=head1 NAME
 
Parse::Eyapp::TokenGen - Support for Using Parse::Eyapp as a Data Generator 
 
=head1 INTRODUCTION

For a introduction to data generation using L<Parse::Eyapp> see
L<Parse::Eyapp::datagenerationtut>.

=head1 METHODS

=head2 set_tokengens

Receives the parser object and the pairs 

    token => generator

Sets the generator attribute of the tokens.
Though not strictly necessary, the generator is
a L<Test::LectroTest::Generator> object.

=head2 set_weights

Receives the parser object and the pairs 

    token => weight

Sets the weight attribute of the tokens.
The weight is a floating number.

=head2 set_tokenweightsandgenerators

Receives the parser object and the pairs 

    token => [weight, generator]

or

    token => weight

and sets the weight and generator attributes of the tokens.
An example can be found in C<examples/generator/GenSupport.pm>:

  $parser->set_tokenweightsandgenerators(
    NUM => [ 2, Int(range=>[0, 9], sized=>0)],
    VAR => [
              0,  # At the beginning, no variables are defined
              Gen {
                return  Elements(keys %st)->generate if keys %st;
                return Int(range=>[0, 9], sized=>0)->generate;
              },
            ],
    VARDEF => [ 
                2,  
                String( length=>[1,2], charset=>"A-NP-Z", size => 100 )
              ],
    '=' => 2, '-' => 1, '+' => 2, 
    '*' => 4, '/' => 2, '^' => 0.5, 
    ';' => 1, '(' => 1, ')' => 2, 
    ''  => 2, 'error' => 0,
  );


=head2 token_weight

Receives the parser object and the token and returns the weight.
If an additional weight is provided the weight for the token is set.

=head2 token_generator

Receives the parser object and the token and returns the generator.
If an additional generator is provided the generator for the token is set.

=head2 deltaweight

Has the syntax:

  $parser->deltaweight(TOKEN1 => deltaweight1, TOKEN2 => deltaweight2, ...)

increases the weight of the respective token by the associated amount.

=head2 pushdeltaweight

As C<deltaweight> but the current weights of the involved tokens
are saved in a stack

=head2 popweight

Restores the weights of the tokens that were previously saved
with C<pushdeltaweight>

=head1 SEE ALSO

=over

=item * L<Parse::Eyapp::datagenerationtut>


=item * L<Test::LectroTest::Generator> by Tom Moertel 

=item *  The Design and Implementation of a Grammar-based Data Generator (1992) 
by Peter M. Maurer, Software Practice and Experience 
L<http://www.cs.ubc.ca/local/reading/proceedings/spe91-95/spe/./vol22/issue3/spe756pm.pdf>

=item * yagg: an easy-to-use generator for structured test inputs
by David Coppit and Jiexin Lian.
ASE '05: Proceedings of the 20th IEEE/ACM international Conference on Automated software engineering.
2005, pages 356-359. 

=over 2

=item * L<http://search.cpan.org/perldoc?yagg::Tutorial>, 

=item * L<http://www.cs.wm.edu/~coppit/wiki/images/4/4e/yagg_short.pdf>,

=item * L<http://www.cs.wm.edu/~coppit/wiki/images/6/69/wm-cs-2005-13.pdf>

=back

=item * 
Writing Randomly by Randall Schwartz. 
Linux Magazine Column 04 (Sep 1999). 
L<http://www.stonehenge.com/merlyn/LinuxMag/col04.html>

=item * Generating Test Data with Enhanced Context Free Grammars by Peter M. Maurer
L<http://cs.baylor.edu/~maurer/aida/dgl-source/documentation/gen_tst.pdf>

=item * Modules as Programs by Brian d Foy 
L<http://www252.pair.com/comdog/mastering_perl/Chapters/18.modulinos.html>

=item * How a Script Becomes a Module by Brian d Foy. On Perlmonks: 
L<http://www.perlmonks.org/index.pl?node_id=396759>.



=back

=head1 CONTRIBUTORS

=over 2

=item * Hal Finkel L<http://www.halssoftware.com/> 

=item * G. Williams L<http://kasei.us/>

=item * Thomas L. Shinnick L<http://search.cpan.org/~tshinnic/>

=item * Frank Leray

=back

=head1 AUTHOR
 
Casiano Rodriguez-Leon (casiano@ull.es)

=head1 ACKNOWLEDGMENTS

This work has been supported by CEE (FEDER) and the Spanish Ministry of
I<Educacion y Ciencia> through I<Plan Nacional I+D+I> number TIN2005-08818-C04-04
(ULL::OPLINK project L<http://www.oplink.ull.es/>). 
Support from Gobierno de Canarias was through GC02210601
(I<Grupos Consolidados>).
The University of La Laguna has also supported my work in many ways
and for many years.

A large percentage of  code is verbatim taken from L<Parse::Yapp> 1.05.
The author of L<Parse::Yapp> is Francois Desarmenien.
 
I wish to thank Francois Desarmenien for his L<Parse::Yapp> module, 
to my students at La Laguna and to the Perl Community. Thanks to 
the people who have contributed to improve the module (see L<Parse::Eyapp/CONTRIBUTORS>).
Thanks to Larry Wall for giving us Perl.
Special thanks to Juana.

=head1 LICENCE AND COPYRIGHT
 
Copyright (c) 2006-2008 Casiano Rodriguez-Leon (casiano@ull.es). All rights reserved.

Parse::Yapp copyright is of Francois Desarmenien, all rights reserved. 1998-2001
 
These modules are free software; you can redistribute it and/or
modify it under the same terms as Perl itself. See L<perlartistic>.
 
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.