I realized this fact while looking at Google’s style guide for C++

Do not use RTTI, except in unit-tests. If you find yourself in need of writing code that behaves differently based on the class of an object, consider one of the alternatives to querying the type.

Virtual methods are the preferred way of executing different code paths depending on a specific subclass type. This puts the work within the object itself.

If the work belongs outside the object and instead in some processing code, consider a double-dispatch solution, such as the Visitor design pattern. This allows a facility outside the object itself to determine the type of class using the built-in type system.

If you think you truly cannot use those ideas, you may use RTTI. But think twice about it. Then think twice again. Do not hand-implement an RTTI-like workaround. The arguments against RTTI apply just as much to workarounds like class hierarchies with type tags.

That was an eye-opener to me. I didn’t know what double-dispatch is all about. Turns out that it’s the heart of the Visitor’s Pattern (although the example at dofactory.com is not ideal because they do not provide overloads for the visit() function and they cast all types to the base).

Double-Dispatch is the ability to dynamically select a method according to the run-time type of the caller (single dispatch) and the run-time type of the argument as well.

To close out, remember before you use dynamic casting in your code to think if there is a better way to achieve the same results using function overloads, virtual functions or double dispatch.

NSERT INTO wp_posts (ID, post_author, post_date, post_content, post_title) VALUES (5, 1, ‘2008-02-03 20:06:31′, ‘marco’’s long text’, ‘hello world’);

so I had a regular expression that would capture anything between two apostrophes

‘(?<text>[^’]+)’

The problem is escaped apostrophes in the text itself. Like in the example above marco’’s long text it would stop at the first apostrophe.

So, in short,  to get around that, I did a simple ORing like this:

‘(?<text>([^’]|[’]{2})+)’

Seems very simple, but it took me a while to see the light.

• I would love to change the world, but they won’t give me the source code
• There are 10 types of people, those who understand binary, and those who don’t
• There is no place like 127.0.0.1
• Oh, please, Give me a <br/>
• I’m not married, I’m only loosely coupled
• To understand recursion, you must first understand recursion
• Girls are like Internet domain names, the ones I like are already taken
• How many people can read hex if only you and dead people can read hex?

Here is a patch that fixes it.

reference: http://drupal.org/node/118926

#define rotlFixed(x,n) (((x) << (n)) | ((x) >> (32 - (n))))

#define rotrFixed(x,n) (((x) >> (n)) | ((x) << (32 - (n))))

The macro above can be trivially converted to a function and used in C# for example.

Most probably we will be using Athanasuis font.

Anyways, I want to save the script here in case the original site goes down or something.

The script is released under Apache License, Version 2.0

if you have a few minutes check them out. each episode is like 5 minutes long.

Here is episode #2 but definitely check out the other episodes as well in the related videos section.

In his second post he used an example of shuffling three-card deck 600,000 times to explain how naive solutions can be dangerous. The post is extremely well written. I enjoyed every bit of it. However I had two questions that I couldn’t find an answer for in Jeff’s post. Why exactly 3 permutations (out of the 6 possible ones) are biased? and why those 3 specifically are biased and not any other permutations?

I spent sometime thinking about it and using a pencil and a paper I was able to get some answers.
First here is the naive method: (I reversed the loop to be as similar as possible to the correct method)

for (int i = cards.Length - 1; i >= 0; i--)
{
    int n = random.Next(cards.Length);
    Swap(ref cards[i], ref cards[n]);
}

And here is the correct one (Knuth Shuffle)

for (int i = cards.Length - 1; i > 0; i--)
{
    int n = rand.Next(i + 1);
    Swap(ref cards[i], ref cards[n]);
}

Now let’s agree on some facts real quick. For a three-card deck:

1. There are exactly 6 unique possible permutations for that deck (3!)
2. Using the Naive shuffling method, there are 27 possible sequences of random-numbers on any given run (3³)

The answer to the first question above, is that 27 mod 6 is equal to 3. What that means is there are 3 extra sequences of random numbers that have to map to 1 (or 2 or 3) of the 6 unique permutations of the deck.

To answer the second question we have to note something first about using swapping to perform a shuffle, take a look at the state of the deck at each iteration given the following random numbers:

Notice how the two different sequences of random-numbers resulted in the same permutation of the deck. Now remember there are 27 possible sequences and only 6 unique permutations. if we divide 27/6 we get 4 (with remainder 3) which means there are at least 4 paths (or sequences) for every unique permutation of the deck, the 3 extra possible sequence lead to 3 of the unique permutations giving them an advantage over the other 3.

so basically we have 6 permutations of the deck, 3 of them have 4 random-number sequences that lead to them, and the other 3 have 5 sequences that lead to them.

In this particular example if you follow the algorithm above and try the following random-number sequences you will get the same deck permutation for all 5.

• 1,1,2
• 3,1,3
• 2,2,2
• 1,3,1
• 2,3,3

Conclusion

The problem with the Naive shuffling method is swapping! The fact that swapping elements in 2 (or more) different sequences can lead to the same deck permutation is a subtle problem.

The Knuth shuffle algorithm avoids that problem by ensuring N! possible random sequences where N is the number of elements in a deck (or any container).

To declare a pointer to an int called pNumber:

int *pNumber;

To declare a pointer to a function called pFunc (that has a string parameter and returns an int):

int (* pFunc)(string);

in red is the variable name, in purple is the type.

To declare a function that returns a pointer to a function:

int (* GetFuncPointer(void) )(string);

in red is a normal function declaration, in purple is the return type of that function.
S o basically int(*)(string) is the type of the function pointer.

If we want to declare a function that takes a function pointer as a parameter then we would write something like this:

void RegisterCallBack( int(*)(string) ); /* unnamed parameter */

or

void RegisterCallBack( int(*myCallback)(string) ); /* named parameter */

A prettier way to use function pointers is to use typedef to declare an alias. The typedef syntax is exactly the same as declaring a regular variable (or a function pointer).

typedef int(*FunctionPointer)(string);

now we can use FunctionPointer like this:

FunctionPointer GetFuncPointer(void);

Click For More Information…

So I invested 15 minutes researching that issue and found out that Mr. Compiler is friendly enough to let you know if it was not possible to fulfill your request to inline a certain function by issuing a warning.

For Microsoft’s VC8 compiler warning C4710 is turned off by default, you can turn it on by doing any of the following (depends on your choice):

1. #pragma warning (default : 4710)
2. #pragma warning (custom_warning_level : 4710)

For GCC the -Winline switch can be used to achieve the same thing.

1. download the drivers from www.nvidia.com (usually a file with .run extension)
2. download the kernel header files — apt-get install linux-headers-$(uname -r)
3. execute the command — sh path to the nvidia driver here

There is another method I found, that seems to work for a lot of people:

1. apt-get install module-assistant
2. m-a prepare
3. m-a auto-install nvidia

quoting a phrase on my favorite anagram generator site “All the life’s wisdom can be found in anagrams. Anagrams never lie.”

here are a few interesting anagrams for the word developers:

• Peeve Lords (that’s us for the customers)
• Deep Solver
• Speed Lover (for the performance obsessed ones)
• Deep Lovers

Anagrams are amazing..

consider the following example:
template<class T> class A
{
T::x(y); // ambiguous: calling a function or constructing an object?
// without ‘typename’ this will be interpreted as a function call
typedef char C;
A::C d;
}

The statement A::C d; is ill-formed. The class A also refers to A<T> and thus depends on a template parameter. You must add the keyword typename to the beginning of this declaration:

typename A::C d;

You can also use the keyword typename in place of the keyword class in template parameter declarations.

typename was introduced after the keyword class to solve the problems shown above, but both keywords are equivalent in declaring template parameters.

We were using the SessionID as a unique key to store some information about the behavior of the user surfing the site.

The SessionID was getting changed with every page request.

The trivial solution was adding a global.asax file to the project.

^\d{5}(?:-\d{4})?$|^[a-zA-Z]\d[a-zA-Z]\s?\d[a-zA-Z]\d$

more details on the format of Canadian zip codes

Note that this method will only work if you have the following registry key set to the correct value..
under HKEY_Current_User/Control Panel/Input Method, set EnableHexNumpad to 1

Use the Character Map to find the hexadecimal Unicode values for different characters.

Also, it’s worth noting that if you are using MS Word you can simply type in the Unicode hex value first and then press Alt+x. The hex number will be replaced by it’s equivalent Unicode character automagically.

Consider having an overloaded method, one overload takes a parameter of type long, another of type int, now if you want to pass in the number ‘15′ for example, these suffixes will help you choose which overload to actually invoke by appending a letter (or two) to the numeric literal.

Note that the suffixes are case-insensitive.

If you are a .net developer (specially an asp.net one) you certainly will see the benefit of this cheat sheet. Personally I have wasted my time before trying to format an integer to print in a certain way and of course i didn’t have the correct format-specifier right off the top of my head so i had to hunt down the information on Microsoft’s slow-and-poorly-searchable msdn which is certainly something i try to avoid!

reference: Scott Gutherie’s blog

• It’s monospaced (i.e. fixed width)
• The characters ‘0′ and ‘o’ are very distinguishable (which helps avoid a common mistake)
• It’s compact, compared to Courier New
• It looks very pleasant

Make sure you have the ClearType effect turned on (Control Panel->Display->Appearance->Effects)

I’m glad I found this font, and that’s why I’m sharing it, It’s way better than Courier New which used to be my favorite actually.

• It creates properties to the related entities/tables in the database, some people like to call this feature Deep Properties!
• no need to create CRUD stored procedures for every table in the db
• you can do queries on the fly, WHERE clauses, ORDER BY clauses and aggregate functions
• It’s open-source and free
• the classes are generated using a tool, no more tedious DAL writing
• for your convenience you get “Scaffolding forms”.
• it uses parameterized dynamic sql, which makes all those great features above possible
• It has providers for MS Sql Server and MySQL

If you are an asp.net developer you should give it a try, or at least check it out, it’ll be worth your while.