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• Remote connection to SQL Server Express fails

  - by worlds-apart89

  I have two computers that share the same Internet IP address. Using one of the computers, I can remotely connect to a SQL Server database on the other. Here is my connection string: SqlConnection connection = new SqlConnection(@"Data Source=192.168.1.101\SQLEXPRESSNI,1433;Network Library=DBMSSOCN;Initial Catalog=FirstDB;Persist Security Info=True;User ID=username;Password=password;"); 192.168.1.101 is the server, SQLEXPRESSNI is the SQL Server instance name, and FirstDB is the name of the database. Now, I have another computer with a different Internet IP address. I want to connect to the server above using the third computer that does not belong to my local area network. I dont have access to that third computer at the moment, so I want to use (if possible) the client computer in LAN again. SqlConnection connection = new SqlConnection(@"Data Source=SharedInternetIP\SQLEXPRESSNI,1433;Network Library=DBMSSOCN;Initial Catalog=FirstDB;Persist Security Info=True;User ID=username;Password=password;"); Does not work Note that I am a beginner, so I am not quite sure what I am doing even though I know what I want to do. By passing the Internet IP to the SqlConnection object rather than the local IP address, how can I successfully connect to the server computer, using the client computer in the same network? Also note that my ultimate goal is to connect to the server with an external client, but I don't have access to that computer right now. I'd appreciate any help.

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• Why initialize an object to empty

  - by ProgEnthu

  I am learning windows programming with the help of MSDN.Why would somebody initialize an object like the following? WNDCLASS wc = { }; Will this zero all the memory of the object? Whole source code is following: #ifndef UNICODE #define UNICODE #endif #include <windows.h> LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam); int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE, PWSTR pCmdLine, int nCmdShow) { // Register the window class. const wchar_t CLASS_NAME[] = L"Sample Window Class"; WNDCLASS wc = { }; wc.lpfnWndProc = WindowProc; wc.hInstance = hInstance; wc.lpszClassName = CLASS_NAME; RegisterClass(&wc); // Create the window. HWND hwnd = CreateWindowEx( 0, // Optional window styles. CLASS_NAME, // Window class L"Learn to Program Windows", // Window text WS_OVERLAPPEDWINDOW, // Window style // Size and position CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, NULL, // Parent window NULL, // Menu hInstance, // Instance handle NULL // Additional application data ); if (hwnd == NULL) { return 0; } ShowWindow(hwnd, nCmdShow); // Run the message loop. MSG msg = { }; while (GetMessage(&msg, NULL, 0, 0)) { TranslateMessage(&msg); DispatchMessage(&msg); } return 0; } LRESULT CALLBACK WindowProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam) { switch (uMsg) { case WM_DESTROY: PostQuitMessage(0); return 0; case WM_PAINT: { PAINTSTRUCT ps; HDC hdc = BeginPaint(hwnd, &ps); FillRect(hdc, &ps.rcPaint, (HBRUSH) (COLOR_WINDOW+1)); EndPaint(hwnd, &ps); } return 0; } return DefWindowProc(hwnd, uMsg, wParam, lParam); }

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• could not execute a stored procedure(using DAAB) from a client(aspx page) to a wcf service

  - by user1144695

  i am trying to store data to sql database from a asp.net client website through a stored procedure(using DAAB) in a wcf service hosted in a asp.net empty website.When i try to store data to the DB i get the following error: ** - The server was unable to process the request due to an internal error. For more information about the error, either turn on IncludeExceptionDetailInFaults (either from ServiceBehaviorAttribute or from the <serviceDebug> configuration behavior) on the server in order to send the exception information back to the client, or turn on tracing as per the Microsoft .NET Framework SDK documentation and inspect the server trace logs. ** When i try to debug i get the following exception: Activation error occured while trying to get instance of type Database, key "" in the code-- Database db = EnterpriseLibraryContainer.Current.GetInstance<Database>("MyInstance"); where my app.config is <?xml version="1.0"?> <configuration> <configSections> <section name="dataConfiguration" type="Microsoft.Practices.EnterpriseLibrary.Data.Configuration.DatabaseSettings, Microsoft.Practices.EnterpriseLibrary.Data, Version=5.0.414.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35" requirePermission="true"/> </configSections> <dataConfiguration defaultDatabase="MyInstance"/> <connectionStrings> <add name="MyInstance" connectionString="Data Source=BLRKDAS307581\KD;Integrated Security=True;User ID=SAPIENT\kdas3;Password=ilove0LINUX" providerName="System.Data.SqlClient" /> </connectionStrings> <startup> <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0"/> </startup> </configuration> Can anyone help me with it? Thanks in advance...

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• How to design authentication in a thick client, to be fail safe?

  - by Jay

  Here's a use case: I have a desktop application (built using Eclipse RCP) which on start, pops open a dialog box with 'UserName' and 'Password' fields in it. Once the end user, inputs his UserName and Password, a server is contacted (a spring remote-servlet, with the client side being a spring httpclient: similar to the approaches here.), and authentication is performed on the server side. A few questions related to the above mentioned scenario: If said this authentication service were to go down, what would be the best way to handle further proceedings? Authentication is something that I cannot do away with. Would running the desktop client in a "limited" mode be a good idea? For instance, important features/menus/views will be disabled, rest of the application will be accessible? Should I have a back up authentication service running on a different machine, working as a backup? What are the general best-practices in this scenario? I remember reading about google gears and how it would let you edit and do stuff offline - should something like this be designed? Please let me know your design/architectural comments/suggestions. Appreciate your help.

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• Python program to search for specific strings in hash values (coding help)

  - by Diego

  Trying to write a code that searches hash values for specific string's (input by user) and returns the hash if searchquery is present in that line. Doing this to kind of just learn python a bit more, but it could be a real world application used by an HR department to search a .csv resume database for specific words in each resume. I'd like this program to look through a .csv file that has three entries per line (id#;applicant name;resume text) I set it up so that it creates a hash, then created a string for the resume text hash entry, and am trying to use the .find() function to return the entire hash for each instance. What i'd like is if the word "gpa" is used as a search query and it is found in s['resumetext'] for three applicants(rows in .csv file), it prints the id, name, and resume for every row that has it.(All three applicants) As it is right now, my program prints the first row in the .csv file(print resume['id'], resume['name'], resume['resumetext']) no matter what the searchquery is, whether it's in the resumetext or not. lastly, are there better ways to doing this, by searching word documents, pdf's and .txt files in a folder for specific words using python (i've just started reading about the re module and am wondering if this may be the route, rather than putting everything in a .csv file.) def find_details(id2find): resumes_f=open("resume_data.csv") for each_line in resumes_f: s={} (s['id'], s['name'], s['resumetext']) = each_line.split(";") resumetext = str(s['resumetext']) if resumetext.find(id2find): return(s) else: print "No data matches your search query. Please try again" searchquery = raw_input("please enter your search term") resume = find_details(searchquery) if resume: print resume['id'], resume['name'], resume['resumetext']

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• Why do browsers encode special characters differently with ajax requests?

  - by Andrei Oniga

  I have a web application that reads the values of a few input fields (alphanumeric) and constructs a very simple xml that is passes to the server, using jQuery's $.ajax() method. The template for that xml is: <request> <session>[some-string]</session> <space>[some-string]</space> <plot>[some-string]</plot> ... </request> Sending such requests to the server when the inputs contain Finnish diacritical characters (such as ä or ö) raises a problem in terms of character encoding with different browsers. For instance, if I add the word Käyttötarkoitus" in one of the inputs, here's how Chrome and Firefox send EXACTLY the same request to the server: Chrome: <request> <session>{string-hidden}</session> <space>2080874</space> <plot>Käyttötarkoitus</plot> ... </request> FF 12.0: <request> <session>{string-hidden}</session> <space>2080874</space> <plot>Käyttötarkoitus</plot> ... </request> And here is the code fragment that I use to send the requests: $.ajax({ type: "POST", url: url, dataType: 'xml;charset=UTF-8', data: xml, success: function(xml) { // }, error: function(jqXHR, textStatus, errorThrown) { // } }); Why do I get different encodings and how do I get rid of this difference? I need to fix this problem because it's causing other on the server-side.

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• Scala path dependent return type from parameter

  - by Rich Oliver

  In the following code using 2.10.0M3 in Eclipse plugin 2.1.0 for 2.10M3. I'm using the default setting which is targeting JVM 1.5 class GeomBase[T <: DTypes] { abstract class NewObjs { def newHex(gridR: GridBase, coodI: Cood): gridR.HexRT } class GridBase { selfGrid => type HexRT = HexG with T#HexTr def uniformRect (init: NewObjs) { val hexCood = Cood(2 ,2) val hex: HexRT = init.newHex(selfGrid, hexCood)// won't compile } } } Error message: Description Resource Path Location Type type mismatch; found: GeomBase.this.GridBase#HexG with T#HexTr required: GridBase.this.HexRT (which expands to) GridBase.this.HexG with T#HexTr GeomBase.scala Why does the compiler think the method returns the type projection GridBase#HexG when it should be this specific instance of GridBase? Edit transferred to a simpler code class in responce to comments now getting a different error message. package rStrat class TestClass { abstract class NewObjs { def newHex(gridR: GridBase): gridR.HexG } class GridBase { selfGrid => def uniformRect (init: NewObjs) { val hex: HexG = init.newHex(this) //error here } class HexG { val test12 = 5 } } } . Error line 11:Description Resource Path Location Type type mismatch; found : gridR.HexG required: GridBase.this.HexG possible cause: missing arguments for method or constructor TestClass.scala /SStrat/src/rStrat line 11 Scala Problem Update I've switched to 2.10.0M4 and updated the plug-in to the M4 version on a fresh version of Eclipse and switched to JVM 1.6 (and 1.7) but the problems are unchanged.

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• invalid scalar hex value 0x8000000 and over

  - by kioto

  Hi. I found a problem getting hex value from yaml file. It couldn't get hex value 0x80000000 and over. Following is a sample C++ program. // ymlparser.cpp #include <iostream> #include <fstream> #include "yaml-cpp/yaml.h" int main(void) { try { std::ifstream fin("hex.yaml"); YAML::Parser parser(fin); YAML::Node doc; parser.GetNextDocument(doc); int num1; doc["hex1"] >> num1; printf("num1 = 0x%x\n", num1); int num2; doc["hex2"] >> num2; printf("num2 = 0x%x\n", num2); return 0; } catch(YAML::ParserException& e) { std::cout << e.what() << "\n"; } } hex.yaml hex1: 0x7FFFFFFF hex2: 0x80000000 Error message is here. $ ./ymlparser num1 = 0x7fffffff terminate called after throwing an instance of 'YAML::InvalidScalar' what(): yaml-cpp: error at line 2, column 7: invalid scalar Aborted Environment yaml-cpp : getting from svn, March.22.2010 or v0.2.5 OS : Ubuntu 9.10 i386 I need to get hex the value on yaml-cpp now, but I have no idea. Please tell me how to get it another way. Thanks,

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• Fastest XML parser for small, simple documents in Java

  - by Varkhan

  I have to objectify very simple and small XML documents (less than 1k, and it's almost SGML: no namespaces, plain UTF-8, you name it...), read from a stream, in Java. I am using JAXP to process the data from my stream into a Document object. I have tried Xerces, it's way too big and slow... I am using Dom4j, but I am still spending way too much time in org.dom4j.io.SAXReader. Does anybody out there have any suggestion on a faster, more efficient implementation, keeping in mind I have very tough CPU and memory constraints? [Edit 1] Keep in mind that my documents are very small, so the overhead of staring the parser can be important. For instance I am spending as much time in org.xml.sax.helpers.XMLReaderFactory.createXMLReader as in org.dom4j.io.SAXReader.read [Edit 2] The result has to be in Dom format, as I pass the document to decision tools that do arbitrary processing on it, like switching code based on the value of arbitrary XPaths, but also extracting lists of values packed as children of a predefined node. [Edit 3] In any case I eventually need to load/parse the complete document, since all the information it contains is going to be used at some point. (This question is related to, but different from, http://stackoverflow.com/questions/373833/best-xml-parser-for-java )

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• Database Programming in C#, returning output from Stored Proc

  - by jpavlov

  I am working at gaining an understanding at how to interface stored procedures with applications. My example is simple, but it doesn't display my columns and rows in the command prompt, instead it display System.Data.SqlClient.SqlDataReader. How do I display the rows from my stored procudure? ----Stored Proc-- ALTER PROCEDURE dbo.SelectID AS SELECT * FROM tb_User; ----- Below is the code: using System; using System.Data.SqlClient; using System.IO; namespace ExecuteStoredProc { class Program { static void Main(string[] args) { SqlConnection cnnUserMan; SqlCommand cmmUser; //SqlDataReader drdUser; //Instantiate and open the connection cnnUserMan = new SqlConnection("Data Source=.\\SQLEXPRESS;AttachDbFilename=c:\\Program Files\\Microsoft SQL Server\\MSSQL10.SQLEXPRESS\\MSSQL\\DATA\\UserDB.mdf; Integrated Security=True;Connect Timeout=30;User Instance=True"); cnnUserMan.Open(); //Instantiate and initialize command cmmUser = new SqlCommand("SelectID", cnnUserMan); cmmUser.CommandType = System.Data.CommandType.StoredProcedure; //drdUser = cmmUser.ExecuteReader(); Console.WriteLine(cmmUser.ExecuteReader()); Console.ReadLine(); } } } Thanks.

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• How to Object Array to List

  - by Peter Black

  (C#) I have 2 classes. 1 is called Employee. The other is my "main". I am trying to take a list and assign each value in list to an array of Employee object. //Inside "Main" class int counter = NameList.Count; Employee[] employee = new Employee[counter]; for (int i = 0; i <= counter; i++) { employee[i].Name = NameList[i]; employee[i].EmpNumber = EmpNumList[i]; employee[i].DateOfHire = DOHList[i]; employee[i].Salary = SalaryList[i]; employee[i].JobDescription = JobDescList[i]; employee[i].Department = DeptList[i]; } This returns the error: An unhandled exception of type 'System.NullReferenceException' occurred in Pgm4.exe Additional information: Object reference not set to an instance of an object. I think this means that I am not calling the list properly. Any help would be much appreciated. Thank you.

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• How to know which image is being viewed in UIScrollView? Also, is it possible to loop scrolling for

  - by bruin

  This is what I'm trying to do, and I'm not sure if it's possible using UIScrollView. First, I don't care about zooming, all I care is that the user is able to scroll through images just like the Photo App, this I got. But how do I know which image he is viewing while using UIScrollView? For instance, if he stops on the 3rd image out of 10 images in the view, how do I know he's on that image? I can't find a way to access the index (is this accessible)?? Also, bonus question, once the user scrolls to the last image, I don't want the scrolling to stop but I want it to loop so that image 1 comes after image 10. And vice versa, if you scroll left passed image 1, you'll see image 10. I'm not asking for the logic, I can do this in an array very simply, I just don't know how to access (if it's even possible) the indexing of the images in the scroll view. If it's not, does anyone have a solution to do this? thanks in advance!

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• Can this code cause a memory leak (Arduino)

  - by tbraun89

  I have a arduino project and I created this struct: struct Project { boolean status; String name; struct Project* nextProject; }; In my application I parse some data and create Project objects. To have them in a list there is a pointer to the nextProject in each Project object expect the last. This is the code where I add new projects: void RssParser::addProject(boolean tempProjectStatus, String tempData) { if (!startProject) { startProject = true; firstProject.status = tempProjectStatus; firstProject.name = tempData; firstProject.nextProject = NULL; ptrToLastProject = &firstProject; } else { ptrToLastProject->nextProject = new Project(); ptrToLastProject->nextProject->status = tempProjectStatus; ptrToLastProject->nextProject->name = tempData; ptrToLastProject->nextProject->nextProject = NULL; ptrToLastProject = ptrToLastProject->nextProject; } } firstProject is an private instance variable and defined in the header file like this: Project firstProject; So if there actually no project was added, I use firstProject, to add a new one, if firstProject is set I use the nextProject pointer. Also I have a reset() method that deletes the pointer to the projects: void RssParser::reset() { delete ptrToLastProject; delete firstProject.nextProject; startProject = false; } After each parsing run I call reset() the problem is that the memory used is not released. If I comment out the addProject method there are no issues with my memory. Someone can tell me what could cause the memory leak?

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• In what order should the Python concepts be explained to absolute beginners?

  - by Tomaž Pisanski

  I am teaching Python to undergraduate math majors. I am interested in the optimal order in which students should be introduced to various Python concepts. In my view, at each stage the students should be able to solve a non-trivial programming problem using only the tools available at that time. Each new tool should enable a simpler solution to a familiar problem. A selection of numerous concepts available in Python is essential in order to keep students focused. They should also motivated and should appreciate each newly mastered tool without too much memorization. Here are some specific questions: For instance, my predecessor introduced lists before strings. I think the opposite is a better solution. Should function definitions be introduced at the very beginning or after mastering basic structured programming ideas, such as decisions (if) and loops (while)? Should sets be introduced before dictionaries? Is it better to introduce reading and writing files early in the course or should one use input and print for most of the course? Any suggestions with explanations are most welcome.

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• Java - Removing duplicates in an ArrayList

  - by Will

  I'm working on a program that uses an ArrayList to store Strings. The program prompts the user with a menu and allows the user to choose an operation to perform. Such operations are adding Strings to the List, printing the entries etc. What I want to be able to do is create a method called removeDuplicates().This method will search the ArrayList and remove any duplicated values. I want to leave one instance of the duplicated value(s) within the list. I also want this method to return the total number of duplicates removed. I've been trying to use nested loops to accomplish this but I've been running into trouble because when entries get deleted, the indexing of the ArrayList gets altered and things don't work as they should. I know conceptually what I need to do but I'm having trouble implementing this idea in code. Here is some pseudo code: start with first entry; check each subsequent entry in the list and see if it matches the first entry; remove each subsequent entry in the list that matches the first entry; after all entries have been examined, move on to the second entry; check each entry in the list and see if it matches the second entry; remove each entry in the list that matches the second entry; repeat for entry in the list Here's the code I have so far: public int removeDuplicates() { int duplicates = 0; for ( int i = 0; i < strings.size(); i++ ) { for ( int j = 0; j < strings.size(); j++ ) { if ( i == j ) { // i & j refer to same entry so do nothing } else if ( strings.get( j ).equals( strings.get( i ) ) ) { strings.remove( j ); duplicates++; } } } return duplicates; }

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• Conditional insert as a single database transaction in HSQLDB 1.8?

  - by Kevin Pauli

  I'm using a particular database table like a "Set" data structure, i.e., you can attempt to insert the same row several times, but it will only contain one instance. The primary key is a natural key. For example, I want the following series of operations to work fine, and result in only one row for Oklahoma: insert into states_visited (state_name) values ('Oklahoma'); insert into states_visited (state_name) values ('Texas'); insert into states_visited (state_name) values ('Oklahoma'); I am of course getting an error due to the duplicate primary key on subsequent inserts of the same value. Is there a way to make the insert conditional, so that these errors are not thrown? I.e. only do the the insert if the natural key does not already exist? I know I could do a where clause and a subquery to test for the row's existence first, but it seems that would be expensive. That's 2 physical operations for one logical "conditional insert" operation. Anything like this in SQL? FYI I am using HSQLDB 1.8

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• How to implement Administrator rights in Java Application?

  - by Yatendra Goel

  I am developing a Data Modeling Software that is implemented in Java. This application converts the textual data (stored in a database) to graphical form so that users can interpret the data in a more efficient form. Now, this application will be accessed by 3 kinds of persons: 1. Managers (who can fill the database with data and they can also view the visual form of the data after entering the data into the database) 2. Viewers (who can only view the visual form of data that has been filled by managers) 3. Administrators (who can create and manage other administrators, managers and viewers) Now, how to implement 3 diff. views of the same application. Note: Managers, Viewers and Administrators can be located in any part of the world and should access the application through internet. One idea that came in my mind is as follows: Step1: Code all the business logic in EJBs so that it can be used in distributed environment (means which can be accessed by several users through internet) Step2: Code 3 Swing GUI Clients: One for administrators, one for managers and one for viewers. These 3 GUI clients can access business logic written in EJBs. Step3: Distribute the clients corresponding to their users. For instance, manager client to managers. =================================QUESTIONS======================================= Q1. Is the above approach is correct? Q2. This is very common functionality that various softwares have. So, Do they implement this kind of functionality through this way or any other way? Q3. If any other approach would be more better, then what is that approach?

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• problem with PHP class function ()

  - by lusey

  hello this is my first question here and i hope you can help me .. I am trying to find a soloution of the towers of hanoi problem by three search ways (BFS-DFS-IDS) so I use "state" class whitch defined by 5 variables as here : class state { var $tower1 = array(); var $tower2 = array(); var $tower3 = array(); var $depth; var $neighbors = array(); and it also has many function one of them is getneighbors() which supposed to fill the array $neighbors with state neighbors and they are from the type "state" and here is the function : function getneighbors () { $temp=$this->copy(); $neighbor1= $this->copy(); $neighbor2= $this->copy(); $neighbor3= $this->copy(); $neighbor4= $this->copy(); $neighbor5= $this->copy(); $neighbor6= $this->copy(); if(!Empty($temp->tower1)) { if(!Empty($neighbor1->tower2)) { if(end($neighbor1->tower1) < end($neighbor1->tower2)) { array_unshift($neighbor1->tower2,array_pop($neighbor1->tower1)); array_push($neighbors,$neighbor1); }} else { array_unshift($neighbor1->tower2, array_pop($neighbor1->tower1)); array_push($neighbors,$neighbor1); } if(!Empty($neighbor2->tower3)) { if(end($neighbor2->tower1) < end($neighbor2->tower3)) { array_unshift($neighbor2->tower3, array_pop($neighbor2->tower1)); array_push($neighbors,$neighbor2); }} else { array_unshift($neighbor2->tower3,array_shift($neighbor2->tower1)); array_push($neighbors,$neighbor2); } } if(!Empty($temp->tower2)) { if(!Empty($neighbor3->tower1)) { if(end($neighbor3->tower2) < end($neighbor3->tower1)) { array_unshift($neighbor3->tower1,array_shift($neighbor3->tower2)); array_push($neighbors,$neighbor3); } } else { array_unshift($neighbor3->tower1,array_shift($neighbor3->tower2)); array_push($neighbors,$neighbor3); } if(!Empty($neighbor4->tower3)) { if(end($neighbor4->tower2) < end($neighbor4->tower3)) { array_unshift($neighbor4->tower1,array_shift($neighbor4->tower2)); array_push($neighbors,$neighbor4); } } else{ array_unshift($neighbor4->tower3,array_shift($neighbor4->tower2)); array_push($neighbors,$neighbor4); } } if(!Empty($temp->tower3)) { if(!Empty($neighbor5->tower1)) { if(end($neighbor5->tower3) < end($neighbor5->tower1)) {array_unshift($neighbor5->tower1,array_shift($neighbor5->tower3)); array_push($neighbors,$neighbor5); } } else{ array_unshift($neighbor5->tower1,array_shift($neighbor5->tower3)); array_push($neighbors,$neighbor5);} if(!Empty($neighbor6->tower2)) { if(end($neighbor6->tower3) < end($neighbor6->tower2)) { array_unshift($neighbor6->tower2,array_shift($neighbor6->tower3)); array_push($neighbors,$neighbor6); }} else{ array_unshift($neighbor6->tower2,array_shift($neighbor6->tower3)); array_push($neighbors,$neighbor6);} } return $neighbors; } note that toString and equals and copy are defined too now the problem is that when I call getneighbors() it returns an empty $neighbors array can you pleas tell me the problem ?

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• What is the best / proper idiom in django for modifying a field during a .save() where you need to o

  - by MDBGuy

  Hi, say I've got: class LogModel(models.Model): message = models.CharField(max_length=512) class Assignment(models.Model): someperson = models.ForeignKey(SomeOtherModel) def save(self, *args, **kwargs): super(Assignment, self).save() old_person = #????? LogModel(message="%s is no longer assigned to %s"%(old_person, self).save() LogModel(message="%s is now assigned to %s"%(self.someperson, self).save() My goal is to save to LogModel some messages about who Assignment was assigned to. Notice that I need to know the old, presave value of this field. I have seen code that suggests, before super().save(), retrieve the instance from the database via primary key and grab the old value from there. This could work, but is a bit messy. In addition, I plan to eventually split this code out of the .save() method via signals - namely pre_save() and post_save(). Trying to use the above logic (Retrieve from the db in pre_save, make the log entry in post_save) seemingly fails here, as pre_save and post_save are two seperate methods. Perhaps in pre_save I can retrieve the old value and stick it on the model as an attribute? I was wondering if there was a common idiom for this. Thanks.

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• Is MarshalByRefObject special?

  - by Vilx-

  .NET has a thing called remoting where you can pass objects around between separate appdomains or even physical machines. I don't fully understand how the magic is done, hence this question. In remoting there are two base ways of passing objects around - either they can be serialized (converted to a bunch of bytes and the rebuilt at the other end) or they can inherit from MarshalByRefObject, in which case .NET makes some transparent proxies and all method calls are forwarded back to the original instance. This is pretty cool and works like magic. And I don't like magic in programming. Looking at the MarshalByRefObject with the Reflector I don't see anything that would set it apart from any other typical object. Not even a weird internal attribute or anything. So how is the whole transparent proxy thing organized? Can I make such a mechanism myself? Can I make an alternate MyMarshalByRefObject which would not inherit from MarshalByRefObject but would still act the same? Or is MarshalByRefObject receiving some special treatment by the .NET engine itself and the whole remoting feat is non-duplicatable by mere mortals?

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• how to allow unamed user in svn authz file?

  - by dtrosset

  I have a subversion server running with apache. It authenticates users using LDAP in apache configuration and uses SVN authorizations to limit user access to certain repositories. This works perfectly. Apache DAV svn SVNParentPath /srv/svn SVNListParentPath Off SVNPathAuthz Off AuthType Basic AuthName "Subversion Repository" AuthBasicProvider ldap AuthLDAPBindDN # private stuff AuthLDAPBindPassword # private stuff AuthLDAPURL # private stuff Require valid-user AuthzSVNAccessFile /etc/apache2/dav_svn.authz Subversion [groups] soft = me, and, all, other, developpers Adding anonymous access from one machine Now, I have a service I want to setup (rietveld, for code reviews) that needs to have an anonymous access to the repository. As this is a web service, accesses are always done from the same server. Thus I added apache configuration to allow all accesses from this machine. This did not work until I add an additional line in the authorization file to allow read access to user -. Apache <Limit GET PROPFIND OPTIONS REPORT> Order allow,deny Allow from # private IP address Satisfy Any </Limit> Subversion [Software:/] @soft = rw - = r # <-- This is the added line For instance, before I add this, all users were authenticated, and thus had a name. Now, some accesses are done without a user name! I found this - user name in the apache log files. But does this line equals to * = r that I absolutely do not want to enable, or does it only allows the anonymous unnamed user (that is allowed access only from the rietveld server)?

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• transmit a java.lang.reflect.Proxy over a network

  - by panzi

  Is there a convenient way to transmit an object including its code (the class) over a network (not just the instance data)? Don't ask me why I want to do this. It's in an assignment. I asked several times if that is really what they meant and the didn't rephrase their answer so I guess they really want us to transmit code (not just the field data) over a network. To be honest I have no clue why we need a Proxy in this assignment anyway, just writing a simple class would do IMO. The assignment says that we should instantiate the proxy on the server and transmit it to the client (and yes, they talk about a java.lang.reflect.Proxy, they name this class). Because there is no class file for a proxy I can't deploy that. I guess I would have to somehow read out the bytecode of the generated Proxy, transmit it to the client and then load it. Which makes absolutely no sense at all, but this seems what they want us to do. I don't get why.

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• Which isolation level should I use for the following insert-if-not-present transaction?

  - by Steve Guidi

  I've written a linq-to-sql program that essentially performs an ETL task, and I've noticed many places where parallelization will improve its performance. However, I'm concerned about preventing uniquness constraint violations when two threads perform the following task (psuedo code). Record CreateRecord(string recordText) { using (MyDataContext database = GetDatabase()) { Record existingRecord = database.MyTable.FirstOrDefault(record.KeyPredicate()); if(existingRecord == null) { existingRecord = CreateRecord(recordText); database.MyTable.InsertOnSubmit(existingRecord); } database.SubmitChanges(); return existingRecord; } } In general, this code executes a SELECT statement to test for record existance, followed by an INSERT statement if the record doesn't exist. It is encapsulated by an implicit transaction. When two threads run this code for the same instance of recordText, I want to prevent them from simultaneously determining that the record doesn't exist, thereby both attempting to create the same record. An isolation level and explicit transaction will work well, except I'm not certain which isolation level I should use -- Serializable should work, but seems too strict. Is there a better choice?

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• How is timezone handled in the lifecycle of an ADO.NET + SQL Server DateTime column?

  - by stimpy77

  Using SQL Server 2008. This is a really junior question and I could really use some elaborate information, but the information on Google seems to dance around the topic quite a bit and it would be nice if there was some detailed elaboration on how this works... Let's say I have a datetime column and in ADO.NET I set it to DateTime.UtcNow. 1) Does SQL Server store DateTime.UtcNow accordingly, or does it offset it again based on the timezone of where the server is installed, and then return it offset-reversed when queried? I think I know that the answer is "of course it stores it without offsetting it again" but want to be certain. So then I query for it and cast it from, say, an IDataReader column to a DateTime. As far as I know, System.DateTime has metadata that internally tracks whether it is a UTC DateTime or it is an offsetted DateTime, which may or may not cause .ToLocalTime() and .ToUniversalTime() to have different behavior depending on this state. So, 2) Does this casted System.DateTime object already know that it is a UTC DateTime instance, or does it assume that it has been offset? Now let's say I don't use UtcNow, I use DateTime.Now, when performing an ADO.NET INSERT or UPDATE. 3) Does ADO.NET pass the offset to SQL Server and does SQL Server store DateTime.Now with the offset metadata? So then I query for it and cast it from, say, an IDataReader column to a DateTime. 4) Does this casted System.DateTime object already know that it is an offset time, or does it assume that it is UTC?

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• Building "isolated" and "automatically updated" caches (java.util.List) in Java.

  - by Aidos

  Hi Guys, I am trying to write a framework which contains a lot of short-lived caches created from a long-living cache. These short-lived caches need to be able to return their entier contents, which is a clone from the original long-living cache. Effectively what I am trying to build is a level of transaction isolation for the short-lived caches. The user should be able to modify the contents of the short-lived cache, but changes to the long-living cache should not be propogated through (there is also a case where the changes should be pushed through, depending on the Cache type). I will do my best to try and explain: master-cache contains: [A,B,C,D,E,F] temporary-cache created with state [A,B,C,D,E,F] 1) temporary-cache adds item G: [A,B,C,D,E,F] 2) temporary-cache removes item B: [A,C,D,E,F] master-cache contains: [A,B,C,D,E,F] 3) master-cache adds items [X,Y,Z]: [A,B,C,D,E,F,X,Y,Z] temporary-cache contains: [A,C,D,E,F] Things get even harder when the values in the items can change and shouldn't always be updated (so I can't even share the underlying object instances, I need to use clones). I have implemented the simple approach of just creating a new instance of the List using the standard Collection constructor on ArrayList, however when you get out to about 200,000 items the system just runs out of memory. I know the value of 200,000 is excessive to iterate, but I am trying to stress my code a bit. I had thought that it might be able to somehow "proxy" the list, so the temporary-cache uses the master-cache, and stores all of it's changes (effectively a Memento for the change), however that quickly becomes a nightmare when you want to iterate the temporary-cache, or retrieve an item at a specific index. Also given that I want some modifications to the contents of the list to come through (depending on the type of the temporary-cache, whether it is "auto-update" or not) and I get completly out of my depth. Any pointers to techniques or data-structures or just general concepts to try and research will be greatly appreciated. Cheers, Aidos

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