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  • Should the 12-String be in it's own class and why? Java

    - by MayNotBe
    This is my first question here. I will amend it as instructed. This is regarding a homework project in my first Java programming class (online program). The assignment is to create a "stringed instrument" class using (among other things) an array of String names representing instrument string names ("A", "E", etc). The idea for the 12-string is beyond the scope of the assignment (it doesn't have to be included at all) but now that I've thought of it, I want to figure out how to make it work. Part of me feels like the 12-String should have it's own class, but another part of me feels that it should be in the guitar class because it's a guitar. I suppose this will become clear as I progress but I thought I would see what kind of response I get here. Also, why would they ask for a String[] for the instrument string names? Seems like a char[] makes more sense. Thank you for any insight. Here's my code so far (it's a work in progress): public class Guitar { private int numberOfStrings = 6; private static int numberOfGuitars = 0; private String[] stringNotes = {"E", "A", "D", "G", "B", "A"}; private boolean tuned = false; private boolean playing = false; public Guitar(){ numberOfGuitars++; } public Guitar(boolean twelveString){ if(twelveString){ stringNotes[0] = "E, E"; stringNotes[1] = "A, A"; stringNotes[2] = "D, D"; stringNotes[3] = "G, G"; stringNotes[4] = "B, B"; stringNotes[5] = "E, E"; numberOfStrings = 12; } } public int getNumberOfStrings() { return numberOfStrings; } public void setNumberOfStrings(int strings) { if(strings == 12 || strings == 6) { if(strings == 12){ stringNotes[0] = "E, E"; stringNotes[1] = "A, A"; stringNotes[2] = "D, D"; stringNotes[3] = "G, G"; stringNotes[4] = "B, B"; stringNotes[5] = "E, E"; numberOfStrings = strings; } if(strings == 6) numberOfStrings = strings; }//if else System.out.println("***ERROR***Guitar can only have 6 or 12 strings***ERROR***"); } public void getStringNotes() { for(int i = 0; i < stringNotes.length; i++){ if(i == stringNotes.length - 1) System.out.println(stringNotes[i]); else System.out.print(stringNotes[i] + ", "); }//for }

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  • Web Design for the Web 2.0 Age

    A well crafted website is vital to the success of any new business these days. Launch parties have replaced ribbon cuttings and websites often precede the opening of store doors. Giving your business... [Author: Case Ernsting - Web Design and Development - April 05, 2010]

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  • Is "If a method is re-used without changes, put the method in a base class, else create an interface" a good rule-of-thumb?

    - by exizt
    A colleague of mine came up with a rule-of-thumb for choosing between creating a base class or an interface. He says: Imagine every new method that you are about to implement. For each of them, consider this: will this method be implemented by more than one class in exactly this form, without any change? If the answer is "yes", create a base class. In every other situation, create an interface. For example: Consider the classes cat and dog, which extend the class mammal and have a single method pet(). We then add the class alligator, which doesn't extend anything and has a single method slither(). Now, we want to add an eat() method to all of them. If the implementation of eat() method will be exactly the same for cat, dog and alligator, we should create a base class (let's say, animal), which implements this method. However, if it's implementation in alligator differs in the slightest way, we should create an IEat interface and make mammal and alligator implement it. He insists that this method covers all cases, but it seems like over-simplification to me. Is it worth following this rule-of-thumb?

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  • Android app, No error message but has stopped unexpectedly [migrated]

    - by user74722
    Does anyone know what is my problem. I do not have any compile error messages however when i run the app it crashes and stops unexpectedly. Here is my codes. Thank you in advance. ListView l ; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_final_project); String arr[]={"Red","Green","Blue","Yellow","Cyan"}; l=(ListView) findViewById(R.id.listView1); ArrayAdapter<String> adapter=new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_list_item_1, arr); l.setAdapter(adapter); Button buttonOne = (Button) findViewById(R.id.button1); buttonOne.setOnClickListener(new OnClickListener(){ @Override public void onClick(View v){ setContentView(R.layout.layout_save); // setContentView(R.layout.activity_final_project); //startActivity(new Intent("com.example.finalproject.layout_save")); } }); }

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  • Which order to define getters and setters in? [closed]

    - by N.N.
    Is there a best practice for the order to define getters and setters in? There seems to be two practices: getter/setter pairs first getters, then setters (or the other way around) To illuminate the difference here is a Java example of getter/setter pairs: public class Foo { private int var1, var2, var3; public int getVar1() { return var1; } public void setVar1(int var1) { this.var1 = var1; } public int getVar2() { return var2; } public void setVar2(int var2) { this.var2 = var2; } public int getVar3() { return var3; } public void setVar3(int var3) { this.var3 = var3; } } And here is a Java example of first getters, then setters: public class Foo { private int var1, var2, var3; public int getVar1() { return var1; } public int getVar2() { return var2; } public int getVar3() { return var3; } public void setVar1(int var1) { this.var1 = var1; } public void setVar2(int var2) { this.var2 = var2; } public void setVar3(int var3) { this.var3 = var3; } } I think the latter type of ordering is clearer both in code and in class diagrams but I do not know if that is enough to rule out the other type of ordering.

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  • Where do you start your design - code, UI or workflow?

    - by Mmarquee
    Hi I was discussing this at work, and was wondering where people start their designs? We tend to start with designing code to solve the problem presented to us, but that is probably all of us are (or were) programmers. I was wondering where other people and organisations start their design. Do they start with solving the problem as a coding problem, sit down and design what UI to use, or map out the data or workflow? Thanks

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  • Where do you start your design - code, UI, workflow or whatever?

    - by Mmarquee
    Hi I was discussing this at work, and was wondering where people start their designs? We tend to start with designing code to solve the problem presented to us, but that is probably all of us are (or were) programmers. I was wondering where other people and organisations start their design. Do they start with solving the problem as a coding problem, sit down and design what UI to use, or map out the data or workflow? Thanks

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  • How can i implement the NULL Object Design Pattern in a generic form?

    - by Colour Blend
    Is there a way to implement the null object design pattern in a generic form so that i don't need to implement it for every buisness object. For me, there are two high level classes you'll need for every business class. One for a single record and another for a list. So i think there should be a way to implement the NULL Object design pattern at a high level and not have to implement it for every class. Is there a way and how please?

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  • (Abstract) Game engine design

    - by lukeluke
    I am writing a simple 2D game (for mobile platforms) for the first time. From an abstract point of view, i have the main player controlled by the human, the enemies, elments that will interact with the main player, other living elements that will be controlled by a simple AI (both enemies and non-enemies). The human player will be totally controlled by the player, the other actors will be controlled by AI. So i have a class CActor and a class CActorLogic to start with. I would define a CActor subclass CHero (the main player controlled with some input device). This class will probably implement some type of listener, in order to capture input events. The other players controlled by the AI will be probably a specific subclass of CActor (a subclass per-type, obviously). This seems to be reasonable. The CActor class should have a reference to a method of CActorLogic, that we will call something like CActorLogic::Advance() or similar. Actors should have a visual representation. I would introduce a CActorRepresentation class, with a method like Render() that will draw the actor (that is, the right frame of the right animation). Where to change the animation? Well, the actor logic method Advance() should take care of checking collisions and other things. I would like to discuss the design of a game engine (actors, entities, objects, messages, input handling, visualization of object states (that is, rendering, sound output and so on)) but not from a low level point of view, but from an high level point of view, like i have described above. My question is: is there any book/on line resource that will help me organize things (using an object oriented approach)? Thanks

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  • How to design a C / C++ library to be usable in many client languages?

    - by Brian Schimmel
    I'm planning to code a library that should be usable by a large number of people in on a wide spectrum of platforms. What do I have to consider to design it right? To make this questions more specific, there are four "subquestions" at the end. Choice of language Considering all the known requirements and details, I concluded that a library written in C or C++ was the way to go. I think the primary usage of my library will be in programs written in C, C++ and Java SE, but I can also think of reasons to use it from Java ME, PHP, .NET, Objective C, Python, Ruby, bash scrips, etc... Maybe I cannot target all of them, but if it's possible, I'll do it. Requirements It would be to much to describe the full purpose of my library here, but there are some aspects that might be important to this question: The library itself will start out small, but definitely will grow to enormous complexity, so it is not an option to maintain several versions in parallel. Most of the complexity will be hidden inside the library, though The library will construct an object graph that is used heavily inside. Some clients of the library will only be interested in specific attributes of specific objects, while other clients must traverse the object graph in some way Clients may change the objects, and the library must be notified thereof The library may change the objects, and the client must be notified thereof, if it already has a handle to that object The library must be multi-threaded, because it will maintain network connections to several other hosts While some requests to the library may be handled synchronously, many of them will take too long and must be processed in the background, and notify the client on success (or failure) Of course, answers are welcome no matter if they address my specific requirements, or if they answer the question in a general way that matters to a wider audience! My assumptions, so far So here are some of my assumptions and conclusions, which I gathered in the past months: Internally I can use whatever I want, e.g. C++ with operator overloading, multiple inheritance, template meta programming... as long as there is a portable compiler which handles it (think of gcc / g++) But my interface has to be a clean C interface that does not involve name mangling Also, I think my interface should only consist of functions, with basic/primitive data types (and maybe pointers) passed as parameters and return values If I use pointers, I think I should only use them to pass them back to the library, not to operate directly on the referenced memory For usage in a C++ application, I might also offer an object oriented interface (Which is also prone to name mangling, so the App must either use the same compiler, or include the library in source form) Is this also true for usage in C# ? For usage in Java SE / Java EE, the Java native interface (JNI) applies. I have some basic knowledge about it, but I should definitely double check it. Not all client languages handle multithreading well, so there should be a single thread talking to the client For usage on Java ME, there is no such thing as JNI, but I might go with Nested VM For usage in Bash scripts, there must be an executable with a command line interface For the other client languages, I have no idea For most client languages, it would be nice to have kind of an adapter interface written in that language. I think there are tools to automatically generate this for Java and some others For object oriented languages, it might be possible to create an object oriented adapter which hides the fact that the interface to the library is function based - but I don't know if its worth the effort Possible subquestions is this possible with manageable effort, or is it just too much portability? are there any good books / websites about this kind of design criteria? are any of my assumptions wrong? which open source libraries are worth studying to learn from their design / interface / souce? meta: This question is rather long, do you see any way to split it into several smaller ones? (If you reply to this, do it as a comment, not as an answer)

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  • Appropriate design / technologies to handle dynamic string formatting?

    - by Mark W
    recently I was tasked with implementing a way of adding support for versioning of hardware packet specifications to one of our libraries. First a bit of information about the project. We have a hardware library which has classes for each of the various commands we support sending to our hardware. These hardware modules are essentially just lights with a few buttons, and a 2 or 4 digit display. The packets typically follow the format {SOH}AADD{ETX}, where AA is our sentinel action code, and DD is the device ID. These packet specs are different from one command to the next obviously, and the different firmware versions we have support different specifications. For example, on version 1 an action code of 14 may have a spec of {SOH}AADDTEXT{ETX} which would be AA = 14 literal, DD = device ID, TEXT = literal text to display on the device. Then we come out with a revision with adds an extended byte(s) onto the end of the packet like this {SOH}AADDTEXTE{ETX}. Assume the TEXT field is fixed width for this example. We have now added a new field onto the end which could be used to say specify the color or flash rate of the text/buttons. Currently this java library only supports one version of the commands, the latest. In our hardware library we would have a class for this command, say a DisplayTextArgs.java. That class would have fields for the device ID, the text, and the extended byte. The command class would expose a method which generates the string ("{SOH}AADDTEXTE{ETX}") using the value from the class. In practice we would create the Args class as needed, populate the fields, call the method to get our packet string, then ship that down across the CAN. Some of our other commands specification can vary for the same command, on the same version, depending on some runtime state. For example, another command for version 1 may be {SOH}AA{ETX}, where this action code clears all of the modules behind a specific controller device of their text. We may overload this packet to have option fields with multiple meanings like {SOH}AAOC{ETX} where OC is literal text, which tells the controller to only clear text on a specific module type, and to leave the others alone, or the spec could also have an option format of {SOH}AADD{ETX} to clear the text off a a specific device. Currently, in the method which generates the packet string, we would evaluate fields on the args class to determine which spec we will be using when formatting the packet. For this example, it would be along the lines of: if m_DeviceID != null then use {SOH}AADD{ETX} else if m_ClearOCs == true then use {SOH}AAOC{EXT} else use {SOH}AA{ETX} I had considered using XML, or a database to store String.format format strings, which were linked to firmware version numbers in some table. We would load them up at startup, and pass in the version number of the hardwares firmware we are currently using (I can query the devices for their firmware version, but the version is not included in all packets as part of the spec). This breaks down pretty quickly because of the dynamic nature of how we select which version of the command to use. I then considered using a rule engine to possibly build out expressions which could be interpreted at runtume, to evaluate the args class's state, and from that select the appropriate format string to use, but my brief look at rule engines for java scared me away with its complexity. While it seems like it might be a viable solution, it seems overly complex. So this is why I am here. I wouldn't say design is my strongest skill, and im having trouble figuring out the best way to approach this problem. I probably wont be able to radically change the args classes, but if the trade off was good enough, I may be able to convince my boss that the change is appropriate. What I would like from the community is some feedback on some best practices / design methodologies / API or other resources which I could use to accomplish: Logic to determine which set of commands to use for a given firmware version Of those command, which version of each command to use (based on the args classes state) Keep the rules logic decoupled from the application so as to avoid needing releases for every firmware version Be simple enough so I don't need weeks of study and trial and error to implement effectively.

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  • Why does mobile first responsive design tend to not use max-width queries alongside the min-width queries?

    - by Sam
    First off, I understand the basic principles behind mobile first responsive web design, and totally agree with them. But one thing I don't understand: In my experience, not all styles for small screens can be used for the larger version of a website. For example, usually smaller versions tend to have larger clickable areas, hamburger navigation, etc. So I sometimes have to override these specific styles, aside from just progressively enhancing the base styles. So I was wondering: why is max-width rarely mentioned (or used) in the context of mobile-first responsive web design? Because it looks like it could be used to isolate styles for smaller screens that are not useful for larger screens, and would thus prevent unnecessary duplication of code. A quote which mentions min-width as typically mobile-first, but not max-width: Mobile first, from a coding perspective, means that your base style is typically a single-column, fully-fluid layout. You use @media (min-width: whatever) to add a grid-based layout on top of that. from: http://gomakethings.com/mobile-first-and-internet-explorer/ EDIT: So to be more specific: I was wondering if there is a reason to exclude max-width from a mobile-first responsive design (as it seems like it can be useful for writing your css as DRY as possible, as some styles for small screens will not be used for bigger screens).

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  • Design Book–Fourth(last) Section (Physical Abstraction Optimization)

    - by drsql
    In this last section of the book, we will shift focus to the physical abstraction layer optimization. By this I mean the little bits and pieces of the design that is specifically there for performance and are actually part of the relational engine (read: the part of the SQL Server experience that ideally is hidden from you completely, but in 2010 reality it isn’t quite so yet.  This includes all of the data structures like database, files, etc; the optimizer; some coding, etc. In my mind, this...(read more)

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  • Dealing with a fundamental design flaw when you're new to the project

    - by Matt Phillips
    I've just started working on an open source project with around 30 developers in it. I'm working on fixing some of the bugs as a way to get into the "loop" and become a regular committer to the project. The problem is I think I've uncovered a fundamental design flaw that's causing one of the bugs I'm working on. But I feel like if I blast this on the mailing list I'm going to come off as arrogant, and some of the discussions I've had about the issue are butting heads with some of the people. How should I go about this?

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  • Challenges in multi-player Android Game Server with RESTful Nature

    - by Kush
    I'm working on an Android Game based on Contract Bridge, as a part of my college Summer Internship project. The game will be multi-player such that 4 Android devices can play it, so there's no BOT or CPU player to be developed. At the time of getting project, I realized that most of the students had already worked on the project but none of their works is reusable now (for variety of reasons like, undocumented code and design architecture, different platform implementation). I have experience working on several open source projects and hence I emphasis to work out on this project such that components I make become reusable as much as possible. Now, as the game is multi-player and entire game progress will be handled on server, I'm currently working on Server's design, since I wanted to make game server reusable such that any client platform can use it, I was previously confused in selecting Socket or REST for Game Server's design, but later finalized to work on REST APIs for the server. Now, since I have to keep all players in-sync while they make movements in game, on server I've planned to use Database which will keep all players' progress, specific for each table (in Bridge, 4 players play on single table, and server will handle many such game tables). I don't know if its an appropriate decision to use database as shared medium to track progress of each game table (let me know if there's an appropriate or better option). Obviously, when game is completed for the table, data for that table on server's database is discarded. Now the problem is that, access to REST service is an HTTP call, so as long as client doesn't make any request, server will remain idle, and consider a situation where A player has played a card on his device and the device requests to apply this change on the server. Now, I need to let rest of the three devices know that the player has played a card, and also update view on their device. AFAIK, REST cannot provide a sort-of Push-notification system, since the connection to the server is not persistent. One solution that I thought was to make each device constantly poll the server for any change (like every 56 ms) and when changes are found, reflect it on the device. But I feel this is not an elegant way, as every HTTP request is expensive. (and I choose REST to make game play experience robust since, a mobile device tends to get disconnected from Internet, and if there's Socket-like persistent connection then entire game progress is subject to lost. Also, portability on client-end is important) Also, imagining a situation where 10 game tables are in progress and 40 players are playing, a server must be capable to handle flooded HTTP requests from all the devices which make it every 56 ms. So I wonder if the situation is assumed as DoS attack. So, explaining the situation, am I going on the right track for the server design? I wanted to be sure before I proceed much further with the code.

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  • choosing Database and Its Design for Rails

    - by Gaurav Shah
    I am having a difficulty in deciding the database & its structure. Let us say the problem is like this. For my product I have various customers( each is an educational institute) Each customer have their own sub-clients ( Institution have students) Each student record will have some basic information like "name" & "Number" . There are also additional information that a customer(institution) might want to ask sub-client(student) like "email" or "semester" I have come up with two solutions : 1. Mysql _insititution__ id-|- Description| __Student__ id-|-instituition_id-|-Name-|-Number| __student_additional_details__ student_id -|- field_name -|- Value Student_additional_details will have multiple records for each student depending upon number of questions asked from institution. 2.MongoDb _insititution___ id-|- Description| _Student__ id-|-instituition_id-|-Name-|-Number|-otherfield1 -|- otherfield2 with mongo the structure itself can be dynamic so student table seems really good in mongo . But the problem comes when I have to relate student with institution . So which one is a better design ? Or some other idea ?

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  • PASS Conference 2011 Topic: Multitenant Design and Sharding with SQL Azure

    - by Herve Roggero
    I am really happy to announce that I have been accepted as a speaker at the 2011 PASS Conference in Seattle. The topic? It will be about SQL Azure scalability using shards, and the Data Federation feature of SQL Azure. I will also talk extensively about the community open-source sharding library Enzo SQL Shard (enzosqlshard.codeplex.com) and show how to make the most out of it. In general, the presentation will provide details about how to properly design an application for sharding, how to make it work for SQL Server, SQL Azure, and how to leverage the upcoming Data Federation technology that Microsoft is planning. The primary objective is to turn sharding an implementation concern, not a development concern. Using a library like Enzo SQL Shard will help you achieve this objective. If you come to PASS Summit this year, come see me and mention you saw this blog!

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  • Human vs human android chess game design

    - by Plejo
    First of all I am total amateur in game development and sorry for my poor English. I want to make android human vs human chess game. So I am wondering how to design it? scenario 1: User connect to server, find opponent and send moves to server using socket, so match is running on a server side. I think this is not good idea because move should be validated on client side - or do I have to validate moves on client side? I do not think this is good solution because game is seperated. scenario 2: Using hole punching technique so server is needed only for connection between players, so game is running on android devices. which approach do you suggest? Or is there any better solution? Which server is best to use?

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  • When should complexity be removed?

    - by ElGringoGrande
    Prematurely introducing complexity by implementing design patterns before they are needed is not good practice. But if you follow all (or even most of) the SOLID principles and use common design patterns you will introduce some complexity as features and requirements are added or changed to keep your design as maintainable and flexible as needed. However once that complexity is introduced and working like a champ when do you removed it? Example. I have an application written for a client. When originally created there where several ways to give raises to employees. I used the strategy pattern and factory to keep the whole process nice and clean. Over time certain raise methods where added or removed by the application owner. Time passes and new owner takes over. This new owner is hard nosed, keeps everything simple and only has one single way to give a raise. The complexity needed by the strategy pattern is no longer needed. If I where to code this from the requirements as they are now I would not introduce this extra complexity (but make sure I could introduce it with little or no work should the need arise). So do I remove the strategy implementation now? I don't think this new owner will ever change how raises are given. But the application itself has demonstrated that this could happen. Of course this is just one example in an application where a new owner takes over and has simplified many processes. I could remove dozens of classes, interfaces and factories and make the whole application much more simple. Note that the current implementation does works just fine and the owner is happy with it (and surprised and even happier that I was able to implement her changes so quickly because of the discussed complexity). I admit that a small part of this doubt is because it is highly likely the new owner isn't going to use me any longer. I don't really care that somebody else will take this over since it has not been a big income generator. But I do care about 2 (related) things I care a bit that the new maintainer will have to think a bit harder when trying to understand the code. Complexity is complexity and I don't want to anger the psycho maniac coming after me. But even more I worry about a competitor seeing this complexity and thinking I just implement design patterns to pad my hours on jobs. Then spreading this rumor to hurt my other business. (I have heard this mentioned.) So... In general should previously needed complexity be removed even though it works and there has been a historically demonstrated need for the complexity but you have no indication that it will be needed in the future? Even if the question above is generally answered "no" is it wise to remove this "un-needed" complexity if handing off the project to a competitor (or stranger)?

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  • Help Us Pick the First T-Shirt Design to Promote How-To Geek

    - by Eric Z Goodnight
    Here’s your first peek at How-To Geek’s new line of merchandise! Tell us what you think, what you like, and what you actually would like to own in this first round of potential HTG tee shirts. If you like the content here at HTG, we’d love to hear back from you—we made these for you, the readers, and we hope to hear what suits you and if you like what we’ve got to offer. Check them out, tell us your thoughts in the comments section (or send us emails at [email protected]) and fill out our poll in the section below.  The design that you like the most will be professionally printed and sold right here at howtogeek.com. Interested in buying one of them right now? Jump to the bottom to be notified when they’re ready for be bought and shipped right to you. How to Own Your Own Website (Even If You Can’t Build One) Pt 3 How to Sync Your Media Across Your Entire House with XBMC How to Own Your Own Website (Even If You Can’t Build One) Pt 2

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  • A leader election algorithm for an oriented hypercube

    - by mick
    I'm stuck with some problem where I have to design a leader election algorithm for an oriented hypercube. This should be done by using a tournament with a number of rounds equal to the dimension D of the hypercube. In each stage d, with 1 <= d < D two candidate leaders of neighbouring d-dimensional hypercubes should compete to become the single candidate leader of the (d+1)-dimensional hypercube that is the union of their respective hypercubes.

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  • Is dynamic casting Entities A good design?

    - by Milo
    For my game, Everything inherits from Entity, then other things like Player, PhysicsObject, etc, inherit from Entity. The physics engine sends collision callbacks which has an Entity* to the B that A collided on. Then, lets say A is a Bullet, A tries to cast the entity as a player, if it succeeds, it reduces the player's health. Is this a good design? The problem I have with a message system is that I'd need messages for everything, like: entity.sendMessage(SET_PLAYER_HEALTH,16); So that's why I think casting is cleaner.

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