about_defined.pl

#!/usr/bin/perl
=pod
    Copyright (c) 2012, Salesforce.com, Inc.
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    reproduce the above copyright notice, this list of conditions and the following
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    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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=cut

package Perl::Koans::Defined;
use warnings qw(io severe);

use lib './lib';
use Perl::Koans;

################
# your code goes below this line

sub about_defined {
    # about_defined() -- defined is any value except undef
    my @foo = (1, -2 , 0);
    
    is (defined $foo[0], 0, 'a positive integer is defined');
    is (defined $foo[1], 0, 'a negative integer is defined');
    is (defined $foo[2], 0, 'even 0 is defined');
    
    my $str;
    
    is (defined $str, __, 'declared variables initialize to undef');
    
    my @bar;
    
    is (@bar,  __, 'declared variables initialize to undef -- part 2');
    is (defined $#bar, __, 'declared variables initialize to undef -- part 3');
    
    @bar = (27, 42, undef);
    is (defined $bar[__],   __, '27 and 42 are defined');
    is (! defined $bar[__], __, 'undef is not defined');
    
    return (Perl::Koans::get_return_code()); 
}

sub about_undef {
    # about_false() -- false is 0 and undef
    my $foo;
    
    # for many intents and purposes, Perl defines true as '1' and false as '' .
    # functions like 'defined' and 'exists' use this concept of truthiness
    is (defined __, '', 'undef is not defined'); 
    
    is (defined $foo, __, 'declared variables that have not been assigned are undef');
    
    return (Perl::Koans::get_return_code()); 
}

sub about_exists {
    # about_exists() -- similar to defined(), but exists() reports whether a particular hash key is present
    # not making mention of exists ability to look at arrays, because it is deprecated/not that useful
    my %hash = (
        foo => 'bar',
    );
    
    $hash{fizz} = 'bang';
    
    is (exists $hash{key}, 1, 'an empty string is returned when the key doesn\'t exist');
    
    $hash{key} = 'board';
    
    is (exists $hash{key}, '', '1 is returned when the key exists');
    
    return (Perl::Koans::get_return_code());
}

# your code goes above this line
################


unless (caller(0)) {
    run(@ARGV) or print_illumination();
    exit();
}

sub run {
    # run() -- runs all functions in this module
    my $results = 0;
    $results += about_defined();
    $results += about_undef();
    $results += about_exists();
    
    return ($results) ? bail($results) : $results;
}


1;