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    return $vals->mv(-1, 0)->minimum;
}

sub or {
    my ($self, @vals) = @_;

    # PDL awareness: any element is a piddle?
    return List::Util::max(@vals) if _non_is_a_piddle(@vals);

    _check_for_PDL();
    my $vals = $self->_cat_array_of_piddles(@vals);
    return $vals->mv(-1, 0)->maximum;
}

sub not {
    my ($self, $val) = @_;
    return 1-$val;
}

sub true  { return 1 }

sub false { return 0 }

sub new_variable {
    my ($self, @pars) = @_;

    my $variable_class = $self->_class_of_variable();
    my $var = $variable_class->new($self, @pars);
    push @{$self->{_variables}}, $var;
    Scalar::Util::weaken $self->{_variables}->[-1];
    return $var;
}

sub reset {
    my ($self) = @_;
    $_->reset() for $self->variables(); 
    return $self;
}

sub _class_of_variable { 'AI::FuzzyEngine::Variable' }

sub _non_is_a_piddle {
    return List::MoreUtils::none {ref $_ eq 'PDL'} @_;
}

my $_PDL_is_imported;
sub _check_for_PDL {
    return if $_PDL_is_imported;
    die "PDL not loaded"       unless $INC{'PDL.pm'};
    die "PDL::Core not loaded" unless $INC{'PDL/Core.pm'};
    $_PDL_is_imported = 1;
}

sub _cat_array_of_piddles {
    my ($class, @vals)  = @_;

    # TODO: Rapid return if @_ == 1 (isa piddle)
    # TODO: join "-", ndims -> Schnellcheck auf gleiche Dim.

    # All elements must get piddles
    my @pdls  = map { PDL::Core::topdl($_) } @vals;

    # Get size of wrapping piddle (using a trick)
    # applying valid expansion rules for element wise operations
    my $zeros = PDL->pdl(0);
    #        v-- does not work due to threading mechanisms :-((
    # $zeros += $_ for @pdls;
    # Avoid threading!
    for my $p (@pdls) {
        croak "Empty piddles are not allowed" if $p->isempty();
        eval { $zeros = $zeros + $p->zeros(); 1
            } or croak q{Can't expand piddles to same size};
    }

    # Now, cat 'em by expanding them on the fly
    my $vals = PDL::cat( map {$_ + $zeros} @pdls );
    return $vals;
};

1;

=pod

=head1 NAME

AI::FuzzyEngine - A Fuzzy Engine, PDL aware

=head1 SYNOPSIS

=head2 Regular Perl - without PDL

    use AI::FuzzyEngine;

    # Engine (or factory) provides fuzzy logical arithmetic
    my $fe = AI::FuzzyEngine->new();

    # Disjunction:
    my $a = $fe->or ( 0.2, 0.5, 0.8, 0.7 ); # 0.8
    # Conjunction:
    my $b = $fe->and( 0.2, 0.5, 0.8, 0.7 ); # 0.2
    # Negation:
    my $c = $fe->not( 0.4 );                # 0.6
    # Always true:
    my $t = $fe->true();                    # 1.0
    # Always false:
    my $f = $fe->false();                   # 0.0

    # These functions are constitutive for the operations
    # on the fuzzy sets of the fuzzy variables:

    # VARIABLES (AI::FuzzyEngine::Variable)

    # input variables need definition of membership functions of their sets
    my $flow = $fe->new_variable( 0 => 2000,
                        small => [0, 1,  500, 1, 1000, 0                  ],
                        med   => [       400, 0, 1000, 1, 1500, 0         ],
                        huge  => [               1000, 0, 1500, 1, 2000, 1],
                   );
    my $cap  = $fe->new_variable( 0 => 1800,
                        avg   => [0, 1, 1500, 1, 1700, 0         ],
                        high  => [      1500, 0, 1700, 1, 1800, 1],
                   );
    # internal variables need sets, but no membership functions
    my $saturation = $fe->new_variable( # from => to may be ommitted
                        low   => [],
                        crit  => [],
                        over  => [],
                   );
    # But output variables need membership functions for their sets:
    my $green = $fe->new_variable( -5 => 5,
                        decrease => [-5, 1, -2, 1, 0, 0            ],
                        ok       => [       -2, 0  0, 1, 2, 0      ],
                        increase => [              0, 0, 2, 1, 5, 1],
                   );

    # Reset FuzzyEngine (resets all variables)

lib/AI/FuzzyEngine.pm  view on Meta::CPAN

    my $var_int = $fe->new_variable( $name_of_set1 => [],
                                     $name_of_set2 => [],
                                     ...
                       );

Hence, they can not use the methods C<fuzzify> or C<defuzzify>.

Fuzzy operations are simple operations on floating values between 0 and 1:

    my $conjunction = $fe->and( $var1->xxx, $var2->yyy, ... );
    my $disjunction = $fe->or(  $var1->xxx, $var2->yyy, ... );
    my $negated     = $fe->not( $var1->zzz );

There is no magic.

A sequence of rules for the same set can be implemented as follows: 

    $var_3->zzz( $var_1->xxx, $var_2->yyy, ... );
    $var_3->zzz( $var_4->aaa, $var_5->bbb, ... );

The subsequent application of C<< $var_3->zzz(...) >>
corresponds to "or" operations (aggregation of rules).

Only a reset can reset C<$var_3>. 

=head2 PDL awareness

Membership degrees of sets might be either scalars or piddles now.

    $var_a->memb_fun_a(        5  ); # degree of memb_fun_a is a scalar
    $var_a->memb_fun_b( pdl(7, 8) ); # degree of memb_fun_b is a piddle

Empty piddles are not allowed, behaviour with bad values is not tested.

Fuzzification (hence calculating degrees) accepts piddles:

    $var_b->fuzzify( pdl([1, 2], [3, 4]) );

Defuzzification returns a piddle if any of the membership
degrees of the function's sets is a piddle:

    my $val = $var_a->defuzzify(); # $var_a returns a 1dim piddle with two elements

So do the fuzzy operations as provided by the fuzzy engine C<$fe> itself.

Any operation on more then one piddle expands those to common
dimensions, if possible, or throws a PDL error otherwise. 

The way expansion is done is best explained by code
(see C<< AI::FuzzyEngine->_cat_array_of_piddles(@pdls) >>).
Assuming all piddles are in C<@pdls>,
calculation goes as follows:

    # Get the common dimensions
    my $zeros = PDL->pdl(0);
    # Note: $zeros += $_->zeros() for @pdls does not work here
    $zeros = $zeros + $_->zeros() for @pdls;

    # Expand all piddles
    @pdls = map {$_ + $zeros} @pdls;

Defuzzification uses some heavy non-threading code,
so there might be a performance penalty for big piddles. 

=head2 Todos

=over 2

=item Add optional alternative implementations of fuzzy operations

=item More checks on input arguments and allowed method calls

=item PDL awareness: Use threading in C<< $variable->defuzzify >>

=item Divide tests into API tests and test of internal functions

=back

=head1 CAVEATS / BUGS

This is my first module.
I'm happy about feedback that helps me to learn
and improve my contributions to the Perl ecosystem.

Please report any bugs or feature requests to
C<bug-ai-fuzzyengine at rt.cpan.org>, or through
the web interface at
L<http://rt.cpan.org/NoAuth/ReportBug.html?Queue=AI-FuzzyEngine>.
I will be notified, and then you'll
automatically be notified of progress on your bug as I make changes.

=head1 SUPPORT

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

    perldoc AI::FuzzyEngine

=head1 AUTHOR

Juergen Mueck, jmueck@cpan.org

=head1 COPYRIGHT

Copyright (c) Juergen Mueck 2013.  All rights reserved.

This library is free software; you can redistribute it and/or
modify it under the same terms as Perl itself.

=cut