scan() you'll get a nice output of the moves to stdout.


Sets the run time states display callback to \&states_display_callback.

This display callback accepts a reference to the solver and also the following arguments in key => value pairs:

"state" - the expanded state. "depth" - the depth of the state. "move" - the move leading to this state from its parent.




Shlomi Fish,


Shlomi Fish <>


This software is Copyright (c) 2007 by Shlomi Fish.

This is free software, licensed under:

  The MIT (X11) License


Please report any bugs or feature requests on the bugtracker website

When submitting a bug or request, please include a test-file or a patch to an existing test-file that illustrates the bug or desired feature.



You can find documentation for this module with the perldoc command.

  perldoc Games::LMSolve::Base


The following websites have more information about this module, and may be of help to you. As always, in addition to those websites please use your favorite search engine to discover more resources.

Bugs / Feature Requests

Please report any bugs or feature requests by email to bug-games-lmsolve at, or through the web interface at You will be automatically notified of any progress on the request by the system.

Source Code

The code is open to the world, and available for you to hack on. Please feel free to browse it and play with it, or whatever. If you want to contribute patches, please send me a diff or prod me to pull from your repository :)

  git clone git://