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• Go/Obj-C style interfaces with ability to extend compiled objects after initial release

  - by Skrylar

  I have a conceptual model for an object system which involves combining Go/Obj-C interfaces/protocols with being able to add virtual methods from any unit, not just the one which defines a class. The idea of this is to allow Ruby-ish open classes so you can take a minimalist approach to library development, and attach on small pieces of functionality as is actually needed by the whole program. Implementation of this involves a table of methods marked virtual in an RTTI table, which system functions are allowed to add to during module initialization. Upon typecasting an object to an interface, a Go-style lookup is done to create a vtable for that particular mapping and pass it off so you can have comparable performance to C/C++. In this case, methods may be added /afterwards/ which were not previously known and these new methods allow newer interfaces to be satisfied; while I like this idea because it seems like it would be very flexible (disregarding the potential for spaghetti code, which can happen with just about any model you use regardless). By wrapping the system calls for binding methods up in a set of clean C-compatible calls, one would also be able to integrate code with shared libraries and retain a decent amount of performance (Go does not do shared linking, and Objective-C does a dynamic lookup on each call.) Is there a valid use-case for this model that would make it worth the extra background plumbing? As much as this Dylan-style extensibility would be nice to have access to, I can't quite bring myself to a use case that would justify the overhead other than "it could make some kinds of code more extensible in future scenarios."

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• Architecture a for a central renderer rather than self-rendering

  - by The Communist Duck

  For the architectural side of rendering, there's two main ways: having each object render itself, and having a single renderer which renders everything. I'm currently aiming for the second idea, for the following reasons: The list can be sorted to only use shaders once. Else each object would have to bind the shader, because it's not sure if it's active. The objects could be sorted and grouped. Easier to swap APIs. With a few macro lines, it can be easy to swap between a DirectX renderer and an OpenGL renderer (not a reason for my project, but still a good point) Easier to manage rendering code Of course, if anyone has strong recommendations for the first method, I will listen to them. But I was wondering how make this work. First idea The renderer has a list of pointers to the renderable components of each entity, which register themselves on RenderCompoent creation. However, I'm worrying that this may end up as a lot of extra pointer weight. But I can sort the list of pointers every so often. Second idea The entire list of entities is passed to the renderer each render call. The renderer then sorts the list (each call, or maybe once?) and gets what it wants. That's a lot of passing and/or sorting, however. Other ideas ??? PROFIT Anyone got ideas? Thank you.

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• How to fix Java problem installing Matlab 2012a (64-bit) in Ubuntu 12.04 (64 bit)?

  - by Sabyasachi

  I am trying to install Matlab 2012a (64-bit) in Ubuntu 12.04LTS (64-bit). I have installed Java 7. My Java version is: sabyasachi@sabyasachi-ubuntu:~/Downloads/R2012a_UNIX$ java -version java version "1.7.0_05" Java(TM) SE Runtime Environment (build 1.7.0_05-b05) Java HotSpot(TM) 64-Bit Server VM (build 23.1-b03, mixed mode I am getting the following error while installing Matlab: sabyasachi@sabyasachi-ubuntu:~/Downloads/R2012a_UNIX$ ./install Preparing installation files ... Installing ... /tmp/mathworks_18824/sys/java/jre/glnxa64/jre/bin/java: error while loading shared libraries: libjli.so: cannot open shared object file: No such file or directory Finished How can I fix this problem? When I use -v (verbose) option I am getting the following: sabyasachi@sabyasachi-ubuntu:~/Downloads/R2012a_UNIX$ sudo ./install -v Preparing installation files ... -> DVD = /home/sabyasachi/Downloads/R2012a_UNIX -> ARCH = glnxa64 -> DISPLAY = :0 -> TESTONLY = 0 -> JRE_LOC = /tmp/mathworks_26521/sys/java/jre/glnxa64/jre -> LD_LIBRARY_PATH = /tmp/mathworks_26521/bin/glnxa64 Command to run: /tmp/mathworks_26521/sys/java/jre/glnxa64/jre/bin/java -splash:"/home/sabyasachi/Downloads/R2012a_UNIX/java/splash.png" -Djava.ext.dirs=/tmp/mathworks_26521/sys/java/jre/glnxa64/jre/lib/ext:/tmp/mathworks_26521/java/jar:/tmp/mathworks_26521/java/jarext:/tmp/mathworks_26521/java/jarext/axis2/:/tmp/mathworks_26521/java/jarext/guice/:/tmp/mathworks_26521/java/jarext/webservices/ com/mathworks/professionalinstaller/Launcher -root "/home/sabyasachi/Downloads/R2012a_UNIX" -tmpdir "/tmp/mathworks_26521" Installing ... /tmp/mathworks_26521/sys/java/jre/glnxa64/jre/bin/java: error while loading shared libraries: libjli.so: cannot open shared object file: No such file or directory Finished sabyasachi@sabyasachi-ubuntu:~/Downloads/R2012a_UNIX$

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• Which Graphics/Geometry abstraction to choose?

  - by Robz

  I've been thinking about the design for a browser app on the HTML5 canvas that simulates a 2D robot zooming around, sensing the world around it. I decided to do this from scratch just for fun. I need shapes, like polygons, circles, and lines in order to model the robot and the world it lives in. These shapes need to be drawn with different appearance attributes, like border/fill style/width/color. I also need to have geometry functions to detect intersections and containment for the robot's sensors and so that the robot doesn't go inside stuff. One idea for functions is to have two totally separate libraries, one to implement graphics (like drawShape(context, shape)) and one for geometry operations (like shapeIntersectsShape(shape1, shape2)). Or, in a more object-oriented approach, the shape objects themselves could implement methods to do their own graphics (shape.draw(context)) and geometry operations (shape1.intersects(shape2)). Then there is the data itself: whether the data to draw a shape and the data to do geometric operations on that shape should be encapsulated within the same object, or be separate structures (where one would contain the other, or both be contained inside another structure). How do existing applications that do graphics/geometry stuff deal with this? Is there one model that is best, or is each good for certain applications? Should the fact that I'm using Javascript instead of a more classical language change how I approach the design?

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• How to implement child-parent aggregation link in C++?

  - by Giorgio

  Suppose that I have three classes P, C1, C2, composition (strong aggregation) relations between P <>- C1 and P <>- C2, i.e. every instance of P contains an instance of C1 and an instance of C2, which are destroyed when the parent P instance is destroyed. an association relation between instances of C1 and C2 (not necessarily between children of the same P). To implement this, in C++ I normally define three classes P, C1, C2, define two member variables of P of type boost::shared_ptr<C1>, boost::shared_ptr<C2>, and initialize them with newly created objects in P's constructor, implement the relation between C1 and C2 using a boost::weak_ptr<C2> member variable in C1 and a boost::weak_ptr<C1> member variable in C2 that can be set later via appropriate methods, when the relation is established. Now, I also would like to have a link from each C1 and C2 object to its P parent object. What is a good way to implement this? My current idea is to use a simple constant raw pointer (P * const) that is set from the constructor of P (which, in turn, calls the constructors of C1 and C2), i.e. something like: class C1 { public: C1(P * const p, ...) : paren(p) { ... } private: P * const parent; ... }; class P { public: P(...) : childC1(new C1(this, ...)) ... { ... } private: boost::shared_ptr<C1> childC1; ... }; Honestly I see no risk in using a private constant raw pointer in this way but I know that raw pointers are often frowned upon in C++ so I was wondering if there is an alternative solution.

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• An alternative to multiple inheritance when creating an abstraction layer?

  - by sebf

  In my project I am creating an abstraction layer for some APIs. The purpose of the layer is to make multi-platform easier, and also to simplify the APIs to the feature set that I need while also providing some functionality, the implementation of which will be unique to each platform. At the moment, I have implemented it by defining and abstract class, which has methods which creates objects that implement interfaces. The abstract class and these interfaces define the capabilities of my abstraction layer. The implementation of these in my layer should of course be arbitrary from the POV view of my application, but I have done it, for my first API, by creating chains of subclasses which add more specific functionality as the features of the APIs they expose become less generic. An example would probably demonstrate this better: //The interface as seen by the application interface IGenericResource { byte[] GetSomeData(); } interface ISpecificResourceOne : IGenericResource { int SomePropertyOfResourceOne {get;} } interface ISpecificResourceTwo : IGenericResource { string SomePropertyOfResourceTwo {get;} } public abstract class MyLayer { ISpecificResourceOne CreateResourceOne(); ISpecificResourceTwo CreateResourceTwo(); void UseResourceOne(ISpecificResourceOne one); void UseResourceTwo(ISpecificResourceTwo two); } //The layer as created in my library public class LowLevelResource : IGenericResource { byte[] GetSomeData() {} } public class ResourceOne : LowLevelResource, ISpecificResourceOne { int SomePropertyOfResourceOne {get{}} } public class ResourceTwo : ResourceOne, ISpecificResourceTwo { string SomePropertyOfResourceTwo {get {}} } public partial class Implementation : MyLayer { override UseResourceOne(ISpecificResourceOne one) { DoStuff((ResourceOne)one); } } As can be seen, I am essentially trying to have two inheritance chains on the same object, but of course I can't do this so I simulate the second version with interfaces. The thing is though, I don't like using interfaces for this; it seems wrong, in my mind an interface defines a contract, any class that implements that interface should be able to be used where that interface is used but here that is clearly not the case because the interfaces are being used to allow an object from the layer to masquerade as something else, without the application needing to have access to its definition. What technique would allow me to define a comprehensive, intuitive collection of objects for an abstraction layer, while their implementation remains independent? (Language is C#)

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• Sorting objects before rendering

  - by dreta

  I'm trying to implement a scene graph and in all the articles i've come across there is talk about object sorting. So you'd sort your objects by "material" for example. Now untill i sat down and started implementing it, i kind of took this for granted, because it made sense. But now i'm wondering what does sorting actually change? In my engine, i have a manager for UBOs, i use those to store data that'll be shared between programs, at the moment that only involves time, camera and projection matrices and lights (i'm not worrying about managing which lights affect which objects ATM). Now for each model i have to change the model to world matrix uniform, no sorting is going to change that. So is the jump from changing this matrix to also setting a material for each object that bad? I vaguely remember reading somewhere that each time you change something in the pipeline, it has to get flushed and that can cause performance issues. But for each drawing call i'm setting up a model to world matrix anyway, so what sense does it make to ever be concerned about this? BTW is there any information about whether changing a uniform and calling glBufferSubData is more (or less) expensive.

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• Interview Questions in OOP

  - by Fero

  Hi all, I faced the below interview questions in OOP under PHP language. Kindly clear my clarifications regarding this. I am very confused. As i am a beginner to OOP i got too confused. Could anyone clarify these things clearly? Difference between Abstract class and interface. Interviewer : Let us consider abstract class contains three abstract methods such as a,b,c and interface contains three methods a,b,c. In this case these do the same functionality. Then why are going for abstract and why are we going for interface. Me : ? static keyword. Interviewer: We call static method without creating object by using scope resolution operator in PHP. As well as we can able to call concrete methods also. Then what is need of static keyword there? Me : .... final keyword. Interviewer: Give me any scenario of using final keyword. Me : For db connection related method Interviewer: Other than that? Me: ... Constructor. Interviewer: What is the use of constructor? Me : There is no need for object to access this. It will call automatically when the class calls. Interviewer: Other than that? Me : .... Thanks in advance...

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• OnTrigger not firing consistently

  - by Lautaro

  I have a Prefab called Player which has a Body and a Sword. The game uses 2 instances of Player, Player1 and Player2. I use Player1 to strike Player2. This is code on the sword. My hope is that Sword of Player1 will log on contct with Body of Player2. It happens but only the first hit and then i have to hit several times before another strike is logged. But when i look at log from OnTriggerStay it looks like the TriggerExit is never detected untill long after the sword is gone. void OnTriggerEnter(Collider other) { //Play sound to confirm collision var sm = ObjectDirectory.soundManager; sm.PlaySoundClip(sm.gui_02); Debug.Log(other.name + " - ENTER" ); } void OnTriggerStay(Collider other) { Debug.Log(other.name + " - collision" ); } void OnTriggerExit(Collider other) { Debug.Log(other.name + " - HAS LEFT" ); } DEBUG LOG: Player2 - ENTER UnityEngine.Debug:Log(Object) SwordControl:OnTriggerEnter(Collider) (at Assets/Scripts/SwordControl.cs:28) Player2 - collision UnityEngine.Debug:Log(Object) SwordControl:OnTriggerStay(Collider) (at Assets/Scripts/SwordControl.cs:34) (The last debug log then repeated hundreds of times long after the sword of player 1 had withdrawn and was in no contact with player 2 ) EDIT: Further tests shows that if i move player1 backwards away form player2 i trigger the OnTriggerExit. Even if the sword is not touching Player2 since after the blow. However even after OnTriggerExit it takes many tries untill i can get another blow registered.

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• How to prevent duplicate data access methods that retrieve similar data?

  - by Ronald Wildenberg

  In almost every project I work on with a team, the same problem seems to creep in. Someone writes UI code that needs data and writes a data access method: AssetDto GetAssetById(int assetId) A week later someone else is working on another part of the application and also needs an AssetDto but now including 'approvers' and writes the following: AssetDto GetAssetWithApproversById(int assetId) A month later someone needs an asset but now including the 'questions' (or the 'owners' or the 'running requests', etc): AssetDto GetAssetWithQuestionsById(int assetId) AssetDto GetAssetWithOwnersById(int assetId) AssetDto GetAssetWithRunningRequestsById(int assetId) And it gets even worse when methods like GetAssetWithOwnerAndQuestionsById start to appear. You see the pattern that emerges: an object is attached to a large object graph and you need different parts of this graph in different locations. Of course, I'd like to prevent having a large number of methods that do almost the same. Is it simply a matter of team discipline or is there some pattern I can use to prevent this? In some cases it might make sense to have separate methods, i.e. getting an asset with running requests may be expensive so I do not want to include these all the time. How to handle such cases?

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• design in agile process

  - by ying

  Recently I had an interview with dev team in a company. The team uses agile + TDD. The code exercise implements a video rental store which generates statement to calc total rental fee for each type of video (new release, children, etc) for a customer. The existing code use object like: Statement to generate statement and calc fee where big switch statement sits to use enum to determine how to calc rental fee customer holds a list of rentals movie base class and derived class for each type of movie (NEW, CHILDREN, ACTION, etc) The code originally doesn't compile as the owner was assumed to be hit by a bus. So here is what I did: outlined the improvement over object model to have better responsibility for each class. use strategy pattern to replace switch statement and weave them in config But the team says it's waste of time because there is no requirement for it and UAT test suite works and is the only guideline goes into architecture decision. The underlying story is just to get pricing feature out and not saying anything about how to do it. So the discussion is focused on why should time be spent on refactor the switch statement. In my understanding, agile methodology doesn't mean zero design upfront and such code smell should be avoided at the beginning. Also any unit/UAT test suite won't detect such code smell, otherwise sonar, findbugs won't exist. Here I want to ask: is there such a thing called agile design in the agile methodology? Just like agile documentation. how to define agile design upfront? how to know enough is enough? In my understanding, ballpark architecture and data contract among components should be defined before/when starting project, not the details. Am I right? anyone can explain what the team is really looking for in this kind of setup? is it design aspect or agile aspect? how to implement minimum viable product concept in the agile process in the real world project? Is it must that you feel embarrassed to be MVP?

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• Rotation and translation like in GTA 1 OpenGL

  - by user1876377

  Okay, so I have a figure in XZ plain. I want to move it forward/backward and rotate at it's own Y axis, then move forward again in the rotation's direction, like the character in GTA 1. Code so far: Init: spaceship_position = glm::vec3(0,0,0); spaceship_rotation = glm::vec3(0,0,0); spaceship_scale = glm::vec3(1, 1, 1); Draw: glm::mat4 transform = glm::scale<float>(spaceship_scale) * glm::rotate<float>(spaceship_rotation.x, 1, 0, 0) * glm::rotate<float>(spaceship_rotation.y, 0, 1, 0) * glm::rotate<float>(spaceship_rotation.z, 0, 0, 1) * glm::translate<float>(spaceship_position); drawMesh(spaceship, texture, transform); Update: switch (key.keysym.sym) { case SDLK_UP: spaceship_position.z += 0.1; break; case SDLK_DOWN: spaceship_position.z -= 0.1; break; case SDLK_LEFT: spaceship_rotation.y += 1; break; case SDLK_RIGHT: spaceship_rotation.y -= 1; break; } So this only moves on the Z axis, but how can I move the object on both Z and X axis where the object is facing?

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• Building a template engine - starting point

  - by Anirudh

  We're building a Django-based project with a template component. This component will be separate from the project as such and can be Django/Python, Node, Java or whatever works. The template has to be rendered into HTML. The templates will contain references to objects with properties that are defined in the DB, say, a Bus. For eg, it could be something like [object type="vehicle" weight="heavy"] and it would have to pull a random object from the DB fulfilling the criteria : type="vehicle" weight="heavy" (bus/truck/jet) and then substitute that tag with an image, say, of a Bus. Also it would have to be able to handle some processing. Eg: What is [X type="integer" lte="10"] + [Y type="integer" lte="10"] [option X+Y correct_ans="true"] [option X-Y correct_ans="false"] [option X+y+1 correct_ans="false"] The engine would be expected to fill in a random integer value <= 10 for X and Y and show radioboxes for each of the options. Would also have to store the fact that the first option is the correct answer. Does it to make sense to write something from the scratch? Or is it better to use an existing templating system (like Django's own templating system) as a starting point? Any suggestions on how I can approach this?

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• Update to SQL Server Configuration Scripting Utility

  - by Bill Graziano

  Last spring I released a utility to script SQL Server configuration information on CodePlex.  I’ve been making small changes in this application as my needs have changed.  The application is a .NET 2.0 console application.  This utility serves two needs for me.  First it helps with disaster recovery.  All server level objects (logins, jobs, linked servers, audits) are scripted to a single file per object type.  This enables the scripts to be easily run against a DR server.  If these are checked into source control you can view the history of the script and find out what changed and when. The second goal is to capture what changed inside a database.  Objects inside a database (tables, stored procedures, views, etc.) are each scripted to their own file.  This makes it easier to track the changes to an object over time.  This does include permissions and role membership so you can capture security changes.  My assumption is that a database backup is the primary method of disaster recovery for databases so this utility is designed to capture changes to objects.  You can find the full list of changes from the original on the Downloads page on CodePlex.

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• Alternative to NV Occlusion Query - getting the number of fragments which passed the depth test

  - by Etan

  In "modern" environments, the "NV Occlusion Query" extension provide a method to get the number of fragments which passed the depth test. However, on the iPad / iPhone using OpenGL ES, the extension is not available. What is the most performant approach to implement a similar behaviour in the fragment shader? Some of my ideas: Render the object completely in white, then count all the colors together using a two-pass shader where first a vertical line is rendered and for each fragment the shader computes the sum over the whole row. Then, a single vertex is rendered whose fragment sums all the partial sums of the first pass. Doesn't seem to be very efficient. Render the object completely in white over a black background. Downsample recursively, abusing the hardware linear interpolation between textures until being at a reasonably small resolution. This leads to fragments which have a greyscale level depending on the number of white pixels where in their corresponding region. Is this even accurate enough? ... ?

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• Can higher-order functions in FP be interpreted as some kind of dependency injection?

  - by Giorgio

  According to this article, in object-oriented programming / design dependency injection involves a dependent consumer, a declaration of a component's dependencies, defined as interface contracts, an injector that creates instances of classes that implement a given dependency interface on request. Let us now consider a higher-order function in a functional programming language, e.g. the Haskell function filter :: (a -> Bool) -> [a] -> [a] from Data.List. This function transforms a list into another list and, in order to perform its job, it uses (consumes) an external predicate function that must be provided by its caller, e.g. the expression filter (\x -> (mod x 2) == 0) [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] selects all even numbers from the input list. But isn't this construction very similar to the pattern illustrated above, where the filter function is the dependent consumer, the signature (a -> Bool) of the function argument is the interface contract, the expression that uses the higher-order is the injector that, in this particular case, injects the implementation (\x -> (mod x 2) == 0) of the contract. More in general, can one relate higher-order functions and their usage pattern in functional programming to the dependency injection pattern in object-oriented languages? Or in the inverse direction, can dependency injection be compared to using some kind of higher-order function?

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• Platform game collisions with Block

  - by Sri Harsha Chilakapati

  I am trying to create a platform game and doing wrong collision detection with the blocks. Here's my code // Variables GTimer jump = new GTimer(1000); boolean onground = true; // The update method public void update(long elapsedTime){ MapView.follow(this); // Add the gravity if (!onground && !jump.active){ setVelocityY(4); } // Jumping if (isPressed(VK_SPACE) && onground){ jump.start(); setVelocityY(-4); onground = false; } if (jump.action(elapsedTime)){ // jump expired jump.stop(); } // Horizontal movement setVelocityX(0); if (isPressed(VK_LEFT)){ setVelocityX(-4); } if (isPressed(VK_RIGHT)){ setVelocityX(4); } } // The collision method public void collision(GObject other){ if (other instanceof Block){ // Determine the horizontal distance between centers float h_dist = Math.abs((other.getX() + other.getWidth()/2) - (getX() + getWidth()/2)); // Now the vertical distance float v_dist = Math.abs((other.getY() + other.getHeight()/2) - (getY() + getHeight()/2)); // If h_dist > v_dist horizontal collision else vertical collision if (h_dist > v_dist){ // Are we moving right? if (getX()<other.getX()){ setX(other.getX()-getWidth()); } // Are we moving left? else if (getX()>other.getX()){ setX(other.getX()+other.getWidth()); } } else { // Are we moving up? if (jump.active){ jump.stop(); } // We are moving down else { setY(other.getY()-getHeight()); setVelocityY(0); onground = true; } } } } The problem is that the object jumps well but does not fall when moved out of platform. Here's an image describing the problem. I know I'm not checking underneath the object but I don't know how. The map is a list of objects and should I have to iterate over all the objects??? Thanks

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• Should we encourage coding styles in favor of developer's autonomy, or discourage it in favor of consistency?

  - by Saeed Neamati

  A developer writes if/else blocks with one-line code statements like: if (condition) // Do this one-line code else // Do this one-line code Another uses curly braces for all of them: if (condition) { // Do this one-line code } else { // Do this one-line code } A developer first instantiates an object, then uses it: HelperClass helper = new HelperClass(); helper.DoSomething(); Another developer instantiates and uses the object in one line: new HelperClass().DoSomething(); A developer is more easy with arrays, and for loops: string[] ordinals = new string[] {'First', 'Second', 'Third'}; for (i = 0; i < ordinals.Length; i++) { // Do something } Another writes: List<string> ordinals = new List<string>() {'First', 'Second', 'Third'}; foreach (string ordinal in ordinals) { // Do something } I'm sure that you know what I'm talking about. I call it coding style (cause I don't know what it's called). But whatever we call it, is it good or bad? Does encouraging it have an effect of higher productivity of developers? Should we ask developers to try to write code the way we tell them, so to make the whole system become style-consistent?

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• C++ Windows Forms application unhandled exception error when textbox empty

  - by cmorris1441

  I'm building a temperature conversion application in Visual Studio for a C++ course. It's a Windows Forms application and the code that I've written is below. There's other code to of course, but I'm not sure you need it to help me. My problem is, when I run the application if I don't have anything entered into either the txtFahrenheit or txtCelsius2 textboxes I get the following error: "An unhandled exception of type 'System.FormatException' occurred in mscorlib.dll" The application only works right now when a number is entered into both of the textboxes. I was told to try and use this: Double::TryParse() but I'm brand new to C++ and can't figure out how to use it, even after checking the MSDN library. Here's my code: private: System::Void btnFtoC_Click(System::Object^ sender, System::EventArgs^ e) { // Convert the input in the Fahrenheit textbox to a double datatype named fahrenheit for manipulation double fahrenheit = Convert::ToDouble(txtFahrenheit->Text); // Set the result string to F * (5/9) -32 double result = fahrenheit * .5556 - 32; // Set the Celsius text box to display the result string txtCelsius->Text = result.ToString(); } private: System::Void btnCtoF_Click(System::Object^ sender, System::EventArgs^ e) { // Convert the input in the Celsius textbox to a double datatype name celsius for manipulation double celsius = Convert::ToDouble(txtCelsius2->Text); // Set the result2 string to C * (9/5) + 32 double result2 = celsius * 1.8 + 32; // Set the Fahrenheit text box to display the result2 string txtFahrenheit2->Text = result2.ToString(); }

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• Using a Vertex Buffer and DrawUserIndexedPrimitives?

  - by MattMcg

  Let's say I have a large but static world and only a single moving object on said world. To increase performance I wish to use a vertex and index buffer for the static part of the world. I set them up and they work fine however if I throw in another draw call to DrawUserIndexedPrimitives (to draw my one single moving object) after the call to DrawIndexedPrimitives, it will error out saying a valid vertex buffer must be set. I can only assume the DrawUserIndexedPrimitive call destroyed/replaced the vertex buffer I set. In order to get around this I must call device.SetVertexBuffer(vertexBuffer) every frame. Something tells me that isn't correct as that kind of defeats the point of a buffer? To shed some light, the large vertex buffer is the final merged mesh of many repeated cubes (think Minecraft) which I manually create to reduce the amount of vertices/indexes needed (for example two connected cubes become one cuboid, the connecting faces are cut out), and also the amount of matrix translations (as it would suck to do one per cube). The moving objects would be other items in the world which are dynamic and not fixed to the block grid, so things like the NPCs who move constantly. How do I go about handling the large static world but also allowing objects to freely move about?

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• Versioning APIs

  - by Sharon

  Suppose that you have a large project supported by an API base. The project also ships a public API that end(ish) users can use. Sometimes you need to make changes to the API base that supports your project. For example, you need to add a feature that needs an API change, a new method, or requires altering of one of the objects, or the format of one of those objects, passed to or from the API. Assuming that you are also using these objects in your public API, the public objects will also change any time you do this, which is undesirable as your clients may rely on the API objects remaining identical for their parsing code to work. (cough C++ WSDL clients...) So one potential solution is to version the API. But when we say "version" the API, it sounds like this also must mean to version the API objects as well as well as providing duplicate method calls for each changed method signature. So I would then have a plain old clr object for each version of my api, which again seems undesirable. And even if I do this, I surely won't be building each object from scratch as that would end up with vast amounts of duplicated code. Rather, the API is likely to extend the private objects we are using for our base API, but then we run into the same problem because added properties would also be available in the public API when they are not supposed to be. So what is some sanity that is usually applied to this situation? I know many public services such as Git for Windows maintains a versioned API, but I'm having trouble imagining an architecture that supports this without vast amounts of duplicate code covering the various versioned methods and input/output objects. I'm aware that processes such as semantic versioning attempt to put some sanity on when public API breaks should occur. The problem is more that it seems like many or most changes require breaking the public API if the objects aren't more separated, but I don't see a good way to do that without duplicating code.

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• Are long methods always bad?

  - by wobbily_col

  So looking around earlier I noticed some comments about long methods being bad practice. I am not sure I always agree that long methods are bad (and would like opinions from others). For example I have some Django views that do a bit of processing of the objects before sending them to the view, a long method being 350 lines of code. I have my code written so that it deals with the paramaters - sorting / filtering the queryset, then bit by bit does some processing on the objects my query has returned. So the processing is mainly conditional aggregation, that has complex enough rules it can't easily be done in the database, so I have some variables declared outside the main loop then get altered during the loop. varaible_1 = 0 variable_2 = 0 for object in queryset : if object.condition_condition_a and variable_2 > 0 : variable 1+= 1 ..... ... . more conditions to alter the variables return queryset, and context So according to the theory I should factor out all the code into smaller methods, so That I have the view method as being maximum one page long. However having worked on various code bases in the past, I sometimes find it makes the code less readable, when you need to constantly jump from one method to the next figuring out all the parts of it, while keeping the outermost method in your head. I find that having a long method that is well formatted, you can see the logic more easily, as it isn't getting hidden away in inner methods. I could factor out the code into smaller methods, but often there is is an inner loop being used for two or three things, so it would result in more complex code, or methods that don't do one thing but two or three (alternatively I could repeat inner loops for each task, but then there will be a performance hit). So is there a case that long methods are not always bad? Is there always a case for writing methods, when they will only be used in one place?

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• Lubuntu customized cdrom installation crashes

  - by SBarve

  I have created customized live cd of lubuntu and it is customized using uck. After burning the CDROM and using the cdrom for installation of same CD the installation works fine on HP desktop but it fails on Dell desktop. Here is the error. Can someone help to sort out this error. We are sorry; the installer crashed. After you close this window, we will allow you to file a bug report using the integrated bug reporting tool. This will gather information about your system and your installation process. The details will be sent to our bug tracker and a developer will attend to the problem as soon as possible. Traceback (most recent call last): File "/usr/lib/ubiquity/plugins/ubi-timezone.py", line 173, in geoname-cb for result in json.loads (message.response_body.data): File "/usr/lib/python2.7/json/_init_.py", line 326, in loads return_default_decoder.decode(s) File "/usr/lib/python2.7/json/decoder.py", line 366, in decode obj, end=self.raw_decode(S, idx=_w(S,0).end ()) File "/usr/lib/python2.7/json/decoder.py", line 384, in raw_decode raise ValueError ("No JSON object could be decoded") ValueError: No JSON object could be decoded.

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• Understanding Application binary interface (ABI)

  - by Tim

  I am trying to understand the concept of Application binary interface (ABI). From The Linux Kernel Primer: An ABI is a set of conventions that allows a linker to combine separately compiled modules into one unit without recompilation, such as calling conventions, machine interface, and operating-system interface. Among other things, an ABI defines the binary interface between these units. ... The benefits of conforming to an ABI are that it allows linking object files compiled by different compilers. From Wikipedia: an application binary interface (ABI) describes the low-level interface between an application (or any type of) program and the operating system or another application. ABIs cover details such as data type, size, and alignment; the calling convention, which controls how functions' arguments are passed and return values retrieved; the system call numbers and how an application should make system calls to the operating system; and in the case of a complete operating system ABI, the binary format of object files, program libraries and so on. I was wondering whether ABI depends on both the instruction set and the OS. Are the two all that ABI depends on? What kinds of role does ABI play in different stages of compilation: preprocessing, conversion of code from C to Assembly, conversion of code from Assembly to Machine code, and linking? From the first quote above, it seems to me that ABI is needed for only linking stage, not the other stages. Is it correct? When is ABI needed to be considered? Is ABI needed to be considered during programming in C, Assembly or other languages? If yes, how are ABI and API different? Or is it only for linker or compiler? Is ABI specified for/in machine code, Assembly language, and/or of C?

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• Flickering problem with world matrix

  - by gnomgrol

  I do have a pretty wierd problem today. As soon as I try to change my translation- or rotationmatrix for an object to something else than (0,0,0), the object starts to flicker (scaling works fine). It rapid and randomly switches between the spot it should be in and a crippled something. I first thought that the problem would be z-fighting, but now Im pretty sure it isn't. I have now clue at all what it could be, here are two screenshots of the two states the plant is switching between. I already used PIX, but could find anything of use (Im not a very good debugger anyway) I would appreciate any help, thanks a lot! Important code: D3DXMatrixIdentity(&World); D3DXVECTOR3 rotaxisX = D3DXVECTOR3(1.0f, 0.0f, 0.0f); D3DXVECTOR3 rotaxisY = D3DXVECTOR3(0.0f, 1.0f, 0.0f); D3DXVECTOR3 rotaxisZ = D3DXVECTOR3(0.0f, 0.0f, 1.0f); D3DXMATRIX temprot1, temprot2, temprot3; D3DXMatrixRotationAxis(&temprot1, &rotaxisX, 0); D3DXMatrixRotationAxis(&temprot2, &rotaxisY, 0); D3DXMatrixRotationAxis(&temprot3, &rotaxisZ, 0); Rotation = temprot1 *temprot2 * temprot3; D3DXMatrixTranslation(&Translation, 0.0f, 10.0f, 0.0f); D3DXMatrixScaling(&Scale, 0.02f, 0.02f, 0.02f); //Set objs world space using the transformations World = Translation * Rotation * Scale; shader: cbuffer cbPerObject { matrix worldMatrix; matrix viewMatrix; matrix projectionMatrix; }; // Change the position vector to be 4 units for proper matrix calculations. input.position.w = 1.0f; // Calculate the position of the vertex against the world, view, and projection matrices. output.position = mul(input.position, worldMatrix); output.position = mul(output.position, viewMatrix); output.position = mul(output.position, projectionMatrix);

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