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|
#!perl
###############################################################################
=comment
Perl Weekly Challenge 095, Task #2: Demo Stack
=cut
###############################################################################
#--------------------------------------#
# Copyright © 2021 PerlMonk Athanasius #
#--------------------------------------#
#==============================================================================
package Stack;
#==============================================================================
use strict;
use warnings;
use Regexp::Common qw( number );
#------------------------------------------------------------------------------
sub new
#------------------------------------------------------------------------------
{
my ($class, $throw) = @_;
my %self = ( throw => $throw // 1,
top => -1,
items => [] );
return bless \%self, $class;
}
#------------------------------------------------------------------------------
sub push
#------------------------------------------------------------------------------
{
my ($self, $item) = @_;
$item =~ / ^ $RE{num}{real} $ /x or die qq[ERROR: "$item" is not a number];
push @{ $self->{items} }, $item;
++$self->{top};
}
#------------------------------------------------------------------------------
sub pop
#------------------------------------------------------------------------------
{
my ($self) = @_;
my $item;
if ($self->{top} >= 0)
{
$item = pop @{ $self->{items} };
--$self->{top};
}
elsif ($self->{throw})
{
die "ERROR: Cannot pop() an empty stack\n";
}
return $item;
}
#------------------------------------------------------------------------------
sub top
#------------------------------------------------------------------------------
{
my ($self) = @_;
my $item;
if ($self->{top} >= 0)
{
$item = $self->{items}->[ $self->{top} ];
}
elsif ($self->{throw})
{
die "ERROR: There is no top() on an empty stack\n";
}
return $item;
}
#------------------------------------------------------------------------------
sub min
#------------------------------------------------------------------------------
{
my ($self) = @_;
my $min;
if ($self->{top} >= 0)
{
$min = $self->{items}->[ 0 ];
for my $i (1 .. scalar @{ $self->{items} } - 1)
{
my $new_min = $self->{items}->[ $i ];
$min = $new_min if $new_min < $min;
}
}
elsif ($self->{throw})
{
die "ERROR: There is no min() for an empty stack\n";
}
return $min;
}
#------------------------------------------------------------------------------
sub display
#------------------------------------------------------------------------------
{
my ($self) = @_;
my $stack = "Stack: (empty)\n";
if ($self->{top} >= 0)
{
my $width = length $self->{items}->[ $self->{top} ];
for my $item (@{ $self->{items} }[ 0 .. $self->{top} - 1 ])
{
my $new_width = length $item;
$width = $new_width if $new_width > $width;
}
my $top = 1;
my $bar = sprintf '+-%s-+', '-' x $width;
$stack = "Stack: $bar\n";
for my $item (reverse @{ $self->{items} })
{
$stack .= sprintf " | %*s |%s\n %s\n",
$width, $item, $top ? ' <- top' : '', $bar;
$top = 0;
}
}
return $stack;
}
###############################################################################
1;
###############################################################################
|
