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  • Script language native extensions - avoiding name collisions and cluttering others' namespace

    - by H2CO3
    I have developed a small scripting language and I've just started writing the very first native library bindings. This is practically the first time I'm writing a native extension to a script language, so I've run into a conceptual issue. I'd like to write glue code for popular libraries so that they can be used from this language, and because of the design of the engine I've written, this is achieved using an array of C structs describing the function name visible by the virtual machine, along with a function pointer. Thus, a native binding is really just a global array variable, and now I must obviously give it a (preferably good) name. In C, it's idiomatic to put one's own functions in a "namespace" by prepending a custom prefix to function names, as in myscript_parse_source() or myscript_run_bytecode(). The custom name shall ideally describe the name of the library which it is part of. Here arises the confusion. Let's say I'm writing a binding for libcURL. In this case, it seems reasonable to call my extension library curl_myscript_binding, like this: MYSCRIPT_API const MyScriptExtFunc curl_myscript_lib[10]; But now this collides with the curl namespace. (I have even thought about calling it curlmyscript_lib but unfortunately, libcURL does not exclusively use the curl_ prefix -- the public APIs contain macros like CURLCODE_* and CURLOPT_*, so I assume this would clutter the namespace as well.) Another option would be to declare it as myscript_curl_lib, but that's good only as long as I'm the only one who writes bindings (since I know what I am doing with my namespace). As soon as other contributors start to add their own native bindings, they now clutter the myscript namespace. (I've done some research, and it seems that for example the Perl cURL binding follows this pattern. Not sure what I should think about that...) So how do you suggest I name my variables? Are there any general guidelines that should be followed?

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  • Collision detection code style

    - by Marian Ivanov
    Not only there are two useful broad-phase algorithms and a lot of useful narrowphase algorithms, there are also multiple code styles. Arrays vs. calling Make an array of broadphase checks, then filter them with narrowphase checks, then resolve them. function resolveCollisions(thingyStructure * a,thingyStructure * b,int index){ possibleCollisions = getPossibleCollisions(b,a->get(index)); for(i=0; i<possibleCollitionsNumber; i++){ if(narrowphase(possibleCollisions[i],a[index])) { collisions->push(possibleCollisions[i]); }; }; for(i=0; i<collitionsNumber; i++){ //CODE FOR RESOLUTION }; }; Make the broadphase call the narrowphase, and the narrowphase call the resolution function resolveCollisions(thingyStructure * a,thingyStructure * b,int index){ broadphase(b,a->get(index)); }; function broadphase(thingy * with, thingy * what){ while(blah){ //blahcode narrowphase(what,collidingThing); }; }; Events vs. in-the-loop Fire an event. This abstracts the check away, but it's trickier to make an equal interaction. a[index] -> collisionEvent(eventdata); //much later int collisionEvent(eventdata){ //resolution gets here } Resolve the collision inside the loop. This glues narrowphase and resolution into one layer. if(narrowphase(possibleCollisions[i],a[index])) { //CODE GOES HERE }; The questions are: Which of the first two is better, and how am I supposed to make a zero-sum Newtonian interaction under B1.

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  • For a Javascript library, what is the best or standard way to support extensibility

    - by Michael Best
    Specifically, I want to support "plugins" that modify the behavior of parts of the library. I couldn't find much information on the web about this subject. But here are my ideas for how a library could be extensible. The library exports an object with both public and "protected" functions. A plugin can replace any of those functions, thus modifying the library's behavior. Advantages of this method are that it's simple and that the plugin's functions can have full access to the library's "protected" functions. Disadvantages are that the library may be harder to maintain with a larger set of exposed functions and it could be hard to debug if multiple plugins are involved (how to know which plugin modified which function?). The library provides an "add plugin" function that accepts an object with a specific interface. Internally, the library will use the plugin instead of it's own code if appropriate. With this method, the internals of the library can be rearranged more freely as long as it still supports the same plugin interface. This could also support having different plugin interfaces to modify different parts of the library. A disadvantage of this method is that the plugins may have to re-implement code that is already part of the library since the library's internal functions are not exported. The library provides a "set implementation" function that accepts an object inherited from a specific base object. The library's public API calls functions in the implementation object for any functionality that can be modified and the base implementation object includes the core functionality, with both external (to the API) and internal functions. A plugin creates a new implementation object, which inherits from the base object and replaces any functions it wants to modify. This combines advantages and disadvantages of both the other methods.

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  • QapTcha error issue. Works locally, not on live server [migrated]

    - by BlassFemur
    I am adding QapTcha (http://demos.myjqueryplugins.com/qaptcha/) to a website that I am working on and I'm getting the error "Uncaught TypeError: Cannot read property 'error' of null". What's weird to me is everything is working perfectly locally. No errors or anything. Once I uploaded via ftp to the live server, I get the above error. Below is the block of code that seems to be generating the error: Slider.draggable({ revert: function(){ if(opts.autoRevert) { if(parseInt(Slider.css("left")) (bgSlider.width()-Slider.width()-10)) return false; else return true; } }, containment: bgSlider, axis:'x', stop: function(event,ui){ if(ui.position.left (bgSlider.width()-Slider.width()-10)) { // set the SESSION iQaptcha in PHP file $.post(opts.PHPfile,{ action : 'qaptcha', qaptcha_key : inputQapTcha.attr('name') }, function(data) { if(!data.error) Uncaught TypeError: Cannot read property 'error' of null { Slider.draggable('disable').css('cursor','default'); inputQapTcha.val(''); TxtStatus.text(opts.txtUnlock).addClass('dropSuccess').removeClass('dropError'); form.find('input[type=\'submit\']').removeAttr('disabled'); if(opts.autoSubmit) form.find('input[type=\'submit\']').trigger('click'); } },'json'); } } }); I'm not really sure what's going on as to why it works locally and not on the server. Any help/ suggestions would be appreciated. Thanks

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  • Does the HTMLEditor control raise any client-side events?

    - by SAMIR BHOGAYTA
    The HTML Editor has three modes: Design, HTML Text and preview mode. Design mode is in an IFrame. HTML Text is prensented in a TextArea and preview mode is in another Iframe. The code rendered about these three modes is as below. iframe id="editor1_ctl02_ctl00" name="editor1_ctl02_ctl00" marginheight="0" marginwidth="0" frameborder="0" src="javascript:false;" style="height:100%;width:100%;display:none;border-width:0px;" /iframe textarea id="editor1_ctl02_ctl01" class="ajax__htmleditor_htmlpanel_default" style="height:100%;width:100%;display:none;" /textarea iframe id="editor1_ctl02_ctl02" name="editor1_ctl02_ctl02" marginheight="0" marginwidth="0" frameborder="0" src="javascript:false;" style="height:100%;width:100%;display:none;border-width:0px;" /iframe In design mode, we can use the following JavaScript to append a callback function in onKeypress event. script type="text/javascript" var count = 0; function pageLoad() { $get('editor1_ctl02_ctl00').contentWindow.document.body.onkeypress = function() { count++; $get('cc').innerHTML = "you input " + count + "charactors"; }; } /script As a same way, you can append another keypress event on TextArea and preview IFrame.

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  • Take care to unhook Anonymous Delegates

    - by David Vallens
    Anonymous delegates are great, they elimiante the need for lots of small classes that just pass values around, however care needs to be taken when using them, as they are not automatically unhooked when the function you created them in returns. In fact after it returns there is no way to unhook them. Consider the following code.   using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Diagnostics; namespace ConsoleApplication1 { class Program { static void Main(string[] args) { SimpleEventSource t = new SimpleEventSource(); t.FireEvent(); FunctionWithAnonymousDelegate(t); t.FireEvent(); } private static void FunctionWithAnonymousDelegate(SimpleEventSource t) { t.MyEvent += delegate(object sender, EventArgs args) { Debug.WriteLine("Anonymous delegate called"); }; t.FireEvent(); } } public class SimpleEventSource { public event EventHandler MyEvent; public void FireEvent() { if (MyEvent == null) { Debug.WriteLine("Attempting to fire event - but no ones listening"); } else { Debug.WriteLine("Firing event"); MyEvent(this, EventArgs.Empty); } } } } If you expected the anonymous delegates do die with the function that created it then you would expect the output Attempting to fire event - but no ones listeningFiring eventAnonymous delegate calledAttempting to fire event - but no ones listening However what you actually get is Attempting to fire event - but no ones listeningFiring eventAnonymous delegate calledFiring eventAnonymous delegate called In my example the issue is just slowing things down, but if your delegate modifies objects, then you could end up with dificult to diagnose bugs. A solution to this problem is to unhook the delegate within the function var myDelegate = delegate(){Console.WriteLine("I did it!");}; MyEvent += myDelegate; // .... later MyEvent -= myDelegate;

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  • Why doesn't the "scroll bar" on my laptop touchpad work?

    - by Antonio Guzman Belmont
    EDIT, from Google translate: Well buy my laptop with windows 7 and the touchpad has some arrows up and down to q deslises finger on the right side as if the q scroll the scroll bar handles, recently installed Ubuntu 11.10 and there is also served by the touchpad scroll so to speak but then asked me and I did update (late hours) and longer term attempt q dezlizar my finger down the right side of the touchpad and now low, anyone can tell me I can do about q to q and windows function as and ubuntu 11.10, I think now I have ubuntu 4.12 EDIT.2 (minimal tidy-up) I bought my laptop with Windows 7 installed. The touchpad has up/down arrows on the right side, as if this would scroll. When I installed Ubuntu 11.10, I was able to use this touchpad scroll function. I recently did an update (at some late hours) and i can no longer use right side of the touchpad to scroll. Can anyone tell me how to get the same function as I had in Windows and Ubuntu 11.10 ? I think I now have Ubuntu 12.04 Original question: Bueno compre mi lap con windows 7 y en el touchpad tiene unas flechitas arriba y abajo para q deslises el dedo del lado derecho como si fuese el scroll q maneja la barra de desplazamiento, recientemente instale ubuntu 11.10 y ahi servia tambien el scroll del touchpad por asi decirlo pero luego me pidio actualizar y lo hice(tardo horas) y ya q termino intento dezlizar mi dedo para bajar por la parte derecha del touchpad y ahora no baja, alguien me puede decir q puedo hacer al respecto para q funcione como e windows y en ubuntu 11.10, ahora tengo ubuntu 12.04 creo

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  • Dealing with curly brace soup

    - by Cyborgx37
    I've programmed in both C# and VB.NET for years, but primarily in VB. I'm making a career shift toward C# and, overall, I like C# better. One issue I'm having, though, is curly brace soup. In VB, each structure keyword has a matching close keyword, for example: Namespace ... Class ... Function ... For ... Using ... If ... ... End If If ... ... End If End Using Next End Function End Class End Namespace The same code written in C# ends up very hard to read: namespace ... { class ... { function ... { for ... { using ... { if ... { ... } if ... { ... } } } // wait... what level is this? } } } Being so used to VB, I'm wondering if there's a technique employed by c-style programmers to improve readability and to ensure that your code ends up in the correct "block". The above example is relatively easy to read, but sometimes at the end of a piece of code I'll have 8 or more levels of curly braces, requiring me to scroll up several pages to figure out which brace ends the block I'm interested in.

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  • What are the requirements to test a website using jquery.get() ? [migrated]

    - by Frankie
    I am working on a simple website. It has to search quite a few text files in different sub-folders. The rest of the page uses jquery, so I would like to use it for this also. The function I am looking at is .get() for downloading the files. So my main question is, can I test this on my local computer (Ubuntu Linux) or do I have to have it uploaded to a server? Also, if there's a better way to go about this, that would be nice to know. However, I'm more worried about getting it working. Thanks, Frankie PS: Heres the JS/jQuery code for downloading the files to an array. g_lists = new Array(); $(":checkbox").each(function(i){ if ($(this).attr("name") != "0") { var path = "../" + $(this).attr("name") + ".txt"; $("#bot").append("<br />" + path); // debug $.get(path, function(data){ g_lists[i] = data; $("#bot").html(data); }); } else { g_lists[i] = ""; } }); Edit: Just a note about the path variable. I think it's correct, but I'm not 100% sure. I'm new to web development. Here's some examples it produces and the directory tree of the site. Maybe it will help, can't hurt. . +-- include ¦   +-- jquery.js ¦   +-- load.js +-- index.xhtml +-- style.css +-- txt    +-- Scripting_Tools    +-- Editors.txt    +-- Other.txt Examples of path: ../txt/Scripting_Tools/Editors.txt ../txt/Scripting_Tools/Other.txt Well I'm a new user, so I can't "answer" my own question, so I'll just post it here: After asking for help on a IRC chat channel specific to jQuery, I was told I could use this on a local host. To do this I installed Apache web server, and copied my site into it's directory. More information on setting it up can be found here: http://www.howtoforge.com/ubuntu_debian_lamp_server Then to run the site I navigated my browser to "localhost" and everything works.

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  • Using PDO with MVC

    - by mister martin
    I asked this question at stackoverflow and received no response (closed as duplicate with no answer). I'm experimenting with OOP and I have the following basic MVC layout: class Model { // do database stuff } class View { public function load($filename, $data = array()) { if(!empty($data)) { extract($data); } require_once('views/header.php'); require_once("views/$filename"); require_once('views/footer.php'); } } class Controller { public $model; public $view; function __construct() { $this->model = new Model(); $this->view = new View(); // determine what page we're on $page = isset($_GET['view']) ? $_GET['view'] : 'home'; $this->display($page); } public function display($page) { switch($page) { case 'home': $this->view->load('home.php'); break; } } } These classes are brought together in my setup file: // start session session_start(); require_once('Model.php'); require_once('View.php'); require_once('Controller.php'); new Controller(); Now where do I place my database connection code and how do I pass the connection onto the model? try { $db = new PDO('mysql:host='.DB_HOST.';dbname='.DB_DATABASE.'', DB_USERNAME, DB_PASSWORD); $db->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION); } catch(PDOException $err) { die($err->getMessage()); } I've read about Dependency Injection, factories and miscellaneous other design patterns talking about keeping SQL out of the model, but it's all over my head using abstract examples. Can someone please just show me a straight-forward practical example?

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  • Validate that a Checkbox is checked using javascript

    - by H(at)Ni
    I was facing a challenge yesterday that I was creating a Visual webpart and I wanted to validate the a submit button is only visible if the user checked a "I agree to terms" checkbox. Something was weired that I tested my code on a normal asp.net website and it worked perfectly while it had a different behaviour inside the webpart which is whenever I check the checkbox, the button is enabled but it will not fire the asp.net validators in client side. It posts back the page and then the validators appear after that. So, I tried to change my type of thinking and I reached a different solution is that to call a javascript function whenever the button is clicked and then check if the checkbox is clicked or not. To illustrate more, here are an example to what I'm saying: 1. Button in aspx page: <asp:Button OnClientClick="CheckForCondition();"  ValidationGroup="CompaniesSection" ID="btnCompaniesSubmit"                         runat="server" Text="Submit" /> 2. CheckForCondition() function: <script language="javascript" type="text/javascript">                         function CheckForCondition() {                             if ($jq('#<%= ChkCompanyCheck.ClientID %>:checked').val() == undefined) {                                 $jq('#lblCheckBox').show();                                 return false;                             }                             else {                                 $jq('#lblCheckBox').hide();                                 return true;                             }                         }                      </script> 3. lblCheckBox is simply a label that shows a red asterisk beside the checkbox to indicate that it's a required field. <label id="lblCheckBox" style="color:Red;display:none">*</label>

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  • How to calculate square root in PHP [explained] [on hold]

    - by Enes Imsirovic
    At first code ! Don't forget embed the JQuery ! <html> <head> <title>Simple jQuery and PHP Square Root example</title> <script src="js/jquery-1.10.1.js" type="text/javascript"></script> <script type="text/javascript"> $(document).ready(function() { $('#form').submit(function(){ var number = $('#number').val(); $.ajax({type:"post",url:"calculate.php",data:"number=" +number,success:function(msg){$('#result').hide(); $("#result").html("<h3>" + msg + "</h3>").fadeIn("slow"); } }); return false; }); }); </script> </head> <body> <form id="form" action="calculate.php" method="post"> Enter number: <input id="number" type="text" name="number" /> <input id="submit" type="submit" value="Calculate Square Root" name="submit"/> </form> <p id="result"></p> </body> </html> Second code witch would be connected with first : calculate.php <?php if($_POST['number']==null){ echo "Please Enter a Number"; }else { if (!is_numeric($_POST['number'])) { echo "Please enter only numbers"; }else{ echo "Square Root of " .$_POST['number'] ." is ".sqrt($_POST['number']); } } ?> Chiefly for begginers, to see the power of PHP :) xD Load this on your localhost.. PHP files and JS : https://mega.co.nz/#!Et8zWSBb!KX2PFxa2Pzw_l-wi6QU8xi_eKTlHbtQuBsT_DvXrifk At least it look like this : http://imgur.com/vNnDRQ3

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  • Automatically triggering standard spaceship controls to stop its motion

    - by Garan
    I have been working on a 2D top-down space strategy/shooting game. Right now it is only in the prototyping stage (I have gotten basic movement) but now I am trying to write a function that will stop the ship based on it's velocity. This is being written in Lua, using the Love2D engine. My code is as follows (note- object.dx is the x-velocity, object.dy is the y-velocity, object.acc is the acceleration, and object.r is the rotation in radians): function stopMoving(object, dt) local targetr = math.atan2(object.dy, object.dx) if targetr == object.r + math.pi then local currentspeed = math.sqrt(object.dx*object.dx+object.dy*object.dy) if currentspeed ~= 0 then object.dx = object.dx + object.acc*dt*math.cos(object.r) object.dy = object.dy + object.acc*dt*math.sin(object.r) end else if (targetr - object.r) >= math.pi then object.r = object.r - object.turnspeed*dt else object.r = object.r + object.turnspeed*dt end end end It is implemented in the update function as: if love.keyboard.isDown("backspace") then stopMoving(player, dt) end The problem is that when I am holding down backspace, it spins the player clockwise (though I am trying to have it go the direction that would be the most efficient at getting to the angle it would have to be) and then it never starts to accelerate the player in the direction opposite to it's velocity. What should I change in this code to get that to work? EDIT : I'm not trying to just stop the player in place, I'm trying to get it to use it's normal commands to neutralize it's existing velocity. I also changed math.atan to math.atan2, apparently it's better. I noticed no difference when running it, though.

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  • What is logical cohesion, and why is it bad or undesirable?

    - by Matt Fenwick
    From the c2wiki page on coupling & cohesion: Cohesion (interdependency within module) strength/level names : (from worse to better, high cohesion is good) Coincidental Cohesion : (Worst) Module elements are unrelated Logical Cohesion : Elements perform similar activities as selected from outside module, i.e. by a flag that selects operation to perform (see also CommandObject). i.e. body of function is one huge if-else/switch on operation flag Temporal Cohesion : operations related only by general time performed (i.e. initialization() or FatalErrorShutdown?()) Procedural Cohesion : Elements involved in different but sequential activities, each on different data (usually could be trivially split into multiple modules along linear sequence boundaries) Communicational Cohesion : unrelated operations except need same data or input Sequential Cohesion : operations on same data in significant order; output from one function is input to next (pipeline) Informational Cohesion: a module performs a number of actions, each with its own entry point, with independent code for each action, all performed on the same data structure. Essentially an implementation of an abstract data type. i.e. define structure of sales_region_table and its operators: init_table(), update_table(), print_table() Functional Cohesion : all elements contribute to a single, well-defined task, i.e. a function that performs exactly one operation get_engine_temperature(), add_sales_tax() (emphasis mine). I don't fully understand the definition of logical cohesion. My questions are: what is logical cohesion? Why does it get such a bad rap (2nd worst kind of cohesion)?

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  • Questions before I revamp my rendering engine to use shaders (GLSL)

    - by stephelton
    I've written a fairly robust rendering engine using OpenGL ES 1.1 (fixed-function.) I've been looking into revamping the engine to use OpenGL ES 2.0, which necessitates that I use shaders. I've been absorbing information all day long and still have some questions. Firstly, lighting. The fixed-function pipeline is guaranteed to have at least 8 lights available. My current engine finds lights that are "close" to the primitives being drawn and enables them; I don't know how many lights are going to be enabled until I draw a given model. Nothing is dynamically allocated in GLSL, so I have to define in a shader some number of lights to be used, right? So if I want to stick with 8, should I write my general purpose shader to have 8 lights and then use uniforms to tell it how many / which lights to use? Which brings me to another question: should I be concerned with the amount of data I'm allocating in a shader? Recent video cards have hundreds of "stream processors." If I've got a fragment shader being used on some number of fragments in a given triangle, I assume they must each have their own stack to work on. Are read-only variables copied here, or read when needed? My initial goal is to rework my code so that it is virtually identical to the current implementation. What I have in mind is to create my own matrix stack so that I can implement something along the lines of push/popMatrix and apply all my translations, rotations, and scales to this matrix, then provide the matrix to the vertex shader so that it can make very quick vertex translations. Is this approach sound? Edit: My original intention was to ask if there was a tutorial that would explain the bare minimum necessary to jump from fixed-function to using shaders. Thanks!

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  • Do objects maintain identity under all non-cloning conditions in PHP?

    - by Buttle Butkus
    PHP 5.5 I'm doing a bunch of passing around of objects with the assumption that they will all maintain their identities - that any changes made to their states from inside other objects' methods will continue to hold true afterwards. Am I assuming correctly? I will give my basic structure here. class builder { protected $foo_ids = array(); // set in construct protected $foo_collection; protected $bar_ids = array(); // set in construct protected $bar_collection; protected function initFoos() { $this->foo_collection = new FooCollection(); foreach($this->food_ids as $id) { $this->foo_collection->addFoo(new foo($id)); } } protected function initBars() { // same idea as initFoos } protected function wireFoosAndBars(fooCollection $foos, barCollection $bars) { // arguments are passed in using $this->foo_collection and $this->bar_collection foreach($foos as $foo_obj) { // (foo_collection implements IteratorAggregate) $bar_ids = $foo_obj->getAssociatedBarIds(); if(!empty($bar_ids) ) { $bar_collection = new barCollection(); // sub-collection to be a component of each foo foreach($bar_ids as $bar_id) { $bar_collection->addBar(new bar($bar_id)); } $foo_obj->addBarCollection($bar_collection); // now each foo_obj has a collection of bar objects, each of which is also in the main collection. Are they the same objects? } } } } What has me worried is that foreach supposedly works on a copy of its arrays. I want all the $foo and $bar objects to maintain their identities no matter which $collection object they become of a part of. Does that make sense?

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  • Are injectable classes allowed to have constructor parameters in DI?

    - by Songo
    Given the following code: class ClientClass{ public function print(){ //some code to calculate $inputString $parser= new Parser($inputString); $result= $parser->parse(); } } class Parser{ private $inputString; public __construct($inputString){ $this->inputString=$inputString; } public function parse(){ //some code } } Now the ClientClass has dependency on class Parser. However, if I wanted to use Dependency Injection for unit testing it would cause a problem because now I can't send the input string to the parser constructor like before as its calculated inside ClientCalss itself: class ClientClass{ private $parser; public __construct(Parser $parser){ $this->parser=$parser; } public function print(){ //some code to calculate $inputString $result= $this->parser->parse(); //--> will throw an exception since no string was provided } } The only solution I found was to modify all my classes that took parameters in their constructors to utilize Setters instead (example: setInputString()). However, I think there might be a better solution than this because sometimes modifying existing classes can cause much harm than benefit. So, Are injectable classes not allowed to have input parameters? If a class must take input parameters in its constructor, what would be the way to inject it properly? UPDATE Just for clarification, the problem happens when in my production code I decide to do this: $clientClass= new ClientClass(new Parser($inputString));//--->I have no way to predict $inputString as it is calculated inside `ClientClass` itself. UPDATE 2 Again for clarification, I'm trying to find a general solution to the problem not for this example code only because some of my classes have 2, 3 or 4 parameters in their constructors not only one.

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  • C++: calling non-member functions with the same syntax of member ones

    - by peoro
    One thing I'd like to do in C++ is to call non-member functions with the same syntax you call member functions: class A { }; void f( A & this ) { /* ... */ } // ... A a; a.f(); // this is the same as f(a); Of course this could only work as long as f is not virtual (since it cannot appear in A's virtual table. f doesn't need to access A's non-public members. f doesn't conflict with a function declared in A (A::f). I'd like such a syntax because in my opinion it would be quite comfortable and would push good habits: calling str.strip() on a std::string (where strip is a function defined by the user) would sound a lot better than calling strip( str );. most of the times (always?) classes provide some member functions which don't require to be member (ie: are not virtual and don't use non-public members). This breaks encapsulation, but is the most practical thing to do (due to point 1). My question here is: what do you think of such feature? Do you think it would be something nice, or something that would introduce more issues than the ones it aims to solve? Could it make sense to propose such a feature to the next standard (the one after C++0x)? Of course this is just a brief description of this idea; it is not complete; we'd probably need to explicitly mark a function with a special keyword to let it work like this and many other stuff.

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  • Collision detection between a sprite and rectangle in canvas

    - by Andy
    I'm building a Javascript + canvas game which is essentially a platformer. I have the player all set up and he's running, jumping and falling, but I'm having trouble with the collision detection between the player and blocks (the blocks will essentially be the platforms that the player moves on). The blocks are stored in an array like this: var blockList = [[50, 400, 100, 100]]; And drawn to the canvas using this: this.draw = function() { c.fillRect(blockList[0][0], blockList[0][1], 100, 100); } I'm checking for collisions using something along these lines in the player object: this.update = function() { // Check for collitions with blocks for(var i = 0; i < blockList.length; i++) { if((player.xpos + 34) > blockList[i][0] && player.ypos > blockList[i][1]) { player.xpos = blockList[i][0] - 28; return false; } } // Other code to move the player based on keyboard input etc } The idea is if the player will collide with a block in the next game update (the game uses a main loop running at 60Htz), the function will return false and exit, thus meaning the player won't move. Unfortunately, that only works when the player hits the left side of the block, and I can't work out how to make it so the player stops if it hits any side of the block. I have the properties player.xpos and player.ypos to help here.

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  • auto tabbing not working on iphone

    - by Sarita
    I have problem with auto tabbing on Iphone or android. This auto tabbing code work perfectly on each browser of pc but not on mobile. please help me. its urgent. $(document).ready(function() { WireAutoTab('<%= PartOne.ClientID %', '<%= PartTwo.ClientID %', 3); WireAutoTab('<%= PartTwo.ClientID %', '<%= PartThree.ClientID %', 2); }); function WireAutoTab(CurrentElementID, NextElementID, FieldLength) { //Get a reference to the two elements in the tab sequence. var CurrentElement = $('#' + CurrentElementID); var NextElement = $('#' + NextElementID); CurrentElement.keyup(function(e) { //Retrieve which key was pressed. var KeyID = (window.event) ? event.keyCode : e.keyCode; //If the user has filled the textbox to the given length and //the user just pressed a number or letter, then move the //cursor to the next element in the tab sequence. if (CurrentElement.val().length >= FieldLength && ((KeyID >= 48 && KeyID <= 90) || (KeyID >= 96 && KeyID <= 105))) NextElement.focus(); }); }

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  • Messaging with KnockoutJs

    - by Aligned
    MVVM Light has Messaging that helps keep View Models decoupled, isolated, and keep the separation of concerns, while allowing them to communicate with each other. This is a very helpful feature. One View Model can send off a message and if anyone is listening for it, they will react, otherwise nothing will happen. I now want to do the same with KnockoutJs View Models. Here are some links on how to do this: http://stackoverflow.com/questions/9892124/whats-the-best-way-of-linking-synchronising-view-models-in-knockout http://www.knockmeout.net/2012/05/using-ko-native-pubsub.html ~ this is a great article describing the ko.subscribable type. http://jsfiddle.net/rniemeyer/z7KgM/ ~ shows how to do the subscription https://github.com/rniemeyer/knockout-postbox will be used to help with the PubSub (described in the blog post above) through the Nuget package. http://jsfiddle.net/rniemeyer/mg3hj/ of knockout-postbox   Implementation: Use syncWith for two-way synchronization. MainVM: self.selectedElement= ko.observable().syncWith (“selectedElement”); ElementListComponentVM example: self.selectedElement= ko.observable().syncWith(“selectedElement”); ko.selectedElement.subscribe(function(){ // do something with the seletion change }); ElementVMTwo: self.selectedElement= ko.observable().syncWith (“selectedElement”); // subscribe example ko.postbox.subscribe(“changeMessage”, function(newValue){ }); // or use subscribeTo this.visible = ko.observable().subscribeTo("section", function(newValue) { // do something here }); · Use ko.toJS to avoid both sides having the same reference (see the blog post). · unsubscribeFrom should be called when the dialog is hidden or closed · Use publishOn to automatically send out messages when an observable changes o ko.observable().publishOn(“section”);

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  • Recreating Doodle Jump in Canvas - Platforms spawning out of reach

    - by kushsolitary
    I have started to recreate Doodle Jump in HTML using Canvas. Here's my current progress. As you can see, if you play it for a few seconds, some platforms will be out of the player's reach. I don't know why is this happening. Here's the code which is responsible for the re-spawning of platforms. //Movement of player affected by gravity if(player.y > (height / 2) - (player.height / 2)) { player.y += player.vy; player.vy += gravity; } else { for(var i = 0; i < platforms.length; i++) { var p = platforms[i]; if(player.vy < 0) { p.y -= player.vy; player.vy += 0.08; } if(p.y > height) { position = 0; var h = p.y; platforms[i] = new Platform(); } if(player.vy >= 0) { player.y += player.vy; player.vy += gravity; } } } Also, here's the platform class. //Platform class function Platform(y) { this.image = new Image(); this.image.src = platformImg; this.width = 105; this.height = 25; this.x = Math.random() * (width - this.width); this.y = y || position; position += height / platformCount; //Function to draw it this.draw = function() { try { ctx.drawImage(this.image, this.x, this.y, this.width, this.height); } catch(e) {} }; } You can also see the whole code on the link I provided. Also, when a platform goes out of the view port, the jump animation becomes quirky. I am still trying to find out what's causing this but can't find any solution.

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  • Retrieving database column using JSON [migrated]

    - by arokia
    I have a database consist of 4 columns (id-symbol-name-contractnumber). All 4 columns with their data are being displayed on the user interface using JSON. There is a function which is responisble to add new column to the database e.g (countrycode). The coulmn is added successfully to the database BUT not able to show the new added coulmn in the user interface. Below is my code that is displaying the columns. Can you help me? table.php $(document).ready(function () { // prepare the data var theme = getDemoTheme(); var source = { datatype: "json", datafields: [ { name: 'id' }, { name: 'symbol' }, { name: 'name' }, { name: 'contractnumber' } ], url: 'data.php', filter: function() { // update the grid and send a request to the server. $("#jqxgrid").jqxGrid('updatebounddata', 'filter'); }, cache: false }; var dataAdapter = new $.jqx.dataAdapter(source); // initialize jqxGrid $("#jqxgrid").jqxGrid( { source: dataAdapter, width: 670, theme: theme, showfilterrow: true, filterable: true, columns: [ { text: 'id', datafield: 'id', width: 200 }, { text: 'symbol', datafield: 'symbol', width: 200 }, { text: 'name', datafield: 'name', width: 100 }, { text: 'contractnumber', filtertype: 'list', datafield: 'contractnumber' } ] }); }); data.php <?php #Include the db.php file include('db.php'); $query = "SELECT * FROM pricelist"; $result = mysql_query($query) or die("SQL Error 1: " . mysql_error()); $orders = array(); // get data and store in a json array while ($row = mysql_fetch_array($result, MYSQL_ASSOC)) { $pricelist[] = array( 'id' => $row['id'], 'symbol' => $row['symbol'], 'name' => $row['name'], 'contractnumber' => $row['contractnumber'] ); } echo json_encode($pricelist); ?>

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  • Pure functional programming and game state

    - by Fu86
    Is there a common technique to handle state (in general) in a functional programming language? There are solutions in every (functional) programming language to handle global state, but I want to avoid this as far as I could. All state in a pure functional manner are function parameters. So I need to put the whole game state (a gigantic hashmap with the world, players, positions, score, assets, enemies, ...)) as a parameter to all functions which wants to manipulate the world on a given input or trigger. The function itself picks the relevant information from the gamestate blob, do something with it, manipulate the gamestate and return the gamestate. But this looks like a poor mans solution for the problem. If I put the whole gamestate into all functions, there is no benefit for me in contrast to global variables or the imperative approach. I could put just the relevant information into the functions and return the actions which will be taken for the given input. And one single function apply all the actions to the gamestate. But most functions need a lot of "relevant" information. move() need the object position, the velocity, the map for collision, position of all enemys, current health, ... So this approach does not seem to work either. So my question is how do I handle the massive amount of state in a functional programming language -- especially for game development?

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  • Testing a codebase with sequential cohesion

    - by iveqy
    I've this really simple program written in C with ncurses that's basically a front-end to sqlite3. I would like to implement TDD to continue the development and have found a nice C unit framework for this. However I'm totally stuck on how to implement it. Take this case for example: A user types a letter 'l' that is captured by ncurses getch(), and then an sqlite3 query is run that for every row calls a callback function. This callback function prints stuff to the screen via ncurses. So the obvious way to fully test this is to simulate a keyboard and a terminal and make sure that the output is the expected. However this sounds too complicated. I was thinking about adding an abstraction layer between the database and the UI so that the callback function will populate a list of entries and that list will later be printed. In that case I would be able to check if that list contains the expected values. However, why would I struggle with a data structure and lists in my program when sqlite3 already does this? For example, if the user wants to see the list sorted in some other way, it would be expensive to throw away the list and repopulate it. I would need to sort the list, but why should I implement sorting when sqlite3 already has that? Using my orginal design I could just do an other query sorted differently. Previously I've only done TDD with command line applications, and there it's really easy to just compare the output with what I'm expected. An other way would be to add CLI interface to the program and wrap a test program around the CLI to test everything. (The way git.git does with it's test-framework). So the question is, how to add testing to a tightly integrated database/UI.

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