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• Connecting std::basic_ofstream<unsigned char> to a FIFO. bad_cast exceptions

  - by Mike B

  Using gcc 4.4.3 on Linux 2.6.32, I get bad_cast exceptions when connecting std::basic_ofstream to a FIFO. Stepping though the debugger, I can see that the error is generated at various places in the standard library because the _M_codecvt member of the stream or filebuf object is NULL. Exactly where it happens depends on the order of operations, but it appears to be the same cause in each. So am I doing something fundamentally stupid here? ofstream and ifstream work fine. Is there some reason that you shouldn't attach a stream of anything besides char to a FIFO? Thanks in advance.

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• How to implement square root and exponentiation on arbitrary length numbers?

  - by tomp

  I'm working on new data type for arbitrary length numbers (only non-negative integers) and I got stuck at implementing square root and exponentiation functions (only for natural exponents). Please help. I store the arbitrary length number as a string, so all operations are made char by char. Please don't include advices to use different (existing) library or other way to store the number than string. It's meant to be a programming exercise, not a real-world application, so optimization and performance are not so necessary. If you include code in your answer, I would prefer it to be in either pseudo-code or in C++. The important thing is the algorithm, not the implementation itself. Thanks for the help.

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• Displaying the error message from web service in jquery validation custom method

  - by Mrt

  Hello, I'm adding a custom method to jquery validation that calls a webservice, but the web service returns more then just a boolean. Is it possible to show the error based on return call of the web service. e.g. say I want an email address to be valid & not in use, so my web service checks this an returns 0 - ok, 1 - not valid, 2 - in use. How can I get jquery to show to correct error message based in the response ?

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• c++11 atomic ordering: extended total order memory_order_seq_cst for locks

  - by itaj

  There's this note in c++11 29.3-p3: [ Note: Although it is not explicitly required that S include locks, it can always be extended to an order that does include lock and unlock operations, since the ordering between those is already included in the "happens before" ordering. - end note ] What does it mean by "always"? I can understand that any certain implementation can be designed to support such an extended S. But in some general implementation that wasn't designed for it, I don't see that S can be extended so. I had sent this question to comp.std.c++ but got no answers there. http://groups.google.com/group/comp.std.c++/browse_frm/thread/5242fa70d0594d1b#

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• Whats the best data-structure for storing 2-tuple (a, b) which support adding, deleting tuples and c

  - by bhups

  Hi So here is my problem. I want to store 2-tuple (key, val) and want to perform following operations: - keys are strings and values are Integers - multiple keys can have same value - adding new tuples - updating any key with new value (any new value or updated value is greater than the previous one, like timestamps) - fetching all the keys with values less than or greater than given value - deleting tuples. Hash seems to be the obvious choice for updating the key's value but then lookups via values will be going to take longer (O(n)). The other option is balanced binary search tree with key and value switched. So now lookups via values will be fast (O(lg(n))) but updating a key will take (O(n)). So is there any data-structure which can be used to address these issues? Thanks.

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• Why do C++ streams use char instead of unsigned char?

  - by Johannes Schaub - litb

  I've always wondered why the C++ Standard library has instantiated basic_[io]stream and all its variants using the char type instead of the unsigned char type. char means (depending on whether it is signed or not) you can have overflow and underflow for operations like get(), which will lead to implementation-defined value of the variables involved. Another example is when you want to output a byte, unformatted, to an ostream using its put function. Any ideas? Note: I'm still not really convinced. So if you know the definitive answer, you can still post it indeed.

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• Where can I find soft-multiply and divide algorithms?

  - by srking

  I'm working on a micro-controller without hardware multiply and divide. I need to cook up software algorithms for these basic operations that are a nice balance of compact size and efficiency. My C compiler port will employ these algos, not the the C developers themselves. My google-fu is so far turning up mostly noise on this topic. Can anyone point me to something informative? I can use add/sub and shift instructions. Table lookup based algos might also work for me, but I'm a bit worried about cramming so much into the compiler's back-end...um, so to speak. Thanks!

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• What's currently the best way to extend Excel using C#?

  - by user169867

  I have the professional versions of VS2008 & VS2010. I wish to add a couple buttons to a toolbar in Excel. When they are clicked I'd like to be able to open a form (either WinForms or WPF is fine) collect a few values from the user in the form and then take that data + read cell values from the current worksheet to perform some database operations. What's currently the best way to do this using C#? I'd greatly appreciate a pointer to any examples / tutorials. My understanding is that VS2010 has improved the process alot but I may have to deal w/ Excel 2003 which I don't think it supports. I get confused between Visual Studio 2008s Extensibility-Shared Addin template and other Office Addin templates I've seen. I'm not sure when which type of solution is appropriate. I'm new to Office development so I'd really appreciate any help to get me going on the right track. Thanks much.

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• Saving CFPropertyLists To Users Folder

  - by stephen blinkhorn

  I'm trying to save a CFPropertyList to a location in the user's home folder. Using the code below I'm getting errorCode = -10 (unknown error). CFURLRef fileURL = CFURLCreateWithFileSystemPath(kCFAllocatorDefault, CFSTR("~/testfile.txt"), kCFURLPOSIXPathStyle, false ); SInt32 errorCode; Boolean status = CFURLWriteDataAndPropertiesToResource(fileURL, xmlData, NULL, &errorCode); If I change the path to something like "/testfile.txt" without the '~' then everything works. How can one save a property list to the current user's home folder? Must one obtain the user's name first and include it in the path such as /users/toffler/testfile.txt?

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• Primary reasons why programming language runtimes use stacks?

  - by manuel aldana

  Many programming language runtime environments use stacks as their primary storage structure (e.g. see JVM bytecode to runtime example). Quickly recalling I see following advantages: Simple structure (pop/push), trivial to implement Most processors are anyway optimized for stack operations, so it is very fast Less problems with memory fragmentation, it is always about moving memory-pointer up and down for allocation and freeing complete blocks of memory by resetting the pointer to the last entry offset. Is the list complete or did I miss something? Are there programming language runtime environments which are not using stacks for storage at all?

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• How to make a cell of TAdvStringGrid editable?

  - by ammu

  I am trying to implement a filter using the component TAdvStringGrid. My requirement is that I want the first row of this component to be editable when double clicked, so that the user can filter data. Borland C++ Builder is used to help achieve this task. I found this event OnCanEditCell. TCanEditCellEvent = procedure (Sender:TObject;Arow,Acol:longint;var canedit:boolean) of object; Within this function I've set canedit = true. This doesn't seem to work. Probably I need to do something more. I am new to Windows and GUI development. So any help would be great. Do I need to call this function from the OnDblClickCell event? How can I get it working? Thanks in advance

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• Error : Implementation for method missing (Delphi Prism)

  - by Ilya

  I wrote my method: LangChange type MainForm = partial class(System.Windows.Forms.Form) private ... method LangChange(); protected method Dispose(disposing: Boolean); override; public constructor; end; implementation ... method LangChange(); begin ... end; However,I have an error Error 1 (PE33) Implementation for method "Compiler.MainForm.LangChange" missing What is wrong?Help please!

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• Java: JSP halt execution on rest of page

  - by bguiz

  Hi, How do you stop a JSP from executing? I have JSPs which kick the user off a page by means of a "forward". public boolean kickIfNotLoggedIn( HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { //code to check if user is logged in req.getRequestDispatcher( ACCESS_DENIED_PAGE).forward(request, response); } In my JSP, I have this code, BEFORE any HTML output: <% //loginHelper.kickIfNotLoggedIn(request, response); if (!loginHelper.kickIfNotLoggedIn(request, response)) { return; } %> If I don't use the return statement, the JSP continues processing, and I get a NullPointerException. If I use the return statement (as is commonly suggested on various sources on the net), I get an IllegalStateException: StandardWrapperValve[jsp]: PWC1406: Servlet.service() for servlet jsp threw exception java.lang.IllegalStateException: PWC3991: getOutputStream() has already been called for this response at org.apache.coyote.tomcat5.CoyoteResponse.getWriter(CoyoteResponse.java:717) at org.apache.coyote.tomcat5.CoyoteResponseFacade.getWriter(CoyoteResponseFacade.java:226) at org.apache.jasper.runtime.JspWriterImpl.initOut(JspWriterImpl.java:187) Any ideas how to fix this, or another way to achieve an access denied page? Thanks

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• Performance implications of finalizers on JVM

  - by Alexey Romanov

  According to this post, in .Net, Finalizers are actually even worse than that. Besides that they run late (which is indeed a serious problem for many kinds of resources), they are also less powerful because they can only perform a subset of the operations allowed in a destructor (e.g., a finalizer cannot reliably use other objects, whereas a destructor can), and even when writing in that subset finalizers are extremely difficult to write correctly. And collecting finalizable objects is expensive: Each finalizable object, and the potentially huge graph of objects reachable from it, is promoted to the next GC generation, which makes it more expensive to collect by some large multiple. Does this also apply to JVMs in general and to HotSpot in particular?

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• Android internet connectivity check problem

  - by Chaoz

  Hello, I'm new to Android development and working on an Android application that requires the phone to be connected to the internet, through either Wifi, EDGE or 3G. This is the code that I'm using: public static boolean isConnected() { ConnectivityManager cm = (ConnectivityManager) getSystemService(Context.CONNECTIVITY_SERVICE); return cm.getActiveNetworkInfo().isConnectedOrConnecting(); } I've also set these permissions in the manifest file: <uses-permission android:name="android.permission.INTERNET" /> <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" /> This works fine in the emulator running version 1.5 of Android when 3G is enabled, but it crashes when I disable the 3G connection. My application throws a null pointer exception when I call isConnectedOrConnecting(). Hope that anyone knows the solution to this. Thanks in advance!

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• Conditionally required jsf validation in a4j form

  - by volothamp

  Hello, I'm having a little problem with using conditionally evaluated expression in jsf/a4j Here's my code <a4j:form> <h:inputText id="id1" value="#{mybean.myvalue}" size="1" required="#{not mybean.condition}" rendered="#{not mybean.condition}" requiredMessage="Put a number in here" /> <h:selectBooleanCheckbox value="#{mybean.condition}"> <a4j:support event="onclick" reRender="id1"/> </h:selectBooleanCheckbox> <a4j:commandButton action="#{mybean.myaction}" value="Do something" /> </a4j:form> The boolean checkbox conditionally enable/disable the validation. This doesn't work: the a4j:commandButton simply skip the validation. Thanks.

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• Sql Server 2000 Stored Procedure Prevent Parallelism or something?

  - by user187305

  I have a huge disgusting stored procedure that wasn't slow a couple months ago, but now is. I barely know what this thing does and I am in no way interested in rewriting it. I do know that if I take the body of the stored procedure and then declare/set the values of the parameters and run it in query analyzer that it runs more than 20x faster. From the internet, I've read that this is probably due to a bad cached query plan. So, I've tried running the sp with "WITH RECOMPILE" after the EXEC and I've also tried putting the "WITH RECOMPLE" inside the sp, but neither of those helped even a little bit. When I look at the execution plan of the sp vs the query, the biggest difference is that the sp has "Parallelism" operations all over the place and the query doesn't have any. Can this be the cause of the difference in speeds? Thank you, any ideas would be great... I'm stuck.

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• How can I get jcifs to play nicely with apache axis

  - by Ben Hammond

  I need to connect Apache Axis 1.4 to a Webservice that uses NTLM authentication to restrict access to its operations. I'm expecting to use Samba Jcifs to handle the NTLM handshake. I found http://hc.apache.org/httpcomponents-client/ntlm.html which gives me fantastic directions for how to wire up HttpClient 4.0 with jcifs. Trouble is, Axis wants to use Http Client 3.0 and the two apis look very different. There are 2 possibilities that I can see Write an object for Axis that lets it plug into HttpClient 4. Figure out how to wire HttpClient 3.0 up with Samba Jcifs. Number 1. looks non-trivial, but possible Number 2. I cannot find any encouraging messages on the web describing how to do this. My question is: has anyone successfully connected samba jcifs with HttpClient 3.0 ? Has anyone already created an Axis HttpSender object that works with HttpClient 4 ? Is there some better alternative that I have not considered?

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• How might one implement FileTimeToSystemTime?

  - by Billy ONeal

  Hello :) I'm writing a simple wrapper around the Win32 FILETIME structure. boost::datetime has most of what I want, except I need whatever date type I end up using to interpolate with Windows APIs without issues. To that end, I've decided to write my own things for doing this -- most of the operations aren't all that complicated. I'm implementing the TimeSpan - like type at this point, but I'm unsure how I'd implement FileTimeToSystemTime. I could just use the system's built-in FileTimeToSystemTime function, except FileTimeToSystemTime cannot handle negative dates -- I need to be able to represent something like "-12 seconds". How should something like this be implemented? Billy3

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• about the post_save signal and created argument

  - by panchicore

  the docs says: post_save django.db.models.signals.post_save created A boolean; True if a -new- record was create. and I have this: from django.db.models.signals import post_save def handle_new_user(sender, instance, created, **kwargs): print "--------> save() "+str(created) post_save.connect(handle_new_user, sender=User) when I do in shell: u = User(username="cat") u.save() >>> --------> save() True u.username = "dog" u.save() >>> --------> save() True I expect a -------- save() False when I save() the second time because is an update? not?

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• Comparing datetimes does not work

  - by Koning Baard XIV

  I'm creating a Rails application which uses MySQL. I have a table in my DB like this: create_table "pastes", :force => true do |t| t.string "title" t.text "body" t.string "syntax" t.boolean "private" t.datetime "expire" t.string "password" t.datetime "created_at" t.datetime "updated_at" end I want to show only the non-expired pastes to people, so I do this: @pastes = Paste.find(:all, :conditions => "expire < '#{Time.now.strftime('%Y-%m-%d %H:%M:%S')}'") However, even that returns ALL pastes. Not just those that are not expired yet. Can anyone help me? Thanks Oh, changing < to > returns no pastes, not even the non-expired ones :(

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• Tridion Core Service - Transaction roll back isnt working

  - by Tamir Lahav

  We are using the core service in ASP.NET custom page in order to create pages and components and sevenral updates (checkout,save and chekin). we want those operations to work in transaction, we tried to implement it acording to some examples over the net. However we didn't succeded operating the rollback. It seems that the operation are immediately performed without waiting for the comit . The code we used for simple check out - roll back operation for example is TransactionOptions txOptions = new TransactionOptions { IsolationLevel = IsolationLevel.ReadCommitted }; using (TransactionScope scope = new TransactionScope( TransactionScopeOption.Required, txOptions)) { using (CoreService2010Client m_client = new CoreService2010Client()) { PageData pp = m_client.CheckOut("tcm:309-36311-64", false, new ReadOptions()) as PageData; } scope.Dispose(); } We also added this recomended configuration to the web config bindings section What are we missing ?

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• How to use a object whose copy constructor and copy assignment is private?

  - by coanor

  In reading TCPL, I got a problem, as the title refered, and then 'private' class is: class Unique_handle { private: Unique_handle& operator=(const Unique_handle &rhs); Unique_handle(const Unique_handle &rhs); public: //... }; the using code is: struct Y { //... Unique_handle obj; }; and I want to execute such operations: int main() { Y y1; Y y2 = y1; } although, these code are come from TCPL, but I still can not got the solution... Can anybody help me, appreciate.

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• Why is forwarding variadic parameters invalid?

  - by awesomeyi

  Consider the variadic function parameter: func foo(bar:Int...) -> () { } Here foo can accept multiple arguments, eg foo(5,4). I am curious about the type of Int... and its supported operations. For example, why is this invalid? func foo2(bar2:Int...) -> () { foo(bar2); } Gives a error: Could not find an overload for '_conversion' that accepts the supplied arguments Why is forwarding variadic parameters invalid? What is the "conversion" the compiler is complaining about?

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• ContextSwitchDeadlock Was Detected error in C#

  - by assassin

  Hi, I am running a C# application, and during run-time I get the following error: The CLR has been unable to transition from COM context 0x20e480 to COM context 0x20e5f0 for 60 seconds. The thread that owns the destination context/apartment is most likely either doing a non pumping wait or processing a very long running operation without pumping Windows messages. This situation generally has a negative performance impact and may even lead to the application becoming non responsive or memory usage accumulating continually over time. To avoid this problem, all single threaded apartment (STA) threads should use pumping wait primitives (such as CoWaitForMultipleHandles) and routinely pump messages during long running operations. Can anyone please help me out with the problem here? Thanks a lot.

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