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  • Inheritance - initialization problem

    - by dumbquestion
    I have a c++ class derived from a base class in a framework. The derived class doesn't have any data members because I need it to be freely convertible into a base class and back - the framework is responsible for loading and saving the objects and I can't change it. My derived class just has functions for accessing the data. But there are a couple of places where I need to store some temporary local variables to speed up access to data in the base class. mydata* MyClass::getData() { if ( !m_mydata ) { // set to NULL in the constructor m_mydata = some_long_and complex_operation_to_get_the_data_in_the_base() } return m_mydata; } The problem is if I just access the object by casting the base class pointer returned from the framework to MyClass* the ctor for MyClass is never called and m_mydata is junk. Is there a way of only initializing the m_mydata pointer once?

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  • Sorting a value pair in Javascript

    - by Bradley M. Davis
    I must be missing the proper term or else I'm sure I could find the answer by searching... in any case, here's what I want to do. Through javascript, I get four variables (A, B, C, and D) that I would like to sort, and still keep track of the variable name (since it's encoded with meaning information). Sample Data: A = 2; B = 1; C = 4; D = 3; What I need to do now is sort them in value order (4,3,2,1) such that I can actually know the variable name ordering (C,D,A,B).

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  • Nested loop with dependent bounds trip count

    - by aaa
    hello. just out of curiosity I tried to do the following, which turned out to be not so obvious to me; Suppose I have nested loops with runtime bounds, for example: t = 0 // trip count for l in 0:N for k in 0:N for j in max(l,k):N for i in k:j+1 t += 1 t is loop trip count is there a general algorithm/way (better than N^4 obviously) to calculate loop trip count? I am working on the assumption that the iteration bounds depend only on constant or previous loop variables.

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  • I don't get this C/C++ Joke

    - by Buttercup
    After reading this article on thedailywtf.com, I'm not sure that I really got the joke. It says there that some guy changed the code from int function() { int x; char data_string[15]; ... x = 2; strcpy(data_string,"data data data"); ... } to int function() { int x = 2; char data_string[15] = "data data data"; ... } everywhere in the code and that for some reason did inflate the size of the executable from 1 to 2 CDs (or maybe it didn't do that?). Obviously I'm not familiar enough with C/C++ to get this joke, but what seems strangest is that the 2nd code listing seems "cleaner"—at least from what I've been told in school (that is that initializing variables is a good thing, not a bad one).

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  • Keeping Computer Science Writing Accessible and Eloquent

    - by Federer
    This question is particularly aimed at descriptions and explanations of what is happening in a computer program, as well as any general advice or approaches for undertaking technical reports in Computer Science at both undergraduate and graduate levels. You see, I am having particular difficulty in the best way to explain what is happening. As in, given any given program from a multi-agent system to a standard webservice, the best and most eloquent way to say exactly what is going on, the logic behind it and it's respective justifications. Should I avoid saying class names? Avoid specifying methods? Keep referring to class variables and any particular references? I'm banging my head against the wall at trying to keep a solid technical foundation and making it accessible to people of all backgrounds. Apologies for the rather vague question. Cheers.

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  • c++ normalizing data sizes across systems

    - by Bocochoco
    I have a struct with three variables: two unsigned ints and an unsigned char. From my understanding, a c++ char is always 1 byte regardless of what operating system it is on. The same can't be said for other datatypes. I am looking for a way to normalize POD's so that when saved into a binary file, the resulting file is readable on any operating system that the code is compiled for. I changed my struct to use a 1-byte alignment by adding #pragma as follows: #pragma pack(push, 1) struct test { int a; } #pragma pack(pop) but that doesn't necessarily mean that int a is exactly 4 bytes on every os, I don't think? Is there a way to ensure that a file saved from my code will always be readable?

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  • how does "recent history" work on sites for php? (PHP)

    - by ggfan
    I'm not sure if there is an explanation on SO for beginners, but if so, could you provide the links. I am interested in creating a "recent viewed" function that shows what links they clicked on before. I'm not sure if this is the 'correct' way to do it, but this is what I have so far... user clicks on a link(say ad.php?posting_id=12). if the user doesn't click on the link, no cookie or session is stored for the link if the user clicks on the link, it sets a cookie for $_cookie['ad.php?posting_id=22'] Each time the user clicks, more cookies are set In the recent viewed function, it gets all the $_cookie variables and displays them. if the user wants to clear the history, just destroy all the cookies I'm not sure if this is the way to do it, but is the viable? If not, what are the steps to create a "recent viewed" function

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  • How much memory is reserved when i declare a string?

    - by Bhagya
    What exactly happens, in terms of memory, when i declare something like: char arr[4]; How many bytes are reserved for arr? How is null string accommodated when I 'strcpy' a string of length 4 in arr? I was writing a socket program, and when I tried to suffix NULL at arr[4] (i.e. the 5th memory location), I ended up replacing the values of some other variables of the program (overflow) and got into a big time mess. Any descriptions of how compilers (gcc is what I used) manage memory?

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  • Do I need to install Glassfish?

    - by Ayusman
    Hi, I am new to glassfish server. i have a question on glassfish usage: can I just use glassfish like a tomcat server without needing an installation? where in, I just take a folder containing glassfish folders, jars etc... dump it in a folder location setup a few environment variables and it runs.. just like tomcat? is it possible with glassfish? also does glassfish installation does any other background things like creating registry entries etc other than creating the glassfish folder structure? TIA Ayusman

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  • Unable to access static var from Document Class in AS3

    - by omidomid
    I have a Document class called "CityModule", and an asset with class "City". Below is the coe for each. For some reason, I am unable to access the static variables of the City class from CityModule: CityModule.as: package { public class CityModule extends MovieClip { public function CityModule() { var buildings:Array = City.getBuildings(); } } } } City.as: package { import flash.display.MovieClip; public class City extends MovieClip { private static var _buildings:Array = [ {className:'City.Generic1', type:'generic'}, {className:'City.Generic2', type:'generic'}, {className:'City.Generic3', type:'generic'} ]; public function City(){ //empty } public static function getBuildings():Array{ return _buildings; } } } Doing this gives me a "Call to a possibly undefined method getBuildings" error. If I instantiate an instance of City, I can see any public/ getters/ setters perfectly fine. But static isn't working...

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  • Should I always release self for failed init methods?

    - by leo
    Should I always release self when there is a failure inside init, or should I only do so if I have initialized instance variables first? To put it another way, is this pattern valid? Is there a time when I shouldn't release self inside an init method, or should I assume that if the control flow enters init, self has at least a retain count of 1? - (id)init { if ((self = [super init]) == nil) { [self release]; return nil; } //do some init stuff if (somethingFailed) { [self release]; return nil; } return self; }

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  • Manage bad_alloc exception in C++ construtor

    - by Jimmy zhang
    I have Java experience and recently am doing some C++ coding. My question is that if I have class A, in which I have to instantiate class B and class C as two of the member variables of A. If in the constructor of A, should I assume that allocations of class B and C never fail, and handle the bad allocation exception in the destructor of A? If I don't make that assumption, meaning that I add some try catch block to catch bad_alloc of class B and class C, then if the allocation exception occurs, should I do clean up in the constructor of A? What are the recommended practices? If "new" generates a bad allocation, what value does the pointer carry?

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  • Fully automated MS SQL Restore

    - by hasen j
    I'm not very fluent with MS-SQL commands. I need a script to restore a database from a .bak file and move the logical_data and logical_log files to a specific path. I can do: restore filelistonly from disk='D:\backups\my_backup.bak' This will give me a result set with a column LogicalName, next I need to use the logical names from the result set in the restore command: restore database my_db_name from disk='d:\backups\my_backups.bak' with file=1, move 'logical_data_file' to 'd:\data\mydb.mdf', move 'logical_log_file' to 'd:\data\mylog.ldf' How do I capture the logical names from the first result set into variables that can be supplied to the "move" command? I think the solution might be trivial, but I'm pretty new to mssql.

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  • How to pass a value between Silverlight pages for WP7?

    - by Sebastian Gray
    I've got a MainPage.xaml page a Detail.xaml page. I've passed variables to the Detail.xaml from MainPage.xaml by using a static variable and referencing it in Detail.xaml (the detail page is acting like a dialog). However once I've updated the content of another object, I want to call a method in MainPage.xaml to refresh the content of that page using the updated object from the Detail.xaml page. I assume I am not using the correct paradigm for this and should probably be using MVVM or something but I'm not familiar with the implementation and was hoping there was a simple way to do this?

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  • Display calculating result in the same page

    - by garcon1986
    Hello, I have a table in my php code. In the second column of the table, normally it displays "---", and after i click the submit button, it will display the calculating result in the same page. For example, <table> <tr><td>1</td><td>---</td></tr> <tr><td>2</td><td>---</td></tr> <tr><td>3</td><td>---</td></tr> </table> And in the same page, it should receive the variables $var1 = $_POST['variable1']; I'm not sure which way to use, ajax or javascript or just css? Do you have any ideas? Thanks

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  • Rails Variable across all controller actions

    - by bob
    Hello, This should be a very simple rails question. I have a variable like the following. @administration = Administration.first I want this variable to be accessible through every controller action across all my controllers so for example if I have a Product controller and inside of it I have the usual CRUD actions, I want the @administration variable as defined above to be put into all the CRUD actions. (It would not be needed in destroy or create or update). I have many controllers throughout my project and I was wondering if there is an easier way than adding it manually through all of the actions that I want it in. I tried a global variable $administration = Administration.first but I run into an issue where it is not updated when I update the actual content of the Administration.first table. Also, I would like to avoid global variables. Any help would be much appreciated. Thanks! :)

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  • User Controls Importing Problem (asp.net)(vb)

    - by Phil
    I have this class that contains vars for db connection; Public Shared s As String Public Shared con As String = WebConfigurationManager.ConnectionStrings("foo").ToString() Public Shared c As New SqlConnection(con) Public Shared x As New SqlCommand(s, c) I import this to my page like this; Imports DBVars I'm then able to access these vars from my page. But if I try to import them into a user control the variables are not available. Am I making an error or is this expected? Thanks.

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  • How to refresh site if $_SESSION variable has changed

    - by 4ndro1d
    I'm writing in my $_SESSION variable from a database, when i clicked a link. public function getProjectById($id){ $query="SELECT * FROM projects WHERE id=\"$id\""; $result=mysql_query($query); $num=mysql_numrows($result); while ($row = mysql_fetch_object($result)) { $_SESSION['projectid'] = $row->id; $_SESSION['projecttitle'] = $row->title; $_SESSION['projectinfo'] = $row->info; $_SESSION['projecttext'] = $row->text; $_SESSION['projectcategory'] = $row->category; } } Now my variable is overwritten and I want to show these variables in my index.php like this: <div id="textContent"> <?php if(isset($_SESSION['projecttext']) && !empty($_SESSION['projecttext'])) { echo $_SESSION['projecttext']; }else { echo 'No text'; } ?></div> But of course, my page will not refresh automatically. How can I do that?

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  • update value of a variable outside a class in VB.NET

    - by dpp
    I have a class derived from a Form, it has textbox for username and password and an OK button. I want it to behave like an InputBox so I can use it like this: Dim Username As String = "" Dim Password As String = "" Dim authorization As New Authorization(Username, Password) authorization.ShowDialog() 'The user will click OK and I will expect the Username and Password to change based on the user input MsgBox(Username & " " & Password) The Authorization class: Public Class Authorization Dim RefUsername As String Dim RefPassword As String Public Sub New(ByRef Username As String, ByRef Password As String) InitializeComponent() RefUsername = Username 'I'm trying to pass reference instead of value RefPassword = Password 'I'm trying to pass reference instead of value End Sub Private Sub OKButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles AuthorizeButton.Click RefUsername = Username.Text 'I'm trying to change value of variable outside the class RefPassword = Password.Text 'I'm trying to change value of variable outside the class Me.Close() End Sub End Class In short, I want to change the value of variables outside the class when the user clicks the OK, how am I going to accomplish that?

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  • PHP to C# and Vice versa

    - by Daniel Sh.
    I'm in this project: A web page that's gonna be used by the front-end company people to query and update data from a SQL DB. I'm working with visual studio and the code behind (C#) is almost done, so the interactions between SQL and C# and ok. My original idea was to work with ASP.NET which is familiar to me, but that's not gonna be possible. I have to switch to PHP. So, today is my first day learning PHP, checking http://php.net/manual/en/index.php and a lot of things seem quite similar to ASP.NET so I guess it won't be that hard. Anyways, some questions popped up quite fast as I wanted to script something else than a "hello world" . Is there an easy way to get/send C# variables from my class using a php page? I've read soemthing about using XML in order to do so, but still I'm scratching my head, is there another, easier, way to do this?

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  • functions in assembler

    - by stupid_idiot
    hi, i have philosophised about the purpose of stack a little bit and after some coding i figured out what is it's strength. The only thing that lies in my stomache is how does it work with functions? I tried to make some easy function for adding two numbers using universal registers but I suppose that's not how does it work in C for example.. where are all the parameters, local variables and where is the result stored? how would you rewrite this to assembler?(how would compiler for C rewrite it?) int function(int a, int &b, int *c){ return a*(b++)+(*c); } i know this example kinda sucks.. but this way i can understand all the possibilities

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  • Cache images provided through script

    - by Wim Haanstra
    I have a script, which by using several querystring variables provides an image. I am also using URL rewriting within IIS 7.5. So images have an URL like this: http://mydomain/pictures/ajfhajkfhal/44/thumb.jpg or http://mydomain/pictures/ajfhajkfhal/44.jpg This is rewritten to: http://mydomain/Picture.aspx?group=ajfhajkfhal&id=44&thumb=thumb.jpg or http://mydomain/Picture.aspx?group=ajfhajkfhal&id=44 I added caching rules to IIS to cache JPG images when they are requested. This works with my images that are REAL images on the disk. When images are provided through the script, they are somehow always requested through the script, without being cached. The images do not change that often, so if the cache at least is being kept for 30 minutes (or until file change) that would be best. I am using .NET/C# 4.0 for my website. I tried setting several cache options in C#, but I cant seem to find how to cache these images (client-side), while my static images are cached properly.

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  • Get Data from Windows Form into C# program

    - by Jimmy
    I want my C# program to collect data. Then, when the OK button is clicked, I want this data to be loaded into my program -- such as into variables in Main(), or into data members of a class I have constructed, and I want the form to then go away -- not be hidden, but actually closed. Alas, read as I might in the book I have, the data collected by the form stays in the form, execution proceeds within the form, and the same form is used to display the result of the program's computations. Sheesh. All I want is to capture the form's information, close the form and proceed with my program. I would appreciate some tips on geting data from a form into Main() or into a class's data members. Thanks, Lucky

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  • What is good practice for writing web applications that control daemons (and their config files)

    - by Jones R
    Can someone suggest some basic advice on dealing with web applications that interact with configuration files like httpd.conf, bind zone files, etc. I understand that it's bad practice, in fact very dangerous to allow arbitrary execution of code without fully validating it and so on. But say you are tasked to write a small app that allows one to add vhosts to an apache configuration. Do you have your code execute with full privileges, do you write future variables into a database and have a cron job (with full privileges) execute a script that pulls the vars from the database and throws them into a template config file, etc. Some thoughts & contributions on this issue would be appreciated. tl;dr - how can you securely write a web app to update/create entries in a config file like apache's httpd.conf, etc.

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  • Using Components.utils.import in a firefox extension

    - by jamesatha
    I am trying to create some global variables in a firefox extension. In my content folder, I have two javascript files: 1) Main JS file that holds the functions for the different events, etc 2) A file that stores only an object with the pieces of state I want to maintain. Also, I set the array EXPORTED_SYMBOLS. I am having issues with the following line found in my main JS file: Components.utils.import("resource:///globalVariables.js"); When it is at the top of the file, nothing seems to work. If I move it into the function where I need the variable, the rest of my code works, but the function with this line does nothing. Any advice that would help me with this problem would be great. Thanks

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