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HIRATARA / Data-Monad-0.09 / lib / Data / Monad / List.pm 

            

              
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package Data::Monad::List;
use strict;
use warnings;
use Exporter qw/import/;
use base qw/Data::Monad::Base::MonadZero/;
our @EXPORT = qw/scalar_list list_unit list_zero list_flat_map_multi 
                 list_map_multi list_sequence/;
sub scalar_list(@) { __PACKAGE__->new(map { [$_] } @_) }
sub list_unit { __PACKAGE__->unit(@_) }
sub list_zero { __PACKAGE__->zero(@_) }
sub list_flat_map_multi(&@) { __PACKAGE__->flat_map_multi(@_) }
sub list_map_multi(&@) { __PACKAGE__->map_multi(@_) }
sub list_sequence { __PACKAGE__->sequence(@_) }
sub new {
    my $class = shift;
    bless [@_], $class;
}
sub unit {
    my $class = shift;
    $class->new([@_]);
}
sub zero {
    my $class = shift;
    $class->new();
}
sub flat_map {
    my ($self, $f) = @_;
    (ref $self)->new(map { @{$f->(@$_)} } @$self);
}
sub values {
    my $self = shift;
    @$self;
}
sub scalars {
    my $self = shift;
    map {
        @$_ == 1 or die "contained multiple values.";
        @$_;
    } $self->values;
}
1;
__END__
=head1 NAME
Data::Monad::List - The List monad.
=head1 SYNOPSIS
  use Data::Monad::List;
  my $m = scalar_list(10, 20);
  $m = $m->flat_map(sub {
      my $v = shift;
      scalar_list($v + 1, $v + 2);
  });
  my @result = $m->scalars; # (11, 12, 21, 22)
=head1 DESCRIPTION
Data::Monad::List represents non-deterministic values.
This module is marked B<EXPERIMENTAL>. API could be changed without any notice.
=head1 METHODS
=over 4
=item $list = scalar_list(@single_values)
Is the same as following lines.
  $list = Data::Monad::List->new([$single_values[0]], [$single_values[1]], ...)
=item $list = list_unit(@values)
=item $list = list_zero()
=item $f = list_flat_map_multi(\&f, $list1, $list2, ...)
=item $f = list_map_multi(\&f, $list1, $list2, ...)
=item $list = list_sequence($list1, $list2, ...)
These are shorthand of methods which has the same name.
=item $list = Data::Monad::List->new(\@values1, \@values2, ...)
The constructor of this class.
=item zero
Overrides methods of L<Data::Monad::Base::MonadZero>.
=item unit
=item flat_map
Overrides methods of L<Data::Monad::Base::Monad>.
=item @values = $list->values
Retrieves list of values from C<$list>
=item @single_values = $list->scalars
Retrieves values which was set by the C<scalar_list> method.
=back
=head1 AUTHOR
hiratara E<lt>hiratara {at} cpan.orgE<gt>
=head1 SEE ALSO
L<Data::Monad::Base::Monad>
=head1 LICENSE
This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.
=cut