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• Designing Snake AI

  - by Ronald

  I'm new to this gamedev stackechange but have used the math and cs sites before. So, I'm in a competition to create AI for a snake that will compete with 3 other snakes in 5 minute rounds where the rules are much like the traditional Nokia snake game except that there are 4 snakes, the board is 50x50 and there are a number of small obstacles on the field. Like the Nokia game, your snake grows when you get to the fruit and if you crash into yourself, another snake or the wall you die. The game runs with a 50ms delay between moves and the server sends the new game state every 50ms which the code must analyze and what not and output the next move. The winner is the snake who had the longest length at any point in the game. Tie breakers are decided by kills. So far what I have done is implemented an A* graph search from each snake to determine if my snake is the closest to the apple and if it is, it goes for the apple. Otherwise, I made a neat little algorithm to determine the emptiest area of the board, which my snake goes for, to anticipate the next apple. Other than this I have some small survivability checks to ensure my snake isn't walking into a trap that it can't get out and if it does get stuck, I have something to give it a better chance of getting out. ... Anyway, I've tested my snake on a test server and it does quite well. Generally, my strategy of only going for the apple when its a sure thing and finding space when its not makes it grow faster than any other snakes (some snakes do a similar thing but often just go to the middle or a corner) sometimes it wins these trial games but is more often than not beaten by the same snake who seems to have the edge on survivability(my snake grows quicker but then dies somehow and this other snake just plods slowly along and wins on consistency. So I was wondering about any ideas anyone has to try and improve my snake. Or maybe ideas at a new approach to take. My functions and classes are good so changes that might seem drastic shouldn't be too bad. I encourage all ideas. Any thoughts ??

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• If most of team can't follow the architecture, what do you do?

  - by Chris

  Hi all, I'm working on a greenfields project with two other developers. We're all contractors, and myself and one other just started working on the project while the orginal one has been doing most of the basic framework coding. In the past month, my fellow programmer and I have been just frustrated by the design descisions done by our co-worker. Here's a little background information: The application at face value appeared to be your standard n-layered web application using C# on the 3.5 framework. We have a data layer, business layer and a web interface. But as we got deeper into the project we found some very interesting things that have caused us some troubles. There is a custom data access sqlHelper type base which only accepts dictionary key/valued entries and returns only data tables. There are no entity objects, but there are some massive objects which do everything and then are tossed into session for persitance. The general idea is that the pages (.aspx) don't do anything, while the controls (.ascx) do everything. The general flow is that a client clicks on a button, which goes to a user control base which passes a process request to the 'BLL' class which goes to the page processor, which then goes to a getControlProcessor, which at last actually processes the request. The request itself is made up of a dictionary which is passing a string valued method name, stored procedure name, a control name and possibly a value. All switching of the processing is done by comparing the string values of the control names and method names. Pages are linked together via a common header control that uses a combination of javascript and tables to create a hyperlink effect. And as I found out yesterday, a simple hyperlink between one page and another does not work because of the need to have quite a bit of information in session to determine which control to display on a page. My fellow programmer and I both believe that this is a strange and uncommon approach to web application development. Both of us have been in this business for over five years and neither of us have seen this approach. My question is this, how would we approach our co-worker and voice our concerns and what should we do if he does not want to accept the criteic? We both do not want to insult the work that has been done, but feel that going forward will create a nightmare for development. Thanks for your comments.

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• What does path finding in internet routing do and how is it different from A*?

  - by alan2here

  Note: If you don't understand this question then feel free to ask clarification in the comments instead of voting down, it might be that this question needs some more work at the moment. I've been directed here from the Stack Excange chat room Root Access because my question didn't fit on Super User. In many aspects path finding algorithms like A star are very similar to internet routing. For example: A node in an A* path finding system can search for a path though edges between other nodes. A router that's part of the internet can search for a route though cables between other routers. In the case of A*, open and closed lists are kept by the system as a whole, sepratly from any individual node as well as each node being able to temporarily store a state involving several numbers. Routers on the internet seem to have remarkable properties, as I understand it: They are very performant. New nodes can be added at any time that use a free address from a finite (not tree like) address space. It's real routing, like A*, there's never any doubling back for example. Similar IP addresses don't have to be geographically nearby. The network reacts quickly to changes to the networks shape, for example if a line is down. Routers share information and it takes time for new IP's to be registered everywhere, but presumably every router doesn't have to store a list of all the addresses each of it's directions leads most directly to. I'm looking for a basic, general, high level description of the algorithms workings from the point of view of an individual router. Does anyone have one? I presume public internet routers don't use A* as the overheads would be to large, and scale to poorly. I also presume there is a single method worldwide because it seems as if must involve a lot of transferring data to update and communicate a reasonable amount of state between neighboring routers. For example, perhaps the amount of data that needs to be stored in each router scales logarithmically with the number of routers that exist worldwide, the detail and reliability of the routing is reduced over increasing distances, there is increasing backtracking involved in parts of the network that are less geographically uniform or maybe each router really does perform an A* style search, temporarily maintaining open and closed lists when a packet arrives.

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• Interaction of a GUI-based App and Windows Service

  - by psubsee2003

  I am working on personal project that will be designed to help manage my media library, specifically recordings created by Windows Media Center. So I am going to have the following parts to this application: A Windows Service that monitors the recording folder. Once a new recording is completed that meets specific criteria, it will call several 3rd party CLI Applications to remove the commercials and re-encode the video into a more hard-drive friendly format. A controller GUI to be able to modify settings of the service, specifically add new shows to watch for, and to modify parameters for the CLI Applications A standalone (GUI-based) desktop application that can perform many of the same functions as the windows service, expect manually on specific files instead of automatically based on specific criteria. (It should be mentioned that I have limited experience with an application of this complexity, and I have absolutely zero experience with Windows Services) Since the 1st and 3rd bullet share similar functionality, my design plan is to pull the common functionality into a separate library shared by both parts applications, but these 2 components do not need to interact otherwise. The 2nd and 3rd bullets seem to share some common functionality, both will have a GUI, both will have to help define similar parameters (one to send to the service and the other to send directly to the CLI applications), so I can see some advantage to combining them into the same application. On the other hand, the standalone application (bullet #3) really does not need to interact with the service at all, except for possibly sharing a few common default parameters that can easily be put into an XML in a common location, so it seems to make more sense to just keep everything separate. The controller GUI (2nd bullet) is where I am stuck at the moment. Do I just roll this functionality (allow for user interaction with the service to update settings and criteria) into the standalone application? Or would it be a better design decision to keep them separate? Specifically, I'm worried about adding the complexity of communicating with the Windows Service to the standalone application when it doesn't need it. Is WCF the right approach to allow the controller GUI to interact with the Windows Service? Or is there a better alternative? At the moment, I don't envision a need for a significant amount of interaction, maybe just adding a new task once in a while and occasionally tweaking a parameter, but when something is changed, I do expect the windows service to immediately use the new settings.

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• Adding JavaScript to your code dependent upon conditions

  - by DavidMadden

  You might be in an environment where you code is source controlled and where you might have build options to different environments.  I recently encountered this where the same code, built on different configurations, would have the website at a different URL.  If you are working with ASP.NET as I am you will have to do something a bit crazy but worth while.  If someone has a more efficient solution please share. Here is what I came up with to make sure the client side script was placed into the HEAD element for the Google Analytics script.  GA wants to be the last in the HEAD element so if you are doing others in the Page_Load then you should do theirs last. The settings object below is an instance of a class that holds information I collection.  You could read from different sources depending on where you stored your unique ID for Google Analytics. *** This has been formatted to fit this screen. *** if (!IsPostBack) { if (settings.GoogleAnalyticsID != null || settings.GoogleAnalyticsID != string.Empty) { string str = @"//<!CDATA[ var _gaq = _gaq || []; _gaq.push(['_setAccount', '"  + settings.GoogleAnalyticsID + "']); _gaq.push(['_trackPageview']);  (function () {  var ga = document.createElement('script');  ga.type = 'text/javascript';  ga.async = true;  ga.src = ('https:' == document.location.protocol  ? 'https://ssl' :  'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0];  s.parentNode.insertBefore(ga, s);})();"; System.Web.UI.HtmlControls.HtmlGenericControl si =  new System.Web.UI.HtmlControls.HtmlGenericControl(); si.TagName = "script"; si.Attributes.Add("type", @"text/javascript"); si.InnerHtml = sb.ToString(); this.Page.Header.Controls.Add(si); } } The code above will prevent the code from executing if it is a PostBack and then if the ID was not able to be read or something caused the settings to be lost by accident. If you have larger function to declare, you can use a StringBuilder to separate the lines. This is the most compact I wished to go and manage readability.

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• Separating logic and data in browser game

  - by Tesserex

  I've been thinking this over for days and I'm still not sure what to do. I'm trying to refactor a combat system in PHP (...sorry.) Here's what exists so far: There are two (so far) types of entities that can participate in combat. Let's just call them players and NPCs. Their data is already written pretty well. When involved in combat, these entities are wrapped with another object in the DB called a Combatant, which gives them information about the particular fight. They can be involved in multiple combats at once. I'm trying to write the logic engine for combat by having combatants injected into it. I want to be able to mock everything for testing. In order to separate logic and data, I want to have two interfaces / base classes, one being ICombatantData and the other ICombatantLogic. The two implementers of data will be one for the real objects stored in the database, and the other for my mock objects. I'm now running into uncertainties with designing the logic side of things. I can have one implementer for each of players and NPCs, but then I have an issue. A combatant needs to be able to return the entity that it wraps. Should this getter method be part of logic or data? I feel strongly that it should be in data, because the logic part is used for executing combat, and won't be available if someone is just looking up information about an upcoming fight. But the data classes only separate mock from DB, not player from NPC. If I try having two child classes of the DB data implementer, one for each entity type, then how do I architect that while keeping my mocks in the loop? Do I need some third interface like IEntityProvider that I inject into the data classes? Also with some of the ideas I've been considering, I feel like I'll have to put checks in place to make sure you don't mismatch things, like making the logic for an NPC accidentally wrap the data for a player. Does that make any sense? Is that a situation that would even be possible if the architecture is correct, or would the right design prohibit that completely so I don't need to check for it? If someone could help me just layout a class diagram or something for this it would help me a lot. Thanks. edit Also useful to note, the mock data class doesn't really need the Entity, since I'll just be specifying all the parameters like combat stats directly instead. So maybe that will affect the correct design.

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• Is this an effective monetization method for an Android game? [on hold]

  - by Matthew Page

  The short version: I plan to make an Android puzzle game where the user tries to get 3-6 numbers to their predetermined goal numbers. The free version of the app will have three predetermined levels (easy, medium, hard). The full version ($0.99, probably) will have a level generator where there will be unlimited easy, medium, or hard levels, as well as a custom difficulty option where users can set specific vales to the number of numbers to equate to their goal, the number of buttons to use, etc. Users will also have the option to get a one-time "hint" for a fee of $0.49, or unlimited hints for a one-time fee of $2.99. The long version: Mechanics of Game and Victory The application is a number puzzle. When the user begins a new game, depending on the input by the user, between 3 and 6 numbers show up on the top of the screen, and between 3 and 6 buttons show up on the bottom of the screen. The buttons all have two options: to increase every number the same way, or decrease every number the same way. The buttons either use addition / subtraction, multiplication / division, or exponents / roots, all depending on the number displayed on the button. Addition buttons are green, multiplication buttons are blue, and exponential buttons are red. The user wins when all of the numbers displayed on the screen equate to their goal number, displayed below each number. Monetization If the user is playing the full (priced) version of the app, upon the start of the game, the user will be confronted with a dialogue asking for the number of buttons and the number of numbers to equate in the game. Then, based on the user input, a random puzzle will be generated. If the user is playing the free version of the app, the user will be asked to either play an “easy”, “hard”, or “expert” puzzle. A pre-determined puzzle from each category will be used in the game. If the user has played that puzzle before, a dialogue will show saying this to the user and advertising the full version of the app. The full version of the app will also be advertised upon the successful or in successful completion of a puzzle. Upon exiting this advertisement, another full screen advertisement will appear from a third party. Also, the solution to the puzzle should be stored by the program, and if the user pays a small fee, he/she can see a hint to the solution to the program. In the free version of the app, the user may use their first hint for free. Also, the user can use unlimited hints for a slightly larger fee. Is this an effective monetization method?

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• Should library classes be wrapped before using them in unit testing?

  - by Songo

  I'm doing unit testing and in one of my classes I need to send a mail from one of the methods, so using constructor injection I inject an instance of Zend_Mail class which is in Zend framework. Example: class Logger{ private $mailer; function __construct(Zend_Mail $mail){ $this->mail=$mail; } function toBeTestedFunction(){ //Some code $this->mail->setTo('some value'); $this->mail->setSubject('some value'); $this->mail->setBody('some value'); $this->mail->send(); //Some } } However, Unit testing demands that I test one component at a time, so I need to mock the Zend_Mail class. In addition I'm violating the Dependency Inversion principle as my Logger class now depends on concretion not abstraction. Does that mean that I can never use a library class directly and must always wrap it in a class of my own? Example: interface Mailer{ public function setTo($to); public function setSubject($subject); public function setBody($body); public function send(); } class MyMailer implements Mailer{ private $mailer; function __construct(){ $this->mail=new Zend_Mail; //The class isn't injected this time } function setTo($to){ $this->mailer->setTo($to); } //implement the rest of the interface functions similarly } And now my Logger class can be happy :D class Logger{ private $mailer; function __construct(Mailer $mail){ $this->mail=$mail; } //rest of the code unchanged } Questions: Although I solved the mocking problem by introducing an interface, I have created a totally new class Mailer that now needs to be unit tested although it only wraps Zend_Mail which is already unit tested by the Zend team. Is there a better approach to all this? Zend_Mail's send() function could actually have a Zend_Transport object when called (i.e. public function send($transport = null)). Does this make the idea of a wrapper class more appealing? The code is in PHP, but answers doesn't have to be. This is more of a design issue than a language specific feature

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• What is the most appropriate testing method in this scenario?

  - by Daniel Bruce

  I'm writing some Objective-C apps (for OS X/iOS) and I'm currently implementing a service to be shared across them. The service is intended to be fairly self-contained. For the current functionality I'm envisioning there will be only one method that clients will call to do a fairly complicated series of steps both using private methods on the class, and passing data through a bunch of "data mangling classes" to arrive at an end result. The gist of the code is to fetch a log of changes, stored in a service-internal data store, that has occurred since a particular time, simplify the log to only include the last applicable change for each object, attach the serialized values for the affected objects and return this all to the client. My question then is, how do I unit-test this entry point method? Obviously, each class would have thorough unit tests to ensure that their functionality works as expected, but the entry point seems harder to "disconnect" from the rest of the world. I would rather not send in each of these internal classes IoC-style, because they're small and are only made classes to satisfy the single-responsibility principle. I see a couple possibilities: Create a "private" interface header for the tests with methods that call the internal classes and test each of these methods separately. Then, to test the entry point, make a partial mock of the service class with these private methods mocked out and just test that the methods are called with the right arguments. Write a series of fatter tests for the entry point without mocking out anything, testing the entire functionality in one go. This looks, to me, more like "integration testing" and seems brittle, but it does satisfy the "only test via the public interface" principle. Write a factory that returns these internal services and take that in the initializer, then write a factory that returns mocked versions of them to use in tests. This has the downside of making the construction of the service annoying, and leaks internal details to the client. Write a "private" initializer that take these services as extra parameters, use that to provide mocked services, and have the public initializer back-end to this one. This would ensure that the client code still sees the easy/pretty initializer and no internals are leaked. I'm sure there's more ways to solve this problem that I haven't thought of yet, but my question is: what's the most appropriate approach according to unit testing best practices? Especially considering I would prefer to write this test-first, meaning I should preferably only create these services as the code indicates a need for them.

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• rotating an object on an arc

  - by gardian06

  I am trying to get a turret to rotate on an arc, and have hit a wall. I have 8 possible starting orientations for the turrets, and want them to rotate on a 90 degree arc. I currently take the starting rotation of the turret, and then from that derive the positive, and negative boundary of the arc. because of engine restrictions (Unity) I have to do all of my tests against a value which is between [0,360], and due to numerical precision issues I can not test against specific values. I would like to write a general test without having to go in, and jury rig cases //my current test is: // member variables public float negBound; public float posBound; // found in Start() function (called immediately after construction) // eulerAngles.y is the the degree measure of the starting y rotation negBound = transform.eulerAngles.y-45; posBound = transform.eulerAngles.y+45; // insure that values are within bounds if(negBound<0){ negBound+=360; }else if(posBound>360){ posBound-=360; } // called from Update() when target not in firing line void Rotate(){ // controlls what direction if(transform.eulerAngles.y>posBound){ dir = -1; } else if(transform.eulerAngles.y < negBound){ dir = 1; } // rotate object } follows is a table of values for my different cases (please excuse my force formatting) read as base is the starting rotation of the turret, neg is the negative boundry, pos is the positive boundry, range is the acceptable range of values, and works is if it performs as expected with the current code. |base-|-neg-|-pos--|----------range-----------|-works-| |---0---|-315-|--45--|-315-0,0-45----------|----------| |--45--|---0---|--90--|-0-45,54-90----------|----x----| |-135-|---90--|-180-|-90-135,135-180---|----x----| |-180-|--135-|-225-|-135-180,180-225-|----x----| |-225-|--180-|-270-|-180-225,225-270-|----x----| |-270-|--225-|-315-|-225-270,270-315-|----------| |-315-|--270-|---0---|--270-315,315-0---|----------| I will need to do all tests from derived, or stored values, but can not figure out how to get all of my cases to work simultaneously. //I attempted to concatenate the 2 tests: if((transform.eulerAngles.y>posBound)&&(transform.eulerAngles.y < negBound)){ dir *= -1; } this caused only the first case to be successful // I attempted to store a opposite value, and do a void Rotate(){ // controlls what direction if((transform.eulerAngles.y > posBound)&&(transform.eulerAngles.y<oposite)){ dir = -1; } else if((transform.eulerAngles.y < negBound)&&(transform.eulerAngles.y>oposite)){ dir = 1; } // rotate object } this causes the opposite situation as indicated on the table. What am I missing here?

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• SDL - Getting a single keypress event instead of a keystate?

  - by MrKatSwordfish

  Right now I'm working on a simple SDL project, but I've hit an issue when trying to get a single keypress event to skip past a splash screen. Right now, there are 4 start-up splash screens that I would like to be able to skip with a single keypress (of any key). My issue is that, as of now, if I hold down a key, it skips through each splash screen to the very last one immediately. The splash screens are stored as an array of SDL surfaces which are all loaded at the initialization of the state. I have an variable called currentSplashImage that controls which element of the array is being rendered on the screen. I've set it up so that whenever there's a SDL_KEYDOWN event, it triggers a single incrementation of the currentSplashImage variable. So, I'm really not sure why my code isn't working correctly. For some reason, when I hold down a button, it seems to be treating the held button as a new key press event every time it ticks through the code. Does anyone know how I can go about fixing this issue? [Here's a snippet of code that I've been using...] void SplashScreenState::handleEvents() { SDL_PollEvent( &localEvent ); if ( localEvent.type == SDL_KEYDOWN ) { if ( currentSplashImage < 3 && currentSplashImage >= 0) { currentSplashImage++; } } else if ( localEvent.type == SDL_QUIT ) { smgaEngine.setRunning(false); } } I should also mention that the SDL_Event 'localEvent' is part of the GameState parent class, while this event handling code is part of a SplashScreenState subclass. If anyone knows why this is happening, or if there is any way to improve my code, It'd be helpful to me! :D I'm still a very new programmer, trying to learn. UPDATE: I added a std::cout line to that the code runs multiple times with a single KEYDOWN event. I also tried disabling SDL_EnableKeyRepeat, but it didn't fix the issue. void SplashScreenState::handleEvents() { SDL_PollEvent( &localEvent ); if ( localEvent.type == SDL_KEYDOWN ) { if ( currentSplashImage < 3 && currentSplashImage >= 0) { currentSplashImage++; std::cout << "KEYDOWN.."; //<---- test cout line } } else if ( localEvent.type == SDL_QUIT ) { smgaEngine.setRunning(false); } } This prints out "KEYDOWN..KEYDOWN..KEYDOWN.." in the cout stream when a button is held.

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• Hierachies....from the Top Down

  - by Joe G

  I've been struggling with how to write on the topic of the importance of hierarchy design.  It's not so much that hierarchies haven't always been important, it's more of that with Fusion, the timing of when the hierarchies are designed should take a higher priority.    I will attempt to explain..... When I was implementing applications, back in the day, we had the list of detailed account values to enter with the obvious parent accounts. Then, after the setup was complete and things were functioning, the reporting phase started.  Users explained the elements that they want on the reports, what totals should be included, and how things should be compared.  Frequently, there was at least one calculation that became a nightmare either because it was based on very specific things that didn't relate to anything else or because it was "hardcoded" so that when something changed, someone need to "fix" the report. With Fusion, the process changes slightly.  You still want to enter all of the detailed accounts, but before you start adding parent values, you should investigate the reporting requirements from the top-down.  It's better to build hierarchies based on the reporting requirements than it is to build reports based on random hierarchies. Build reports based on hierarchies that resemble the reports themselves, and maintain the hierarchies without rework of the reports. For example, if you look at an income statement, you may have line items for Material Costs, Employee Costs, Travel & Entertainment, and Total Operating Expenses.  In your hierarchy, you have detail values that roll up to Material Costs, Employee Costs, and Travel & Entertainment which roll up to Total Operating Expenses. Balances are stored automatically in the cube for each of these.  When you define the report, you pick each of these members - no calculations required.  If a new detail value is added, you simply add it to the hierarchy, and there is no need to modify the report. I realize that there are always exceptions that require special handling, but I am confident that you will end up with much fewer exceptions if you make reporting a priority and design your hierarchies from the top-down.

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• How is a switch statement better than a series of if statements? [closed]

  - by user1276078

  Possible Duplicate: Should I use switch statements or long if…else chains? I'm working on a small program that will conduct an Insertion Sort. A number will be inputted through the keyboard and stored in a variable I called "num." I've decided to use a switch statement in order to obtain the number inputted. switch( e.getKeyCode() ) { case KeyEvent.VK_0: num = 0; break; case KeyEvent.VK_1: num = 1; break; case KeyEvent.VK_2: num = 2; break; case KeyEvent.VK_3: num = 3; break; case KeyEvent.VK_4: num = 4; break; case KeyEvent.VK_5: num = 5; break; case KeyEvent.VK_6: num = 6; break; case KeyEvent.VK_7: num = 7; break; case KeyEvent.VK_8: num = 8; break; case KeyEvent.VK_9: num = 9; break; } I realized one other course of action could have been to use a set of if statements. if( e.getKeyCode() == KeyEvent.VK_0 ) num = 0; else if( e.getKeyCode() == KeyEvent.VK_1 ) num = 1; etc. for every number up until 9. I then wondered what the essential difference is between a switch statement and a series of if statements. I know it saves space and time to write, but it's not that much. So, my question is, aside from the space, does a switch statement differ from a series of if statments in any way? Is it faster, less error-prone, etc.? This question really doesn't affect my code that much. I was just wondering. Also, this question pertains to the JAVA language, not any other programming language.

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• C Programming arrays, I dont understand how I would go about making this program, If anyone can just guide me through the basic outline please :) [on hold]

  - by Rashmi Kohli

  Problem The temperature of a car engine has been measured, from real-world experiments, as shown in the table and graph below: Time (min) Temperature (oC) 0 20 1 36 2 61 3 68 4 77 5 110 Use linear regression to find the engine’s temperature at 1.5 minutes, 4.3 minutes, and any other time specified by the user. Background In engineering, many times we measure several data points in an experiment, but then we need to predict a value that we have not measured which lies between two measured values, such as the problem statement above. If the relation between the measured parameters seems to be roughly linear, then we can use linear regression to find the relationship between those parameters. In the graph of the problem statement above, the relation seems to be roughly linear. Hence, we can apply linear regression to the above problem. Assuming y {y0, y1, …yn-1} has a linear relation with x {x0, x1, … xn-1}, we can say that: y = mx+b where m and b can be found with linear regression as follows: For the problem in this lab, using linear regression gives us the following line (in blue) compared to the measured curve (in red). As you can see, there is usually a difference between the measured values and the estimated (predicted) values. What linear regression does is to minimize those differences and still give us a straight line (blue). Other methods, such as non-linear regression, are also possible to achieve higher accuracy and better curve fitting. Requirements Your program should first print the table of the temperatures similar to the way it’s printed in the problem statement. It should then calculate the temperature at minute 1.5 and 4.3 and show the answers to the user. Next, it should prompt the user to enter a time in minutes (or -1 to quit), and after reading the user’s specified time it should give the value of the engine’s temperature at that time. It should then go back to the prompt. Hints •Use a one dimensional array to store the temperature values given in the problem statement. •Use functions to separate tasks such as calculating m, calculating b, calculating the temperature at a given time, printing the prompt, etc. You can then give your algorithm as well as you pseudo code per function, as opposed to one large algorithm diagram or one large sequence of pseudo code.

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• Advantages to Multiple Methods over Switch

  - by tandu

  I received a code review from a senior developer today asking "By the way, what is your objection to dispatching functions by way of a switch statement?" I have read in many places about how pumping an argument through switch to call methods is bad OOP, not as extensible, etc. However, I can't really come up with a definitive answer for him. I would like to settle this for myself once and for all. Here are our competing code suggestions (php used as an example, but can apply more universally): class Switch { public function go($arg) { switch ($arg) { case "one": echo "one\n"; break; case "two": echo "two\n"; break; case "three": echo "three\n"; break; default: throw new Exception("Unknown call: $arg"); break; } } } class Oop { public function go_one() { echo "one\n"; } public function go_two() { echo "two\n"; } public function go_three() { echo "three\n"; } public function __call($_, $__) { throw new Exception("Unknown call $_ with arguments: " . print_r($__, true)); } } Part of his argument was "It (switch method) has a much cleaner way of handling default cases than what you have in the generic __call() magic method." I disagree about the cleanliness and in fact prefer call, but I would like to hear what others have to say. Arguments I can come up with in support of Oop scheme: A bit cleaner in terms of the code you have to write (less, easier to read, less keywords to consider) Not all actions delegated to a single method. Not much difference in execution here, but at least the text is more compartmentalized. In the same vein, another method can be added anywhere in the class instead of a specific spot. Methods are namespaced, which is nice. Does not apply here, but consider a case where Switch::go() operated on a member rather than a parameter. You would have to change the member first, then call the method. For Oop you can call the methods independently at any time. Arguments I can come up with in support of Switch scheme: For the sake of argument, cleaner method of dealing with a default (unknown) request Seems less magical, which might make unfamiliar developers feel more comfortable Anyone have anything to add for either side? I'd like to have a good answer for him.

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• "Whole-team" C++ features?

  - by Blaisorblade

  In C++, features like exceptions impact your whole program: you can either disable them in your whole program, or you need to deal with them throughout your code. As a famous article on C++ Report puts it: Counter-intuitively, the hard part of coding exceptions is not the explicit throws and catches. The really hard part of using exceptions is to write all the intervening code in such a way that an arbitrary exception can propagate from its throw site to its handler, arriving safely and without damaging other parts of the program along the way. Since even new throws exceptions, every function needs to provide basic exception safety — unless it only calls functions which guarantee throwing no exception — unless you disable exceptions altogether in your whole project. Hence, exceptions are a "whole-program" or "whole-team" feature, since they must be understood by everybody in a team using them. But not all C++ features are like that, as far as I know. A possible example is that if I don't get templates but I do not use them, I will still be able to write correct C++ — or will I not?. I can even call sort on an array of integers and enjoy its amazing speed advantage wrt. C's qsort (because no function pointer is called), without risking bugs — or not? It seems templates are not "whole-team". Are there other C++ features which impact code not directly using them, and are hence "whole-team"? I am especially interested in features not present in C. Update: I'm especially looking for features where there's no language-enforced sign you need to be aware of them. The first answer I got mentioned const-correctness, which is also whole-team, hence everybody needs to learn about it; however, AFAICS it will impact you only if you call a function which is marked const, and the compiler will prevent you from calling it on non-const objects, so you get something to google for. With exceptions, you don't even get that; moreover, they're always used as soon as you use new, hence exceptions are more "insidious". Since I can't phrase this as objectively, though, I will appreciate any whole-team feature. Appendix: Why this question is objective (if you wonder) C++ is a complex language, so many projects or coding guides try to select "simple" C++ features, and many people try to include or exclude some ones according to mostly subjective criteria. Questions about that get rightfully closed regularly here on SO. Above, instead, I defined (as precisely as possible) what a "whole-team" language feature is, provide an example (exceptions), together with extensive supporting evidence in the literature about C++, and ask for whole-team features in C++ beyond exceptions. Whether you should use "whole-team" features, or whether that's a relevant concept, might be subjective — but that only means the importance of this question is subjective, like always.

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• How to synchronize the ball in a network pong game?

  - by Thaars

  I’m developing a multiplayer network pong game, my first game ever. The current state is, I’ve running the physic engine with the same configurations on the server and the clients. The own paddle movement is predicted and get just confirmed by the authoritative server. Is a difference detected between them, I correct the position at the client by interpolation. The opponent paddle is also interpolated 200ms to 100ms in the past, because the server is broadcasting snapshots every 100ms to each client. So far it works very well, but now I have to simulate the ball and have a problem to understanding the procedure. I’ve read Valve’s (and many other) articles about fast-paced multiplayer several times and understood their approach. Maybe I can compare my ball with their bullets, but their advantage is, the bullets are not visible. When I have to display the ball, and see my paddle in the present, the opponent in the past and the server is somewhere between it, how can I synchronize the ball over all instances and ensure, that it got ever hit by the paddle even if the paddle is fast moving? Currently my ball’s position is simply set by a server update, so it can happen, that the ball bounces back, even if the paddle is some pixel away (because of a delayed server position). Until now I’ve got no synced clock over all instances. I’m sending a client step index with each update to the server. If the server did his job, he sends the snapshot with the last step index of each client back to the clients. Now I’m looking for the stored position at the returned step index and compare them. Do I need a common clock to sync the ball? EDIT: I've tried to sync a common clock for the server and all clients with a timestamp. But I think it's better to use an own stepping instead of a timestamp (so I don't need to calculate with the ping and so on - and the timestamp will never be exact). The physics are running 60 times per second and now I use this for keeping them synchronized. Is that a good way? When the ball gets calculated by each client, the angle after bouncing can differ because of the different position of the paddles (the opponent is 200ms in the past). When the server is sending his ball position, velocity and angle (because he knows the position of each paddle and is authoritative), the ball could be in a very different position because of the different angles after bouncing (because the clients receive the server data after 100ms). How is it possible to interpolate such a huge difference? I posted this question some days ago at stackoverflow, but got no answer yet. Maybe this is the better place for this question.

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• Imperative vs. component based programming [closed]

  - by AlexW

  I've been thinking about how programming and more specifically the teaching of programming is advocated amongst the community (online). Often I've heard that Ruby and RoR is an ideal platform for learning to program. I completely disagree... RoR and Ruby are based on the application of the component based paradigm, which means they are ideal for rapid application development. This is much like the MVC model in PHP and ASP.NET But, learning a proper imperative language like Java or C/C++ (or even Perl and PHP) is the only way for a new programmer to explore logic itself, and not get too bogged down in architectural concerns like the need for separation of concerns, and the preference for components. Maybe it's a personal preference thing. I rather think that the most interesting aspects to programming are the procedural bits of code I write that actually do stuff rather than the project planning, and modelling that comes about from fully object oriented engineering or simply using the MVC model. I know this may sound confused to some of you. I feel strongly though that the best way for programming to be taught is through imperative and procedural methods. Architectural (component) methods come later, if at all. After all, none of the amazing algorithms that exist were based on OOP practice! It's all procedural code when it comes to the 'magic'. OOP is useful in creating products and utilities. Algorithms are what makes things happen, and move data around, and so imperative (and/or procedural) code are what matters most. When I see programmers recommending Ruby on Rails to newbie developers, I think it's just so wrong. Just because you write less code with Ruby does not make it easier to do! It's the opposite... you have to know loads more to appreciate its succinct nature. New coders who really want to understand the nuts and bolts of coding need to go away and figure out writing methods/functions (i.e. imperative programming) and working in procedural style, in order to grasp the fundamentals, first, before looking into architectural ways of working. So, my question is: should Ruby ever be recommended as a first language? I think no (obviously)... what arguments are there for it?

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• Is it dangerous for me to give some of my Model classes Control-like methods?

  - by Pureferret

  In my personal project I have tried to stick to MVC, but I've also been made aware that sticking to MVC too tightly can be a bad thing as it makes writing awkward and forces the flow of the program in odd ways (i.e. some simple functions can be performed by something that normally wouldn't, and avoid MVC related overheads). So I'm beginning to feel justified in this compromise: I have some 'manager programs' that 'own' data and have some way to manipulate it, as such I think they'd count as both part of the model, and part of the control, and to me this feels more natural than keepingthem separate. For instance: One of my Managers is the PlayerCharacterManager that has these methods: void buySkill(PlayerCharacter playerCharacter, Skill skill); void changeName(); void changeRole(); void restatCharacter(); void addCharacterToGame(); void createNewCharacter(); PlayerCharacter getPlayerCharacter(); List<PlayerCharacter> getPlayersCharacter(Player player); List<PlayerCharacter> getAllCharacters(); I hope the mothod names are transparent enough that they don't all need explaining. I've called it a manager because it will help manage all of the PlayerCharacter 'model' objects the code creates, and create and keep a map of these. I may also get it to store other information in the future. I plan to have another two similar classes for this sort of control, but I will orchestrate when and how this happens, and what to do with the returned data via a pure controller class. This splitting up control between informed managers and the controller, as opposed to operating just through a controller seems like it will simplify my code and make it flow more. My question is, is this a dangerous choice, in terms of making the code harder to follow/test/fix? Is this somethign established as good or bad or neutral? I oculdn't find anything similar except the idea of Actors but that's not quite why I'm trying to do. Edit: Perhaps an example is needed; I'm using the Controller to update the view and access the data, so when I click the 'Add new character to a player button' it'll call methods in the controller that then go and tell the PlayerCharacterManager class to create a new character instance, it'll call the PlayerManager class to add that new character to the player-character map, and then it'll add this information to the database, and tell the view to update any GUIs effected. That is the sort of 'control sequence' I'm hoping to create with these manager classes.

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• When a co-worker asks you to teach him what you know, do you share the information or keep it to yourself? [closed]

  - by Chuck

  I am the only developer/DBA in a small IT department. There is another guy who can do it, but he's more of a backup as he spends his time working on IT support stuff. Anyway we have a new hire and I've been training him on the IT support side of things. Seems like he is eager to learn and be productive, but nobody is going out of their way to show him anything. He's been asking me to teach him database design, SQL, etc. For some reason, the boss has him working with me. He is also sending him to meetings that I go to, yet he hasn't said outright that I have to teach him anything. Meanwhile, the boss insists on doing a lot of the support work himself (i.e. he hoards information and doesn't delegate to anyone). I'm a little bit on the fence. First, the new guy doesn't yet have a strong foundation on the IT support functions which is where we really need help at this time. Second, I paid thousands of dollars for classes and spent many hours learning this stuff. Is it my responsibility to teach others skills that I had to learn on my own? Others here really aren't quick to share information so I'm not sure that I should either in this environment. I do know that if I get him involved, and get him started on projects, then I'd be responsible for his mistakes. I had to take the heat for the other guy when he made mistakes. OTOH the guy wants to learn something, is motivated, and I don't want to stop him. We've had our share of slackers in the group and it's nice to have someone who is willing to work for a change. So what would you guys do? Would you teach him the skills that you spent all of that time learning? Set him up with a test database on his PC and recommend some books for him? Encourage him to get a strong foundation in IT support first and ask later? We haven't had a new hire in years, let alone one that is interested in what I do, so this is new to me.

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• Ad-hoc reporting similar to Microstrategy/Pentaho - is OLAP really the only choice (is OLAP even sufficient)?

  - by TheBeefMightBeTough

  So I'm getting ready to develop an API in Java that will provide all dimensions, metrics, hierarchies, etc to a user such that they can pick and choose what they want (say, e.g., dimensions of Location (a store) and Weekly, and the metric Product Sales $), provide their choices to the api, and have it spit out an object that contains the answer to their question (the object would probably be a set of cells). I don't even believe there will be much drill up/down. The data warehouse the APIwill interface with is in a standard form (FACT tables, dimensions, star schema format). My question is, is an OLAP framework such as Mondrian the only way to achieve something akin to ad-hoc reporting? I can envisage a really large Cube (or VirtualCube) that contains most of the dimensions and metrics the user could ever want, which would give the illusion of ad-hoc reporting. The problem is that there is a ton of setup to do (so much XML) to get the framework to work with the data. Further it requires specific knowledge, such as MDX, and even moreso learning the framework peculiars (Mondrian API). Finally, I am not positive it will scale much better than simply making queries against a SQL database. OLAP to me feels like very old technology. Is performance really an issue anymore? The alternative I can think of would be dynamic SQL. If the existing tables in the data warehouse conform to a naming scheme (FACT_, DIM_, etc), or if a very simple config file/ database table containing config information existed that stored which tables are fact tables, which are dimensions, and what metrics are available, then couldn't the api read from that and assembly the appropriate sql query? Would this necessarily be harder than learning MDX, Mondrian (or another OLAP framework), and creating all the cubes? In general, I feel that OLAP is at the same time too powerful (supports drill up/down, complex functions) and outdated and am reluctant to base my architecture on it. However, I am unsure if the alternative(s), such as rolling my own ad-hoc reporting framework using dynamic SQL would remove any complexity while still fulfilling requirements, both functional and non-functional (e.g., scalability; some FACT tables have many millions of rows). I also wonder about other techniques (e.g., hive). Has anyone here tried to do ad-hoc reporting? Any advice? I expect this project to take a pretty long time (3 months min, but probably longer), so I just do not want to commit to an architecture without being absolutely sure of its pros and cons. Thanks so much.

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• openGL textures in bitmap mode

  - by evenex_code

  For reasons detailed here I need to texture a quad using a bitmap (as in, 1 bit per pixel, not an 8-bit pixmap). Right now I have a bitmap stored in an on-device buffer, and am mounting it like so: glBindBuffer(GL_PIXEL_UNPACK_BUFFER, BFR.G[(T+1)%2]); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, W, H, 0, GL_COLOR_INDEX, GL_BITMAP, 0); The OpenGL spec has this to say about glTexImage2D: "If type is GL_BITMAP, the data is considered as a string of unsigned bytes (and format must be GL_COLOR_INDEX). Each data byte is treated as eight 1-bit elements..." Judging by the spec, each bit in my buffer should correspond to a single pixel. However, the following experiments show that, for whatever reason, it doesn't work as advertised: 1) When I build my texture, I write to the buffer in 32-bit chunks. From the wording of the spec, it is reasonable to assume that writing 0x00000001 for each value would result in a texture with 1-px-wide vertical bars with 31-wide spaces between them. However, it appears blank. 2) Next, I write with 0x000000FF. By my apparently flawed understanding of the bitmap mode, I would expect that this should produce 8-wide bars with 24-wide spaces between them. Instead, it produces a white 1-px-wide bar. 3) 0x55555555 = 1010101010101010101010101010101, therefore writing this value ought to create 1-wide vertical stripes with 1 pixel spacing. However, it creates a solid gray color. 4) Using my original 8-bit pixmap in GL_BITMAP mode produces the correct animation. I have reached the conclusion that, even in GL_BITMAP mode, the texturer is still interpreting 8-bits as 1 element, despite what the spec seems to suggest. The fact that I can generate a gray color (while I was expecting that I was working in two-tone), as well as the fact that my original 8-bit pixmap generates the correct picture, support this conclusion. Questions: 1) Am I missing some kind of prerequisite call (perhaps for setting a stride length or pack alignment or something) that will signal to the texturer to treat each byte as 8-elements, as it suggests in the spec? 2) Or does it simply not work because modern hardware does not support it? (I have read that GL_BITMAP mode was deprecated in 3.3, I am however forcing a 3.0 context.) 3) Am I better off unpacking the bitmap into a pixmap using a shader? This is a far more roundabout solution than I was hoping for but I suppose there is no such thing as a free lunch.

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• The term "interface" in C++

  - by Flexo

  Java makes a clear distinction between class and interface. (I believe C# does also, but I have no experience with it). When writing C++ however there is no language enforced distinction between class and interface. Consequently I've always viewed interface as a workaround for the lack of multiple inheritance in Java. Making such a distinction feels arbitrary and meaningless in C++. I've always tended to go with the "write things in the most obvious way" approach, so if in C++ I've got what might be called an interface in Java, e.g.: class Foo { public: virtual void doStuff() = 0; ~Foo() = 0; }; and I then decided that most implementers of Foo wanted to share some common functionality I would probably write: class Foo { public: virtual void doStuff() = 0; ~Foo() {} protected: // If it needs this to do its thing: int internalHelperThing(int); // Or if it doesn't need the this pointer: static int someOtherHelper(int); }; Which then makes this not an interface in the Java sense anymore. Instead C++ has two important concepts, related to the same underlying inheritance problem: virtual inhertiance Classes with no member variables can occupy no extra space when used as a base "Base class subobjects may have zero size" Reference Of those I try to avoid #1 wherever possible - it's rare to encounter a scenario where that genuinely is the "cleanest" design. #2 is however a subtle, but important difference between my understanding of the term "interface" and the C++ language features. As a result of this I currently (almost) never refer to things as "interfaces" in C++ and talk in terms of base classes and their sizes. I would say that in the context of C++ "interface" is a misnomer. It has come to my attention though that not many people make such a distinction. Do I stand to lose anything by allowing (e.g. protected) non-virtual functions to exist within an "interface" in C++? (My feeling is the exactly the opposite - a more natural location for shared code) Is the term "interface" meaningful in C++ - does it imply only pure virtual or would it be fair to call C++ classes with no member variables an interface still?

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• Laptop freezes and seems to crash, but continues working after waiting for a few minutes [closed]

  - by Corwin

  I've had this old notebook laying around and because i was missing a second machine (My wife usually steals the first ;) ) I considered installing Linux. As a php developer I work with Linux servers (usually fedora) on a daily basis and because its an older machine that I want to use for development, linux seemed the best option. Speedwise I expected a good experience, better than Windows 7 on the same machine. The results where terrible. I tried ubuntu 12.04. The shell never got past showing the background. The system doesn't freeze since the mouse still works and I can use ctrl+alt+f2 etc to enter terminal mode. I expected hardware problems en even exchanged the harddisk en Ram memory. No luck though, so I started over and tried 11.10 Same results so I tried 10.04.4 which did install properly. Not sure if unity was the problem, but it seems likely. But then I tried simply things like surfing on the net, the system frooze and I thought it crashed so after a few minutes I pulled the plug and rebooted. But it happened again and I waited. After a few minutes the system came back to life like nothing happened. Long story short. Besides the fact that the entire interface is very sluggish, any and all graphical functions freezes the system. The more elaborate the animation would be, the longer it freezes. I switch chromium from window to fullscreenmode and had to wait 15 minutes to continue. I don't see the animation that's probably supposed to be in between. It just freezes and then after unfreezing its fullscreen. I don't think its a bug. I suspect the problem is with my graphics card. Like I said, its and old system. So old that I can't even find the original Ati drivers anywere. (I'll post the details of my system at the end of my post) I'm at a loss as to what to do next. I tried other Distro's. So far only dreamlinux works normally. Linux Mint won't start as a live CD. I think I simply need a driver update but I can't find them anywhere. Does anyone have the same experience ? Maybe even someone who has or had the same notebook running Ubuntu at some point ? Anyway, here are the specs: http://www.nec-driver.com/nec-driver/NEC-Versa-P550---FP550-Driver_421.html

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• Integrating with a payment provider; Proper and robust OOP approach

  - by ExternalUse

  History We are currently using a so called redirect model for our online payments (where you send the payer to a payment gateway, where he inputs his payment details - the gateway will then return him to a success/failure callback page). That's easy and straight-forward, but unfortunately quite inconvenient and at times confusing for our customers (leaving the site, changing their credit card details with an additional login on another site etc). Intention & Problem description We are now intending to switch to an integrated approach using an exchange of XML requests and responses. My problem is on how to cater with all (or rather most) of the things that may happen during processing - bearing in mind that normally simplicity is robust whereas complexity is fragile. Examples User abort: The user inputs Credit Card details and hits submit. An XML message to the provider's gateway is sent and waiting for response. The user hits "stop" in his browser or closes the window. ignore_user_abort() in PHP may be an option - but is that reliable? might it be better to redirect the user to a "please wait"-page, that in turn opens an AJAX or other request to the actual processor that does not rely on the connection? Database goes away sounds over-complicated, but with e.g. a webserver in the States and a DB in the UK, it has happened and will happen again: User clicks together his order, payment request has been sent to the provider but the response cannot be stored in the database. What approach could I use, using PHP to sort of start an SQL like "Transaction" that only at the very end gets committed or rolled back, depending on the individual steps? Should then neither commit or roll back have happened, I could sort of "lock" the user to prevent him from paying again or to improperly account for payments - but how? And what else do I need to consider technically? None of the integration examples of e.g. Worldpay, Realex or SagePay offer any insight, and neither Google or my search terms were good enough to find somebody else's thoughts on this. Thank you very much for any insight on how you would approach this!

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