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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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  • Php getting too many connections error from MySQL

    - by uzioriluzan
    Hello everyone, I am using MySQL and PHP with 2 application servers and 1 database server. With the increase of the number of users (around 1000 by now), I'm getting the following error : SQLSTATE[08004] [1040] Too many connections The parameter "max_connections" is set to "1000" in my.cnf and "mysql.max_persistent" is set to -1 in php.ini. There are at most 1500 apache processes running at a time since the "MaxClients" apache parameter is equal to 750 and we have 2 application servers. Should I raise the "max_connections" to 1500 as indicated in here? Or should I set "mysql.max_persistent" to 750 (we use PDO with persistent connections for performance reasons since the database server is not the same as the application servers)? Or should I try something else? Thanks in advance!

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  • How can I find out how many rows of a matrix satisfy a rather complicated criterion (in R)?

    - by Brani
    As an example, here is a way to get a matrix of all possible outcomes of rolling 4 (fair) dice. z <- as.matrix(expand.grid(c(1:6),c(1:6),c(1:6),c(1:6))) As you may already have understood, I'm trying to work out a question that was closed, though, in my opinion, it's a challenging one. I used counting techniques to solve it (I mean by hand) and I finaly arrived to a number of outcomes, with a sum of subset being 5, equal to 1083 out of 1296. That result is consistent with the answers provided to that question, before it was closed. I was wondering how could that subset of outcomes (say z1, where dim(z1) = [1083,4] ) be generated using R. Do you have any ideas? Thank you.

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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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  • 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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  • How do I change the list using mutable lists in Racket or Scheme?

    - by exOne
    I need your help Can anyone help me? first question This procedure should modify each element which’s index in the list is even. The value of the element should be equal to the new-element. For example: (define number-list (1 56 8 1 43 9 78)) (modify-even-indices number-list 10) The new list: 1 10 8 10 43 10 78 second question This problem is the extended version of Question 1. (modify-even-odd-indices my-list new-element modification-type) This procedure should modify each element according to the modification-type. The modification-type can be even or odd. For example: (define number-list (1 56 8 1 43 9 78)) (modify-even-odd-indices number-list 10 ‘even’) The new list: 1 10 8 10 43 10 78 (modify-even-odd-indices number-list 10 ‘odd’) The new list: 10 56 10 1 10 9 10

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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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  • How to validate the following

    - by user281180
    I have the following code <% using(Ajax.BeginForm("UpdatePassword", new AjaxOptions{UpdateTargetId="Password"})) { %> <div id="Password"> <table> <tr> <td>New password</td><td><%=Html.Password("newPassword") %></td> </tr> <tr> <td>Confirm new password</td> <td><%=Html.Password("confirmPassword")%><%= Html.ValidationMessage("confirmPassword") %> </td> </tr> </table> <% } % Can someone help me how to proceed to validating that the confirmPassword is equal the new password, and if not the message is displayed in the html.validationMessage()...

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  • How it is better to organise a large database of addresses?

    - by shurik2533
    How it is better to organise a large database of addresses? It is need to create mysql database of addresses. How it is better for organising? I have two variants: 1) cuontries id|name 1 |Russia cities id|name 1 |Moscow 2 |Saratov villages id|name streets id|name 1 |Lenin st. places id|name |country_id|city_id|village_id|street_id|building_number|office|flat_number|room_number 1 |somebuilding |1 |1 |NULL |1 |31 |12a |NULL |NULL For simplification I use not all making addresses. If any part does not participate in the address it is equal NULL 2) addressElements id|name 1 |country 2 |city 3 |village 4 |street 5 |office 6 |flat_number 7 |room_number addressValues id|addressElement_id|value 1 |1 |Russia 2 |2 |Saratov 3 |2 |Moscow 4 |3 |Prostokvashino 5 |4 |Lenin st. places id| name 1 | somebuilding places_has_addressValues place_id|addressValue_id 1 |1 1 |3 1 |5 UPD. I have decided to make as follows

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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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  • php nested for statements?

    - by Dashiell0415
    I'm trying to process a for loop within a for loop, and just a little wary of the syntax... Will this work? Essentially, I want to run code for every 1,000 records while the count is equal to or less than the $count... Will the syntax below work, or is there a better way? for($x = 0; $x <= 700000; $x++) { for($i = 0; $i <= 1000; $i++) { //run the code } }

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  • Filter objects within two seconds of one another using SQLAlchemy

    - by Arrieta
    Hello: I have two tables with a column 'date'. One holds (name, date) and the other holds (date, p1, p2). Given a name, I want to use the date in table 1 to query p1 and p2 from table two; the match should happen if date in table one is within two seconds of date in table two. How can you accomplish this using SQLAlchemy? I've tried (unsuccessfully) to use the between operator and with a clause like: td = datetime.timedelta(seconds=2) q = session.query(table1, table2).filter(table1.name=='my_name').\ filter(between(table1.date, table2.date - td, table2.date + td)) Any thoughts?

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  • sql boolean truth test: zero OR null

    - by AK
    Is there way to test for both 0 and NULL with one equality operator? I realize I could do this: WHERE field = 0 OR field IS NULL But my life would be a hundred times easier if this would work: WHERE field IN (0, NULL) (btw, why doesn't that work?) I've also read about converting NULL to 0 in the SELECT statement (with COALESCE). The framework I'm using would also make this unpleasant. Realize this is oddly specific, but is there any way to test for 0 and NULL with one WHERE predicate?

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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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  • JQuery multiple-choice quiz script: how to ensure the correct answer is available?

    - by DavidR
    I have a function. I pass to it an object with a list of questions and answers. I generate a random number from a range equal to the number of questions in the object. The script check to see if that question has been asked, and if not, it asks it, the correct answer is then passed to a variable correct. I want to give 4 possible answers, each one randomly selected from the list of possible answers. I have this. I just want to know what is the best way to ensure that the correct answer is placed in the list. So far, this is what I have: it puts four answers into four targeted boxes. I want to ensure that the correct answer is in a randomly selected box. function getRandom(limit) { return Math.floor(Math.random() * limit ) } $("#answers > .answer").each(function(i){ r = getRandom(total_questions); $(this).text(answers[r]) });

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  • Facebook FB.api post how to specify a target

    - by Laurent Luce
    I am using FB.api OpenGraph to post a message on the user's wall. I would like the link target to be equal to '_blank' so it opens in a new tab. Is it possible ? The Facebook documentation doesn't give much details. var params = {}; params['message'] = 'message'; params['name'] = 'name'; params['link'] = 'http://link'; params['picture'] = 'http://picture'; params['description'] = 'description'; FB.api('/me/feed', 'post', params, function(response) { if (!response || response.error) { alert('Error occured'); } else { alert('Post ID: ' + response); } });

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  • Why is visual studio not aware that an integer's value is changing? (debugging)

    - by incrediman
    I have a few simple lines of code (below). [bp] indicates a breakpoint. for(int i=0;i<300;i++){} int i=0; cout<<i; [bp] for (i=0;i<200;i++){} When I debug this in visual studio, it tells me that i is equal to 300 on the breakpoint. Annoyingly, 0 is printed to the console. Is there any way to make it realize that two variables in different scopes can actually have the same name? I also want to add some code to the second loop and then debug it - but when I try to do that, i is consistently shown as 300. Very annoying.

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  • ASP.Net mysterious behaviour

    - by kalan
    Does anyone have any idea why this works (expression in the if-clause) if (!(childNode.Roles != null && !Helper.HasEqualElements((string[])childNode.Roles, System.Web.Security.Roles.GetRolesForUser()))) AddNode(childNode, parentNode); And this doesn't if (childNode.Roles == null || Helper.HasEqualElements((string[])childNode.Roles, System.Web.Security.Roles.GetRolesForUser())) AddNode(childNode, parentNode); The problem is that the second if-clause sometimes doesn't work. Though it always works in debug mode, but it sometimes fails while running. And the strange thing is that these two pieces of code seems absolutely equal for me.

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  • Specific Strings And NSScanner

    - by Garry
    I need to determine whether a string (sourceString) contains another string (queryString) and if it does, at what offset. I'm guessing that NSScanner might do the trick but I don't fully understand the documentation. Let's say sourceString = @"What's the weather in London today?" If I set queryString to equal @"What's the weather", I'd like a method that would determine that, in this case, YES (sourceString does contain queryString) and the offset is 0 (i.e. at the start of sourceString). Any suggestions?

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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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  • 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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  • Finding greatest product of two lists, but keep getting #unspecific

    - by user1787030
    (define (greatest-product lst1 lst2) (define (helper lst addtimes total toacc) (cond ((null? lst) '()) ((= (countatoms lst) 1) (display total)) ((= addtimes (cadr lst)) (helper (cdr lst) 1 total total)) (else (helper lst (+ 1 addtimes) (+ toacc total) toacc)))) (cond ((> (helper lst1 0 0 (car lst1)) (helper lst2 0 0 (car lst2))) (helper lst1 0 0 (car lst1))) ((< (helper lst1 0 0 (car lst1)) (helper lst2 0 0 (car lst2))) (helper lst2 0 0 (car lst2))) ((= (helper lst1 0 0 (car lst1)) (helper lst2 0 0 (car lst2))) (display 'equal)))) Scheme keeps returning back that it cannot perform the procedure with #unspecific Im running it with (display (greatest-product '(1 2 3) '(4 5 6))) (display (greatest-product '(1 2 3) '(1 2 3))) (display (greatest-product '(1 2 3) '())) what is wrong with it? the problem seems to be occurring

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  • Why MySQL multiple-column index is overpopulated?

    - by actual
    Consider following MySQL table: CREATE TABLE `log` ( `what` enum('add', 'edit', 'remove') CHARACTER SET ascii COLLATE ascii_bin NOT NULL, `with` int(10) unsigned NOT NULL, KEY `with_what` (`with`,`what`) ) ENGINE=InnoDB; INSERT INTO `log` (`what`, `with`) VALUES ('add', 1), ('edit', 1), ('add', 2), ('remove', 2); As I understand, with_what index must have 2 unique entries on its first with level and 3 unique entries in what "subindex". But MySQL reports 4 unique entries for each level. In other words, number of unique elements for each level is always equal to number of rows in log table. Is that a bug, a feature or my misunderstanding?

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  • Question on preprocessor directives

    - by dotnetdev
    If I use proprocessor directives to define which code an OS will run, like so: #if winXP // Compiling for Windows XP platformName = "Microsoft Windows XP"; #elif win2000 // Compiling for Windows 2000 platformName = "Microsoft Windows 2000"; #elif win7 // Compiling for Windows 7 platformName = "Microsoft Windows 7"; #else // Unknown platform specified platformName = "Unknown"; How does the system pick up which OS is being used? This is an example from the book Visual C# 2010 Recipes, where the author says that the platformName variable (declaration ommitted), wil equal the OS above. Thanks

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  • C++ Segementation 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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