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• Save QList<int> to QSettings

  - by Tobias

  Hello, I want to save a QList<int> to my QSettings without looping through it. I know that I could use writeArray() and a loop to save all items or to write the QList to a QByteArray and save this but then it is not human readable in my INI file.. Currently I am using the following to transform my QList<int> to QList<QVariant>: QList<QVariant> variantList; //Temp is the QList<int> for (int i = 0; i < temp.size(); i++) variantList.append(temp.at(i)); And to save this QList<Variant> to my Settings I use the following code: QVariant list; list.setValue(variantList); //saveSession is my QSettings object saveSession.setValue("MyList", list); The QList is correctly saved to my INI file as I can see (comma seperated list of my ints) But the function crashes on exit. I already tried to use a pointer to my QSettings object instead but then it crashes on deleting the pointer ..

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• Load binary file using fstream

  - by Kirill V. Lyadvinsky

  I'm trying to load binary file using fstream in the following way: #include <iostream #include <fstream #include <iterator #include <vector using namespace std; int main() { basic_fstream<uint32_t file( "somefile.dat", ios::in|ios::binary ); vector<uint32_t buffer; buffer.assign( istream_iterator<uint32_t, uint32_t( file ), istream_iterator<uint32_t, uint32_t() ); cout << buffer.size() << endl; return 0; } But it doesn't work. In Ubuntu it crashed with std::bad_cast exception. In MSVC++ 2008 it just prints 0. I know that I could use file.read to load file, but I want to use iterator and operator>> to load parts of the file. Is that possible? Why the code above doesn't work?

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• Dependency Injection and decoupling of software layers

  - by cs31415

  I am trying to implement Dependency Injection to make my app tester friendly. I have a rather basic doubt. Data layer uses SqlConnection object to connect to a SQL server database. SqlConnection object is a dependency for data access layer. In accordance with the laws of dependency injection, we must not new() dependent objects, but rather accept them through constructor arguments. Not wanting to upset the DI gods, I dutifully create a constructor in my DAL that takes in SqlConnection. Business layer calls DAL. Business layer must therefore, pass in SqlConnection. Presentation layer calls Business layer. Hence it too, must pass in SqlConnection to business layer. This is great for class isolation and testability. But didn't we just couple the UI and Business layers to a specific implementation of the data layer which happens to use a relational database? Why do the Presentation and Business layers need to know that the underlying data store is SQL? What if the app needs to support multiple data sources other than SQL server (such as XML files, Comma delimited files etc.) Furthermore, what if I add another object upon which my data layer is dependent on (say, a second database). Now, I have to modify the upper layers to pass in this new object. How can I avoid this merry-go-round and reap all the benefits of DI without the pain?

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• Practical differences between classes and structs in .net (not conceptual)?

  - by Gulshan

  Whenever I tried to search about differences between classes and structs in C# or .net, I ended up with the conceptual overview of the two things like value type or the reference type, where the variables are allocated etc. But I need some practical differences. I have found some like different behavior of assignment operator, having constructors etc. Can anybody provide some more practical differences which will be directly useful while coding? Like the things works with one but not with other or same operation showing different behavior. And some common mistakes regarding these two. Also please suggest where to consider using a struct instead of a class. And where the structs should not be used.

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• Parsing CSV string and binding it to listbox

  - by Amit Ranjan

  I have splitted comma separated values in an string array, something like this str[0] ="210" str[1] ="abc.pdf" str[2] = "211" str[3] = "xyz.docx" and so on. Please note 0,2,4,6,8 [even positions] are having number and odd positions are having string. I am having a class Attachmodel Public Class AttachmentModel Private _attachmentID As Integer = 0 Private _attachmentPath As String = "" ''' <summary> ''' Get Set Attachment ID ''' </summary> ''' <value></value> ''' <returns></returns> ''' <remarks></remarks> Public Property AttachmentID() As Integer Get Return _attachmentID End Get Set(ByVal value As Integer) _attachmentID = value End Set End Property ''' <summary> ''' Get Set Attachment Path ''' </summary> ''' <value></value> ''' <returns></returns> ''' <remarks></remarks> Public Property AttachmentPath() As String Get Return _attachmentPath End Get Set(ByVal value As String) _attachmentPath = value End Set End Property End Class In the above i want to set the values and bind it to the grid, using List

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• Java 'Prototype' pattern - new vs clone vs class.newInstance

  - by Guillaume

  In my project there are some 'Prototype' factories that create instances by cloning a final private instance. The author of those factories says that this pattern provides better performance than calling 'new' operator. Using google to get some clues about that, I've found nothing really relevant about that. Here is a small excerpt found in a javdoc from an unknown project javdoc from an unknown project Sadly, clone() is rather slower than calling new. However it is a lot faster than calling java.lang.Class.newInstance(), and somewhat faster than rolling our own "cloner" method. For me it's looking like an old best practice of the java 1.1 time. Does someone know more about this ? Is this a good practice to use that with 'modern' jvm ?

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• How do I copy object in Qt?

  - by Martin

  I'm using Qt and have some real basic problems. I have created my own widget MyTest that have a variable obj. I need to set this variable obj from an object outside of the widget so that the variable is copied not just a pointer to another object. I get an error message and can't figure out how to do this basic stuff. This is the code I'm using: MyTest.h: class MyTest : public QWidget { Q_OBJECT public: void setObj(QObject &inobj); QObject obj; .... } MyTest.cpp: void MyTest::setObj(QObject &inobj) { obj = inobj; //HERE I get the error message: "illegal access from 'QObject' to protected/private member 'QObject::operator=(const QObject &)'" } main.cpp: int main(int argc, char *argv[]) { QApplication a(argc, argv); QObject *ob = new QObject(); MyTest w; w.setObj(*ob); } Thanks for your help!

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• How To Generate Parameter Set for the Diffie-Hellman Key Agreement Algorithm in Android

  - by sebby_zml

  Hello everyone, I am working on mobile/server security related project. I am now stuck in generating a Diffie-Hellman key agreement part. It works fine in server side program but it is not working in mobile side. Thus, I assume that it is not compactible with Android. I used the following class to get the parameters. It returns a comma-separated string of 3 values. The first number is the prime modulus P. The second number is the base generator G. The third number is bit size of the random exponent L. My question is is there anything wrong with the code or it is not compactible for android?What kind of changes should I do? Your suggestion and guidance would be very much help for me. Thanks a lot in advance. public static String genDhParams() { try { // Create the parameter generator for a 1024-bit DH key pair AlgorithmParameterGenerator paramGen = AlgorithmParameterGenerator.getInstance("DH"); paramGen.init(1024); // Generate the parameters AlgorithmParameters params = paramGen.generateParameters(); DHParameterSpec dhSpec = (DHParameterSpec)params.getParameterSpec(DHParameterSpec.class); // Return the three values in a string return ""+dhSpec.getP()+","+dhSpec.getG()+","+dhSpec.getL(); } catch (NoSuchAlgorithmException e) { } catch (InvalidParameterSpecException e) { } return null; } Regards, Sebby

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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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• Error while excuting a simple boost thread program

  - by Eternal Learner

  Hi All, Could you tell mw what is the problem with the below boost::thread program #include<iostream> #include<boost/thread/thread.hpp> boost::mutex mutex; class A { public: A() : a(0) {} void operator()() { boost::mutex::scoped_lock lock(mutex); } private: int a; }; int main() { boost::thread thr1(A()); boost::thread thr2(A()); thr1.join(); thr2.join(); } I get the error message: error: request for member 'join' in 'thr1', which is of non-class type 'boost::thread()(A ()())' BoostThread2.cpp:30: error: request for member 'join' in 'thr2', which is of non-class type 'boost::thread ()(A ()())'

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• Fastest way to generate delimited string from 1d numpy array

  - by Abiel

  I have a program which needs to turn many large one-dimensional numpy arrays of floats into delimited strings. I am finding this operation quite slow relative to the mathematical operations in my program and am wondering if there is a way to speed it up. For example, consider the following loop, which takes 100,000 random numbers in a numpy array and joins each array into a comma-delimited string. import numpy as np x = np.random.randn(100000) for i in range(100): ",".join(map(str, x)) This loop takes about 20 seconds to complete (total, not each cycle). In contrast, consider that 100 cycles of something like elementwise multiplication (x*x) would take than one 1/10 of a second to complete. Clearly the string join operation creates a large performance bottleneck; in my actual application it will dominate total runtime. This makes me wonder, is there a faster way than ",".join(map(str, x))? Since map() is where almost all the processing time occurs, this comes down to the question of whether there a faster to way convert a very large number of numbers to strings.

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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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• SQL Query with multiple values in one column

  - by lp1

  I've been beating my head on the desk tring to figure this one out. I have a table that stores job information, and reasons for a job not being completed. The reasons are numeric,01,02,03,etc. You can have two reason for a pending job. If you select two reasons, they are stored in the same column, seperated by a comma. This is anExample from the JOBID table: Job_Number User_Assigned PendingInfo 1 user1 01,02 Now, there is another table named Pending, that stores what those values actually represent. 01=Not enough info, 02=Not enough time, 03=Waiting Review. Example: Pending_Num PendingWord 01 Not Enough Info 02 Not Enough Time What I'm trying to do is query the database to give me all the job numbers, users, pendinginfo, and pending reason. I can break out the first value, but can't figure out how to do the second. What my limited skills have so far: *select Job_number,user_assigned,SUBSTRING(pendinginfo,0,3),pendingword from jobid,pending where SUBSTRING(pendinginfo,0,3)=pending.pending_num and pendinginfo!='00,00' and pendinginfo!='NULL'* What I would like to see for this example would be: Job_Number User_Assigned PendingInfo PendingWord PendingInfo PendingWord 1 User1 01 Not Enough Info 02 Not Enough Time Thanks in advance

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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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• 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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• 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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• Precision of cos(atan2(y,x)) versus using complex <double>, C++

  - by Ivan

  Hi all, I'm writing some coordinate transformations (more specifically the Joukoswky Transform, Wikipedia Joukowsky Transform), and I'm interested in performance, but of course precision. I'm trying to do the coordinate transformations in two ways: 1) Calculating the real and complex parts in separate, using double precision, as below: double r2 = chi.x*chi.x + chi.y*chi.y; //double sq = pow(r2,-0.5*n) + pow(r2,0.5*n); //slow!!! double sq = sqrt(r2); //way faster! double co = cos(atan2(chi.y,chi.x)); double si = sin(atan2(chi.y,chi.x)); Z.x = 0.5*(co*sq + co/sq); Z.y = 0.5*si*sq; where chi and Z are simple structures with double x and y as members. 2) Using complex : Z = 0.5 * (chi + (1.0 / chi)); Where Z and chi are complex . There interesting part is that indeed the case 1) is faster (about 20%), but the precision is bad, giving error in the third decimal number after the comma after the inverse transform, while the complex gives back the exact number. So, the problem is on the cos(atan2), sin(atan2)? But if it is, how the complex handles that? Thanks!

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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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• Nusphere PHPEd: PHP Function Hints Lost Arguments?

  - by Eli

  Hi All, My PHPEd suddenly stopped showing arguments and arg order in the hints, and now just shows a basic description of the function. Before I go digging around in the config files, has anyone else had this problem? Thanks! Edit: Sorry, I may not have been entirely clear on this. There is no problem with my own classes, only with the actual php functions. Example: How it used to work: I type a PHP function, say strpos. As soon as I type the '(' at the end of it, I get the little yellow box, showing something like this: int strpos ( string $haystack , mixed $needle [, int $offset=0 ] ) with the first argument bold. If I type it, and then a comma, it bolds the second arg, and so on. This is really nice, since PHP functions are a bit scrambled as far as argument order, and I don't have to look them up every time. How it works now: I type a php function, say strpos. As soon as I type the '(' at the end of it, I get the little yellow box. It says something like "strpos - Returns the numeric position of the first occurrence of needle in the haystack string." There are no arguments shown, which makes the little box basically worthless - I know what strpos does, I just want a reminder of the argument order. I think this may be a problem with the included PHPDoc, which I never use, but may be the source of the data for the hint box. I did recently upgrade to 5.6, but ended up removing it and restoring 5.2. I installed to a different folder, and uninstalled from there, but it may have overwritten something in the original folder? I'm using v5.2 (5220). Thanks!

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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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• 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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• 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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• Python - Open default mail client using mailto, with multiple recipients

  - by victorhooi

  Hi, I'm attempting to write a Python function to send an email to a list of users, using the default installed mail client. I want to open the email client, and give the user the opportunity to edit the list of users or the email body. I did some searching, and according to here: http://www.sightspecific.com/~mosh/WWW_FAQ/multrec.html It's apparently against the RFC spec to put multiple comma-delimited recipients in a mailto link. However, that's the way everybody else seems to be doing it. What exactly is the modern stance on this? Anyhow, I found the following two sites: http://2ality.blogspot.com/2009/02/generate-emails-with-mailto-urls-and.html http://www.megasolutions.net/python/invoke-users-standard-mail-client-64348.aspx which seem to suggest solutions using urllib.parse (url.parse.quote for me), and webbrowser.open. I tried the sample code from the first link (2ality.blogspot.com), and that worked fine, and opened my default mail client. However, when I try to use the code in my own module, it seems to open up my default browser, for some weird reason. No funny text in the address bar, it just opens up the browser. The email_incorrect_phone_numbers() function is in the Employees class, which contains a dictionary (employee_dict) of Employee objects, which themselves have a number of employee attributes (sn, givenName, mail etc.). Full code is actually here (http://stackoverflow.com/questions/2963975/python-converting-csv-to-objects-code-design) from urllib.parse import quote import webbrowser .... def email_incorrect_phone_numbers(self): email_list = [] for employee in self.employee_dict.values(): if not PhoneNumberFormats.standard_format.search(employee.telephoneNumber): print(employee.telephoneNumber, employee.sn, employee.givenName, employee.mail) email_list.append(employee.mail) recipients = ', '.join(email_list) webbrowser.open("mailto:%s?subject=%s&body=%s" % (recipients, quote("testing"), quote('testing')) ) Any suggestions? Cheers, Victor

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