Using a standard deck of playing cards we can display the first n digits of the constant PI. For example using a single deck of cards, you can display the following digits of PI:

3.14159265358979323846264

In the above example we cannot display the next digit, which happens to be a ‘3′, because we have already used 4 cards of the number ‘3′ from a single deck.

Write a function that takes d - the number of card decks; and returns the number of digits of PI you can display using the cards. So for d(deck) = 1, the function should return 24 (the number of starting digits of PI).

Take ‘Ace’ as the digit ‘1′ and ‘10′ as the digit ‘0′. A list of the million digits of PI can be found here.

Preferably the solution should be in PHP, but other languages are welcome.

import java.awt.event.*;

But in the spirit of ‘programming into the language’, what we can do is try to simulate a ‘package-like’ concept in PHP. Take the following directory structure.

So now if we want to import the ‘login.php’ file in our code we must be able to do the following with a newly created ‘import’ function:

import("com.codediesel.Security.login");

This will include the ‘login.php’ file from the ‘com/codediesel/Security’ directory. To include all the files from the ‘Security’ directory we can do the following:

import("com.codediesel.Security.*);

As you can see that this is actually quite different from what the actual package concept implies, which is to import related classes.

Anyways, taking it as a conceptual idea only the code for the import function is shown below:

<?php
 
$basePath = "./";
 
function import($classPath)
{
    global $basePath;
 
    /* If the path ends with a '.*' then include
       all the files in the last given directory.
    */
    if(preg_match('/(\.\*)$/', $classPath))
    {
        $importFilePath = substr($classPath, 0, strlen($classPath) - 2);
        $importFilePath = str_replace(".", "/", $importFilePath);
        $d= dir($basePath . $importFilePath);
 
        while(false !== ($file = $d->read())) 
        {
            /* Reject parent, current directories and sub directories */
            if(($file == '.')  ||
               ($file == '..') ||
               (is_dir($d->path . "/" . $file)))
            {
                continue;
            }
 
            require_once($basePath . $importFilePath . "/" . $file);
        }
    } else {
        /* If a single file is specified */
        $importFile = str_replace(".", "/", $classPath) . ".php";
    	require_once($basePath . $importFile);
    }
}
 
?>

Please note that this is just an idea. Detailed error handling is not included to keep the code conceptually simple to understand. It would be fun if readers could bounce around some thoughts.

Now the Problems

The first main problem is that this is not exactly what the package concept implies. What we are essentially doing is dressing-up the ‘include’ concept in new clothes.

The second is that for multiple file inclusion as shown above, we cannot predict in which sequence the files will be included, which can raise some dependency issues.

Including a large number of files can incur a small performance hit. This can be better handled if developed as a PECL extension.

Data Generation

Once you connect ADG to your MySQL server and register a database, you are ready to go. Generating the test data is quite simple. First you create a project for your data generation work. Once done, you select the table and fields you want to generate data for, select the type of test data to generate – dates, urls, names etc. Set the total number of records to generate and then run the project. This will create the test data for your database project. The test data can be saved directly to the connected database or you can save it as a separate SQL script, YAML or CSV file. Below is a sample screenshot of a data generation project.

The Advanced Data Generator comes with a very useful repository of real-life like data, in order to generate meaningful test-data for the database. You can also use custom SQL scripts or Macros to generate custom string data.

In closing

Although not free, its a small price to pay for the excellent automation it provides during database creation.

Write a program which finds a four digit number AABB which is a perfect square. A and B represent different digits.

If you are posting solutions, then please make them in php, as this is what this blog is related around, but if would like to submit in any other language you are welcome, as requested by Evans in the comments.

I invite readers to send me problems you find interesting which can be incorporated in future posts. Just ensure that problems are not too easy or too hard. An easy problem doesn’t challenge you, while a hard one destroys the motivation to solve it. You can mail problems to me at metapix[at]gmail.com with the subject ‘problems’. Don’t forget to include your name.

How Fiddler works

The proxy bascially sits between the Windows WinINET interface and the internet. WinInet is high level API to work with HTTP, FTP, and Gopher protocols.

Installing Fiddler

Fiddler is an HTTP Proxy running on port 8888 on your local PC. You can configure any application which accepts a HTTP Proxy to run through Fiddler so you can debug the particular applications traffic. WinINET-based applications (E.g. Microsoft Office, Internet Explorer, etc) should automatically use Fiddler while it’s running and the “Capture Traffic” box is checked on the Fiddler File menu.

Current versions of Internet Explorer, Google Chrome, Apple Safari, and Opera all automatically use Fiddler when Fiddler is configured to Capture Traffic.

If your browser does not automatically use a proxy then you can configure it to point to address: 127.0.0.1, port: 8888.

Logging with Fiddler

You can easily log HTTP traffic using Fiddler to track down bugs from your browser or website and save it to a file. This can be quite handy if you need to send the logs to the testing team.

Transfer timelines

Like many other browser addons, Fiddler also supports transfer timelines.

Extending Fiddler Using Rules

Fiddler lets you modify its HTTP request or response by using the JScript.NET scripting language. You can also write your own plugins to change Fiddlers behavior in any .NET language. Sadly being from the php camp I do not have much experience there.

Text Encode/Decode Wizard

I specially like the ‘Text Wizard’ which lets you process text in a variety of formats. You can encode/decode data using: Base64, URLEncode, HexEncode, JS string, HTML Encode, UTF-7, Deflated SAML.

HTTP Performance tuning

The author of Fiddler, Eric Lawrence, has an excellent article that goes into the details on HTTP performance tuning.

Fiddler in a Nutshell

Fiddler is an excellent tool for both troubleshooting client/server applications and tweaking the performance of web applications. There are many more things you can do with Fiddler for which this post cannot do justice. Fiddler gives you an inside view into the mechanics of HTTP requests and responses, allowing you to understand what your application is doing. With that knowledge under your belt, you can write better, faster, and lighter applications.

Currently the software includes three tools:
a. Visualizer : Helps to browse components and associations using one simple unified view.
b. Navigator : Interactive visual representation of all code associations.
c. Search : Incremental search for any type of component, including classes and methods.

Visualizer

The visualizer presents the application components and associations in a graphical representation. Each component of the application appears as a node and associations appear as edges, with the association name given on the edges. When there are many associations of a given type, the associations are grouped into a sub-node. The graph can be traversed: expanding nodes to reveal associated components while the layout automatically adjusts.

The following is a visualization of the Amazon API class I had posted about earlier.

Another visualization of Wordpress 2.8, centered on index.php.
(Click image to view a larger version)

Navigator

The navigator presents the components and associations of the application which were discovered by the analyzer. It starts from a given selected component and shows all associated components. This includes inbound and outbound associations. The following figure shows the navigator with the Wordpress ‘wp_meta()’ function selected.

Search

The search feature lets you search for components by name or a partial name using wild cards.

Price

nWire is not OpenSource, but a 30-day trial is available. Single user license will cost you $59. If you are dealing with plethora of heavy applications, than the price is worth it.

Installation

Papercut is a Windows application requiring .NET Framework 3.5 . Thankfully no installation is required as the application can be run directly. Upon activation it sits in the system tray and pops a message when a email is received from a local web application.

The messages can then be viewed in the Papercut window.

In all a simple and useful tool for any web developer.

1. Browsers Quirks – Despite the standardization in browsers, there will remain some quirks in various browsers that you will need to iron out on a regular basis.
2. Personalize Content – It may be required to deliver different type of content depending on the browser type (although it is usually not recommended); whether mobile or otherwise.
3. Illegal Access – Prevent bandwidth hogging bots and poorly programmed clients from downloading your content.

Below is a sample header for my site when using Firefox.

http://www.codediesel.com/
 
GET / HTTP/1.1
Host: www.codediesel.com
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.6)
Gecko/2009011913 Firefox/3.0.6 FirePHP/0.2.4
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-us,en;q=0.5
Accept-Encoding: gzip,deflate
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive

PHP already has a builtin function - get_browser() that lets you determine the capabilities of the user’s browser, but it requires a browscap.ini to be installed, which sadly is not bundled with PHP, and also the function can slow down your php script. The other way to get a user agent is to use php server variables like below,

echo $_SERVER['HTTP_USER_AGENT'];

In this post we will use the Net_UserAgent_Detect Pear package to determine user agents.

Installation

Net_UserAgent_Detect being a Pear package we will use the Pear installer as below. I recommend to always use the Pear installer to download packages rather than downloading it manually as the Pear installer automatically downloads any dependent packages.

pear install Net_UserAgent_Detect-2.5.1

Usage

Usage is quite simple. For example the following code:

<?php
 
require_once 'Net/UserAgent/Detect.php';
 
echo Net_UserAgent_Detect::getUserAgent();
 
?>

will return the following string on Firefox 3.0.6: This can be quite useful if you need to log the users browser or OS type.

Mozilla/5.0 (Windows; U; Windows NT 5.1; 
en-US; rv:1.9.0.6) Gecko/2009011913 Firefox/3.0.6 FirePHP/0.2.4

getUserAgent() is only one of the many methods available in the class.

<?php
 
require_once 'Net/UserAgent/Detect.php';
 
echo('Browser String: '.Net_UserAgent_Detect::getBrowserString())."<br>";
echo('OS String: '.Net_UserAgent_Detect::getOSString())."<br>";
echo('Javascript: '.Net_UserAgent_Detect::getFeature('javascript'));
 
?>

Some other useful functions to directly test the type of browser are:
isIE()
isNavigator( )
isNetscape( )

So to detect if the user is running Firefox:

$browser = Net_UserAgent_Detect::isNetscape();

Check digit calculation

The check digit is calculated as follows:
1. Add the digits in the odd-numbered positions together and multiply by three.
2. Add the digits in the even-numbered positions to the above result.
3. Find the result modulo 10 (i.e. the remainder when the result is divided by 10).
4. If the result is not zero, subtract the result from ten.

Code

<?php
 
 
function generate_upc_checkdigit($upc_code)
{
    $odd_total  = 0;
    $even_total = 0;
 
    for($i=0; $i<11; $i++)
    {
        if((($i+1)%2) == 0) {
            /* Sum even digits */
            $even_total += $upc_code[$i];
        } else {
            /* Sum odd digits */
            $odd_total += $upc_code[$i];
        }
    }
 
    $sum = (3 * $odd_total) + $even_total;
 
    /* Get the remainder MOD 10*/
    $check_digit = $sum % 10;
 
    /* If the result is not zero, subtract the result from ten. */
    return ($check_digit > 0) ? 10 - $check_digit : $check_digit;
}
 
echo generate_upc_checkdigit("72438451112");
 
?>