Constructing an Object (The Finished Object)

by Andrew Johnson

July 5, 2001 —

The spin() method is the most complex as it does all the real work of
simulating the slot machine (the object itself just stores the current
state of the machine and ancillary data). The first thing we will need
to do is figure out how much is being bet on this spin:

sub spin {
my $self = shift;
my $bet = $self->bet(shift);
$bet = < $bet < 3? $bet : 3;
$bet = $bet < $self->credits()? $bet : $self->credits();

We obtain the $bet value by calling the bet() method with the second
argument (if any). We then check that the bet doesn't exceed 3, and
finally check that it doesn't exceed our remaining credits. Next, we
get the spin result itself:

my $spin = join('', map{$symbols[rand @symbols]}1..3);
$self->{spin} = $spin;

Here we have used map() to create a list of three random elements from
the @symbols array and joined them into a single string, and we set
the 'spin' attribute of the object. Now we need to calculate the payoff
for this spin:

my $payoff = 0;
if($spin =~ /^(\d)\1\1$/){
$payoff = $payoff{$spin}->($bet);
} elsif ($spin =~ /^[123][123][123]$/) {
$payoff = $payoff{any}->($bet);
}

We first check if the spin contains three matching digits (using a
regex). If so, then we call the subroutine from the %payoff hash to
obtain the payoff for that spin. The special case of 'any' is taken
care of by the elsif clause. Lastly, we need to adjust the attributes:

$self->{credits} -= $bet;
$self->{credits} += $payoff;
$self->{paid} = $payoff;
$self->{win} = $payoff;
}

We first subtract the $bet amount from the credits before adding any
payoff (we could have done this in one step). Then we set the 'paid'
attribute to equal the current payoff before finally setting the 'win'
attribute to the payoff as well. Why? If the payoff is zero, then the
win will be false; if there is a payoff, then the value will be true.
So, rather than setting it to 0 or 1, we simply set it to the payoff
itself.

Now we have a complete object oriented slot module. The complete module
looks like this:

package Slot;
use strict;
my %payoff = (
"777" => sub {$_[0] * 500},
"333" => sub {$_[0] * 80},
"222" => sub {$_[0] * 20},
"111" => sub {$_[0] * 5},
"any" => sub {$_[0] * 2},
"000" => sub {$_[0] * 1},
);

my @symbols = (0,7,0,3,0,2,0,1);

sub new {
my $class = shift;
my $credits = shift || 100;
my $self = {credits => $credits,
bet => 1,
win => 0,
paid => 0,
spin => undef,
};
bless $self, $class;
}

sub credits {
my $self = shift;
$self->{credits};
}
sub bet {
my $self = shift;
$self->{bet} = shift||$self->{bet};
}

sub spin {
my $self = shift;
my $bet = $self->bet(shift);
$bet = $bet < 3? $bet : 3;
$bet = $bet < $self->credits()? $bet : $self->credits();
my $spin = join('', map{$symbols[rand @symbols]}1..3);
$self->{spin} = $spin;
my $payoff = 0;
if($spin =~ /^(\d)\1\1$/){
$payoff = $payoff{$spin}->($bet);
} elsif ($spin =~ /^[123][123][123]$/) {
$payoff = $payoff{any}->($bet);
}
$self->{credits} -= $bet;
$self->{credits} += $payoff;
$self->{paid} = $payoff;
$self->{win} = $payoff;
}

sub display_results {
my $self = shift;
print join(" ", split //, $self->{spin}),"\n";
if ($self->{win}){
print "Winner paid: $self->{paid} credits!!\n\n";
} else {
print "Better luck next time\n\n";
}

}
1;
__END__

And here is the interactive test script:

#!/usr/bin/perl -w
use strict;
use Slot;
my $slot = Slot->new(100);
while(1){
my $credits = $slot->credits();
my $curr_bet = $slot->bet();
last if $credits < 1;

print "You have $credits remaining: max bet is 3\n";
print "Enter your bet [$curr_bet]: ";

chomp(my $bet = );
last if $bet eq 'q';
$bet ||= $curr_bet;

$slot->spin($bet);
$slot->display_results();
}

print "Game Over\n";
print "You have ", $slot->credits(), " remaining\n";
print "Thank you for playing\n";
__END__

I have played a few times and I always seem to lose my credits in a
short time

ITworld