@$self{ qw( INDEX COUNT FIRST LAST ) } = ( $index, $index + 1, 0, $index == $max ? 1 : 0 );
$$self{ qw( PREV ) } = [ @{ $self->{ _DATASET } }[ map { $index - 1 + $_ * $size } 0 .. ($dim - 1) ] ];
$$self{ qw( NEXT ) } = [ @{ $self->{ _DATASET } }[ map { $index + 1 + $_ * $size } 0 .. ($dim - 1) ] ];
@$self{ qw( INDEX COUNT FIRST LAST ) } = ( $index, $index + 1, 0, $index == $max ? 1 : 0 );
$$self{ qw( PREV ) } = [ @{ $self->{ _DATASET } }[ map { $index - 1 + $_ * $size } 0 .. ($dim - 1) ] ];
$$self{ qw( NEXT ) } = [ @{ $self->{ _DATASET } }[ map { $index + 1 + $_ * $size } 0 .. ($dim - 1) ] ];