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• overloading new operator in c++

  - by Angus

  I have a code for best fit algorithm. I want to try to use the best fit algorithm using the operator new. Every time I create an object I should give it from the already allocated memory say, 1]20 2]12 3]15 4]6 5]23 respectively. which ever minimum amount fits to the objects size(eg.21) I wanted to do it for different object types, so I need to write the overloaded operator new to be common functionality for all the class objects. Can I do it through friend functions, or is there any possible way to do it.

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• MySQL LEFT JOIN issue with three WHERE statements

  - by jhat

  I am building a note taking app for myself with tag filtering functions, but am having an issue when trying to grab notes with the tags. The tag filter needs to use AND not IN, because it will help better narrow down what I am looking for. My tables are configured like this: + notes note_id | note_title | note_uid + tags tag_id | tag_title + notes_tags nt_id | nt_note_id | nt_tag_id The notes_tags table keeps track of all notes' tags. I am not worried about returning any information about tags, so here is an example LEFT JOIN I am using currently to only get notes with only 1 tag. SELECT * FROM notes_tags LEFT JOIN notes ON note_id = nt_note_id WHERE note_uid IN ( 1 ) AND nt_tag_id = 10 This query runs perfect, it grabs all of the notes with that single tag. However, I am having issues "pinpointing" my notes using a query like this: SELECT * FROM notes_tags LEFT JOIN notes ON note_id = nt_note_id WHERE note_uid IN ( 1 ) AND nt_tag_id = 10 AND nt_tag_id = 11 What am I doing wrong with the syntax?

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• Are sessions modifiable by the client/user?

  - by Sev

  In my PHP Web-App I use sessions to store the user's data. For exmaple, if a user logs in, then an instance of the User class is generated and stored in a Session. I have access levels associated with each user to determine their privileges. Store the user in a session by: $_SESSION['currentUser'] = new User($_POST['username']); For example: if($_SESSION['currentUser'] -> getAccessLevel() == 1) { //allow administration functions } where getAccessLevel() is simply a get method in the User class that returns the _accesslevel member variable. Is this secure? Or can the client somehow modify their access level through session manipulation of some sort?

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• func_get_args detect context

  - by Steve

  I have a script where it accepts a varying number of arguments. I want to use func_get_args to perform operations on said arguments. If I have one function like this: function Something() { foreach(func_get_args($this) as $functions) { // Do something } // Return.. } I want to be able to call this function in, for example, another function to add/save entries. The add/save function would have arguments 'title', 'description' etc.. I basically want to know if there is a way to detect the context of a function call. Can I pass something to func_get_args that will let it know that its called in a certain function? So if I do: function Save($title, $desc) { $vars = $this->Something(); } I want $vars to contain $title and $desc after modifying them.

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• Why does OpenGL have to completely break backwards compatablity?

  - by directx

  I'm not sure if this only applies to JOGL or the entire OpenGL project in general. But there seems to be a vast difference between versions 3.x and 2.x; Code that works on one version will not work on another. It looks to me like the library designers intentionally renamed various classes, packages, and functions just to screw up the existing code. I've never seen anything like this before. The problem is I'm not sure which library to use now, and when looking at code it's not so easy to figure out whether it's supposed to run on 2.x or 3.x.

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• c++ compilation error

  - by clamp

  hello, i got a compile error which i do not understand. i have a h/cpp file combination that does not contain a class but just defines some utility functions. when i try to use a struct that is defined in another class i get the error: error C2027: use of undefined type so, stripped down to the problem, the h file looks like this namespace A { void foo(B::C::SStruct const & Var); } the definition of SStruct is in a class which is in another h-file, that is of course included. namespace B { Class C { struct SStruct { }; } } what am i missing here? thanks!

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• How can I login linux using C or C++

  - by jnblue

  I need to programmely switch the current user to another,then the followed code should be executed in the environment(such as path,authority..) of another user. I've find the 'chroot()','setuid()' may be associated with my case, but these functions need the root authority, I don't have root authority, but I have the password of the second user. what should I do? I have tried shell "su - " can switch current user, can this command help me in my C++ code? Don't laugh at me if my question is very stupid, I'm a true freshman on linux. :) Thanks!

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• More compact way to do this?

  - by Macha

  I have a couple of functions that loop around the surrounding cells of a cell. The grid is contained inside an array. In my code, I have checks to make sure it's not one of the edge cells, as checking an undefined cell causes an error. As such, I have code like this: if(x > 0) { var firstX = x - 1; } else { var firstX = x; } if(x < 199) { var lastX = x + 1; } else { var lastX = x; } if(y > 0) { var firstY = y - 1; } else { var firstY = y; } if(y < 199) { var lastY = y + 1; } else { var lastY = y; } A lot of lines of code to do very little. Is there a more elegant way to do this?

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• Calling C++ function from C.

  - by claws

  I know this. Calling C function from C++: If my application was in C++ and I had to call functions from a library written in C. Then I would have used //main.cpp extern "C" void C_library_function(int x, int y);//prototype C_library_function(2,4);// directly using it. This wouldn't mangle the name C_library_function and linker would find the same name in its input *.lib files and problem is solved. Calling C++ function from C??? But here I'm extending a large application which is written in C and I need to use a library which is written in C++. Name mangling of C++ is causing trouble here. Well I cannot use C++ compiler over my C project because thats breaking lot of other stuff. What is the way out? By the way I'm using MSVC

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• Is pthread_spin_trylock safe inside of sigsegv handler of multithreaded application?

  - by TWMouton

  I am trying to implement a handler that on SIGSEGV will collect some information such as process-id, thread-id and a backtrace and write this information to a file/pipe/socket. The problem lies in that there is the (probably pretty high) possibility that if one thread experienced a SIGSEGV that the others will shortly follow. If two threads happen to make it to the bit of code where they're writing their report out at the same time then they'll interleave their writing (to the same file). I know that I should only be using async-signal-safe functions as detailed in signal(7) I also have seen at least two cases here and video linked in top answer here where others have used pthread_spin_trylock to get around this problem. Is this a safe way to prevent the above problem?

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• How to call AJAX API function from Windows App?

  - by stiopa

  Some company is providing me with web-based API for using their services. I have no problem calling this API functions from within web brower: <html xmlns="http://www.w3.org/1999/xhtml"> <head> <script type="text/javascript" src="http://someaddress.com?&key=somekey"></script> <script type="text/javascript"> var object = new SomeObject(); object.SomeFunction(); </script> </head> I am interested in return value of SomeFunction(). How would I get this return value from windows application?

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• Callback Timer function in C++

  - by user3596609

  I am trying to implement a callback timer function in C++ which should do a callback after a timeout. I am listening on a socket and then waiting for messages on it. so if I have something like getMessages() and I want to pass the timer function in it as an argument. So how can it be implemented that after the receive of a message, the timer is started and the callback happens if there is a timeout before the next messages arrives. I am new to callback functions. Any help is greatly appreciated. Thanks!

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• Why does the Win32-API have so many custom types?

  - by sub

  I'm new to the Win32 API and the many new types begin to confuse me. Some functions take 1-2 ints and 3 UINTS as arguments. Why can't they just use ints? What are UINTS? Then, there are those other types: DWORD LPCWSTR LPBOOL Again, I think the "primitive" C types would be enough - why introduce 100 new types? This one was a pain: WCHAR* I had to iterate through it and push_back every character to an std::string as there wasn't another way to convert it to one. Horrible. Why WCHAR? Why reinvent the wheel? They could have just used char* instead, or?

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• C++ Static Array Initialization - Memory Issue

  - by donalmg

  Hi, I have a header file which contains a member variable declaration of a static char array: class ABC { public: static char newArray[4]; // other variables / functions private: void setArray(int i, char * ptr); } In the CPP file, I have the array initialized to NULL: char ABC::newArray[4] = {0}; In the ABC constructor, I need to overwrite this value with a value constructed at runtime, such as the encoding of an integer: ABC::ABC() { int i; //some int value defined at runtime memset(newArray, 0, 4); // not sure if this is necessary setArray(i,newArray); } ... void setArray(int i, char * value) { // encoding i to set value[0] ... value [3] } When I return from this function, and print the modified newArray value, it prints out many more characters than the 4 specified in the array declaration. Any ideas why this is the case. I just want to set the char array to 4 characters and nothing further. Thanks...

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• Is there a way to read 10000 lines from a file in python?

  - by windsound

  I am relatively new in python, was working on C a lot. Since I was seeing so many new functions in python that I do not know, I was wondering if there is a function that can request 10000 lines from a file in python. Something like this is what I expect if that kind of function exist: lines = get_10000_lines(file_pointer) Did python have a build-in function or is there any module that I can download for this? If not, how do I do this to be easiest way. I need to analyze a huge file so I want to read 10000 lines and analyze per time to save memory. Thanks for helping!

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• returning values from function or method multiple times by only calling the class once

  - by Sokhrat Sikar

  I have a members.php file that shows my websites members. I echo members name by using foreach method. A method of Members class returns an array, then I use foreach loop in the members.php file to echo the members. I am trying to aovid writing php code in my members.php file. Is there a way to avoid using foreach inside members.php file? For example, is it possible to return value from a method couple of times? (by only calling the object once). Just like how we normally call the functions? This question doesn't make sense, but I am just trying to see if there is a away around this issue?

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• Undefined reference to "func" when compiled with GCC

  - by hotlemontea

  I implement a link list in two files in linklist.h and linklist.c, and I call some functions defined in linklist.h in main function of main.c. linklist.h is included in both linklist.c and main.c. When I compile this program by GCC with Makefile, the error named "undefined reference to xxx" occurs. I think my Makefile is written correctly as below. So what is the possible reason for this linking error CC=gcc CFLAGS= -g -O2 TARGET=target OBJECTS=main.o linklist.o TARGET: $(OBJECTS) $(CC) $(CFLAGS) $(OBJECTS) -o $(TARGET) clean: rm target $(OBJECTS) main.o:linklist.h linklist.o:linklist.h

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• PotgreSQL 2D array to rows

  - by PostGreSQL newbie

  Hello, I am new to PostgreSQL array's. I am trying to a write a procedure to convert array-into-rows, and wanted following output: alphabet | number ---------+---------- A | 10 B | 10 C | 6 D | 9 E | 3 from following: id | alphabet_series -------+-------------------------------------------------------------------------------------------------- 1 | {{A,10},{B,10},{C,6},{D,9},{E,3},{F,9},{I,10},{J,17},{K,16},{L,17},{M,20},{N,13},{O,19}} I have searched for array-to-rows functions, but they all seems to accept 1-d array. but in this case, it is 2-d array. Any pointers will be appreciated. Many thanks.

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• Changing the way widgets are rendered/displayed in a form on the template

  - by user334017

  I have a form with a few other embedded forms and some various widgets. The widgets are all saved in an array $form['elements'] and for some of them, I want to display labels and things, but for others I only want to display the basic rendering. foreach($form['elements'] as $elem) echo $elem->render(); this displays everything about the widget. The way it is right now, I couldn't for example call $elem['..'] because the different subforms appear in a random order and have different variable names. I assume I could still put some checks in the template, but it seems easier to fix this in the widget class, like override one of the render functions or something. How would I go about doing this or do you have any links that could help me understand how do do this? on a side note, one of my widgets is the sfWidgetFormChoice and I have no clue where it actually renders or how renderer_classes work

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• Method to register method to be called when event is raised

  - by zaidwaqi

  I have a Panel which contains 20 PictureBox controls. If a user clicks on any of the controls, I want a method within the Panel to be called. How do I do this? public class MyPanel : Panel { public MyPanel() { for(int i = 0; i < 20; i++) { Controls.Add(new PictureBox()); } } // DOESN'T WORK. // function to register functions to be called if the pictureboxes are clicked. public void RegisterFunction( <function pointer> func ) { foreach ( Control c in Controls ) { c.Click += new EventHandler( func ); } } } How do I implement RegisterFunction()? Also, if there are cool C# features that can make the code more elegant, please share.

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• Page layout breaks only in Opera which is weird?

  - by Qwibble

  Okay so I'm working on an admin panel, in which everything should always be only within the view port until you hit the minimum widths and heights set. The current version of it can be seen here (its still in development) : http://qwibbledesigns.co.uk/preview/Admin/ In layout terms, it works flawlessly in all browsers, even down to ie6 =D. However, opera doesn't like it, and for some reason, always add's extra space to the bottom of the page, making it have an extra scrollbar, and I can't fathom it out which is highly annoying. Jquery is used to set the height of the container, sidebar, and content area so that they're always within the browser view port, and these functions rerun when the window is resized. I therefore cannot work out the the life of me what's wrong with opera. Would anyone mind taking a look and seeing if they can work it out? =D

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• Initializing a array after declaration

  - by robUK

  Hello, gcc 4.4.3 c89 I have the following code as a sample of what I am trying to do. I don't know the actual size of the array, until I enter the function. However, I don't think I can set the array size after I have declared it. I need it global as some other functions will need to access the device names. Many thanks for any suggestions, /* global */ char *devices_names[]; void fill_devices(size_t num_devices) { devices_names[num_devices]; /* start filling */ }

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• Singly-Linked Lists insert_back and isIncreasing

  - by rezivor

  I just finished writing a program that I can add, remove or print objects to a list, but I am having difficulty implementing two more functions that is insert_back, which inserts a value to the end of a list. Also,I have to modify the representation of a List and alter whatever methods are necessary to make insert_back run in constant time: O(1). This new operation should have the signature: void List::insert_back( const Object& data ); Also, isIncreasing, For example, for a list containing head-() (11) (8) (15) (3), isIncreasing() should return false. However, it would return true when working on a list containing head- () (7) (9) (15). This new operation should have the signature: bool List::isIncreasing() const; Thank you

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• using ajax url to call function

  - by Steven Vanerp

  Hopefully I can ask this correctly cuz I know what I want it to do but can't seem to find any answers from searching. I have a func.php page where I have all my functions and I want ajax to use one function from that page. func.php function toptable() { echo"something happens in here"; } index.php <?php include 'func.php'; ?> <script type="text/javascript"> function check_username() { uname=document.getElementById("username").value; var params = "user_id="+uname; var url = "topoftable()"; $.ajax({ type: 'POST', url: url, dataType: 'html', data: params, beforeSend: function() { document.getElementById("right").innerHTML= 'checking' ; }, complete: function() { }, success: function(html) { document.getElementById("right").innerHTML= html ; } }); } </script> Make sense?

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• What is the precedence of characters when sorting in MySQL, PHP, or just in general?

  - by FireCoding

  Question: Where can I find the precedence of characters when sorting in MySQL, PHP, or just in general on Linux and Windows OS? For example, everybody knows that a comes before b when performing an ascending sort on a string in MySQL. But what about other characters? Does the dollar-sign $ come before asterisk * ? Does a space come before an exclamation-mark? etc... What dictates the sort order? Does it use underlying ascii / UTF-8 values? Is it different for different technologies? Technologies to consider: Databases - MySQL / SQL / SQLite / Oracle / etc Programming languages (for string-sorting functions) - PHP / Javascript / ASP.NET / Visual C# / Python / Ruby / Objective C OS (i.e., sorting files by filename) - Windows / Linux / MacOS / iOS / Android

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