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• Practical non-Turing-complete languages?

  - by Kyle Cronin

  Nearly all programming languages used are Turing Complete, and while this affords the language to represent any computable algorithm, it also comes with its own set of problems. Seeing as all the algorithms I write are intended to halt, I would like to be able to represent them in a language that guarantees they will halt. Regular expressions used for matching strings and finite state machines are used when lexing, but I'm wondering if there's a more general, broadly language that's not Turing complete? edit: I should clarify, by 'general purpose' I don't necessarily want to be able to write all halting algorithms in the language (I don't think that such a language would exist) but I suspect that there are common threads in halting proofs that can be generalized to produce a language in which all algorithms are guaranteed to halt. There's also another way to tackle this problem - eliminate the need for theoretically infinite memory. Once you limit the amount of memory the machine is allowed, the number of states the machine is in is finite and countable, and therefore you can determine if the algorithm will halt (by not allowing the machine to move into a state it's been in before).

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• Need some clarification on Bankers Algorithm

  - by Moonshield

  Hi, just a quick query about safe/unsafe states in Dijkstra's Banker's algorithm... If one of the processes in the snapshot of the system (for example the one below) already has all of its needs fulfilled and there are not sufficient resources available to fulfil the needs of any of the other processes, is the system in a safe state? I know normally we assume that once a process receives its required resources it will terminate soon after and return all resources, but is this assumption factored in when we calculate the state of the system? Allocated Maximum Available | A | B | A | B A | B ---+---+--- ---+---+--- ---+--- P1 | 1 | 2 P1 | 1 | 2 1 | 3 P2 | 5 | 3 P2 | 7 | 8

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• retriving hearders in all pages of word

  - by udaya

  Hi I am exporting data from php page to word,, there i get 'n' number of datas in each page .... How to set the maximum number of data that a word page can contain ,,,, I want only 20 datas in a single page This is the coding i use to export the data to word i got the data in word format but the headers are not available for all the pages ex: Page:1 slno name country state Town 1 vivek india tamilnadu trichy 2 uday india kerala coimbatore like this i am getting many details but in my page:2 i dont get the headers like name country state and town....But i can get the details like kumar america xxxx yyyy i want the result to be like slno name country state town n chris newzealand ghgg jkgj Can i get the headers If it is not possible Is there anyway to limit the number of details being displayed in each page //EDIT YOUR MySQL Connection Info: $DB_Server = "localhost"; //your MySQL Server $DB_Username = "root"; //your MySQL User Name $DB_Password = ""; //your MySQL Password $DB_DBName = "cms"; //your MySQL Database Name $DB_TBLName = ""; //your MySQL Table Name $sql = "SELECT (SELECT COUNT(*) FROM tblentercountry t2 WHERE t2.dbName <= t1.dbName and t1.dbIsDelete='0') AS SLNO ,dbName as Namee,t3.dbCountry as Country,t4.dbState as State,t5.dbTown as Town FROM tblentercountry t1 join tablecountry as t3, tablestate as t4, tabletown as t5 where t1.dbIsDelete='0' and t1.dbCountryId=t3.dbCountryId and t1.dbStateId=t4.dbStateId and t1.dbTownId=t5.dbTownId order by dbName limit 0,50"; //Optional: print out title to top of Excel or Word file with Timestamp //for when file was generated: //set $Use_Titel = 1 to generate title, 0 not to use title $Use_Title = 1; //define date for title: EDIT this to create the time-format you need //$now_date = DATE('m-d-Y H:i'); //define title for .doc or .xls file: EDIT this if you want $title = "Country"; /* Leave the connection info below as it is: just edit the above. (Editing of code past this point recommended only for advanced users.) */ //create MySQL connection $Connect = @MYSQL_CONNECT($DB_Server, $DB_Username, $DB_Password) or DIE("Couldn't connect to MySQL:" . MYSQL_ERROR() . "" . MYSQL_ERRNO()); //select database $Db = @MYSQL_SELECT_DB($DB_DBName, $Connect) or DIE("Couldn't select database:" . MYSQL_ERROR(). "" . MYSQL_ERRNO()); //execute query $result = @MYSQL_QUERY($sql,$Connect) or DIE("Couldn't execute query:" . MYSQL_ERROR(). "" . MYSQL_ERRNO()); //if this parameter is included ($w=1), file returned will be in word format ('.doc') //if parameter is not included, file returned will be in excel format ('.xls') IF (ISSET($w) && ($w==1)) { $file_type = "vnd.ms-excel"; $file_ending = "xls"; }ELSE { $file_type = "msword"; $file_ending = "doc"; } //header info for browser: determines file type ('.doc' or '.xls') HEADER("Content-Type: application/$file_type"); HEADER("Content-Disposition: attachment; filename=database_dump.$file_ending"); HEADER("Pragma: no-cache"); HEADER("Expires: 0"); /* Start of Formatting for Word or Excel */ IF (ISSET($w) && ($w==1)) //check for $w again { /* FORMATTING FOR WORD DOCUMENTS ('.doc') */ //create title with timestamp: IF ($Use_Title == 1) { ECHO("$title\n\n"); } //define separator (defines columns in excel & tabs in word) $sep = "\n"; //new line character WHILE($row = MYSQL_FETCH_ROW($result)) { //set_time_limit(60); // HaRa $schema_insert = ""; FOR($j=0; $j<mysql_num_fields($result);$j++) { //define field names $field_name = MYSQL_FIELD_NAME($result,$j); //will show name of fields $schema_insert .= "$field_name:\t"; IF(!ISSET($row[$j])) { $schema_insert .= "NULL".$sep; } ELSEIF ($row[$j] != "") { $schema_insert .= "$row[$j]".$sep; } ELSE { $schema_insert .= "".$sep; } } $schema_insert = STR_REPLACE($sep."$", "", $schema_insert); $schema_insert .= "\t"; PRINT(TRIM($schema_insert)); //end of each mysql row //creates line to separate data from each MySQL table row PRINT "\n----------------------------------------------------\n"; } }ELSE{ /* FORMATTING FOR EXCEL DOCUMENTS ('.xls') */ //create title with timestamp: IF ($Use_Title == 1) { ECHO("$title\n"); } //define separator (defines columns in excel & tabs in word) $sep = "\t"; //tabbed character //start of printing column names as names of MySQL fields FOR ($i = 0; $i < MYSQL_NUM_FIELDS($result); $i++) { ECHO MYSQL_FIELD_NAME($result,$i) . "\t"; } PRINT("\n"); //end of printing column names //start while loop to get data WHILE($row = MYSQL_FETCH_ROW($result)) { //set_time_limit(60); // HaRa $schema_insert = ""; FOR($j=0; $j<mysql_num_fields($result);$j++) { IF(!ISSET($row[$j])) $schema_insert .= "NULL".$sep; ELSEIF ($row[$j] != "") $schema_insert .= "$row[$j]".$sep; ELSE $schema_insert .= "".$sep; } $schema_insert = STR_REPLACE($sep."$", "", $schema_insert); //following fix suggested by Josue (thanks, Josue!) //this corrects output in excel when table fields contain \n or \r //these two characters are now replaced with a space $schema_insert = PREG_REPLACE("/\r\n|\n\r|\n|\r/", " ", $schema_insert); $schema_insert .= "\t"; PRINT(TRIM($schema_insert)); PRINT "\n"; } } ?

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• Why use multiple OpenGL context

  - by Luca

  For rendering I have a current GL context, associated to a window. In the case the application render multiple scenes (for example using accumulation or different viewports) I think it is ok to reuse the same context. My question, indeed, is: why should I use multiple GL context? I red on ARB_framebuffer_object extension spec that MakeCurrent call could be expansive, and in the case the ARB_framebuffer_object extension is present I can render on a generic buffer without using MakeCurrent. Apparently the only reason to use multiple GL context is to avoid to setup context state (pixel store, transfer, point size, polygon stipple...) or to have avaialable multiple render buffers configuration (one context with accumulation, another without). How to determine when is better an alternative context instead of setting context state? Thankyou all!

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• mysql view performance

  - by vamsivanka

  I have a table for about 100,000 users in it. First Case: explain select * from users where state = 'ca' when i do an explain plan for the above query i got the cost as 5200 Second Case: Create or replace view vw_users as select * from users Explain select * from vw_users where state = 'ca' when i do an explain plan on the second query i got the cost as 100,000. How does the where clause in the view work ?? Is the where clause applied after the view retrieves all the rows. Please let know, how can i fix this issue. Thanks

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• .NET and Closing SQL Server connections

  - by user307076

  I am having a hard time figuring out why the following constructor will not close connnections. When I view the active connections. Here is the code that I have. Public Sub New(ByVal UserID As Integer) Dim oConn As New SqlConnection(ConfigurationManager.ConnectionStrings("connStr").ToString()) Dim cmd As New SqlCommand("stored proc", oConn) Dim sdr As SqlDataReader cmd.CommandType = CommandType.StoredProcedure cmd.Parameters.AddWithValue("@userID", UserID) oConn.Open() sdr = cmd.ExecuteReader() Try If Not sdr.HasRows Then sdr.Close() If Not oConn Is Nothing Then If oConn.State <> ConnectionState.Closed Then oConn.Close() End If End If cmd.Dispose() Exit Sub End If 'User has account in WATS, proceed to load account information While sdr.Read _firstname = Convert.ToString(sdr("First Name")) _lastname = Convert.ToString(sdr("Last Name")) End While Catch ex As Exception 'Throw New Exception("User Error: " + ex.Message) Finally sdr.Close() If Not oConn Is Nothing Then If oConn.State <> ConnectionState.Closed Then oConn.Close() End If End If cmd.Dispose() End Try End Sub

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• NHibernate Tutorial Run-Time Error: HibernateException

  - by Kashif

  I'm a newbie at NHibernate so please go easy on me if I have asked a stupid question... I am following the tutorial for NHibernate posted here and am getting a run-time error of type "HibernateException" The code in question looks like this: using System; using System.Collections.Generic; using System.Linq; using System.Text; using FirstSolution; using NHibernate.Cfg; using NHibernate.Tool.hbm2ddl; using NUnit.Framework; namespace FirstSolution.Tests { [TestFixture] public class GenerateSchema_Fixture { [Test] public void Can_generate_schema() { var cfg = new Configuration(); cfg.Configure(); cfg.AddAssembly(typeof(Product).Assembly); new SchemaExport(cfg).Execute(false, true, false); } } } The line I am getting the error at is: cfg.AddAssembly(typeof(Product).Assembly); The inner-most exception is: The IDbCommand and IDbConnection implementation in the assembly System.Data.SqlServerCe could not be found And here's my stack trace: at NHibernate.Connection.ConnectionProvider.ConfigureDriver(IDictionary`2 settings) at NHibernate.Connection.ConnectionProvider.Configure(IDictionary`2 settings) at NHibernate.Connection.ConnectionProviderFactory.NewConnectionProvider(IDictionary`2 settings) at NHibernate.Tool.hbm2ddl.SchemaExport.Execute(Action`1 scriptAction, Boolean export, Boolean justDrop) at NHibernate.Tool.hbm2ddl.SchemaExport.Execute(Boolean script, Boolean export, Boolean justDrop) at FirstSolution.Tests.GenerateSchema_Fixture.Can_generate_schema() in C:\Users\Kash\Documents\Visual Studio 2010\Projects\FirstSolution\FirstSolution\GenerateSchema_Fixture.cs:line 23 at HibernateUnitTest.Form1.button1_Click(Object sender, EventArgs e) in C:\Users\Kash\Documents\Visual Studio 2010\Projects\FirstSolution\HibernateUnitTest\Form1.cs:line 23 at System.Windows.Forms.Control.OnClick(EventArgs e) at System.Windows.Forms.Button.OnClick(EventArgs e) at System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent) at System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks) at System.Windows.Forms.Control.WndProc(Message& m) at System.Windows.Forms.ButtonBase.WndProc(Message& m) at System.Windows.Forms.Button.WndProc(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m) at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam) at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg) at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(IntPtr dwComponentID, Int32 reason, Int32 pvLoopData) at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context) at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context) at System.Windows.Forms.Application.Run(Form mainForm) at HibernateUnitTest.Program.Main() in C:\Users\Kash\Documents\Visual Studio 2010\Projects\FirstSolution\HibernateUnitTest\Program.cs:line 18 at System.AppDomain._nExecuteAssembly(RuntimeAssembly assembly, String[] args) at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args) at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly() at System.Threading.ThreadHelper.ThreadStart_Context(Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean ignoreSyncCtx) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ThreadHelper.ThreadStart() I've made sure that System.Data.SqlServerCe has been referenced and that its Copy Local property is set to True. The error persists, however. Your help would be appreciated. Thanks.

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• .NET and Closing MSSQL connections

  - by user307076

  I am having a hard time figuring out why the following constructor will not close connnections. When I view the active connections. Here is the code that I have. Public Sub New(ByVal UserID As Integer) Dim oConn As New SqlConnection(ConfigurationManager.ConnectionStrings("connStr").ToString()) Dim cmd As New SqlCommand("stored proc", oConn) Dim sdr As SqlDataReader cmd.CommandType = CommandType.StoredProcedure cmd.Parameters.AddWithValue("@userID", UserID) oConn.Open() sdr = cmd.ExecuteReader() Try If Not sdr.HasRows Then sdr.Close() If Not oConn Is Nothing Then If oConn.State <> ConnectionState.Closed Then oConn.Close() End If End If cmd.Dispose() Exit Sub End If 'User has account in WATS, proceed to load account information While sdr.Read _firstname = Convert.ToString(sdr("First Name")) _lastname = Convert.ToString(sdr("Last Name")) End While Catch ex As Exception 'Throw New Exception("User Error: " + ex.Message) Finally sdr.Close() If Not oConn Is Nothing Then If oConn.State <> ConnectionState.Closed Then oConn.Close() End If End If cmd.Dispose() End Try End Sub

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• What is the best way to create PDF reports with iText and zip them together?

  - by Suresh S

  I have to create a pdf report using apache itext api and report should be zipped .For example there is a report to be generated for people staying in a location of a state. for each state there are many locations, for each location , details of eachh people under the location should be saved as pdf (for each people) finally all the pdf for a location should be zipped ,this way finally all zip files for all locations should be zipped and placed under the zip file for states . my question is how best we can develop code in java. i want a skeleton framework to do the above functionality . i thought of using recursion method.also let me know from experienced users of zip api, will there be any error during creation of many zip files.

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• Flash FLVPlayback states

  - by rob5408

  I'm writing my own class to manage a skin for an FLVPlayback component. It works 90% of the time, but sometimes the state get really messed up. Specifically, the video is playing, meaning I can see it play and the VideoEvent.PLAYHEAD_UPDATE event is firing, but when I poll the FLVPlayback component about its playing property, it returns false. I assume this may be because 'buffering' is kind of a subset of 'playing', but I cannot confirm this in the documentation. I guess another way to ask this question is, "Does the FLVPlayback component ever buffer while it is in a stopped state?"

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• Weaknesses of Hibernate

  - by Sinuhe

  I would like to know which are the weak points of Hibernate 3. This is not pretended to be a thread against Hibernate. I think it will be a very useful knowledge for decide if Hibernate is the best option for a project or for estimating its time. A weakness can be: A bug Where JDBC or PLSQL are better Performance issues ... Also, can be useful to know some solutions for that problems, better ORM or techniques, or it will be corrected in Hibernate 4. For example, AFAIK, Hibernate will have a very bad performance updating 10000 rows comparing to JDBC in this query: update A set state=3 where state=2

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• WCF Troubleshooting from ASP.NET Client -- Help!

  - by Kobojunkie

  I am trying to call a method in my service that is as below, from an ASP.NET application. public bool ValidateUser(string username, string password) { try { // String CurrentLoggedInWindowsUserName = WindowsIdentity.GetCurrent().Name; // //primary identity of the call // String CurrentServiceSecurityContextPrimaryIdentityName = // ServiceSecurityContext.Current.PrimaryIdentity.Name; // } catch (Exception ex) { FaultExceptionFactory fct = new FaultExceptionFactory(); throw new FaultException<CustomFaultException>(fct.CreateFaultException(ex)); } return false; } The Config for the client end of my service is as below <binding name="WSHttpBinding_IMembershipService" closeTimeout="00:01:00" openTimeout="00:01:00" receiveTimeout="00:10:00" sendTimeout="00:01:00" bypassProxyOnLocal="false" transactionFlow="false" hostNameComparisonMode="StrongWildcard" maxBufferPoolSize="524288" maxReceivedMessageSize="65536" messageEncoding="Text" textEncoding="utf-8" useDefaultWebProxy="false" allowCookies="false"> <readerQuotas maxDepth="32" maxStringContentLength="8192" maxArrayLength="16384" maxBytesPerRead="4096" maxNameTableCharCount="16384" /> <reliableSession ordered="true" inactivityTimeout="00:10:00" enabled="false" /> <security mode="Message"> <transport clientCredentialType="Windows" proxyCredentialType="None" realm="" /> <message clientCredentialType="Windows" negotiateServiceCredential="true" algorithmSuite="Default" establishSecurityContext="true" /> </security> </binding> Problem I keep having is when I call it; I get the following exception message. Server Error in '/' Application. The communication object, System.ServiceModel.Channels.ServiceChannel, cannot be used for communication because it is in the Faulted state. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.ServiceModel.CommunicationObjectFaultedException: The communication object, System.ServiceModel.Channels.ServiceChannel, cannot be used for communication because it is in the Faulted state. Stack Trace: [CommunicationObjectFaultedException: The communication object, System.ServiceModel.Channels.ServiceChannel, cannot be used for communication because it is in the Faulted state.] System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg) +7596735 System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type) +275 System.ServiceModel.ICommunicationObject.Close(TimeSpan timeout) +0 System.ServiceModel.ClientBase`1.System.ServiceModel.ICommunicationObject. Close(TimeSpan timeout) +142 System.ServiceModel.ClientBase`1.Close() +38 System.ServiceModel.ClientBase`1.System.IDisposable.Dispose() +4 Controls.Membership.accountLogin.ValidateUserCredentials(String UserName, String Password) in C:\ Petition.WebClient\Controls\ Membership\accountLogin.ascx.cs:49 Controls.Membership.accountLogin.Login1_Authenticate(Object sender, AuthenticateEventArgs e) in C:\ WebClient\ Controls\Membership \accountLogin.ascx.cs:55 I am not entirely sure why I keep getting this. Just in case, here is how I call my service from the client private bool ValidateUserCredentials(string UserName, string Password) { bool boolReturnValue = false; using(Members.MembershipServiceClient client = new Controls.Members.MembershipServiceClient()) { try { boolReturnValue = client.ValidateUser(UserName, Password); } catch (FaultException<CustomFaultException> ex) { throw ex; } } return boolReturnValue; } Anyone have any idea what I need to do in this case?

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• Excel Data List Validation in Powershell

  - by idazuwaika

  Hi, I have a range named "STATE". I want to set data validation in range ("A1") to only take value within this range using Powershell. Below is what I have tried. Does not work. I dont know what to put as 4th and 5th parameters. The first 3 are Excel constants equivalent to xlValidateList, xlValidAlertStop and xlBetween respectively. $ws.Range("A1").Validation.Add(3, 1, 1, "=STATE", 0) Please help. Thanks.

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• Add step dynamic for ASP.NET Wizard control

  - by Yongwei Xing

  Hi all Is there any way to add steps dynamic in Wizard controls and keep the current state? Best Regards,

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• LINQ query and lambda expressions

  - by user329269

  I'm trying to write a LINQ query and am having problems. I'm not sure if lambda expressions are the answer or not but I think they may be. I have two combo boxes on my form: "State" and "Color". I want to select Widgets from my database based on the values of these two dropdowns. My widgets can be in one of the following states: Not Started, In Production, In Finishing, In Inventory, Sold. Widgets can have any color in the 'color' table in the database. The 'state' combobox has selections "Not Sold," "In Production/Finishing", "Not Started," "In Production," "In Finishing," "In Inventory," "Sold." (I hope these are self-explanatory.) The 'color' dropdown has "All Colors," and a separate item for each color in the database. How can I create a LINQ query to select the widgets I want from the database based on the dropdowns?

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• How to I serialize a large graph of .NET object into a SQL Server BLOB without creating a large bu

  - by Ian Ringrose

  We have code like: ms = New IO.MemoryStream bin = New System.Runtime.Serialization.Formatters.Binary.BinaryFormatter bin.Serialize(ms, largeGraphOfObjects) dataToSaveToDatabase = ms.ToArray() // put dataToSaveToDatabase in a Sql server BLOB But the memory steam allocates a large buffer from the large memory heap that is giving us problems. So how can we stream the data without needing enough free memory to hold the serialized objects. I am looking for a way to get a Stream from SQL server that can then be passed to bin.Serialize() so avoiding keeping all the data in my processes memory. Likewise for reading the data back... Some more background. This is part of a complex numerical processing system that processes data in near real time looking for equipment problems etc, the serialization is done to allow a restart when there is a problem with data quality from a data feed etc. (We store the data feeds and can rerun them after the operator has edited out bad values.) Therefore we serialize the object a lot more often then we de-serialize them. The objects we are serializing include very large arrays mostly of doubles as well as a lot of small “more normal” objects. We are pushing the memory limit on a 32 bit system and make the garage collector work very hard. (Effects are being made elsewhere in the system to improve this, e.g. reusing large arrays rather then create new arrays.) Often the serialization of the state is the last straw that courses an out of memory exception; our peak memory usage is while this serialization is being done. I think we get large memory pool fragmentation when we de-serialize the object, I expect there are also other problem with large memory pool fragmentation given the size of the arrays. (This has not yet been investigated, as the person that first looked at this is a numerical processing expert, not a memory management expert.) Are customers use a mix of Sql Server 2000, 2005 and 2008 and we would rather not have different code paths for each version of Sql Server if possible. We can have many active models at a time (in different process, across many machines), each model can have many saved states. Hence the saved state is stored in a database blob rather then a file. As the spread of saving the state is important, I would rather not serialize the object to a file, and then put the file in a BLOB one block at a time. Other related questions I have asked How to Stream data from/to SQL Server BLOB fields? Is there a SqlFileStream like class that works with Sql Server 2005?

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• Proper way in MVVM to drive visual states.

  - by firoso

  Given a content presenter that can display one of 4 different application pages, and I want to fade/otherwise animate a transition between pages based on view model state. Ideally I'd like to have these all defined within a DataTemplate, and then trigger transitions based on an enum from the view model, so that when some enum representing state changes, the transitions trigger to the appropriate page. Is there a known best practice to handle things like this? Immediately coming to mind is the possibiltiy to use Enter and Exit actions on data triggers to play storyboards, but this definately doesn't use the parts and states model, so I'd like to shy away from that. I've also tried using the DataStateSwitchBehavior from the codeplex Expression project, but found it to be incompatable with the latest builds of WPF 4.0/Blend 4 RC's SDK. Does anyone have any ideas on how to handle this elegantly? I'm using the MVVM-Light framework. Also I'd like to point out that as long as this resides on a DataTemplate in a Resource Dictionary, code-behind is not an option without refactoring.

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• Function-Local Static Const variable Initialization semantics.

  - by Hassan Syed

  The questions are in bold, for those that cannot be bothered reading a question in depth. This is a followup to this question. It is to do with the initialization semantics of static variables in functions. Static variables should be initialized once, and their internal state might be altered later - as I (currently) do in the linked question. However, the code in question does not require the feature to change the state of the variable later. Let me clarrify my position, since I don't require the string object's internal state to change. The code is for a trait class for meta programming, and as such would would benifit from a const char * const ptr -- thus Ideally a local cost static const variable is needed. My educated guess is that in this case the string in question will be optimally placed in memory by the link-loader, and that the code is more secure and maps to the intended semantics. This leads to the semantics of such a variable "The C++ Programming language Third Edition -- Stroustrup" does not have anything (that I could find) to say about this matter. All that is said is that the variable is initialized once when the flow of control of the thread first reaches the code. This leads me to ponder if the following code would be sensible, and if not what are the intended semantics ?. #include <iostream> const char * const GetString(const char * x_in) { static const char * const x = x_in; return x; } int main() { const char * const temp = GetString("yahoo"); std::cout << temp << std::endl; const char * const temp2 = GetString("yahoo2"); std::cout << temp2 << std::endl; } The following compiles on GCC and prints "yahoo" twice. Which is what I want -- However it might not be standards compliant (which is why I post this question). It might be more elegant to have two functions, "SetString" and "String" where the latter forwards to the first. If it is standards compliant does someone know of a templates implementation in boost (or elsewhere) ?

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• How do I delete a child entity from a parent collection with Entity Framework 4?

  - by simonjreid

  I'm using Entity Framework 4 and have a one-to-many relationship between a parent and child entity. I'm trying to delete a child using the parent repository by removing it from the parent's children collection: public virtual void RemoveChild(Child child) { children.Remove(child); } When I try to save the changes I get the following error: A relationship from the 'ParentChild' AssociationSet is in the 'Deleted' state. Given multiplicity constraints, a corresponding 'Child' must also in the 'Deleted' state. Surely I don't have to delete the child entity explicitly using a child repository!

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• How to join data frames in R (inner, outer, left, right)?

  - by Dan Goldstein

  Given two data frames df1 = data.frame(CustomerId=c(1:6),Product=c(rep("Toaster",3),rep("Radio",3))) df2 = data.frame(CustomerId=c(2,4,6),State=c(rep("Alabama",2),rep("Ohio",1))) > df1 CustomerId Product 1 Toaster 2 Toaster 3 Toaster 4 Radio 5 Radio 6 Radio > df2 CustomerId State 2 Alabama 4 Alabama 6 Ohio How can I do database style, i.e., sql style, joins? That is, how do I get: An inner join of df1 and df1 An outer join of df1 and df2 A left outer join of df1 and df2 A right outer join of df1 and df2 P.S. IKT-JARQ (I Know This - Just Adding R Questions) Extra credit: How can I do a sql style select statement?

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• How do you do dynamic script evaluation in C#?

  - by Deane

  What is the state of dynamic code evaluation in C#? For a very advanced feature of an app I'm working on, I'd like the users to be able to enter a line of C# code that should evaluate to a boolean. Something like: DateTime.Now.Hours > 12 && DateTime.Now.Hours < 14 I want to dynamically eval this string and capture the result as a boolean. I tried Microsoft.JScript.Eval.JScriptEvaluate, and this worked, but it's technically deprecated and it only works with Javascript (not ideal, but workable). Additionally, I'd like to be able to push objects into the script engine so that they can be used in the evaluation. Some resources I find mentioned dynamically compiling assemblies, but this is more overhead than I think I want to deal with. So, what is the state of dynamic script evaluation in C#? Is it possible, or am I out of luck?

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• Random access gzip stream

  - by jkff

  I'd like to be able to do random access into a gzipped file. I can afford to do some preprocessing on it (say, build some kind of index), provided that the result of the preprocessing is much smaller than the file itself. Any advice? My thoughts were: Hack on an existing gzip implementation and serialize its decompressor state every, say, 1 megabyte of compressed data. Then to do random access, deserialize the decompressor state and read from the megabyte boundary. This seems hard, especially since I'm working with Java and I couldn't find a pure-java gzip implementation :( Re-compress the file in chunks of 1Mb and do same as above. This has the disadvantage of doubling the required disk space. Write a simple parser of the gzip format that doesn't do any decompressing and only detects and indexes block boundaries (if there even are any blocks: I haven't yet read the gzip format description)

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• How can I modify a custom object in an ASP.NET FormView based on a button click?

  - by David

  I have a FormView that modifies an instance of a custom class. The various form controls (TextBox, DropDownList etc.) are working fine. However, I want to include a Button that will modify the state of the DataItem based on some very simple logic. There is no form control which could control this change in a non-confusing way. So I tried adding a Button and modifying the state of the DataItem in the code-behind. But the problem I encounter is that the FormView's DataItem is null/nothing. From reading this SO question it seems the problem is that the item is not databound when the Button's Click event is fired. So, the question; Is it possible to get the DataItem for the FormView during a Button's Click event? and if not: what are my options for implementing this? Thanks in advance. Edit: I can include any code that might help

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• Finding underlying cause of Window 7 Account corruption.

  - by Carl Jokl

  I have been having trouble with my Sister's computer which I built. It is running Windows 7 Ultimate x64. The problem is that I have had problems with the accounts becoming corrupted. First problems manifest themselves in the form of Windows saying the profile failed to be loaded properly and a temporary profile. Eventually the account will not allow login at all. An error message along the lines the authentication service failing the login. I have found information about this problem and how to fix it. The problem being that something has corrupted the account profile and backing up and recreating the accounts fixes the problem. I have been able to fix things and get logins working again but over the period of usually about a week it happens again. Bit by bit the accounts corrupt and then it is back to square one. I am frustrated because I don't know what the underlying cause of the problem is i.e. what is causing the accounts to be corrupted in the first place. At the moment I am just treating the symptoms. I was hoping someone who may have more experience with dealing with this problem might be able to help me find the root cause. Some articles suggest that Norton Internet Security is a big culprit of this problem which is installed. I could try uninstalling Norton and see if it helps. The one thing which is different about this computer to any other I have built is that it has a solid state drive. Actually it has both a hard drive and solid state drive. The documents and settings i.e. the Users directory is stored on the hard drive. This was done following an article about moving the user account data onto a separate drive on Windows 7 which I found on the Internet. Moving the User accounts is more of a pain under Windows 7 and this solution involved creating a low level file system link to the folder from the boot drive (Solid State) to the Hard Drive. The idea is that the computer behaves just as if it is accessing the User's folder from the boot drive but actually the data is stored on the hard drive. This may have nothing to do with the cause of the problem but due to the problem being user account corruption it is a possibility I have not been able to rule out. Any help would be appreciated as I would be glad to see the back of this problem.

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• mdadm: Win7-install created a boot partition on one of my RAID6 drives. How to rebuild?

  - by EXIT_FAILURE

  My problem happened when I attempted to install Windows 7 on it's own SSD. The Linux OS I used which has knowledge of the software RAID system is on a SSD that I disconnected prior to the install. This was so that windows (or I) wouldn't inadvertently mess it up. However, and in retrospect, foolishly, I left the RAID disks connected, thinking that windows wouldn't be so ridiculous as to mess with a HDD that it sees as just unallocated space. Boy was I wrong! After copying over the installation files to the SSD (as expected and desired), it also created an ntfs partition on one of the RAID disks. Both unexpected and totally undesired! . I changed out the SSDs again, and booted up in linux. mdadm didn't seem to have any problem assembling the array as before, but if I tried to mount the array, I got the error message: mount: wrong fs type, bad option, bad superblock on /dev/md0, missing codepage or helper program, or other error In some cases useful info is found in syslog - try dmesg | tail or so dmesg: EXT4-fs (md0): ext4_check_descriptors: Block bitmap for group 0 not in group (block 1318081259)! EXT4-fs (md0): group descriptors corrupted! I then used qparted to delete the newly created ntfs partition on /dev/sdd so that it matched the other three /dev/sd{b,c,e}, and requested a resync of my array with echo repair > /sys/block/md0/md/sync_action This took around 4 hours, and upon completion, dmesg reports: md: md0: requested-resync done. A bit brief after a 4-hour task, though I'm unsure as to where other log files exist (I also seem to have messed up my sendmail configuration). In any case: No change reported according to mdadm, everything checks out. mdadm -D /dev/md0 still reports: Version : 1.2 Creation Time : Wed May 23 22:18:45 2012 Raid Level : raid6 Array Size : 3907026848 (3726.03 GiB 4000.80 GB) Used Dev Size : 1953513424 (1863.02 GiB 2000.40 GB) Raid Devices : 4 Total Devices : 4 Persistence : Superblock is persistent Update Time : Mon May 26 12:41:58 2014 State : clean Active Devices : 4 Working Devices : 4 Failed Devices : 0 Spare Devices : 0 Layout : left-symmetric Chunk Size : 4K Name : okamilinkun:0 UUID : 0c97ebf3:098864d8:126f44e3:e4337102 Events : 423 Number Major Minor RaidDevice State 0 8 16 0 active sync /dev/sdb 1 8 32 1 active sync /dev/sdc 2 8 48 2 active sync /dev/sdd 3 8 64 3 active sync /dev/sde Trying to mount it still reports: mount: wrong fs type, bad option, bad superblock on /dev/md0, missing codepage or helper program, or other error In some cases useful info is found in syslog - try dmesg | tail or so and dmesg: EXT4-fs (md0): ext4_check_descriptors: Block bitmap for group 0 not in group (block 1318081259)! EXT4-fs (md0): group descriptors corrupted! I'm a bit unsure where to proceed from here, and trying stuff "to see if it works" is a bit too risky for me. This is what I suggest I should attempt to do: Tell mdadm that /dev/sdd (the one that windows wrote into) isn't reliable anymore, pretend it is newly re-introduced to the array, and reconstruct its content based on the other three drives. I also could be totally wrong in my assumptions, that the creation of the ntfs partition on /dev/sdd and subsequent deletion has changed something that cannot be fixed this way. My question: Help, what should I do? If I should do what I suggested , how do I do that? From reading documentation, etc, I would think maybe: mdadm --manage /dev/md0 --set-faulty /dev/sdd mdadm --manage /dev/md0 --remove /dev/sdd mdadm --manage /dev/md0 --re-add /dev/sdd However, the documentation examples suggest /dev/sdd1, which seems strange to me, as there is no partition there as far as linux is concerned, just unallocated space. Maybe these commands won't work without. Maybe it makes sense to mirror the partition table of one of the other raid devices that weren't touched, before --re-add. Something like: sfdisk -d /dev/sdb | sfdisk /dev/sdd Bonus question: Why would the Windows 7 installation do something so st...potentially dangerous? Update I went ahead and marked /dev/sdd as faulty, and removed it (not physically) from the array: # mdadm --manage /dev/md0 --set-faulty /dev/sdd # mdadm --manage /dev/md0 --remove /dev/sdd However, attempting to --re-add was disallowed: # mdadm --manage /dev/md0 --re-add /dev/sdd mdadm: --re-add for /dev/sdd to /dev/md0 is not possible --add, was fine. # mdadm --manage /dev/md0 --add /dev/sdd mdadm -D /dev/md0 now reports the state as clean, degraded, recovering, and /dev/sdd as spare rebuilding. /proc/mdstat shows the recovery progress: md0 : active raid6 sdd[4] sdc[1] sde[3] sdb[0] 3907026848 blocks super 1.2 level 6, 4k chunk, algorithm 2 [4/3] [UU_U] [>....................] recovery = 2.1% (42887780/1953513424) finish=348.7min speed=91297K/sec nmon also shows expected output: ¦sdb 0% 87.3 0.0| > |¦ ¦sdc 71% 109.1 0.0|RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRR > |¦ ¦sdd 40% 0.0 87.3|WWWWWWWWWWWWWWWWWWWW > |¦ ¦sde 0% 87.3 0.0|> || It looks good so far. Crossing my fingers for another five+ hours :) Update 2 The recovery of /dev/sdd finished, with dmesg output: [44972.599552] md: md0: recovery done. [44972.682811] RAID conf printout: [44972.682815] --- level:6 rd:4 wd:4 [44972.682817] disk 0, o:1, dev:sdb [44972.682819] disk 1, o:1, dev:sdc [44972.682820] disk 2, o:1, dev:sdd [44972.682821] disk 3, o:1, dev:sde Attempting mount /dev/md0 reports: mount: wrong fs type, bad option, bad superblock on /dev/md0, missing codepage or helper program, or other error In some cases useful info is found in syslog - try dmesg | tail or so And on dmesg: [44984.159908] EXT4-fs (md0): ext4_check_descriptors: Block bitmap for group 0 not in group (block 1318081259)! [44984.159912] EXT4-fs (md0): group descriptors corrupted! I'm not sure what do do now. Suggestions? Output of dumpe2fs /dev/md0: dumpe2fs 1.42.8 (20-Jun-2013) Filesystem volume name: Atlas Last mounted on: /mnt/atlas Filesystem UUID: e7bfb6a4-c907-4aa0-9b55-9528817bfd70 Filesystem magic number: 0xEF53 Filesystem revision #: 1 (dynamic) Filesystem features: has_journal ext_attr resize_inode dir_index filetype extent flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize Filesystem flags: signed_directory_hash Default mount options: user_xattr acl Filesystem state: clean Errors behavior: Continue Filesystem OS type: Linux Inode count: 244195328 Block count: 976756712 Reserved block count: 48837835 Free blocks: 92000180 Free inodes: 243414877 First block: 0 Block size: 4096 Fragment size: 4096 Reserved GDT blocks: 791 Blocks per group: 32768 Fragments per group: 32768 Inodes per group: 8192 Inode blocks per group: 512 RAID stripe width: 2 Flex block group size: 16 Filesystem created: Thu May 24 07:22:41 2012 Last mount time: Sun May 25 23:44:38 2014 Last write time: Sun May 25 23:46:42 2014 Mount count: 341 Maximum mount count: -1 Last checked: Thu May 24 07:22:41 2012 Check interval: 0 (<none>) Lifetime writes: 4357 GB Reserved blocks uid: 0 (user root) Reserved blocks gid: 0 (group root) First inode: 11 Inode size: 256 Required extra isize: 28 Desired extra isize: 28 Journal inode: 8 Default directory hash: half_md4 Directory Hash Seed: e177a374-0b90-4eaa-b78f-d734aae13051 Journal backup: inode blocks dumpe2fs: Corrupt extent header while reading journal super block

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