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  • Forcing a templated object to construct from a pointer

    - by SalamiArmi
    I have a fictional class: template<typename T> class demonstration { public: demonstration(){} ... T *m_data; } At some point in the program's execution, I want to set m_data to a big block of allocated memory and construct an object T there. At the moment, I've been using this code: void construct() { *m_data = T(); } Which I've now realised is probably not the best idea... wont work under certain cirumstances, if T has a private assignment operator for example. Is there a normal/better way to do what I'm attempting here?

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  • On Memory Allocation and C++

    - by Arpan
    And I quote from MSDN http://msdn.microsoft.com/en-us/library/aa366533(VS.85).aspx: The malloc function has the disadvantage of being run-time dependent. The new operator has the disadvantage of being compiler dependent and language dependent. Now the questions folks: a) What do we mean that malloc is run-time dependent? What kind of dynamic memory allocation functions can be independent of run-time? This statement sounds real strange. b) new is language dependent? Of course it should be right? Are HeapAlloc, LocalAlloc etc language independent? c) From a pure performance perspective are the MSVC provided routines preferable? Arpan

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  • Simple explaination of Arraylists

    - by Jeremy
    I'm new to programming and I'm looking for a simple answer to build my foundation of understanding Arrays. I've used google and searched this site. After a bit of trial and error I get how to make and reference Arrays like thing[3] gets you the fourth thing in the thing array(since 0 is the first). which lets me do something like thing[3].getStupidNumber() to get the StupidNumber of the 4th thing in the thing array. Then I get to ArrayLists which seem to have much more utility but I cant make logical sense of them like Arrays. When i search I cant find this or word this correctly and thus far everything else I've learned clicked easily. so say I make an ArrayList thing with 5 things in it. how do i get to the .getStupidNumber() method inside the fourth thing, if possible? I think if I learn this I can learn the rest on my own. Thanks!

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  • Full GC real time is much more that user+sys times

    - by Stas
    Hi. We have a Web Java based application running on JBoss with allowed maximum heap size of about 1.2 GB (total machine physical memory is 2 GB). At some point the application stops responding (to clients) for several minutes. After some analysis we found out that the culprit is the Full GC. Here's an excerpt from the verbose GC log: 74477.402: [Full GC [PSYoungGen: 3648K-0K(332160K)] [PSOldGen: 778476K-589497K(819200K)] 782124K-589497K(1151360K) [PSPermGen: 102671K-102671K(171328K)], 646.1546860 secs] [Times: user=3.84 sys=3.72, real=646.17 secs] What I don't understand is how is it possible that the real time spent on Full GC is about 11 minutes (646 seconds), while user+sys times are just 7.5 seconds. 7.5 seconds sound to me much more logical time to spend for cleaning <200 MB from the old generation. Where does all the other time go? Thanks a lot.

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  • Boost::asio bug in MSVC10 - Failing BOOST_WORKAROUND in ~buffer_debug_check() in buffer.hpp

    - by shaz
    A straight compilation of example http://www.boost.org/doc/libs/1_43_0/doc/html/boost_asio/tutorial/tutdaytime3/src.html results in a runtime null pointer exception. Stack trace points to the buffer_debug_check destructor which contains this comment: // MSVC's string iterator checking may crash in a std::string::iterator // object's destructor when the iterator points to an already-destroyed // std::string object, unless the iterator is cleared first. The test #if BOOST_WORKAROUND(BOOST_MSVC, = 1400) succeeds in MSVC10 and (but) results in a null pointer exception in c:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\include\xutility line 123 _Iterator_base12& operator=(const _Iterator_base12& _Right) { // assign an iterator if (_Myproxy != _Right._Myproxy) _Adopt(_Right._Myproxy->_Mycont); return (*this); } _Right._Myproxy is NULL

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  • Purpose of boost::checked_delete

    - by Channel72
    I don't understand the purpose of boost::checked_delete. The documentation says: The C++ Standard allows, in 5.3.5/5, pointers to incomplete class types to be deleted with a delete-expression. When the class has a non-trivial destructor, or a class-specific operator delete, the behavior is undefined. Some compilers issue a warning when an incomplete type is deleted, but unfortunately, not all do, and programmers sometimes ignore or disable warnings. The supplied function and class templates can be used to prevent these problems, as they require a complete type, and cause a compilation error otherwise. So the C++ standard allows you to delete incomplete types, which causes undefined behavior if the type has a non-trivial destructor. What? How can an incomplete type have any destructor at all? Isn't an incomplete type just a prototype?

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  • Double Inner Join generates unexpected error

    - by Itamar Marom
    In my database I have three tables: Users: UserID (Auto Numbering), UserName, UserPassword and a few other unimportant fields. PrivateMessages: MessageID (Auto Numbering), SenderID and a few other fields defining the message content. MessageStatus: MessageID, ReceiverID, MessageWasRead (Boolean) What I need is a query to which I input a user's id and I get all the private messages he has received. In addition, I also need to receive each message's sender UserName. For this I wrote the following query: SELECT Users.*, PrivateMessages.*, MessageStatus.* FROM PrivateMessages INNER JOIN Users ON PrivateMessages.SenderID = Users.UserID INNER JOIN MessageStatus ON PrivateMessages.MessageID = MessageStatus.MessageID WHERE MessageStatus.ReceiverID=[@userid]; But for some reason when I try saving it in my Access database, I get the following error (translated to English by me, since my office is in a different language): Syntax error (missing operator) at expression: "PrivateMessages.SenderID = Users.UserID INNER JOIN MessageStatus ON PrivateMessages.MessageID = MessageStatus.MessageI". Any ideas what could cause this? Thanks.

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  • C++, create an instance from a static method

    - by Manux
    Hello, let's say I want my users to use only one class, say SpecialData. Now, this data class would have many methods, and depending on the type of data, the methods do different things, internally, but return externally similar results. Therefore my wanting to have one "public" class and other "private", child classes that would change the behavior of methods, etc... It would be amazingly more simple for some types of data that need to be built to do something like this: SpecialData& sm = SpecialData::new_supermatrix(); and new_supermatrix() would return a SuperMatrix instance, which inherits from most behaviors of SpecialData. my header: static SpecialData& new_supermatrix(); my cpp: SpecialData& SpecialData::new_supermatrix()(){ return SuperMatrix(MATRIX_DEFAULT_MAGNITUDE,1000,1239,FLOAT32,etc...); } The problem is, I get this error, which is probably logical due to the circumstances: invalid initialization of non-const reference of type ‘SpecialData&’ from a temporary of type ‘SpecialData’ So, any ideas?

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  • C++ refactor common code with one different statement

    - by user231536
    I have two methods f(vector<int>& x, ....) and g(DBConn& x, ....) where the (....) parameters are all identical. The code inside the two methods are completely identical except for one statement where we do different actions based on the type of x: in f(): we do x.push_back(i) in g(): we do x.DeleteRow(i) What is the simplest way to extract the common code into one method and yet have the two different statements? I am thinking of having a templated functor that overloads operator () (int a) but that seems overkill.

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  • SQL Server 2005 - Understanding ouput of DBCC SHOWCONTIG

    - by user169743
    I'm seeing some slow performance on a SQL Server 2005 database. I've been doing some research regarding SQL Server performance but I'm having difficulty fully understanding the output of SHOWCONTIG and would be very grateful if someone could have a look and offer some suggestions to improve performance. TABLE level scan performed. Pages Scanned................................: 19348 Extents Scanned..............................: 2427 Extent Switches..............................: 3829 Avg. Pages per Extent........................: 8.0 Scan Density [Best Count:Actual Count].......: 63.16% [2419:3830] Logical Scan Fragmentation ..................: 8.40% Extent Scan Fragmentation ...................: 35.15% Avg. Bytes Free per Page.....................: 938.1 Avg. Page Density (full).....................: 88.41%

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  • Passenger problem: "no such file to load" -- /config/environment

    - by Mason Jones
    I've been researching this one and found references to similar problems here and there, but none of them has led to a solution yet. I've installed passenger (2.2.11) and nginx (0.7.64) and when I start things up and hit a Rails URL, I get an error page informing me of a load error: no such file to load -- /path/to/app/config/environment From what I've found online this appears to be some sort of a user/permissions error, but I've tried all the logical fixes: I've made sure that /config/environment.rb is not owned by root, but by a webapp user. I've tried setting passenger_default_user, I've tried setting passenger_user_switching off. I've even tried setting the nginx user, though that shouldn't matter much. I've gotten some differing results, but nothing's actually worked. I'm hoping someone may have the magical combination of settings and permissions for this. I may try backing down to an earlier version of Passenger, because I've never had this issue before; it's been a little while since I set up Passenger though. Thanks for any suggestions.

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  • DependencyProperty Orientation problem

    - by byte
    I am learning WPF and am trying to create my first UserControl. My UserControl consists of StackPanel StackPanel contains a Label and TextBox I am trying to create two Dependency Properties Text for the Label Orientation for the StackPanel - The orientation will affect the position of the Label and TextBox effectively I have successfully created a Text dependency property and bind it to my UserControls . But when I created the Orientation property, I seem to get following error in get property The as operator must be used with a reference type or nullable type ('System.Windows.Controls.Orientation' is a non-nullable value type) public static DependencyProperty OrientationProperty = DependencyProperty.Register("Orientation", typeof(System.Windows.Controls.Orientation), typeof(MyControl), new PropertyMetadata((System.Windows.Controls.Orientation)(Orientation.Horizontal))); public Orientation Orientation { get { return GetValue(OrientationProperty) as System.Windows.Controls.Orientation; } set { SetValue(OrientationProperty, value); } } Appreciate your help.

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  • C++ Array of pointers: delete or delete []?

    - by Jasper
    Cosider the following code: class Foo { Monster* monsters[6]; Foo() { for (int i = 0; i < 6; i++) { monsters[i] = new Monster(); } } virtual ~Foo(); } What is the correct destructor? this: Foo::~Foo() { delete [] monsters; } or this: Foo::~Foo() { for (int i = 0; i < 6; i++) { delete monsters[i]; } } I currently have the uppermost constructor and everything is working okey, but of course I cannot see if it happens to be leaking... Personally, I think the second version is much more logical considering what I am doing. Anyway, what is the "proper" way to do this?

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  • MS SQL 2005 - Understanding ouput of DBCC SHOWCONTIG

    - by user169743
    I'm seeing some slow performance on a MS SQL 2005 database. I've been doing some research regarding MS SQL performance but I'm having difficulty fully understanding the output of SHOWCONTIG and would be very grateful if someone could have a look and offer some suggestions to improve performance. TABLE level scan performed. Pages Scanned................................: 19348 Extents Scanned..............................: 2427 Extent Switches..............................: 3829 Avg. Pages per Extent........................: 8.0 Scan Density [Best Count:Actual Count].......: 63.16% [2419:3830] Logical Scan Fragmentation ..................: 8.40% Extent Scan Fragmentation ...................: 35.15% Avg. Bytes Free per Page.....................: 938.1 Avg. Page Density (full).....................: 88.41%

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  • Inserting into an Associative array?

    - by RedShft
    I'm playing around with associative arrays right now and I can't seem to figure out how to add additional objects to the array. I tried insert but it doesn't recognize both arguments. Also, if I do this it produces an error: Node[bool] test; Node node; Node[bool] temp = [ false:node ]; test ~= temp; //Error 1 Error: cannot append type Node[bool] to type //Node[bool] C:\Users\CP\Documents\Visual Studio //2010\Projects\D\STDS\NPC.d 256 Does this mean you can't use the append operator on associative arrays ?

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  • C++ Segmentation fault in binary_function

    - by noryb009
    I'm using Visual Studio 2010 Beta 2 (also tried with NetBeans), and I'm having a segmentation fault in the following code: // One of the @link s20_3_3_comparisons comparison functors@endlink. template <class _Tp> struct less : public binary_function<_Tp, _Tp, bool> { bool operator()(const _Tp& __x, const _Tp& __y) const { return __x < __y; } //this is the problem line }; I don't know what in my program calls it, but I am trying to find out. (I think it's a map) Does anyone know what to do, or has encountered this before?

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  • I need to do a BASICE For Loop algorithm for a java Pyramid

    - by user1665119
    Question 2. USE THE FOR LOOP. Design and write an algorithm that will read a single positive number from the keyboard and will then print a pyramid out on the screen. The pyramid will need to be of a height equal in lines to the number inputted by the operator. Your program is not to test for negative numbers, nor is it to cater for them. For your test, use the number 7. If you would like to take the problem further, try 18 and watch what happens. Example input: 4 Example output: 1 121 12321 1234321

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  • How to test Text Search accuracy and efficiency?

    - by DEN
    I have created a web application. One of the feature is text search which perform the boolean operator ( NOT, AND, OR) as well. However, I have no idea on calculating the search's accuracy and efficiency. For example: 1 . Probe identification system for a measurement instrument 2 . Pulse-based impedance measurement instrument 3 . Millimeter with filtered measurement mode when the user key in will return the result as below input :measurement instrument Result: 1,2 input : measurement OR instrument NOT milimeter Result: 1,2,3 so, i have no idea on what issue and what algorithm to calculate on the accuracy and efficiency of the text search.. anyone have any idea on that?

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  • new with exception with Microsoft

    - by wsd
    As I'm coding for both Windows and Linux, I have a whole host of problems. Microsoft Visual C++ has no stdint header, but for that I wrote my own. Now I found out that MS C++'s new operator does not throw an exception, so I want to fix this a quickly as possible. I know I can define a Macro with Parameters in Parenthesis, can I define a macro that replaces MyClass x = new MyClass(); with #ifdef MSC_VER if(!(MyClass x = new MyClass()) { throw new std::bad_alloc(); } #else MyClass x = new MyClass(); #endif (or something equivalent), AND works in BOTH MS C++ and G++ ? Or alternatively if that is not possible, a batch file to run over the Code to do this? I have become rather dependent on this exception being thrown.

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  • How to Detect Trusted Connection in Crystal Reports using VB.NET?

    - by Michael
    I have some Crystal Reports connecting to a Sql Server db that I would like to detect whether the connection is trusted or whether I need to supply the log on info (reports are not supplied by me so I can't control the connect method). If I just blindly supply login credentials, it won't connect if it is a trusted connection. The following does not work: oRpt = oCR.OpenReport("C:\MyReport.rpt") if oRpt.Database.Tables(1).ConnectionProperties.Item("Integrated Security") = True then 'trusted connection else 'supply login credentials end if It gives the following error: Operator '=' is not defined for type 'IConnectionProperty' and type 'Boolean'. I cannot find how create a construct in vb.net for IConnectionProperty. I can't find any documents from Crystal that explain it. I am using Crystal Reports XI - Developer

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  • Possible to fire asp.net validation from jQuery?

    - by Abe Miessler
    I have a form with several text boxes on it. I only want to accept floats, but it is likely that users will enter a dollar sign. I'm using the following code to remove dollar signs and validate the content: jQuery: $("#<%= tb.ClientID %>").change(function() { var ctrl = $("#<%= tb.ClientID %>"); ctrl.val(ctrl.val().replace('$','')) }); asp.net validation: <asp:CompareValidator ID="CompareValidator4" runat="server" Type="Double" ControlToValidate="tb" Operator="DataTypeCheck" ValidationGroup="vld_Page" ErrorMessage="Some error" /> My problem is that when someone enters a dollar sign in the TextBox "tb" and changes focus the validation happens first and THEN the jQuery removes the dollar sign. Is it possible to have the jQuery run first or to force the validation to run again after the jQuery executes?

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  • How do I do proximity search in Oracle right?

    - by hko19
    Oracle's NEAR operator for full text search returns a score based on the proximity of two or more query terms. For example: near((dog, bite), 6) matches if 'dog' and 'bite' occurs within 6 words. What if I'd like it to match if either 'dog' or 'cat' or any other type of animal occurs within 6 words of the word 'bite'? I tried: near(((dog OR cat OR animal), bite), 6) but I got: NEAR operand not a phrase, equivalence or another NEAR expression Rather than expanding all possible combination into multiple NEAR and 'or' them together, what is the proper way to write such query?

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  • Data Usage Checker Tools

    - by Lucifer
    Hey All, I am about to begin a project for a new client, and am worried about a few things concerning data usage on their internet plan. We're in an area where most of the major networks don't cover the area, and the ones that do, have very expensive plans, with very low data allowance per month. I need to develop an app, but part of the problem lies with checking database values every 30 seconds. It's pretty important that this check is happening every 30 seconds, as the database is actually updated all day everyday, approx. every 5seconds (apparently). Each row in the database consists of about a page full of text if you were to paste it into MS Word. So, are there any logical ways of minimizing data usage in my case, and also how am I able to see exactly how much data is used just to establish a connection to the database? Are there any tools for this kind of info? Thanks :)

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  • What are the differences between these three patterns of "class" definitions in JavaScript?

    - by user1889765
    Are there any important/subtle/significant differences under the hood when choosing to use one of these three patterns over the others? And, are there any differences between the three when "instantiated" via Object.create() vs the new operator? The pattern that CoffeeScript uses when translating "class" definitions: Animal = (function() { function Animal(name) { this.name = name; } Animal.prototype.move = function(meters) { return alert(this.name + (" moved " + meters + "m.")); }; return Animal; })(); and The pattern that Knockout seems to promote: var DifferentAnimal = function(name){ var self = this; self.name = name; self.move = function(meters){ return alert(this.name + (" moved " + meters + "m.")); }; return {name:self.name, move:self.move}; } and The pattern that Backbone promotes: var OneMoreAnimal= ClassThatAlreadyExists.extend({ name:'', move:function(){} });

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  • Core Data NSFetchedResultsController sorting in certain sequence

    - by Moze
    I'm writing iphone app that has UITableView and uses Core Data. Data in UITableView is shown using NSFetchedResultsController. I use NSPredicate operator "IN" to fetch only needed entries. NSArray *filterArray = [NSArray arrayWithObjects:@"789", @"963", @"445", @"198", nil]; NSPredicate *predicate = [NSPredicate predicateWithFormat:@"id IN %@", filterArray]; Now the problem is that I need to show entries in same sequence they are in filterArray. How can I do it? How I can create NSSortDescriptor that would sort all entries in that way? I tried without sort descriptor, but I get error that NSFetchedResultsController needs sortDescriptor to be set.

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