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#!/usr/bin/env perl
use strict;
use warnings;
use feature qw{ say signatures state };
no warnings qw{ experimental };
# I use `say` instead of `print` because the newlines
# improve readability in the output
my $stack = Stack->new;
$stack->push(2);
$stack->push(-1);
$stack->push(0);
$stack->all; # 2, -1, 0
$stack->pop; # removes 0
$stack->all;
say $stack->top; # prints -1
$stack->push(0);
$stack->all;
say $stack->min; # prints -1
say 'DONE';
exit;
# I think a Moose-style implementation would be good for me
package Stack;
# see min, below.
use List::Util;
# creates a new Stack object. Except for the "min" function,
# there's nothing to keep this from handling anything that a
# scalar can hold: number, string, hashref, arrayref, closure
sub newx ( $class ) {
my $self = {};
$self->{values} = [];
return bless $self, $class;
}
sub new ( $class, @values ) {
my $self = {};
$self->{values} = [];
push $self->{values}->@*, @values;
return bless $self, $class;
}
# 'push' and 'pop' are methods used by Perl's Array type
# to handle stack values, so here we just use them
sub push ( $self, $value ) {
push $self->{values}->@*, $value;
return 1;
}
sub pop ( $self ) {
return pop $self->{values}->@*;
}
# it's harder to reuse subroutines from libraries than
# it is to reuse those provided by Perl, so we have to
# use List::Util and use min's long name rather than
# use List::Util qw{min}, because Perl would think we're
# rewriting min.
sub min ( $self ) {
return List::Util::min( $self->{values}->@* );
}
# the thing I had to remember that push and pop occur from
# the back of the stack, not the front, and thus top is the
# _last_ value, not the _first_. I could use {values}[0]
# if instead I used shift and unshift.
sub top ( $self ) {
return $self->{values}[-1];
return 1;
}
# bookkeeping function so I know what's going on inside
sub all ( $self ) {
say join "\n\t", 'Size: ' . scalar $self->{values}->@*,
$self->{values}->@*, '';
return 1;
}
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