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You're probably familiar with the concept of randomly selecting one from a group. Blindly drawing a slip of paper out of a box is an example. If the box contained 4 slips of paper, marked "red," "green," "blue," and "yellow," drawing one slip would be a random selection. Computerized random selections are pseudo-random, sometimes tending to slant toward certain results, depending on the randomizing algorithm and the operating system the program is running on. Computer randomization is good enough for most requirements, selections tending to even out over many "drawings." However, a person might want to influence the results in certain situations. Maybe a business person has 8000 specialty advertising pens to give away — 1000 red pens, 1000 green pens, 4000 blue pens, and 2000 yellow pens. I'll show you how to implement that influence. Going back to the box with slips of paper drawing analogy, 8000 people would be lined up to participate in the drawing. (We'll just say it's so; you don't have to imagine people lined up for blocks.) The drawing box would contain 1 red slip, 1 green slip, 4 blue slips, and 2 yellow slips, which is the ratio of the colors of the pens. Whenever a person draws a slip, the person is give a pen of that color. Then the slip is put back into the box before the next person draws. That procedure tends to give the pens away in a ratio comparable to the available colors. A computerized version is easy to implement with Perl:
#!/usr/bin/perl
use strict;
srand;
my %Selections = (
'red' => 1,
'green' => 1,
'blue' => 4,
'yellow' => 2,
);
my $Total = 0;
my %Individual = ();
for my $name (keys %Selections)
{
$Selections{$name} = 1 unless $Selections{$name} > 1;
for(1..$Selections{$name})
{
$Individual{$Total} = $name;
$Total++;
}
}
my $Answer = $Individual{int rand $Total};
print "Content-Type: text/html\n\n";
print <<HTML;
<head>
<body bgcolor="white">
<table border="1" cellpadding="12"><tr><td>
Congratulations! You have won a $Answer pen!
</td></tr></table>
</body>
</html>
HTML
The first 3 lines tell the server where Perl is located, limit certain uses of functions and variables, and seed the random number generator. Lines 5 through 10 store the selections. Lines 6 through 9 are the actual lines of available selections. They list the name of the available colors and the number of slips for that color. A "=>" character pair separates the name and number, and the line ends with a comma. The name is between apostrophes, the number is not. When you modify the lines of available selections for your own use, you may have as many name and number selections as you wish. If any of the names contain an apostrophe, the apostrophe must be preceded with a backward slash. Example: \' Lines 12 through 23 determine the total number of choices and "randomly" select one. The browser printing section is composed of lines 25 through 34. The program above prints the result in its own window, which could be a popup window. If you prefer to use SSI, change the browser printing section to: print "Content-Type: text/html\n\n"; print <<HTML; Congratulations! You have won a $Answer pen! HTML For fun, the lines of available selections can be modified to simulate the random answers magic cube or 8-ball divination games provide. http://ofb.net/8ball/answers.html has a list of possible answer selections. (The name of the physical 8-ball game, which starts with the word "magic," is trademarked by a toy company.) For business, the lines of available selections can be modified to present sales or discounts. The lines of available selections might be something like this: '25% off - $75 instead of $100.00!' => 10, '30% off - $70 instead of $100.00!' => 6, '35% off - $65 instead of $100.00!' => 2, '45% off - $55 instead of $100.00!' => 1, '50% off - $50 instead of $100.00!' => 1, The above would tend to provide a 25% discount 10 times out of 20, and a 50% discount 1 time out of 20. The browser printing section could be: print "Content-Type: text/html\n\n"; print <<HTML; $Answer HTML To display a pseudo-random photo, albeit slanted toward your own preference, the lines of available selections might be: '<img src="a.jpg">' => 1; '<img src="b.jpg">' => 3; '<img src="c.jpg">' => 1; The program can be used as a "random" destination selector, too. The lines of available selections might be: 'http://AffinityNumerology.com' => 1, 'http://BontragerConnection.com' => 2, 'http://WillMaster.com' => 3, 'http://MasterCGI.com' => 3, In order to redirect the browser instead of simply printing something, the browser printing section will need to be changed to: print "Location: $Answer\n\n"; And, the link on your web page might be: <a href="/cgi-bin/RandomMagic.cgi"> Click for random destination! </a> If you plan on creating an on-line casino, don't tell the patrons how easy it is to influence results :) Copyright 2001 William Bontrager
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