Technical Thoughts

The art of debugging

modeeb — Thu, 16 Sep 2010 10:49:15 +0000

I was reading “How to think like a computer scientist” and I liked a quote describing the art of debugging by elimination of impossible scenarios…

When you have eliminated the impossible, whatever remains, however improbable, must be the truth.

Sherlock Holmes (The sign of four)

The story behind reading that book is that I was interested to learn Python, just for the fun of it, and I found that book which is aimed for 1st year computer science students. I thought it would be interesting too to join the ride and start learning a new language assuming I had no experience too.

Filed under: Craftsmanship

Movies that inspired Software

modeeb — Sat, 26 Sep 2009 22:18:31 +0000

Antitrust

I will start first with the movies that inspired me at the beginning of my career as a programmer, it was Antitrust. Adapted from the story of Microsoft Antitrust case, the movie is based around a tycoon in software (NURV) with its CEO (who happened to look like Bill Gates ) and a genius computer science graduate who was offered a job at NURV.

I enjoyed the movies because of its programmers’ appeal, credits written in coding style with tags and // Comments, opening soundtrack was amazing, and cast well chosen. Despite the fact that in NURV (Microsoft) code was written in Java, but most details were taken care of.

The point I liked much was when the young boy was contacted by (Bill Gates) in person and offered his dream job that he didn’t even apply for. I liked the feeling of excelling in your field that jobs search for you not the opposite, the excitement of a young boy joining the company he never imagined he could join. The words that really inspired me for years later, was the welcome speech of the CEO when he said about software business:

This business is binary, you are a one or a zero, alive or dead. There is no second place.

You can watch this part here

Monty Python

I didn’t know about this British comic band of the 70′s before a few months ago; that was when I discovered how their Monty Python’s Flying Circus was a favorite for many programmers at that time. For a beginning, Python language was named after this show because programming with the language was supposed to be as much fun as the show was. One of the famous sketches of this show was the Spam sketch below.

In this sketch the word “spam” and “spam with eggs” was introduced frequently in a restaurant menu as an undesired ingredient and later all along the sketch, even the end credits. From this sketch came the word spam that describes unwanted mails. The words “spam” and “eggs” are also used in Python literature. I used to think that Python packages are named eggs because “pythons” are conceived in “eggs” but I think it has also to do with the show.

I don’t know if other movies or shows have inspired software or not but that was the ones I thought of.

Posted in Community Tagged: Community, Creativity

Composite WPF and the Ribbon Control

modeeb — Thu, 27 Aug 2009 18:46:21 +0000

While working for WPF and Composite Application Library (CAL) for the first time, I had some difficulty both understanding their concepts and apply them in the optimal way, but I tried harder.

One of the benefits of CAL I found was the Command Binding which truly facilitates complying to the Model-View-ViewModel UI Design Architecture. But finding an easy implementation for them in all the desired control was not as easy as with default menu items and tool bars. A question on stackoverflow was asking about implementing the Command Binding with the WPF Ribbon which is downloadable within the WPF Futures, and not included in the out-of-box visual studio installation.

The trick was to make custom region adapters as those of menu and tool bar. I have found samples of RibbonRegionAdapter.

To comply with CAL and Model-View-ViewModel, the View containing the Ribbon will be be bound to a ViewModel containing all commands. These commands would be exposed publicly and available to other modules to attach Executed and CanExecute handlers. It is possible also to expose a generic method to add commands at run time by providing their image and location on the ribbon.

I found also open source implementation for binding the docking manager. The Composite WPF Contrib Project on CodePlex contains a TabGroupPaneRegionAdapter for Infragistics TabGroupPane.

Posted in Framework Tagged: .NET Framework, Extensible Application Markup Language, Microsoft Visual Studio, Model-View-ViewModel, Programming, User interface, Windows Presentation Foundation

Augmented Reality

modeeb — Wed, 27 May 2009 14:57:25 +0000

Every great magic trick consists of three parts or acts. The first part is called “The Pledge”. The magician shows you something ordinary: a deck of cards, a bird or a man. He shows you this object. Perhaps he asks you to inspect it to see if it is indeed real, unaltered, normal. But of course… it probably isn’t. The second act is called “The Turn”. The magician takes the ordinary something and makes it do something extraordinary. Now you’re looking for the secret… but you won’t find it, because of course you’re not really looking. You don’t really want to know. You want to be fooled. But you wouldn’t clap yet. Because making something disappear isn’t enough; you have to bring it back. That’s why every magic trick has a third act, the hardest part, the part we call “The Prestige“

From the movie “The Prestige”

I had that feeling when I read an article about Augmented Reality which I haven’t heard of before.

The article mentioned a page developed by General Electric as an example

I went directly to the video and my eyes and mouth were wide open for 5 minutes until I realized what it is

Here is another video showing the “making” …

http://www.gotoandlearn.com/play?id=105

And now after being “enlightened” , I can tell the “trick”

We all know that we can render 3D graphics and change the viewpoint by changing the position (x, y, and z) of the camera object

We also know that with computer vision, we can detect the position and the rotation of a certain pattern on all axis

Combining the two concepts, we can use the computer camera to detect the position of the viewer (the human) relative to the position and rotation of the pattern and then render the 3D graphics respectively

So simple isn’t it, but yet amazing

Posted in Uncategorized Tagged: Augmented Reality, Flash

Historical Debugger and Test Impact Analysis in Visual Studio Team System 2010

modeeb — Wed, 29 Apr 2009 12:54:19 +0000

I was browsing some of the awaited-for Visual Studio 2010 and I found a video about two interesting features related to what we do everyday (and I do not mean coding )

The first feature is related to debugging “history”. Normally, when you find a bug while running your program, you insert multiple breakpoints on the statements you suspect might caused it, and repeat the scenario or restart the debug session.

With history debugging, you don’t need to do so, since the history debugger “logs” every event in your application, so you can “pause” running and inspect all the previous events and may be check if there were “swallowed” exceptions.

The second feature, is when you want to modify some “unit-tested” code either for bug fixing or refactoring, and you want to re-run the impacted tests. Normally it is hard to determine which tests are affected so you run all of them, but with Test Impact Analysis in VS 2010, you can get the impacted tests once you save your modifications, so you can either commit your changes or undo.

Here is the 19 minutes video showing these two features on Channel 9

Historical Debugger and Test Impact Analysis in Visual Studio Team System 2010

Posted in IDE and Tools Tagged: Debugging, Development, IDE and Tools, Microsoft, Refactoring, Testing

C# 4.0: What’s next

modeeb — Wed, 08 Apr 2009 00:16:52 +0000

Since I have talked before about Visual Studio 2010 and Dynamic Typing, it is now time to talk about the upcoming C# 4.0 which we are expecting soon.

To understand how C# evolved and what is the paradigm of C# 4.0, let’s get a quick overview of previous versions.

In 1998 the C# began as a simple, modern, object-oriented, and type-safe programming language for the .NET platform. Since launched in the summer of 2000, C# has become one of the most popular programming languages in use today.

With version 2.0 the language evolved to provide support for generics, anonymous methods, iterators, partial types, and nullable types.

When designing version 3.0 of the language the emphasis was to enable LINQ (Language Integrated Query) which required the addition of:

Implicitly Typed Local Variables.
Extension Methods.
Lambda Expressions.
Object and Collection Initializers.
Anonymous types.
Implicitly Typed Arrays.
Query Expressions and Expression Trees.

Although C# is an object-oriented programming, but C# 3.0 included some capabilities of functional programming to enable LINQ

In version 4.0 the C# programming language continues to evolve, although this time the C# team were inspired by dynamic languages such as Perl, Python, and Ruby.

Another paradigm that is driving language design and innovation is concurrency and that is a paradigm that has certainly influenced the development of Visual Studio 2010 and the .NET Framework 4.0.

Essentially the C# 4.0 language innovations include:

Dynamically Typed Objects.
Optional and Named Parameters.
Improved COM Interoperability.
Safe Co-variance and Contra-variance.

To show these features, I’ll show some examples posted by Doug Holland on his The C# Programming Language Version 4.0 blog post…

Dynamically Typed Objects

In C# today you might need to get an instance of a class and then calls the Add method on that class to get the sum of two integers:

Calculator calc = GetCalculator();
int sum = calc.Add(10,20);

Our code gets all the more interesting if the Calculator class is not statically typed but rather is written in COM, Ruby, Python, or even JavaScript. Even if we knew that the Calculator class is a .NET object but we don’t know specifically which type it is then we would have to use reflection to discover attributes about the type at runtime and then dynamically invoke the Add method.

object calc = GetCalculator();
Type type = calc.GetType();
object result = type.InvokeMember("Add", BindingFlags.InvokeMethod, null,
    new object[] { 10, 20 });
int sum = Convert.ToInt32(result);

With the C# 4.0 we would simply write the following code:

dynamic calc = GetCalculator();
int sum = calc.Add(10,20);

In the above example we are declaring a variable, calc, whose static type is dynamic. We’ll then be using dynamic method invocation to call the Add method and then dynamic conversion to convert the result of the dynamic invocation to a statically typed integer.

Optional and Named Parameters

Another major benefit of using C# 4.0 is that the language now supports optional parameters (like C and C++) and named parameters.

One design pattern you’ll often see as that a particular method is overloaded because the method needs to be called with a variable number of parameters.

In C# 4.0 a method can be refactored to use optional parameters as the following example shows:

public StreamReader OpenTextFile(string path, Encoding encoding =  null, bool
    detectEncoding = false, int bufferSize = 1024) { }

Given this declaration it is now possible to call the OpenTextFile method omitting one or more of the optional parameters.

OpenTextFile("foo.txt", Encoding.UTF8);

It is also possible to use the C# 4.0 support for named parameters and as such the OpenTextFile method can be called omitting one or more of the optional parameters while also specifying another parameter by name.

OpenTextFile("foo.txt", Encoding.UTF8, bufferSize: 1024);

Named arguments must be provided last although when provided they can be provided in any order.

Improved COM Interoperability

When you work with COM interop methods, you had to pass a reference to Missing.Value for unneeded parameters, like the following:

object filename = "test.docx";
object missing = System.Reflection.Missing.Value;

doc.SaveAs(ref filename,
    ref missing, ref missing, ref missing,
    ref missing, ref missing, ref missing,
    ref missing, ref missing, ref missing,
    ref missing, ref missing, ref missing,
    ref missing, ref missing, ref missing);

Now, in C# 4.0 you can only write:

doc.SaveAs(filename);

Notice that you are able to omit the ref modifier although the use of the ref modifier is still required when not performing COM interoperability.

Also it was necessary to ship a Primary Interop Assembly (PIA) along with your managed application. This is not necessary when using C# 4.0 because the compiler will instead inject the interop types directly into the assemblies of your managed application and will only inject those types you’re using and not all of the types found within the PIA.

Safe Co-variance and Contra-variance

Co-variance means that an instance of a subclass can be used when an instance of a parent class is expected, while Contra-variance means that an instance of a super class can be used when an instance of a subclass is expected. When neither is possible, it is called Invariance.

Since version 1.0 arrays in .NET has been co-variant meaning that an array of string can be assigned to an array of object.

string[] strings = new string[] { "Hello" };
object[] objects = names;

Unfortunately arrays in .NET are not safely co-variant. Since objects variable was an array of string the following will succeed.

objects[0] = "Hello World";

Although if an attempt is made to assign an integer to the objects array an ArrayTypeMismatchException is thrown.

objects[0] = 1024;

To achieve safety, both C# 2.0 and C# 3.0 generics are invariant and so a compiler error would result from the following code:

List strings= new List();
List objects = strings;

For the Liskov Substitution Principle (LSP) to be achieved, methods of a derived class need to have contra-variant inputs and co-variant outputs.

Generics with C# 4.0 now support safe co-variance and contra-variance through the use of the in (contra-variant) and out (co-variant) contextual keywords. Let’s take a look at how this changes the definition of the IEnumerable and IEnumerator interfaces.

public interface IEnumerable
{
    IEnumerator GetEnumerator();
}

public interface IEnumerator
{
    T Current { get; }
    bool MoveNext();
}

Given that an IEnumerable collection is read only, there is no ability specified within the interface to insert new elements, it is safe to treat a more derived element as something less derived. With the out contextual keyword we are contractually affirming that IEnumerable is safely co-variant. We can now write the following code without a compiler error:

IEnumerablestrings = GetStrings();
IEnumerable objects = strings;

Using the in contextual keyword we can achieve safe contra-variance, that is treating something less derived as something more derived.

public interface IComparer
{
    int Compare(T x, T y);
}

Given that IComparer is safely contra-variant we can now write the following code:

IComparer objectComparer = GetComparer();
IComparer stringComparer = objectComparer;

It is important to notice that co-variance in IEnumerable refers to the fact that its Current property can return a string instead of an object as output, while contra-variance in IComparer refers to the fact that its Compare method can accept an object instead of a string as input.

Posted in Framework Tagged: C#, Covariance & Contravariance, Dynamic Typing, Framework, Microsoft

Agile and CMMI

modeeb — Tue, 31 Mar 2009 15:30:32 +0000

I wanted to talk about this issue a long time ago, but I didn’t have much to share with you.

My first trigger for this post was few months ago when Software Engineering Institute (SEI) of Carnegie Mellon University published a report under the name CMMI or Agile: Why not embrace both! which is a confirmation by CMMI authors that you can satisfy both requirements.

The report summarizes the history of both paradigms and why it is perceived that CMMI is waterfall while it isn’t. It also summarized the misconceptions in both ideas and how to overcome them. And it ends by a call for action for both practitioners and trainers to bridge the gap between both.

The report also addresses other issues such as:

The Origins of Agile Methods
The Origins of CMMI
Lack of Accurate Information
Terminology Difficulties
There Is Value in Both Paradigms
Challenges When Using Agile
Challenges When Using CMMI
Problems Not Solved by CMMI nor Agile

Yesterday, I have been in a 2-days workshop on the same issue where we have conducted some real life case studies to discover how we can come out with processes that satisfy both, and get useful feedback from experts in both schools.

If I can summarize what I have learnt in those 2 days, it is that you have to be first convinced why you need Agile and why you need CMMI, and when you do, you will be able to select to which level you want to embrace each, and what are the practices that would "add value" to your organization (not only individual projects)

Finally, I would like to refer you to this 2 years old post by Jeff Sutherland in which he says that Scrum supports CMMI level 5

Posted in Agile Tagged: Agile, CMMI, Lessons, Scrum

Thinking out of the “box”

modeeb — Mon, 23 Mar 2009 15:17:56 +0000

Ever got into a dead-end with no one to ask for help, or new ideas to try?

In 1975, one creative guy (not from an IT background) have came out with a “box” of ideas cards to give him clues whenever he gets puzzled and starts looking around without a purpose. He called it Oblique Strategies.

These cards actually doesn’t include answers, rather, it has some phrases that can trigger your mind to try new solutions that you might have not thought of.

The funny thing is that you can use these cards in software engineering and yet you can find it really useful. Here is how.

Posted in IDE and Tools Tagged: Creativity, Ideas, Inspiration

SQL Server data types

modeeb — Wed, 04 Mar 2009 14:27:23 +0000

Actually I have thought to write this post mainly for me as I always forget the differences of the different (yet similar) data types in SQL Server

Here is what I need to remember:

numeric is the same as decimal and they are both exact decimal values
float and real are approximate values
fLoat(n) complies with ISO SQL, n is the mantissa digits
[float(25) - float(53)] are stored in 8 bytes while [float(1) - float(24)] are stored in 4 bytes
real is the same as float(24)
money is an exact decimal value stored on 8 bytes
nchar and nvarchar are the Unicode versions (2 bytes per character) while char and varchar use only 1 byte (so they can still accept UTF-8 characters but not UTF-16 like Japanese or Chinese)

That was some short notes, for the full details you can check

http://msdn.microsoft.com/en-us/library/ms187752.aspx

Posted in Reference Tagged: Data Type, Microsoft, SQL

StyleCop for ReSharper has been released

modeeb — Sun, 22 Feb 2009 03:11:33 +0000

StyleCop for ReSharper has been released last week as a plugin for ReSharper to bring StyleCop code styling issues to ReSharper real-time syntax highlighting, quick-fixes, and Code CleanUp.

Although I personally don’t like many of StyleCop rules, but like ReSharper rules, they can be turned off individually. The plugin performance can also be customized from within the ReSharper options window.

More about StyleCop:

Microsoft StyleCop analyzes C# source code to enforce a set of style and consistency rules. It can be run from inside of Visual Studio or integrated into an MSBuild project. It is another static analysis tool by Microsoft like FxCop, but the later analyzes the compiled object code for design issues, not the source code.

More about ReSharper:

ReSharper^™ is a Visual Studio add-in created by JetBrains (the creator of many software productivity tools like IntelliJ^®IDEA the Java IDE, TeamCity™ the build integration server, and dotTrace^™ Profiler)

I have been using ReSharper almost since I started using Visual Studio and it has always been a complement to it. Even when Visual Studio evolved from 2003 to 2005, and finally 2008, ReSharper has still much to add.

One of the features I like most in ReSharper is its ability to detect syntax and styling error while you type, refactor code quickly, suggest variable names based on classnames, highlight redundant code, make code more readible, find references and jump to it directly if only once.

There has been some talks that Visual Studio 2010 is actually 2008 + ReSharper because of a mistake they made when they posted some snapshots of Visual Studio 2010 with ReSharper menus and screens in it.

Microsoft on the other hand had been promoting one of ReSharper competitors and announced a cooperation with DevExpress to license a free version of CodeRush Express exculsively for C# developers working on Visual Studio.

Posted in IDE and Tools Tagged: Coding Style, Development, IDE and Tools, Microsoft, Programming, Refactoring, ReSharper, StyleCop, Visual Studio