package Example::Tuple;

use overload(
    '""' => \&asString,
);

sub new
{
    my( $class, @coords )= @_;
    return bless \@coords, $class;
}

sub asString
{
    my( $self )= @_;
    return "(" . join(",",@$self) . ")";
}

##</code><code>##

require Example::Tuple;

my $origin= Example::Tuple->new( -3, 5 );
my $dest=   Example::Tuple->new( 2, 1 );
print "Now draw a line from $origin to $dest.\n";

##</code><code>##

Now draw a line from (-3,5) to (2,1).

##</code><code>##

package Example::Tuple;

use overload(
    'eq' => \&isEqual,
);

# ...

sub isEqual
{
    my( $self, $arg, $isReversed )= @_;
    # We ignore $isReversed since ($x eq $y) is also ($y eq $x)
    return 0    # Tuples of different sizes are never equal
        if  @$self != @$arg;
    for my $i (  0 .. $#$self  ) {
        return 0    # Tuples differ if any paired elements differ
            if  $self->[$i] ne $arg->[$i];
    }
    return 1;    # Otherwise they are equal.
}

##</code><code>##

require Example::Tuple;

my $w= Example::Tuple->new( 3, 4 );
my $x= Example::Tuple->new( 4, 3 );
my $y= Example::Tuple->new( 3, 4 );
my $z= $w;
print "w and z are the same object.\n"
    if  $w == $z;
print "$w and $y are at the same position.\n"
    if  $w eq $y;
print "$x and $y are at different positions.\n"
    unless  $x eq $y;

##</code><code>##

package Example::Tuple;

use overload(
    '.' => \&concatString,
);

sub concatString
{
    my( $self, $string, $isReversed )= @_;
    my @new;
    for my $elt (  @$self  ) {
        push @new, $isReversed
            ? $string . $elt
            : $elt . $string;
    }
    return __PACKAGE__->new( @new );
}