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• ASP.NET application - Error when trying to connect to a SQL Server 2008 instance

  - by Pablo Dami

  Hi everyone! Despite that I’m a regular reader of this great forum, this is my first post on it. I believe that this community can help me with the following problem that I have. I’m trying to publish an ASP.NET website over an IIS 6.0 (Windows 2003 Server), and I have some troubles trying to connect to the database. Curiously, I have installed another ASP.NET website into the same IIS 6.0 with the same properties and security parameters and can connect without problems with the same database. The application that works fine is almost the same that the one that can’t connect with SQL Server (actually is the same but with several modifications). I’ll enumarate some information related to the problem: S.O: Windows 2003 Server SQL Server Engine: SQL Server 2008 SQL Server accept remote connections? Yes. ASP.NET version: 2.0.50727 The connections via TCP/IP are enabled to the SQL Server instance? Yes. The corresponding user that I have in the connection string, actually exists into the database with the “owner” role? Yes. ORM Tool used: nHibernate I get the following error when I try to run the aplication into the browser: Error while establishing a connection to the server. When connecting to SQL Server 2005, this failure may occur because the default settings SQL Server does not allow remote connections. (provider: Shared Memory Provider, error: 40 - Could not open a connection to SQL Server) In order to isolate the problem, I made some test. For example, using the web app that works fine I can connect without any problema with the database that uses the web app that can’t. With this evidence I concluded that the problem is within the web app and not into the SQL Server instance. I also google it my problem but sadly I can't find nothing usefull to solve it. If someone can help me I’ll appreciate that. Thank you so much for your time!

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• HSM - cryptoki - opening sessions overhead

  - by Raj

  I am having a query regarding sessions with HSM. I am aware that there is an overhead if you initialise and finalise the cryptoki api for every file you want to encrypt/decrypt. My queries are, Is there an overhead in opening and closing individual sessions for every file, you want to encrypt/decrypt.(C_Initialize/C_Finalize) How many maximum number of sessions can i have for a HSM simultaneously, with out affecting the performance? Is opening and closing the session for processing individual files the best approach or opening a session and processing multiple files and then closing the session the best approach? Thanks

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• SQL query for getting count on same table using left outer join

  - by Sasi

  Hi all, I have a table from which i need to get the count grouped on two columns. the table has two columns one datetime column and another one is success value(-1,1,0) What i am looking for is something like this... count of success value for each month month----success-----count 11------- -1 ------- 50 11------- 1 --------- 50 11------- 0 ------- 50 12------- -1 ------- 50 12------- 1 ------- 50 12------- 0 ------- 50 if there is no success value for a month then the count should be null or zero. I have tried with left outer join as well but of no use it gives the count incorrectly. Thanks in advance Sasi

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• I'm trying to grasp the concept of creating a program that uses a SQL Server database, but I'm used

  - by Sergio Tapia

  How can I make a program use a SQL Server database, and have that program work on whatever computer it's installed on. If you've been following my string of questions today, you'd know that I'm making an open source and free Help Desk suite for small and medium businesses. The client application. The client application is a Windows Forms app. On installation and first launch on every client machine, it'll ask for the address of the main Help Desk server. The server. Here I plan to handle all incoming help requests, show them to the IT guys, and provide WCF services for the Client application to consume. My dilemma lies in that, I know how to make the program run on my local machine; but I'm really stumped on how to make this work for everyone who wants to download and install the server bit on their Windows Server. Would I have to make an SQL Script and have it run on the MS SQL server when a user wants to install the 'server' application? Many thanks to all for your valuable time and effort to teach me. It's really really appreciated. :) Edit: To clarify, each business will have their server completely separate from me. I will have no access whatsoever to them nor will they be in any way connected to me. (I don't know why I should clarify this :P ) So, assuming the have ABSOLUTELY NO DATABASE SERVER installed; what can I do?

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• Which is faster: creating a detailed mesh before execution or tessellating?

  - by Nick Udell

  For simplicity of the problem let's consider spheres. Let's say I have a sphere, and before execution I know the radius, the position and the triangle count. Let's also say the triangle count is sufficiently large (e.g. ~50k triangles). Would it be faster generally to create this sphere mesh before hand and stream all 50k triangles to the graphics card, or would it be faster to send a single point (representing the centre of the sphere) and use tessellation and geometry shaders to build the sphere on the GPU? Would it still be faster if I had 100 of these spheres in different positions? Can I use hull/geometry shaders to create something which I can then combine with instancing?

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• Impossible to be const-correct when combining data and it's lock?

  - by Graeme

  I've been looking at ways to combine a piece of data which will be accessed by multiple threads alongside the lock provisioned for thread-safety. I think I've got to a point where I don't think its possible to do this whilst maintaining const-correctness. Take the following class for example: template <typename TType, typename TMutex> class basic_lockable_type { public: typedef TMutex lock_type; public: template <typename... TArgs> explicit basic_lockable_type(TArgs&&... args) : TType(std::forward<TArgs...>(args)...) {} TType& data() { return data_; } const TType& data() const { return data_; } void lock() { mutex_.lock(); } void unlock() { mutex_.unlock(); } private: TType data_; mutable TMutex mutex_; }; typedef basic_lockable_type<std::vector<int>, std::mutex> vector_with_lock; In this I try to combine the data and lock, marking mutex_ as mutable. Unfortunately this isn't enough as I see it because when used, vector_with_lock would have to be marked as mutable in order for a read operation to be performed from a const function which isn't entirely correct (data_ should be mutable from a const). void print_values() const { std::lock_guard<vector_with_lock>(values_); for(const int val : values_) { std::cout << val << std::endl; } } vector_with_lock values_; Can anyone see anyway around this such that const-correctness is maintained whilst combining data and lock? Also, have I made any incorrect assumptions here?

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• How do I view the full content of a text or varchar(MAX) column in SQL Server 2008 Management Studio

  - by adamjford

  In this live SQL Server 2008 (build 10.0.1600) database, there's an Events table, which contains a text column named Details. (Yes, I realize this should actually be a varchar(MAX) column, but whoever set this database up did not do it that way.) This column contains very large logs of exceptions and associated JSON data that I'm trying to access through SQL Server Management Studio, but whenever I copy the results from the grid to a text editor, it truncates it at 43679 characters. I've read on various locations on the Internet that you can set your Maximum Characters Retrieved for XML Data in Tools > Options > Query Results > SQL Server > Results To Grid to Unlimited, and then perform a query such as this: select Convert(xml, Details) from Events where EventID = 13920 (Note that the data is column is not XML at all. CONVERTing the column to XML is merely a workaround I found from Googling that someone else has used to get around the limit SSMS has from retrieving data from a text or varchar(MAX) column.) However, after setting the option above, running the query, and clicking on the link in the result, I still get the following error: Unable to show XML. The following error happened: Unexpected end of file has occurred. Line 5, position 220160. One solution is to increase the number of characters retrieved from the server for XML data. To change this setting, on the Tools menu, click Options. So, any idea on how to access this data? Would converting the column to varchar(MAX) fix my woes?

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• Output is different for R-value and L-value. Why?

  - by Leonid Volnitsky

  Can someone explain to me why output for R-value is different from L-value? #include <iostream> #include <vector> using namespace std; template<typename Ct> struct ct_wrapper { Ct&& ct; // R or L ref explicit ct_wrapper(Ct&& ct) : ct(std::forward<Ct>(ct)) { std::cout << this->ct[1];}; }; int main() { // L-val vector<int> v{1,2,3}; ct_wrapper<vector<int>&> lv(v); cout << endl << lv.ct[0] << lv.ct[1] << lv.ct[2] << endl; // R-val ct_wrapper<vector<int>&&> rv(vector<int>{1,2,3}); cout << endl << rv.ct[0] << rv.ct[1] << rv.ct[2] << endl; } Output (same for gcc48 and clang32): 2 123 2 003

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• std::conditional compile-time branch evaluation

  - by cmannett85

  Compiling this: template < class T, class Y, class ...Args > struct isSame { static constexpr bool value = std::conditional< sizeof...( Args ), typename std::conditional< std::is_same< T, Y >::value, isSame< Y, Args... >, // Error! std::false_type >::type, std::is_same< T, Y > >::type::value; }; int main() { qDebug() << isSame< double, int >::value; return EXIT_SUCCESS; } Gives me this compiler error: error: wrong number of template arguments (1, should be 2 or more) The issue is that isSame< double, int > has an empty Args parameter pack, so isSame< Y, Args... > effectively becomes isSame< Y > which does not match the signature. But my question is: Why is that branch being evaluated at all? sizeof...( Args ) is false, so the inner std:conditional should not be evaluated. This isn't a runtime piece of code, the compiler knows that sizeof..( Args ) will never be true with the given template types. If you're curious, it's supposed to be a variadic version of std::is_same, not that it works...

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• Specializating a template function that takes a universal reference parameter

  - by David Stone

  How do I specialize a template function that takes a universal reference parameter? foo.hpp: template<typename T> void foo(T && t) // universal reference parameter foo.cpp template<> void foo<Class>(Class && class) { // do something complicated } Here, Class is no longer a deduced type and thus is Class exactly; it cannot possibly be Class &, so reference collapsing rules will not help me here. I could perhaps create another specialization that takes a Class & parameter (I'm not sure), but that implies duplicating all of the code contained within foo for every possible combination of rvalue / lvalue references for all parameters, which is what universal references are supposed to avoid. Is there some way to accomplish this? To be more specific about my problem in case there is a better way to solve it: I have a program that can connect to multiple game servers, and each server, for the most part, calls everything by the same name. However, they have slightly different versions for a few things. There are a few different categories that these things can be: a move, an item, etc. I have written a generic sort of "move string to move enum" set of functions for internal code to call, and my server interface code has similar functions. However, some servers have their own internal ID that they communicate with, some use strings, and some use both in different situations. Now what I want to do is make this a little more generic. I want to be able to call something like ServerNamespace::server_cast<Destination>(source). This would allow me to cast from a Move to a std::string or ServerMoveID. Internally, I may need to make a copy (or move from) because some servers require that I keep a history of messages sent. Universal references seem to be the obvious solution to this problem. The header file I'm thinking of right now would expose simply this: namespace ServerNamespace { template<typename Destination, typename Source> Destination server_cast(Source && source); } And the implementation file would define all legal conversions as template specializations.

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• User defined literal arguments are not constexpr?

  - by Pubby

  I'm testing out user defined literals. I want to make _fac return the factorial of the number. Having it call a constexpr function works, however it doesn't let me do it with templates as the compiler complains that the arguments are not and cannot be constexpr. I'm confused by this - aren't literals constant expressions? The 5 in 5_fac is always a literal that can be evaluated during compile time, so why can't I use it as such? First method: constexpr int factorial_function(int x) { return (x > 0) ? x * factorial_function(x - 1) : 1; } constexpr int operator "" _fac(unsigned long long x) { return factorial_function(x); // this works } Second method: template <int N> struct factorial { static const unsigned int value = N * factorial<N - 1>::value; }; template <> struct factorial<0> { static const unsigned int value = 1; }; constexpr int operator "" _fac(unsigned long long x) { return factorial_template<x>::value; // doesn't work - x is not a constexpr }

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• Cheapest way of binding local variable to closure

  - by mmotorny

  I believe following to be a cheapest way of binding local variable to closure: void ByRValueReference(A&& a) { } std::function<void ()> CreateClosureByRValueReference() { A a; std::function<void ()> f = std::bind(&ByRValueReference, std::move(a)); // !!! return f; } However, it does not compile under Clang 3.1: error: no viable conversion from '__bind<void (*)(A &&), A>' to 'std::function<void ()>' and gcc 4.6.1: /usr/include/c++/4.6/functional:1778:2: error: no match for call to ‘(std::_Bind<void (*(A))(A&&)>) ()’ Am I violating the standard or it's just broken standard libraries?

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• Best way to migrate export/import from SQL Server to oracle

  - by matao

  Hi guys! I'm faced with needing access for reporting to some data that lives in Oracle and other data that lives in a SQL Server 2000 database. For various reasons these live on different sides of a firewall. Now we're looking at doing an export/import from sql server to oracle and I'd like some advice on the best way to go about it... The procedure will need to be fully automated and run nightly, so that excludes using the SQL developer tools. I also can't make a live link between databases from our (oracle) side as the firewall is in the way. The data needs to be transformed in the process from a star schema to a de-normalised table ready for reporting. What I'm thinking about is writing a monster query for SQL Server (which I mostly have already) that will denormalise and read out the data from SQL Server into a flat file using the sql server equivalent of sqlplus as a scheduled task, dump into a Well Known Location, then on the oracle side have a cron job that copies down the file and loads it with sql loader and rebuilds indexes etc. This is all doable, but very manual. Is there one or a combination of FOSS or standard oracle/SQL Server tools that could automate this for me? the Irreducible complexity is the query on one side and building indexes on the other, but I would love to not have to write the CSV dumping detail or the SQL loader script, just say dump this view out to CSV on one side, and on the other truncate and insert into this table from CSV and not worry about mapping column names and all other arcane sqlldr voodoo... best practices? thoughts? comments? edit: I have about 50+ columns all of varying types and lengths in my dataset, which is why I'd prefer to not have to write out how to generate and map each single column...

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• SQL Server 2008 R2

  - by kevchadders

  Hi all, I heard on the grapevine that Microsoft will be releasing SQL Server 2008 R2 within a year. Though I initially thought this was a patch for the just released 2008 version, I realised that it’s actually a completely different version that you would have to pay for. (Am I correct, if you had SQL Server 2008, would you have to pay again if you wanted to upgrade to 2008 R2?) If you’re already running SQL Server 2008, would you say it’s still worth the upgrade? Or does it depend on the size of your company and current setup. For what I’ve initially read, I do get the impression that this version would be more useful for the very high end hardware setup where you want to have very good scalability. With regard to programming, is there any extra enhancements/support in there which you’re aware of that will significantly help .NET Products/Web Development? Initially found a couple of links on it, but I was wondering if anyone had anymore info to share on subject as I couldn’t find nothing on SO about it? Thanks. New SQL Server R2 Microsoft Link on it. Microsoft SQL 2008 R2 EDIT: More information based on the Express Edition One very interesting thing about SQL Server 2008 R2 concerns the Express edition. Previous express versions of SQL Server Express had a database size limit of 4GB. With SQL Server Express 2008 R2, this has now been increased to 10GB !! This now makes the FREE express edition a much more viable option for small & medium sized applications that are relatively light on database requirements. Bear in mind, that this limit is per database, so if you coded your application cleverly enough to use a separate database for historical/archived data, you could squeeze even more out of it! For more information, see here: http://blogs.msdn.com/sqlexpress/archive/2010/04/21/database-size-limit-increased-to-10gb-in-sql-server-2008-r2-express.aspx

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• tcl_findLibrary doesn't work.

  - by user437815

  I'm trying to run freshly compiled program, written with Tcl&Tk. When running it I get an error: felix@Astroserver:~/?????????/Simon$ sudo ./simon1 invalid command name "tcl_findLibrary" I'm running Ubuntu 11.04, I have installed Tcl&Tk (cause I was able to succesfully build the program). If I'm running wish: *% tcl_findLibrary wrong # args: should be "tcl_findLibrary basename version patch initScript enVarName varName"* Could anyone help?

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• SQL problem - select accross multiple tables (user groups)

  - by morpheous

  I have a db schema which looks something like this: create table user (id int, name varchar(32)); create table group (id int, name varchar(32)); create table group_member (foobar_id int, user_id int, flag int); I want to write a query that allows me to so the following: Given a valid user id (UID), fetch the ids of all users that are in the same group as the specified user id (UID) AND have group_member.flag=3. Rather than just have the SQL. I want to learn how to think like a Db programmer. As a coder, SQL is my weakest link (since I am far more comfortable with imperative languages than declarative ones) - but I want to change that. Anyway here are the steps I have identified as necessary to break down the task. I would be grateful if some SQL guru can demonstrate the simple SQL statements - i.e. atomic SQL statements, one for each of the identified subtasks below, and then finally, how I can combine those statements to make the ONE statement that implements the required functionality. Here goes (assume specified user_id [UID] = 1): //Subtask #1. Fetch list of all groups of which I am a member Select group.id from user inner join group_member where user.id=group_member.user_id and user.id=1 //Subtask #2 Fetch a list of all members who are members of the groups I am a member of (i.e. groups in subtask #1) Not sure about this ... select user.id from user, group_member gm1, group_member gm2, ... [Stuck] //Subtask #3 Get list of users that satisfy criteria group_member.flag=3 Select user.id from user inner join group_member where user.id=group_member.user_id and user.id=1 and group_member.flag=3 Once I have the SQL for subtask2, I'd then like to see how the complete SQL statement is built from these subtasks (you dont have to use the SQL in the subtask, it just a way of explaining the steps involved - also, my SQL may be incorrect/inefficient, if so, please feel free to correct it, and point out what was wrong with it). Thanks

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• Using parameterized function calls in SELECT statements. SQL Server

  - by geekzlla

  I have taken over some code from a previous developer and have come across this SQL statement that calls several SQL functions. As you can see, the function calls in the select statement pass a parameter to the function. How does the SQL statement know what value to replace the variable with? For the below sample, how does the query engine know what to replace nDeptID with when it calls, fn_SelDeptName_DeptID(nDeptID) nDeptID IS a column in table Note. SELECT STATEMENT: SELECT nCustomerID AS [Customer ID], nJobID AS [Job ID], dbo.fn_SelDeptName_DeptID(nDeptID) AS Department, nJobTaskID AS JobTaskID, dbo.fn_SelDeptTaskDesc_OpenTask(nJobID, nJobTaskID) AS Task, nStandardNoteID AS StandardNoteID, dbo.fn_SelNoteTypeDesc(nNoteID) AS [Note Type], dbo.fn_SelGPAStandardNote(nStandardNoteID) AS [Standard Note], nEntryDate AS [Entry Date], nUserName as [Added By], nType AS Type, nNote AS Note FROM Note WHERE nJobID = 844261 ORDER BY nJobID, Task, [Entry Date] ====================== Function fn_SelDeptName_DeptID: ALTER FUNCTION [dbo].[fn_SelDeptName_DeptID] (@iDeptID int) RETURNS varchar(25) -- Used by DataCollection for Job Tracking -- if the Deptartment isnt found return an empty string BEGIN -- Return the Department name for the given DeptID. DECLARE @strDeptName varchar(25) IF @iDeptID = 0 SET @strDeptName = '' ELSE BEGIN SET @strDeptName = (SELECT dName FROM Department WHERE dDeptID = @iDeptID) IF (@strDeptName IS NULL) SET @strDeptName = '' END RETURN @strDeptName END ========================== Thanks in advance.

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• connecting clients to server with emulator on different computers

  - by prolink007

  I am writing an application that communicates using sockets. I have a server running on one android emulator on a computer, then i have 2 other clients running on android emulators on 2 other computers. I am trying to get the 2 clients to connect to the server. This works when i run the server and clients on the same computer, but when i attempt to do this on the same wifi network and on separate computers it gives me the following error. The client and server code is posted below. A lot is stripped out just to show the important stuff. Also, after the server starts i telnet into the server and run these commands redir add tcp:5000:6000 (i have also tried without doing the redir but it still says the same thing). Then i start the clients and get the error. Thanks for the help! Both the 5000 port and 6000 port are open on my router. And i have windows firewall disabled on the computer hosting the server. 11-27 18:54:02.274: W/ActivityManager(60): Activity idle timeout for HistoryRecord{44cf0a30 school.cpe434.ClassAidClient/school.cpe434.ClassAid.ClassAidClient4Activity} 11-27 18:57:02.424: W/System.err(205): java.net.SocketException: The operation timed out 11-27 18:57:02.454: W/System.err(205): at org.apache.harmony.luni.platform.OSNetworkSystem.connectSocketImpl(Native Method) 11-27 18:57:02.454: W/System.err(205): at org.apache.harmony.luni.platform.OSNetworkSystem.connect(OSNetworkSystem.java:114) 11-27 18:57:02.465: W/System.err(205): at org.apache.harmony.luni.net.PlainSocketImpl.connect(PlainSocketImpl.java:245) 11-27 18:57:02.465: W/System.err(205): at org.apache.harmony.luni.net.PlainSocketImpl.connect(PlainSocketImpl.java:220) 11-27 18:57:02.465: W/System.err(205): at java.net.Socket.startupSocket(Socket.java:780) 11-27 18:57:02.465: W/System.err(205): at java.net.Socket.<init>(Socket.java:314) 11-27 18:57:02.465: W/System.err(205): at school.cpe434.ClassAid.ClassAidClient4Activity.onCreate(ClassAidClient4Activity.java:102) 11-27 18:57:02.474: W/System.err(205): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047) 11-27 18:57:02.474: W/System.err(205): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2459) 11-27 18:57:02.474: W/System.err(205): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2512) 11-27 18:57:02.474: W/System.err(205): at android.app.ActivityThread.access$2200(ActivityThread.java:119) 11-27 18:57:02.474: W/System.err(205): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1863) 11-27 18:57:02.474: W/System.err(205): at android.os.Handler.dispatchMessage(Handler.java:99) 11-27 18:57:02.474: W/System.err(205): at android.os.Looper.loop(Looper.java:123) 11-27 18:57:02.486: W/System.err(205): at android.app.ActivityThread.main(ActivityThread.java:4363) 11-27 18:57:02.486: W/System.err(205): at java.lang.reflect.Method.invokeNative(Native Method) 11-27 18:57:02.486: W/System.err(205): at java.lang.reflect.Method.invoke(Method.java:521) 11-27 18:57:02.486: W/System.err(205): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860) 11-27 18:57:02.486: W/System.err(205): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618) 11-27 18:57:02.486: W/System.err(205): at dalvik.system.NativeStart.main(Native Method) The server code public class ClassAidServer4Activity extends Activity { ServerSocket ss = null; String mClientMsg = ""; String mClientExtraMsg = ""; Thread myCommsThread = null; public static final int SERVERPORT = 6000; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); TextView tv = (TextView) findViewById(R.id.textView1); tv.setText("Nothing from client yet"); this.myCommsThread = new Thread(new CommsThread()); this.myCommsThread.start(); } class CommsThread implements Runnable { public void run() { // Socket s = null; try { ss = new ServerSocket(SERVERPORT ); } catch (IOException e1) { // TODO Auto-generated catch block e1.printStackTrace(); } while(true) { try { Socket socket = ss.accept(); connectedDeviceCount++; Thread lThread = new Thread(new ListeningThread(socket)); lThread.start(); } catch (IOException e) { e.printStackTrace(); } } } } class ListeningThread implements Runnable { private Socket s = null; public ListeningThread(Socket socket) { // TODO Auto-generated constructor stub this.s = socket; } @Override public void run() { // TODO Auto-generated method stub while (!Thread.currentThread().isInterrupted()) { Message m = new Message(); // m.what = QUESTION_ID; try { if (s == null) s = ss.accept(); BufferedReader input = new BufferedReader( new InputStreamReader(s.getInputStream())); String st = null; st = input.readLine(); String[] temp = parseReadMessage(st); mClientMsg = temp[1]; if(temp.length > 2) { mClientExtraMsg = temp[2]; } m.what = Integer.parseInt(temp[0]); myUpdateHandler.sendMessage(m); } catch (IOException e) { e.printStackTrace(); } } } } } The client code public class ClassAidClient4Activity extends Activity { //telnet localhost 5554 //redir add tcp:5000:6000 private Socket socket; private String serverIpAddress = "192.168.1.102"; private static final int REDIRECTED_SERVERPORT = 5000; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); try { InetAddress serverAddr = InetAddress.getByName(serverIpAddress); socket = new Socket(serverAddr, REDIRECTED_SERVERPORT); } catch (UnknownHostException e1) { mQuestionAdapter.add("UnknownHostException"); e1.printStackTrace(); } catch (IOException e1) { mQuestionAdapter.add("IOException"); e1.printStackTrace(); } } }

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• Why is this std::bind not converted to std::function?

  - by dauphic

  Why is the nested std::bind in the below code not implicitly converted to an std::function<void()> by any of the major compilers (VS2010/2012, gcc, clang)? Is this standard behavior, or a bug? #include <functional> void bar(int, std::function<void()>) { } void foo() { } int main() { std::function<void(int, std::function<void()>)> func; func = std::bind(bar, 5, std::bind(foo)); std::cin.get(); return 0; }

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• Howto read only one line via c++ from a data

  - by Markus Hupfauer

  i tryed to read the first line of a .dat data, but when i tryed to give to text, wich was saved in the .dat data, it print out the whole data, not only one line. the tool is also not looking after breaks or spaces :( Im using the following code: //Vocabel.dat wird eingelesen ifstream f; // Datei-Handle string s; f.open("Vocabeln.dat", ios::in); // Öffne Datei aus Parameter while (!f.eof()) // Solange noch Daten vorliegen { getline(f, s); // Lese eine Zeile cout << s; } f.close(); // Datei wieder schließen getchar(); . So could u help me please ? . Thanks a lot Markus

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• Same address, multiple shared_ptr counters, is it forbidden by C++ standard?

  - by icando

  Suppose I have some needs to do the following (This is just some imaginative code for discussion of the C++ standard, thus I won't discuss why I design it this way, so don't bother me something like: your design is wrong.) T* ptr = new T; shared_ptr<T> p(ptr); shared_ptr<T> q(ptr, SomeDeleterThatDoesnotDeleteButDoSomeOtherStuff()); Suppose the logic guarantees that p or some of its copies lives longer than any copies of q, so practically there won't be any problem. My question is, is it forbidden by C++ standard, e.g. explicitly stated as UB by C++ standard, that different shared_ptr counters share the same address? Thanks.

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• Construct a variadic template of unsigned int recursively

  - by Vincent

  I need a tricky thing in a C++ 2011 code. Currently, I have a metafunction of this kind : template<unsigned int N, unsigned int M> static constexpr unsigned int myFunction() This function can generate number based on N and M. I would like to write a metafunction with input N and M, and that will recursively construct a variadic template by decrementing M. For example, by calling this function with M = 3, It will construct a variadic template called List equal to : List... = myFunction<N, 3>, myFunction<N, 2>, myFunction<N, 1>, myFunction<N, 0> How to do that (if it is possible of course) ?

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• How can I make the storage of C++ lambda objects more efficient?

  - by Peter Ruderman

  I've been thinking about storing C++ lambda's lately. The standard advice you see on the Internet is to store the lambda in a std::function object. However, none of this advice ever considers the storage implications. It occurred to me that there must be some seriously black voodoo going on behind the scenes to make this work. Consider the following class that stores an integer value: class Simple { public: Simple( int value ) { puts( "Constructing simple!" ); this->value = value; } Simple( const Simple& rhs ) { puts( "Copying simple!" ); this->value = rhs.value; } Simple( Simple&& rhs ) { puts( "Moving simple!" ); this->value = rhs.value; } ~Simple() { puts( "Destroying simple!" ); } int Get() const { return this->value; } private: int value; }; Now, consider this simple program: int main() { Simple test( 5 ); std::function<int ()> f = [test] () { return test.Get(); }; printf( "%d\n", f() ); } This is the output I would hope to see from this program: Constructing simple! Copying simple! Moving simple! Destroying simple! 5 Destroying simple! Destroying simple! First, we create the value test. We create a local copy on the stack for the temporary lambda object. We then move the temporary lambda object into memory allocated by std::function. We destroy the temporary lambda. We print our output. We destroy the std::function. And finally, we destroy the test object. Needless to say, this is not what I see. When I compile this on Visual C++ 2010 (release or debug mode), I get this output: Constructing simple! Copying simple! Copying simple! Copying simple! Copying simple! Destroying simple! Destroying simple! Destroying simple! 5 Destroying simple! Destroying simple! Holy crap that's inefficient! Not only did the compiler fail to use my move constructor, but it generated and destroyed two apparently superfluous copies of the lambda during the assignment. So, here finally are the questions: (1) Is all this copying really necessary? (2) Is there some way to coerce the compiler into generating better code? Thanks for reading!

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• How to write these two queries for a simple data warehouse, using ANSI SQL?

  - by morpheous

  I am writing a simple data warehouse that will allow me to query the table to observe periodic (say weekly) changes in data, as well as changes in the change of the data (e.g. week to week change in the weekly sale amount). For the purposes of simplicity, I will present very simplified (almost trivialized) versions of the tables I am using here. The sales data table is a view and has the following structure: CREATE TABLE sales_data ( sales_time date NOT NULL, sales_amt double NOT NULL ) For the purpose of this question. I have left out other fields you would expect to see - like product_id, sales_person_id etc, etc, as they have no direct relevance to this question. AFAICT, the only fields that will be used in the query are the sales_time and the sales_amt fields (unless I am mistaken). I also have a date dimension table with the following structure: CREATE TABLE date_dimension ( id integer NOT NULL, datestamp date NOT NULL, day_part integer NOT NULL, week_part integer NOT NULL, month_part integer NOT NULL, qtr_part integer NOT NULL, year_part integer NOT NULL, ); which partition dates into reporting ranges. I need to write queries that will allow me to do the following: Return the change in week on week sales_amt for a specified period. For example the change between sales today and sales N days ago - where N is a positive integer (N == 7 in this case). Return the change in change of sales_amt for a specified period. For in (1). we calculated the week on week change. Now we want to know how that change is differs from the (week on week) change calculated last week. I am stuck however at this point, as SQL is my weakest skill. I would be grateful if an SQL master can explain how I can write these queries in a DB agnostic way (i.e. using ANSI SQL).

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• clang does not compile but g++ does

  - by user1095108

  Can someone help me with this code: #include <type_traits> #include <vector> struct nonsense { }; template <struct nonsense const* ptr, typename R> typename std::enable_if<!std::is_void<R>::value, int>::type fo(void* const) { return 0; } template <struct nonsense const* ptr, typename R> typename std::enable_if<std::is_void<R>::value, int>::type fo(void* const) { return 1; } typedef int (*func_type)(void*); template <std::size_t O> void run_me() { static struct nonsense data; typedef std::pair<char const* const, func_type> pair_type; std::vector<pair_type> v; v.push_back(pair_type{ "a", fo<&data, int> }); v.push_back(pair_type{ "b", fo<&data, void> }); } int main(int, char*[]) { run_me<2>(); return 0; } clang-3.3 does not compile this code, but g++-4.8.1 does, which of the two compiler is right? Is something wrong with the code, as I suspect? The error reads: a.cpp:32:15: error: no matching constructor for initialization of 'pair_type' (aka 'pair<const char *const, func_type>') v.push_back(pair_type{ "a", fo<&data, int> }); ^ ~~~~~~~~~~~~~~~~~~~~~~~ a.cpp:33:15: error: no matching constructor for initialization of 'pair_type' (aka 'pair<const char *const, func_type>') v.push_back(pair_type{ "b", fo<&data, void> }); ^ ~~~~~~~~~~~~~~~~~~~~~~~~

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