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  • PHP / Zend custom date input formats

    - by mld
    Hi, I'm creating a library component for other developers on my team using PHP and Zend. This component needs to be able to take as input a date (string) and another string telling it the format of that date. Looking through the Zend documentation and examples, I thought I found the solution - $dateObject = Zend_Date('13.04.2006', array('date_format' => 'dd.MM.yyyy')); this line, however, throws an error - call to undefined function. So instead I tried this - $dt = Zend_Locale_Format::getDate('13.04.2006', array('date_format' => 'dd.MM.yyyy')); This gets the job done, but throws an error if a date that is entered isn't valid. The docs make it look like you can use the isDate() function to check validity - Zend_Date::isDate('13.04.2006', array('date_format' => 'dd.MM.yyyy')) but this line always returns false. So my questions - Am I going about this the right way? If not, is there a better way to handle this via Zend or straight PHP? If I do use Zend_Locale_Format::getDate(), do I need to worry about a locale being set elsewhere and changing the results of the call? I'm locked into PHP 5.2.6 on windows, btw... so 5.3+ functions & strptime() are out.

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  • Complex sorting on MySQL database

    - by ChrisR
    I'm facing the following situation. We've got an CMS with an entity with translations. These translations are stored in a different table with a one-to-many relationship. For example newsarticles and newsarticle_translations. The amount of available languages is dynamically determined by the same CMS. When entering a new newsarticle the editor is required to enter at least one translation, which one of the available languages he chooses is up to him. In the newsarticle overview in our CMS we would like to show a column with the (translated) article title, but since none of the languages are mandatory (one of them is mandatory but i don't know which one) i don't really know how to construct my mysql query to select a title for each newsarticle, regardless of the entered language. And to make it all a little harder, our manager asked for the possibilty to also be able to sort on title, so fetching the translations in a separate query is ruled out as far as i know. Anyone has an idea on how to solve this in the most efficient way? Here are my table schema's it it might help > desc news; +-----------------+----------------+------+-----+-------------------+----------------+ | Field | Type | Null | Key | Default | Extra | +-----------------+----------------+------+-----+-------------------+----------------+ | id | int(10) | NO | PRI | NULL | auto_increment | | category_id | int(1) | YES | | NULL | | | created | timestamp | NO | | CURRENT_TIMESTAMP | | | user_id | int(10) | YES | | NULL | | +-----------------+----------------+------+-----+-------------------+----------------+ > desc news_translations; +-----------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-----------------+------------------+------+-----+---------+----------------+ | id | int(10) unsigned | NO | PRI | NULL | auto_increment | | enabled | tinyint(1) | NO | | 0 | | | news_id | int(1) unsigned | NO | | NULL | | | title | varchar(255) | NO | | | | | summary | text | YES | | NULL | | | body | text | NO | | NULL | | | language | varchar(2) | NO | | NULL | | +-----------------+------------------+------+-----+---------+----------------+ PS: i've though about subqueries and coalesce() solutions but those seem rather dirty tricks, wondering if something better is know that i'm not thinking of?

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  • Codeigniter Inputting session data from model for a simple authentication system

    - by user1616244
    Trying to put together a simple login authentication. Been at this for quite sometime, and I can't find where I'm going wrong. Pretty new to Codeigniter and OOP PHP. I know there are authentication libraries out there, but I'm not interested in using those. Model: function login($username, $password){ if ($this->db->table_exists($username)){ $this->db->where('username', $username); $this->db->where('password', $password); $query = $this->db->get($username); if($query->num_rows >= 1) { return true; $data = array( 'username' => $this->input->post('username'), 'login' => true ); $this->session->set_userdata($data); } } } Controller function __construct(){ parent::__construct(); $this->logincheck(); } public function logincheck(){ if ($this->session->userdata('login')){ redirect('/members'); } } If I just echo from the controller: $this-session-all_userdata(); I get an empty array. So the problem seems to be that the $data array in the model isn't being stored in the session.

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  • How to access web.config connection string in C#?

    - by salvationishere
    I have a 32-bit XP running VS 2008 and I am trying to decrypt my connection string from my web.config file in my C# ASPX file. Even though there are no errors returned, my current connection string doesn't display contents of my selected AdventureWorks stored procedure. I entered it: C:\Program Files\Microsoft Visual Studio 9.0\VC>Aspnet_regiis.exe -pe "connectionStrings" -app "/AddFileToSQL2" Then it said "Succeeded". And my web.config section looks like: <connectionStrings> <add name="Master" connectionString="server=MSSQLSERVER;database=Master; Integrated Security=SSPI" providerName="System.Data.SqlClient" /> <add name="AdventureWorksConnectionString" connectionString="Data Source=SIDEKICK;Initial Catalog=AdventureWorks;Integrated Security=True" providerName="System.Data.SqlClient" /> <add name="AdventureWorksConnectionString2" connectionString="Data Source=SIDEKICK;Initial Catalog=AdventureWorks;Persist Security Info=true; " providerName="System.Data.SqlClient" /> </connectionStrings> And my C# code behind looks like: string connString = ConfigurationManager.ConnectionStrings["AdventureWorksConnectionString2"].ConnectionString; Is there something wrong with the connection string in the web.config or C# code behind file?

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  • Friends, templates, overloading <<

    - by Crystal
    I'm trying to use friend functions to overload << and templates to get familiar with templates. I do not know what these compile errors are: Point.cpp:11: error: shadows template parm 'class T' Point.cpp:12: error: declaration of 'const Point<T>& T' for this file #include "Point.h" template <class T> Point<T>::Point() : xCoordinate(0), yCoordinate(0) {} template <class T> Point<T>::Point(T xCoordinate, T yCoordinate) : xCoordinate(xCoordinate), yCoordinate(yCoordinate) {} template <class T> std::ostream &operator<<(std::ostream &out, const Point<T> &T) { std::cout << "(" << T.xCoordinate << ", " << T.yCoordinate << ")"; return out; } My header looks like: #ifndef POINT_H #define POINT_H #include <iostream> template <class T> class Point { public: Point(); Point(T xCoordinate, T yCoordinate); friend std::ostream &operator<<(std::ostream &out, const Point<T> &T); private: T xCoordinate; T yCoordinate; }; #endif My header also gives the warning: Point.h:12: warning: friend declaration 'std::ostream& operator<<(std::ostream&, const Point<T>&)' declares a non-template function Which I was also unsure why. Any thoughts? Thanks.

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  • how to decrease queries in php/mysql array selection loop

    - by Mac Taylor
    hey guys i need to show stories details and tags' names in my php/mysql project . for every story row, there is a filed named : tags that save tags id as an array Table name: stories table filed : tags example of tags filed : 1 5 6 space between them and i have a tag table that looks like this Table name : bt_tags Table fileds : tid,tag now problem : when using while loop to fetch all fields in story table , the page uses 1 query to show every stories' detail but for showing tag's names , i should query another table to find names , we have ids stored in story table now i used for loop between while loop to show tag names but im sure there is a better way to decrease page queries $result = $db->sql_query("SELECT * FROM ".STORY_TABLE." "); while ($row = $db->sql_fetchrow($result)) { //fetching other $vars ---- $tags_id = explode(" ",$row['tags']); $c = count($tags_id); for($i=1;$i<$c-1;$i++){ list($tag_name,$slug) = $db->sql_fetchrow($db->sql_query( 'SELECT `tag`,`slug` FROM `bt_tags` WHERE `tid` = "'.tags_id[$i].'" LIMIT 1' )); $sow_tags = '$tag_name,'; } im not allowed to change anything in database table how can i improve this script and show tag's names without using *for loop ?*

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  • Noise with multi-threaded raytracer

    - by herber88
    This is my first multi-threaded implementation, so it's probably a beginners mistake. The threads handle the rendering of every second row of pixels (so all rendering is handled within each thread). The problem persists if the threads render the upper and lower parts of the screen respectively. Both threads read from the same variables, can this cause any problems? From what I've understood only writing can cause concurrency problems... Can calling the same functions cause any concurrency problems? And again, from what I've understood this shouldn't be a problem... The only time both threads write to the same variable is when saving the calculated pixel color. This is stored in an array, but they never write to the same indices in that array. Can this cause a problem? Multi-threaded rendered image (Spam prevention stops me from posting images directly..) Ps. I use the exactly same implementation in both cases, the ONLY difference is a single vs. two threads created for the rendering.

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  • How am i overriding this C++ inherited member function without the virtual keyword being used?

    - by Gary Willoughby
    I have a small program to demonstrate simple inheritance. I am defining a Dog class which is derived from Mammal. Both classes share a simple member function called ToString(). How is Dog overriding the implementation in the Mammal class, when i'm not using the virtual keyword? (Do i even need to use the virtual keyword to override member functions?) mammal.h #ifndef MAMMAL_H_INCLUDED #define MAMMAL_H_INCLUDED #include <string> class Mammal { public: std::string ToString(); }; #endif // MAMMAL_H_INCLUDED mammal.cpp #include <string> #include "mammal.h" std::string Mammal::ToString() { return "I am a Mammal!"; } dog.h #ifndef DOG_H_INCLUDED #define DOG_H_INCLUDED #include <string> #include "mammal.h" class Dog : public Mammal { public: std::string ToString(); }; #endif // DOG_H_INCLUDED dog.cpp #include <string> #include "dog.h" std::string Dog::ToString() { return "I am a Dog!"; } main.cpp #include <iostream> #include "dog.h" using namespace std; int main() { Dog d; std::cout << d.ToString() << std::endl; return 0; } output I am a Dog! I'm using MingW on Windows via Code::Blocks.

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  • Clean solution to this ruby iterator trickiness?

    - by mstksg
    k = [1,2,3,4,5] for n in k puts n if n == 2 k.delete(n) end end puts k.join(",") # Result: # 1 # 2 # 4 # 5 # [1,3,4,5] # Desired: # 1 # 2 # 3 # 4 # 5 # [1,3,4,5] This same effect happens with the other array iterator, k.each: k = [1,2,3,4,5] k.each do |n| puts n if n == 2 k.delete(n) end end puts k.join(",") has the same output. The reason this is happening is pretty clear...Ruby doesn't actually iterate through the objects stored in the array, but rather just turns it into a pretty array index iterator, starting at index 0 and each time increasing the index until it's over. But when you delete an item, it still increments the index, so it doesn't evaluate the same index twice, which I want it to. This might not be what's happening, but it's the best I can think of. Is there a clean way to do this? Is there already a built-in iterator that can do this? Or will I have to dirty it up and do an array index iterator, and not increment when the item is deleted?

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  • Do I lose the benefits of macro recording if I develop Excel apps in Visual Studio?

    - by DanM
    I've written lots of Excel macros in the past using the following development process: Record a macro. Open the VBA editor. Edit the macro. I'm now experimenting with a Visual Studio 2008 "Excel 2007 Add-In" project (C#), and I'm wondering if I will have to give up this development process. Questions: I know I can still record macros using Excel, but is there any way to access the resulting code in Visual Studio? Or do I just have to copy and paste then C#-ize it? What happens with my "Personal Macro Workbook"? Can I use the macros I have stored in there within C#? Or is there some way to convert them to C#? If there is some support for opening and editing VBA macros in Visual Studio, can you provide a very brief summary of how it works or point me to a good reference? Do you have any other tips for transitioning from writing macros in VBA using Excel's built-in editor to writing them in C# with Visual Studio?

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  • Changing the href attribute on hover with jQuery

    - by AverageJoe
    Ok, I have an html page that is loaded into another html page via PHP (ok so its a PHP page, whatever). The page that is loaded is a list of hyperlinks. I need to change the href attribute to make the hyperlinks relative to the location of the stored images they refer too. When i load the page containing the hyperlinks the links are relative to the web host server, not the server that the page is actually hosted from. Somthing like this: <div #screenshots) <p><a href="image1.htm">Image1</a></p> <p><a href="image2.htm">Image2</a></p> <p><a href="image3.htm">Image3</a></p> <p><a href="image4.htm">Image4</a></p> <p><a href="image5.htm">Image5</a></p> </div> When I mouse over the links, the status bar shows the reference as "http://webHostServer.com/image1.htm". If I click it I get a 404 error. I need the href to change to something like this when I mouse over it: "http://www.actualImageHostServerIPaddress/image1.htm" I looked at this for assitance and came out with the following jQuery code, but for some reason none of it works: $(document).ready(function(){ $("button").click(function() { $("#screenshots a").addClass('ss'); }); $(".ss").each(function() { $(this).data("oldHref", $(this).attr("href")); orig = $(this).attr("href"); over = "http://208.167.244.33/208.167.244.33/"; $(this).hover(function() { $(this).attr("href", $(this).attr("href").replace(orig, over+orig)); }, function() { $(this).attr("href", $(this).data("oldHref")); }); }); When I click the button it dosen't add the class to the anchor tags, so when I hover over them nothing changes. Any help here would be great.

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  • Goldbach theory in C

    - by nofe
    I want to write some code which takes any positive, even number (greater than 2) and gives me the smallest pair of primes that sum up to this number. I need this program to handle any integer up to 9 digits long. My aim is to make something that looks like this: Please enter a positive even integer ( greater than 2 ) : 10 The first primes adding : 3+7=10. Please enter a positive even integer ( greater than 2 ) : 160 The first primes adding : 3+157=160. Please enter a positive even integer ( greater than 2 ) : 18456 The first primes adding : 5+18451=18456. I don't want to use any library besides stdio.h. I don't want to use arrays, strings, or anything besides for the most basic toolbox: scanf, printf, for, while, do-while, if, else if, break, continue, and the basic operators (<,, ==, =+, !=, %, *, /, etc...). Please no other functions especially is_prime. I know how to limit the input to my needs so that it loops until given a valid entry. So now I'm trying to figure out the algorithm. I thought of starting a while loop like something like this: #include <stdio.h> long first, second, sum, goldbach, min; long a,b,i,k; //indices int main (){ while (1){ printf("Please enter a positive integer :\n"); scanf("%ld",&goldbach); if ((goldbach>2)&&((goldbach%2)==0)) break; else printf("Wrong input, "); } while (sum!=goldbach){ for (a=3;a<goldbach;a=(a+2)) for (i=2;(goldbach-a)%i;i++) first = a; for (b=5;b<goldbach;b=(b+2)) for (k=2;(goldbach-b)%k;k++) sum = first + second; } }

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  • C++ variable to const expression

    - by user1344784
    template <typename Real> class A{ }; template <typename Real> class B{ }; //... a few dozen more similar template classes class Computer{ public slots: void setFrom(int from){ from_ = from; } void setTo(int to){ to_ = to; } private: template <int F, int T> void compute(){ using boost::fusion::vector; using boost::fusion::at_c; vector<A<float>, B<float>, ...> v; at_c<from_>(v).operator()(at_c<to_>(v)); //error; needs to be const-expression. }; This question isn't about Qt, but there is a line of Qt code in my example. The setFrom() and setTo() are functions that are called based on user selection via the GUI widget. The root of my problem is that 'from' and 'to' are variables. In my compute member function I need to pick a type (A, B, etc.) based on the values of 'from' and 'to'. The only way I know how to do what I need to do is to use switch statements, but that's extremely tedious in my case and I would like to avoid. Is there anyway to convert the error line to a constant-expression?

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  • How do I use cookies to store users' recent site history(PHP)?

    - by ggfan
    I decided to make a recent view box that allows users to see what links they clicked on before. Whenever they click on a posting, the posting's id gets stored in a cookie and displays it in the recent view box. In my ad.php, I have a definerecentview function that stores the posting's id (so I can call it later when trying to get the posting's information such as title, price from the database) in a cookie. How do I create a cookie array for this? **EXAMPLE:** user clicks on ad.php?posting_id='200' //this is in the ad.php function definerecentview() { $posting_id=$_GET['posting_id']; //this adds 30 days to the current time $Month = 2592000 + time(); $i=1; if (isset($posting_id)){ //lost here for($i=1,$i< ???,$i++){ setcookie("recentviewitem[$i]", $posting_id, $Month); } } } function displayrecentviews() { echo "<div class='recentviews'>"; echo "Recent Views"; if (isset($_COOKIE['recentviewitem'])) { foreach ($_COOKIE['recentviewitem'] as $name => $value) { echo "$name : $value <br />\n"; //right now just shows the posting_id } } echo "</div>"; } How do I use a for loop or foreach loop to make it that whenever a user clicks on an ad, it makes an array in the cookie? So it would be like.. 1. clicks on ad.php?posting_id=200 --- setcookie("recentviewitem[1]",200,$month); 2. clicks on ad.php?posting_id=201 --- setcookie("recentviewitem[2]",201,$month); 3. clicks on ad.php?posting_id=202 --- setcookie("recentviewitem[3]",202,$month); Then in the displayrecentitem function, I just echo however many cookies were set? I'm just totally lost in creating a for loop that sets the cookies. any help would be appreciated

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  • Execute JavaScript from within a C# assembly

    - by ScottKoon
    I'd like to execute JavaScript code from within a C# assembly and have the results of the JavaScript code returned to the calling C# code. It's easier to define things that I'm not trying to do: I'm not trying to call a JavaScript function on a web page from my code behind. I'm not trying to load a WebBrowser control. I don't want to have the JavaScript perform an AJAX call to a server. What I want to do is write unit tests in JavaScript and have then unit tests output JSON, even plain text would be fine. Then I want to have a generic C# class/executible that can load the file containing the JS, run the JS unit tests, scrap/load the results, and return a pass/fail with details during a post-build task. I think it's possible using the old ActiveX ScriptControl, but it seems like there ought to be a .NET way to do this without using SilverLight, the DLR, or anything else that hasn't shipped yet. Anyone have any ideas? update: From Brad Abrams blog namespace Microsoft.JScript.Vsa { [Obsolete("There is no replacement for this feature. Please see the ICodeCompiler documentation for additional help. http://go.microsoft.com/fwlink/?linkid=14202")] Clarification: We have unit tests for our JavaScript functions that are written in JavaScript using the JSUnit framework. Right now during our build process, we have to manually load a web page and click a button to ensure that all of the JavaScript unit tests pass. I'd like to be able to execute the tests during the post-build process when our automated C# unit tests are run and report the success/failure alongside of out C# unit tests and use them as an indicator as to whether or not the build is broken.

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  • Protocol specification in XML

    - by Mathijs
    Is there a way to specify a packet-based protocol in XML, so (de)serialization can happen automatically? The context is as follows. I have a device that communicates through a serial port. It sends and receives a byte stream consisting of 'packets'. A packet is a collection of elementary data types and (sometimes) other packets. Some elements of packets are conditional; their inclusion depends on earlier elements. I have a C# application that communicates with this device. Naturally, I don't want to work on a byte-level throughout my application; I want to separate the protocol from my application code. Therefore I need to translate the byte stream to structures (classes). Currently I have implemented the protocol in C# by defining a class for each packet. These classes define the order and type of elements for each packet. Making class members conditional is difficult, so protocol information ends up in functions. I imagine XML that looks like this (note that my experience designing XML is limited): <packet> <field name="Author" type="int32" /> <field name="Nickname" type="bytes" size="4"> <condition type="range"> <field>Author</field> <min>3</min> <max>6</min> </condition> </field> </packet> .NET has something called a 'binary serializer', but I don't think that's what I'm looking for. Is there a way to separate protocol and code, even if packets 'include' other packets and have conditional elements?

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  • Copy a LinkedList that has a Random Pointer in it

    - by Bragaadeesh
    Hi, First of all this is not a homework, this is an interview question that I got from a company I attended today. You have a singly linked list with the Node structure as the following class Node{ int data; Node next; Node random; } You have a typical singly linked list of length n. The random pointer in each node in the linkedlist randomly points to some Node within the linked list. The Question is to create a copy of the linked list efficiently into a different LinkedList. I said that I will first calculate the Random pointer's position in the linked list and store it in an array. Then create a new linked list normally. Then iterate through the linked list by setting the random pointer where they belong by reading the values stored from the array. I know its a very brute force technique and the interviewer asked me to come up with a better solution but I couldnt. Please can someone answer this? I can explain if the question is not clear.

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  • jquery how to access the an xml node by index?

    - by DS
    Hi, say I've an xml returned from server like this: <persons> <person> <firstname>Jon</firstname> </person> <person> <firstname>Jack</firstname> </person> <person> <firstname>James</firstname> </person> </persons> If I want to access the 3rd firstname node (passed dynamically and stored in i, assumed to be 3 here), how do I do that? My weird attempt follows: var i=3; $(xml).find('firstname').each(function(idx){ if (idx==i) alert($(this).text()); }); It does fetch me the right content... but it just feels wrong to me especially the looping part. Basically I'm looping through the whole tree using .each()! Is there any better approach than this? Something that'd take me to the nth node directly like: alert( $(xml).find('firstname')[idx].text() ); // where idx=n I'm new to jquery so please excuse my jquery coding approach.

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  • Simple jQuery syntax help, don't know where I've gone wrong

    - by Jascination
    I'm having trouble with a jQuery code at the moment, I know WHERE the problem lies, but I don't know what the problem is exactly. Probably very basic, but I'm new to this. You can see a (non)working fiddle here: http://www.jsfiddle.net/CvZeQ/ Basically I want to set different .click function based on whatever is selected (I have 5 image maps, each with a different #mapname, and want each to pertain to a different variable (answer1, answer2, answer3...) so as to store the selected 'answer' for each map.) Here is the code I'm using for one of the maps: $(window).load(function(){ //Get cookies when page loaded var useranswers=$.cookie('survery'); useranswers= JSON.parse (useranswers); // do something with previous answers //#shape functions $('#shape area').hover( function(e){ $('#'+ this.alt).addClass('hover'); }, function(e){ $('#'+ this.alt).removeClass('hover'); } ).click( function(e){ $('img.selected-region').removeClass('selected-region'); }, function(e){ $('#'+ this.alt).addClass('selected-region'); }, function(e){ var answer1 = $(this).attr("class"); }); }); I know the problem lies somewhere with the .click function, but I'm not entirely sure what I've done wrong. Any help would be greatly appreciated.

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  • What kind of data do I pass into a Django Model.save() method?

    - by poswald
    Lets say that we are getting POSTed a form like this in Django: rate=10 items= [23,12,31,52,83,34] The items are primary keys of an Item model. I have a bunch of business logic that will run and create more items based on this data, the results of some db lookups, and some business logic. I want to put that logic into a save signal or an overridden Model.save() method of another model (let's call it Inventory). The business logic will run when I create a new Inventory object using this form data. Inventory will look like this: class Inventory(models.Model): picked_items = models.ManyToManyField(Item, related_name="items_picked_set") calculated_items = models.ManyToManyField(Item, related_name="items_calculated_set") rate = models.DecimalField() ... other fields here ... New calculated_items will be created based on the passed in items which will be stored as picked_items. My question is this: is it better for the save() method on this model to accept: the request object (I don't really like this coupling) the form data as arguments or kwargs (a list of primary keys and the other form fields) a list of Items (The caller form or view will lookup the list of Items and create a list as well as pass in the other form fields) some other approach? I know this is a bit subjective, but I was wondering what the general idea is. I've looked through a lot of code but I'm having a hard time finding a pattern I like.

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  • Javascript Namespace Help

    - by Jason
    Hi, I have a pretty big Javascript script with loads of global variables & functions in it. Then a piece of code that calls one function from this js file: myfunc(); Ok, now I have cloned this script and modified some functionality, all function prototypes and variables are named the same in both scripts. So now I have two scripts loaded and one call to myfunc(), now we have a clash because there are loads of global variables with the same names and two myfunc()s. What I want to do is wrap this cloned script in a namespace, so that I can modify the original call to: clone.myfunc() which will call the new function, but I also want myfunc() to just refer to the original script. In other words I can't touch the original script (no permissions) and I want to be able to use both the clone and the original at runtime. This is the script im cloning: http://pastebin.com/6KR5T3Ah Javascript namespaces seem quite tricky this seems a nice namespace method: var namespace = { foo: function() { } bar: function() { } } ... namespace.foo(); } However that requires using an object, and the script (as posted above) is humongous at nearly 4000 lines, too much to objectize I think? Anyone know a better solution to avoid namespace pollution, with one script I cant touch and one being a clone of that script. Just so I can call myfunc() and clone.myfunc() and all global variables will behave in their respected scope. It's either that, or I go through and modify everything to have unique names, which may take a lifetime This is a Mozilla addon if it helps context wise. Thanks.

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  • R Tree 50,000 foot overview?

    - by roufamatic
    I'm working on a school project that involves taking a lat/long point and finding the top five closest points in a known list of places. The list is to be stored in memory, with the caveat that we must choose an "appropriate data structure" -- that is, we cannot simply store all the places in an array and compare distances one-by-one in a linear fashion. The teacher suggested grouping the place data by US State to prevent calculating the distance for places that are obviously too far away. I think I can do better. From my research online it seems like an R-Tree or one of its variants might be a neat solution. Unfortunately, that sentence is as far as I've gotten with understanding the actual technique, as the literature is simply too dense for my non-academic head. Can somebody give me a really high overview of what the process is for populating an R-Tree with lat/long data, and then traversing the tree to find those 5 nearest neighbors of a given point? Additionally the project is in C, and I don't have to reinvent the wheel on this, so if you've used an existing open source C implementation of an R Tree I'd be interested in your experiences.

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  • C++: Constructor/destructor unresolved when not inline?

    - by Anamon
    In a plugin-based C++ project, I have a TmpClass that is used to exchange data between the main application and the plugins. Therefore the respective TmpClass.h is included in the abstract plugin interface class that is included by the main application project, and implemented by each plugin. As the plugins work on STL vectors of TmpClass instances, there needs to be a default constructor and destructor for the TmpClass. I had declared these in TmpClass.h: class TmpClass { TmpClass(); ~TmpClass(); } and implemented them in TmpClass.cpp. TmpClass::~TmpClass() {} TmpClass::TmpClass() {} However, when compiling plugins this leads to the linker complaining about two unresolved externals - the default constructor and destructor of TmpClass as required by the std::vector<TmpClass> template instantiation - even though all other functions I declare in TmpClass.h and implement in TmpClass.cpp work. As soon as I remove the (empty) default constructor and destructor from the .cpp file and inline them into the class declaration in the .h file, the plugins compile and work. Why is it that the default constructor and destructor have to be inline for this code to compile? Why does it even maatter? (I'm using MSVC++8).

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  • Point covering problem

    - by Sean
    I recently had this problem on a test: given a set of points m (all on the x-axis) and a set n of lines with endpoints [l, r] (again on the x-axis), find the minimum subset of n such that all points are covered by a line. Prove that your solution always finds the minimum subset. The algorithm I wrote for it was something to the effect of: (say lines are stored as arrays with the left endpoint in position 0 and the right in position 1) algorithm coverPoints(set[] m, set[][] n): chosenLines = [] while m is not empty: minX = min(m) bestLine = n[0] for i=1 to length of n: if n[i][0] <= m and n[i][1] > bestLine[1] then bestLine = n[i] add bestLine to chosenLines for i=0 to length of m: if m <= bestLine[1] then delete m[i] from m return chosenLines I'm just not sure if this always finds the minimum solution. It's a simple greedy algorithm so my gut tells me it won't, but one of my friends who is much better than me at this says that for this problem a greedy algorithm like this always finds the minimal solution. For proving mine always finds the minimal solution I did a very hand wavy proof by contradiction where I made an assumption that probably isn't true at all. I forget exactly what I did. If this isn't a minimal solution, is there a way to do it in less than something like O(n!) time? Thanks

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  • C++ and Dependency Injection in unit testing

    - by lhumongous
    Suppose I have a C++ class like so: class A { public: A() { } void SetNewB( const B& _b ) { m_B = _b; } private: B m_B; } In order to unit test something like this, I would have to break A's dependency on B. Since class A holds onto an actual object and not a pointer, I would have to refactor this code to take a pointer. Additionally, I would need to create a parent interface class for B so I can pass in my own fake of B when I test SetNewB. In this case, doesn't unit testing with dependency injection further complicate the existing code? If I make B a pointer, I'm now introducing heap allocation, and some piece of code is now responsible for cleaning it up (unless I use ref counted pointers). Additionally, if B is a rather trivial class with only a couple of member variables and functions, why introduce a whole new interface for it instead of just testing with an instance of B? I suppose you could make the argument that it would be easier to refactor A by using an interface. But are there some cases where two classes might need to be tightly coupled?

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