ch09.069_prob

Perl Best Practices the source code

##############################################################################
## Code fragment (NOT RECOMMENDED) from Chapter 9 of "Perl Best Practices"  ##
##     Copyright (c) O'Reilly & Associates, 2005. All Rights Reserved.      ##
##  See: http://www.oreilly.com/pub/a/oreilly/ask_tim/2001/codepolicy.html  ##
##############################################################################


# Standard modules...
use strict;
use warnings;
use IO::Prompt;
use Carp;
use English qw( -no_match_vars );
use Data::Alias;
use Readonly;

sub odd { 
    my ($n) = @_;
    return $n % 2;
}


sub find_second_odd {
    my $prev_odd_found = 0;
 
    # Check through args...
    for my $num (@_) {
        # Find an odd number...
        if (odd($num)) {
            # Return it if it's not the first (must be the second)...
            return $num if $prev_odd_found;
 
            # Otherwise, remember it's been seen...

            $prev_odd_found = 1;
        }
    }
    # Otherwise, fail
}


if (defined find_second_odd(2..6)) {
    # find_second_odd() returns 5
    # so the if block does execute as expected
    print "expected 1\n";
}
if (defined find_second_odd(2..1)) {
    # find_second_odd() returns undef
    # so the if block is skipped as expected
    print "unexpected 2\n";
}
 
if (defined find_second_odd(2..4)) {
    # find_second_odd() returns an empty string (!)
    # so the if block is unexpectedly executed
    print "unexpected 3\n";
}
 
if (defined find_second_odd(2..3)) {
    # find_second_odd() returns an empty string again (!)
    # so the if block is unexpectedly executed again 
    print "unexpected 4\n";
}