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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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  • 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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  • Visual Studio: Add necessary using directives with macro

    - by Kiril
    Hello guys, I am trying to do the following. Imagine you are reading some LINQ article and you decide to copy/paste some code from the article to a newly created project. In most cases, if you directly compile you will probably get an error for missing a using directives or assembly reference. I am trying to optimize the process where I have to go each keyword, click on it with the mouse and hit Shift + Alt + F10 to add the using directive. I know that it is not that much pain, but for the sake of optimization, is it possible and at what cost? Best Regards, Kiril

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  • Resharper and var

    - by Refracted Paladin
    I have Resharper 4.5 and have found it invaluable so far but I have a concern; It seems to want to make every variable declaration implicit(var). As a relativly new developer how much should I trust ReSharper when it comes to this? Take the below code snippet from a method that Paints Tab Headers. TabPage currentTab = tabCaseNotes.TabPages[e.Index]; Rectangle itemRect = tabCaseNotes.GetTabRect(e.Index); SolidBrush fillBrush = new SolidBrush(Color.Linen); SolidBrush textBrush = new SolidBrush(Color.Black); StringFormat sf = new StringFormat { Alignment = StringAlignment.Center, LineAlignment = StringAlignment.Center }; Resharper wants me to change all 5 of those to var. I have read the following similar post,Use of var keyword in C#, but I would like to know from a Resharper standpoint. Thanks!

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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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  • 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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  • Implementing "Generator" support in a custom language

    - by Roger Alsing
    I've got a bit of fettish for language design and I'm currently playing around with my own hobby language. (http://rogeralsing.com/2010/04/14/playing-with-plastic/) One thing that really makes my mind bleed is "generators" and the "yield" keyword. I know C# uses AST transformation to transform enumerator methods into statemachines. But how does it work in other languages? Is there any way to get generator support in a language w/o AST transformation? e.g. Does languages like Python or Ruby resort to AST transformations to solve this to? (The question is how generators are implemented under the hood in different languages, not how to write a generator in one of them)

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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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  • 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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  • 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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  • 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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  • 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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  • 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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  • Multithreading and booleans

    - by Ikaso
    Hi Everyone, I have a class that contains a boolean field like this one: public class MyClass { private boolean boolVal; public boolean BoolVal { get { return boolVal; } set { boolVal = value; } } } The field can be read and written from many threads using the property. My question is if I should fence the getter and setter with a lock statement? Or should I simply use the volatile keyword and save the locking? Or should I totally ignore multithreading since getting and setting boolean values atomic? regards,

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  • MS Sql Full-text search vs. LIKE expression

    - by Marks
    Hi. I'm currently looking for a way to search a big database (500MB - 10GB or more on 10 tables) with a lot of different fields(nvarchars and bigints). Many of the fields, that should be searched are not in the same table. An example: A search for '5124 Peter' should return all items, that ... have an ID with 5124 in it, have 'Peter' in the title or description have item type id with 5124 in it created by a user named 'peter' or a user whose id has 5124 in it created by a user with '5124' or 'peter' in his street address. How should i do the search? I read that the full-text search of MS-Sql is a lot more performant than a query with the LIKE keyword and i think the syntax is more clear, but i think it cant search on bigint(id) values and i read it has performance problems with indexing and therefore slows down inserts to the DB. In my project there will be more inserting than reading, so this could be a matter. Thanks in advance, Marks

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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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  • 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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  • Can I use Visual Studio 2010's compiler with Visual Studio 2008's Runtime Library?

    - by BillyONeal
    Hello everyone :) I have an application that needs to operate on Windows 2000. I'd also like to use Visual Studio 2010 (mainly because of the change in the definition of the auto keyword). However, I'm in a bit of a bind because I need the app to be able to operate on older OS's, namely: Windows 2000 Windows XP RTM Windows XP SP1 Visual Studio 2010's runtime library depends on the EncodePointer / DecodePointer API which was introduced in Windows XP SP2. If using the alternate runtime library is possible, will this break code that relies on C++0x features added in VS2010, like std::regex?

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  • Resharper Split String literal

    - by Ismael
    I was not lucky in my 15 minutes googling. Maybe bad luck with good keyword? Why does the Resharper suggest spliting a string in function parameter? Example: From this: return PartialView("Categorias", lista); To this: return PartialView("Cat" + "egorias", lista); I checked documentation here: link And it says: Split string literal - Splits string literal into two literals. I want to discover why is this a good practice, what are the fundamental idealogic behind the scenes that achieved this practice. I don't want to do it without knowing why... Help is soooo appreciated.

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  • Getting an odd error, MSSQL Query using `WITH` clause

    - by Aren B
    The following query: WITH CteProductLookup(ProductId, oid) AS ( SELECT p.ProductID, p.oid FROM [dbo].[ME_CatalogProducts] p ) SELECT rel.Name as RelationshipName, pl.ProductId as FromProductId, pl2.ProductId as ToProductId FROM ( [dbo].[ME_CatalogRelationships] rel INNER JOIN CteProductLookup pl ON pl.oid = rel.from_oid ) INNER JOIN CteProductLookup pl2 ON pl2.oid = rel.to_oid WHERE rel.Name = 'BundleItem' AND pl.ProductId = 'MX12345'; Is generating this error: Msg 319, Level 15, State 1, Line 5 Incorrect syntax near the keyword 'with'. If this statement is a common table expression, an xmlnamespaces clause or a change tracking context clause, the previous statement must be terminated with a semicolon. On execution only. There are no errors/warnings in the sql statement in the managment studio. Any ideas?

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  • Are there any online database schema drawing tools?

    - by Pure.Krome
    Hi folks, i wish to draw up some database schemas. Eg, table 1 has zero to many rows in table 2, etc. It's purely for visual purposes (eg. no sql code, etc). Are there any online tools / website that offer this? (please don't say: Use Sql Server Database Diagrams, print screen, upload to image hosting service). thanks :) EDIT: Please take note of the keyword - ONLINE. I don't want any desktop solutions (because I already have one of these).

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  • Run time error '3075' in Access 2007

    - by Thys
    I am getting the following error when I try to open a report in Access 2007. The code works fine in Access 2003. run time error '3075' Syntax error (missing operator) in query expression '[COUNTRY_ID]=' here is the code giving the error... How could I fix this? Private Sub List25_Click() Combo20.SetFocus 'DoCmd.FindRecord List25.ItemData(List25.ListIndex) Forms![Country Rate Administration].Filter = "[COUNTRY_ID]=" & List25.ItemData(List25.ListIndex) Forms![Country Rate Administration].FilterOn = True End Sub Thansk in advance for your help!

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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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  • 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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  • Cross-reference between delphi records

    - by Paul-Jan
    Let's say I have a record TQuaternion and a record TVector. Quaternions have some methods with TVector parameters. On the other hand, TVector supports some operations that have TQuaternion parameters. Knowing that Delphi (Win32) does not allow for forward record declarations, how do I solve this elegantly? Using classes is not really an option here, because I really want to use operator overloading for this rare case where it actually makes good sense. For now I simply moved these particular methods out of the records and into separate functions, the good old-fashioned way. Better suggestions are most welcome.

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