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• LINQ Quicksort is Unstable Except When Cascading

  - by Mystagogue

  On page 64 of "LINQ To Objects Using C# 4.0" (Tony Magennis) he states that LINQ's quicksort ordering algorithm is unstable... ...although this is simply solved by cascading the result into a ThenBy or ThenByDescending operator. Huh? Why would cascading an unstable sortation into another sortation fix the result? In fact, I'd say that isn't possible. The original order, once passed through an unstable sort, is simply lost. What am I missing here?

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• static arrays defined with unspecified size, empty brackets?

  - by ahmadabdolkader

  For the C++ code fragment below: class Foo { int a[]; // no error }; int a[]; // error: storage size of 'a' isn't known void bar() { int a[]; // error: storage size of 'a' isn't known } why isn't the member variable causing an error too? and what is the meaning of this member variable? I'm using gcc version 3.4.5 (mingw-vista special) through CodeBlocks 8.02. On Visual Studio Express 2008 - Microsoft(R) C/C++ Optimizing Compiler 15.00.30729.01 for 80x86, I got the following messages: class Foo { int a[]; // warning C4200: nonstandard extension used : zero-sized array in struct/union - Cannot generate copy-ctor or copy-assignment operator when UDT contains a zero-sized array }; int a[]; void bar() { int a[]; // error C2133: 'a' : unknown size } Now, this needs some explaination too.

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• Running custom Javascript on every page in Mozilla Firefox

  - by saturn

  I have a custom piece of Javascript which I would like to run on every web page from specific domains, or perhaps simply on every web page. (If you are wondering: it is not malicious. It allows to display formulas by using MathJax.) Is that possible? I tried including it in userContent.css, that of course did not work. A simple Greasemonkey script I tried did not insert it. Is it because of the security precautions? (Which would be very logical). Still, there should be a way to do it on the machine I physically control, by changing something in Mozilla chrome directory, shouldn't it? Anyway, how can I do this for myself?

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• Understanding the "Instantiation" of Actionscript/Flash Objects

  - by parallax7d

  Could someone expand and clarify the different logical instantiations of objects in actionscript? So far it seems there are 3 layers of instantiations, for lack of a better term. The first one is declaring a variable/type. Next is instantiating that variable with something solid in the code, like a method or function? Is this just a way to glue things together? Then after that you instantiate it on the stage, is this something you have to do explicitly, or is it a side effect? Is this "3 layer" concept the correct way of looking at it, kind of like the MVC for flash app logic?

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• Creating a Rails query from a hash of user input

  - by Jamie

  I'm attempting to create a fairly complex search engine for a project using a variable number of search criteria. The user input is sorted into an array of hashes. The hashes contain the following information: { :column => "", :value => "", :operator => "", # Such as: =, !=, <, >, etc. :and_or => "", # Two possible values: "and" and "or" } How can I loop through this array and use the information in these hashes to make an ActiveRecord WHERE query?

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• Ruby RegEx not matching valid expression

  - by Matthew Carriere

  I have the following expression: ^\w(\s(+|-|\/|*)\s\w)*$ This simply looks to match a mathematical expression, where a user is prompted for terms separated by basic operators (ex: price + tax) The user may enter more than just 2 terms and one operator (ex: price + tax + moretax) I tested this expression in Rubular http://rubular.com/ With the terms: a + a (MATCH) a + a + a (MATCH) a + a + a + a a a + a a Everything works, but when I use it in Ruby it does not work! expression =~ /^\w(\s(+|-|\/|*)\s\w)*$/ I started picking the expression apart and noticed that if I remove the start of line caret it finds matches but isn't correct. a + a (MATCH) a a (MATCH) <-- this is not correct Why is this expression not working in Ruby code? (I am using Ruby 1.8.7 p174)

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• How does this C# asp.net random password code work?

  - by quakkels

  Hello all, I'm new to .NET and C# and I'm trying to figure out how this code works: public static string CreateRandomPassword(int PasswordLength) { String _allowedChars = "abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNOPQRSTUVWXYZ23456789"; Byte[] randomBytes = new Byte[PasswordLength]; RNGCryptoServiceProvider rng = new RNGCryptoServiceProvider(); rng.GetBytes(randomBytes); char[] chars = new char[PasswordLength]; int allowedCharCount = _allowedChars.Length; for(int i = 0;i<PasswordLength;i++) { /// /// I don't understand how this line works: /// chars[i] = _allowedChars[(int)randomBytes[i] % allowedCharCount]; } return new string(chars); } I think I've got a pretty good handle on most of this. I haven't been able to understand the following line: chars[i] = _allowedChars[(int)randomBytes[i] % allowedCharCount]; I understand that the code generates random binary numbers and uses those random numbers in the for loop to select a character from the _allowedChars string. What I don't get is why this code uses the modulous operator (%) to get the _allowedChars index value. Thanks for any help

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• Calculating co-ordinate of a point on a path given a distance

  - by Alex

  I'm working on a project that surveys the condition of a road or highway using a calibrated trip computer connected to a rugged-PC. An operator keys in defect codes as they travel along a pre-defined route. I need to show an indicator on the map screen that shows the vehicles current position, taking into account the distance data from the trip computer. I know the exact lat lon co-ordinates at the starting point of each section of road, and the road is made up of a series of points. The question is: how can I calculate the lat lon co-ordinates of the vehicle assuming that it has continued on the route and traveled a certain distance (e.g. 1.4km). The co-ordinates would be 'locked onto' the road line, as shown in blue on the diagram below. Thanks, Alex

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• Advanced command line argument parsing in Java?

  - by Bishop87

  Does anyone have any java examples for parsing a series of command line arguements in a robust way? I'm looking to be able to handle something like: java myapp [-l language] [-d int] [-f file1 file2 file3] I want to do this in a robust way so I can provide logical error messages to the user if they mistake a command line-option. Some of these options I'd like to make optional, etc, etc. Also, the -f file list should be able to handle a list of files. Is there some library out there to assist me in handling this?

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• Drupal: Content in blocks from node_reference fields?

  - by Marco

  After only a few weeks of working with Drupal I've come up with a recurring problem, which I don't really have an optimal solution to, so I'm hoping that someone here might be able to give some best practice pointers. What I have is a region inside my node.tpl.php, which is populated with blocks that display content from two different CCK fields of the type node_reference. This works fine when displaying a single node. The problem appears when I need to use a view. For example, lets say I have a news listing, and a single news item view. When I display the single news item I can use the news node node_reference field to reference whatever material I would like to have in my sidebar, but when on the news listing view I would like to reference nodes separately. What would be the best practice to solve this? I'm having a few ideas, but none seem like the logical choice, how would you do?

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• Dynamically allocated structure and casting.

  - by Simone Margaritelli

  Let's say I have a first structure like this: typedef struct { int ivalue; char cvalue; } Foo; And a second one: typedef struct { int ivalue; char cvalue; unsigned char some_data_block[0xFF]; } Bar; Now let's say I do the following: Foo *pfoo; Bar *pbar; pbar = new Bar; pfoo = (Foo *)pbar; delete pfoo; Now, when I call the delete operator, how much memory does it free? sizeof(int) + sizeof(char) Or sizeof(int) + sizeof(char) + sizeof(char) * 0xFF ? And if it's the first case due to the casting, is there any way to prevent this memory leak from happening? Note: please don't answer "use C++ polymorphism" or similar, I am using this method for a reason.

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• How to delete characters and append strings?

  - by devin250

  i am adding a new record to xml file im first quering all existing items and storing the count in an int int number = query.count() and then incrementing number by 1; number = number +1; now i want to format this value in a string having "N00000000" format and the number will ocuppy the last positions Pseudo code: //declare the format string sting format = "N00000000" //calculate the length of number string int length =number.ToString().Length(); // delete as many characters from right to left as the length of number string ??? // finally concatenate both strings with + operator ??? help please

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• Help using Horner's rule and Hash Functions in JAVA?

  - by Matt

  I am trying to use Horner's rule to convert words to integers. I understand how it works and how if the word is long, it may cause an overflow. My ultimate goal is to use the converted integer in a hash function h(x)=x mod tableSize. My book suggests, because of the overflow, you could "apply the mod operator after computing each parenthesized expression in Horner's rule." I don't exactly understand what they mean by this. Say the expression looks like this: ((14*32+15)*32+20)*32+5 Do I take the mod tableSize after each parenthesized expression and add them together? What would it look like with this hash function and this example of Horner's rule?

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• What XSLT processor should I use for Java transformation?

  - by Artic

  What XSLT processor should I use for Java transformation? There are SAXON, Xalan and TrAX. What is the criteria for my choice? I need simple transformation without complicated logical transformations. Need fast and easy to implement solution. APP runs under Tomcat, Java 1.5. I have some jaxp libraries and could not understand what is the version of jaxp used. Thanks in advance. Best regards.

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• How to model a social news feed on Google App Engine

  - by PEZ

  We want to implement a "News feed" where a user can see messages broadcasted by her friends, sorted with newest message first. But the feed should reflect changes in her friends list. (If she adds new friends, messages from those should be included in the feed, and if she removes friends their messages should not be included.) If we use the pubsub-test example and attach a recipient list to each message this means a lot of manipulation of the message recipients lists when users connect and disconnect friends. We first modeled publish-subscribe "fan out" using conventional RDBMS thinking. It seemed to work at first, but then, since the IN operator works the way it does, we quickly realized we couldn't continue on that path. We found Brett Slatkin's presentation from last years Google I/O and we have now watched it a few times but it isn't clear to us how to do it with "dynamic" recipient lists. What we need are some hints on how to "think" when modeling this.

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• Optimal method to create a large string containing several variables?

  - by Runcible

  I want to create a string that contains many variables: std::string name1 = "Frank"; std::string name2 = "Joe"; std::string name3 = "Nancy"; std::string name4 = "Sherlock"; std::string sentence; sentence = name1 + " and " + name2 + " sat down with " + name3; sentence += " to play cards, while " + name4 + " played the violin."; This should produce a sentence that reads Frank and Joe sat down with Nancy to play cards, while Sherlock played the violin. My question is: What is the optimal way to accomplish this? I am concerned that constantly using the + operator is ineffecient. Is there a better way?

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• Is this the right way to get the grand total of processors with WMI on a multi-cpu system?

  - by John Sheares

  I don't have access to a multi-socketed computer, so I am unsure if the following will get the grand total of processors and logical processors. I assume ManagementObjectSearcher will return an instance for each socketed CPU and I just keep a running total? int totalCPUs = 0; int totalLogicalCPUs = 0; ManagementObjectSearcher mos = new ManagementObjectSearcher("Select * from Win32_ComputerSystem"); foreach (var mo in mos.Get()) { string num = mo.Properties["NumberOfProcessors"].Value.ToString(); totalCPUs += Convert.ToInt32(num); num = mo.Properties["NumberOfLogicalProcessors"].Value.ToString(); totalLogicalCPUs += Convert.ToInt32(num); }

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• Implement functionality in PHP?

  - by Rachel

  How can we Implement Bisect Python functionality in PHP Implement function bisect_left($arr, $item); as a pure-PHP routine to do a binary-bisection search for the position at which to insert $item into $list, maintaining the sort order therein. Assumptions: Assume that $arr is already sorted by whatever comparisons would be yielded by the stock PHP < operator, and that it's indexed on ints. The function should return an int, representing the index within the array at which $item would be inserted to maintain the order of the array. The returned index should be below any elements in $arr equal to $item, i.e., the insertion index should be "to the left" of anything equal to $item. Search routine should not be linear! That is, it should honor the name, and should attempt to find it by iteratively bisecting the list and comparing only around the midpoint.

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• n++ vs n=n+1. Which one is faster

  - by piemesons

  Somebody asked me Is n++ faster than n=n+1? My answer:-- ++ is a unary operator in C which(n++) takes only one machine instruction to execute while n=n+1 takes more than one machine instructions to execute. Anyone correct me if I am wrong, but in Assembler it take something like this: n++: inc n n = n + 1; mov ax n add ax 1 mov n ax its not exactli this, but it's near it.but in most cases a good compiler will change n = n + 1 to ++n.So A good compiler will generate same code for both and hence the same time to execute.

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• Kind of stumped with some basic C# constructors.

  - by Sergio Tapia

  public class Parser { Downloader download = new Downloader(); HtmlDocument Page; public Parser(string MovieTitle) { Page = download.FindMovie(MovieTitle); } public Parser(string ActorName) { Page = download.FindActor(ActorName); } } I want to create a constructor that will allow other developers who use this library to easily create a Parser object with the relevant HtmlDocument already loaded as soon as it's done creating it. The problem lies in that a constructor cannot exist twice with the same type of parameters. Sure I can tell the logical difference between the two paramters, but the computer can't. Any suggestions on how to handle this? Thank you!

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• Looking for a better way to integrate a static list into a set of classes

  - by EvilTeach

  I'm trying to expand my sons interest from Warcraft 3 programming into C++ to broaden his horizons to a degree. We are planning on porting a little game that he wrote. The context goes something like this. There are Ships and Missiles, for which Ships will use Missiles and interact with them A Container exists which will hold 'a list' of ships. A Container exists which will hold 'a list' of planets. One can apply a function over all elements in the Container (for_each) Ships and Missles can be created/destroyed at any time New objects automatically insert themselves into the proper container. I cobbled a small example together to do that job, so we can talk about topics (list, templates etc) but I am not pleased with the results. #include <iostream> #include <list> using namespace std; /* Base class to hold static list in common with various object groups */ template<class T> class ObjectManager { public : ObjectManager ( void ) { cout << "Construct ObjectManager at " << this << endl; objectList.push_back(this); } virtual ~ObjectManager ( void ) { cout << "Destroy ObjectManager at " << this << endl; } void for_each ( void (*function)(T *) ) { for (objectListIter = objectList.begin(); objectListIter != objectList.end(); ++objectListIter) { (*function)((T *) *objectListIter); } } list<ObjectManager<T> *>::iterator objectListIter; static list<ObjectManager<T> *> objectList; }; /* initializer for static list */ template<class T> list<ObjectManager<T> *> ObjectManager<T>::objectList; /* A simple ship for testing */ class Ship : public ObjectManager<Ship> { public : Ship ( void ) : ObjectManager<Ship>() { cout << "Construct Ship at " << this << endl; } ~Ship ( void ) { cout << "Destroy Ship at " << this << endl; } friend ostream &operator<< ( ostream &out, const Ship &that ) { out << "I am a ship"; return out; } }; /* A simple missile for testing */ class Missile : public ObjectManager<Missile> { public : Missile ( void ) : ObjectManager<Missile>() { cout << "Construct Missile at " << this << endl; } ~Missile ( void ) { cout << "Destroy Missile at " << this << endl; } friend ostream &operator<< ( ostream &out, const Missile &that ) { out << "I am a missile"; return out; } }; /* A function suitable for the for_each function */ template <class T> void show ( T *it ) { cout << "Show: " << *it << " at " << it << endl; } int main ( void ) { /* Create dummy planets for testing */ Missile p1; Missile p2; /* Demonstrate Iterator */ p1.for_each(show); /* Create dummy ships for testing */ Ship s1; Ship s2; Ship s3; /* Demonstrate Iterator */ s1.for_each(show); return 0; } Specifically, The list is effectively embedded in each ship though the inheritance mechanism. One must have a ship, in order to access the list of ships. One must have a missile in order to be able to access the list of missiles. That feels awkward. My question boils down to "Is there a better way to do this?" Automatic object container creation Automatic object insertion Container access without requiring an object in the list to access it. I am looking for better ideas. All helpful entries get an upvote. Thanks Evil.

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• What programs should I write to truly experience this fancy new language ?

  - by privatehuff

  Tried Scheme at one point, just built up half of a "math" and "string" library before getting bored... Similar experience with Java, but stopped early because I was appalled at the lack of operator overloading. When you try out a new language, is there a program/game/function/exercise/problem that you use to get into the hot meaty center and really EXPERIENCE the language? I've been wanted to try Python, Ruby, some lisps, etc but can't seem to find any meaningful work to do with them, or any reason to use them for anything over languages I already know. Sorry this is a discussion, but you are EXACTLY the people I want to get input from on this

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• Is there an "extended" UIHint attribute to apply CSS styles for DisplayFor - EditorFor templates?

  - by AJ

  Intro: After reading Brad Wilson Metadata series and searching unsuccesfully on google, I was wondering: Question: Has any OS project / code been created that allows you to tag CSS styles in the Meta information, for example in my (buddy) Model, I want to be able to decorate a property with multiple CSS styles (a single style you can fake with UIHint, I want to set many possible styles - and be able to "cross-utilise") eg. public class MyModel { [DisplayCssHint("h5")] [DisplayCssHint("color:#777;")] [EditorCssHint(".myCoolTextClass")] [EditorCssHint(".myOtherCoolTextClass")] public string Title{ get;set; } [DisplayCssHint(".normaltext")] [EditorCssHint(".myCoolTextClass")] [EditorCssHint(".myOtherCoolTextClass")] public string Message {get;set;} } Thoughts: I know that this does not seem like a logical place to put styling information, however as it is metadata and is discriptive... besides it would be nice to do this while prototyping - (especially being able to apply class styles and extending it further - to generate .Less files would really be cool! more to the point I would hate to write it, if its already been done ;). Any links/pointers/idea's would be appreciated. Thanks,

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• Get the number of calendar weeks between 2 dates in C#

  - by Phil Scholtes

  For the purposes of this question, let's assume the user will be from the US and will use the standard Gregorian calendar. So, a calendar week starts on Sunday and ends on Saturday. What I'm trying to do is determine the number of calendar weeks that exist between two dates. A perfect example of my problem exists in October 2010. Between 10/16 and 10/31 there are 4 calendar weeks. View a picture of October 2010 October 10 - October 16 October 17 - October 23 October 24 - October 30 October 31 - November 6 I'd prefer to stay away from any hardcoded logic like: if (Day == DayOfWeek.Saturday && LastDayOfMonth == 31) { ... } Can anyone think of a logical way to do this?

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• Using string.Format for simple things?

  - by Gerrie Schenck

  In my early .Net programming days, I used string.Format() only for complex string concatenations, for example to compile strings as Problem with customer order 234 of date 2/2/2002 and payment id 55543. But now I use string.Format for almost every string concatenation I have to do, also simple ones such as prefixing a string with something. Console.WriteLine(string.Format("\t\t{0}", myString)); Is there any possible overhead on this? Maybe I should use the regular + operator to do these simple operations? What's your opinion on this?

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