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• Basic AI FSM - Handling state transition

  - by Galvanize

  I'm starting to study on how to implement game AI, and it seems to me that a very simple FSM for my Pong demo would be a nice way to start. My vision on implementing this would be to have a basic state interface and a class for each state, then the NPC would have an instance of the current state. The class should have an update method and directions on wich state to go next, depending on the event received. The question is: How do I handle this event? Should I have a regular addEventListener and a costum event system? Or should I check on update for the things that could change the current state? I'm feeling a bit lost, I feel I have a good grasp on the FSM concept but a good implementation seems tricky, thanks in advance.

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• Which logfile(s) log(s) errors reading a cd?

  - by Robert Vila

  I introduce a CD-RW, maybe blank (I really don't know), and after a little movement inside the reader, the CD is ejected without any message at all. I would like to know what is going on and the reason why it is ejected. How can I know that in Natty. The CD reader is working OK because I can read other CD's. It only gave me problems writing from Natty, a few days ago, but with MacOS there was no problem. Thank you Edit: Maybe there is no error, but then, how can I know what is in the Cd if there is anything?

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• Decision for Unchecked Exceptions in Scala

  - by Jatin

  As a java programmer, I have always been critical of Unchecked Exceptions. Mostly programmers use it as an en-route to coding easiness only to create trouble later. Also the programs (though untidy) with checked exceptions are much robust compared to unchecked counterparts. Surprisingly in Scala, there is nothing called Checked Exceptions. All the Java checked and unchecked are unchecked in Scala. What is the motivation behind this decision? For me it opens wide range of problems when using any external code. And if by chance the documentation is poor, it results in KILL.

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• Handling window resize with arbitrary aspect ratios

  - by DormoTheNord

  I'm currently making a 2D game using SFML. I want the aspect ratio to be maintained when the user resizes the window. I also want the game to work with any arbitrary aspect ratio (like any media player would). Here is the code I have so far: void os::GameEngine::setCameraViewport() { sf::FloatRect tempViewport; float viewAspectRatio = (float)aspectRatio.x / aspectRatio.y; float screenAspectRatio = (float)gameWindow.getSize().x / gameWindow.getSize().y; if (viewAspectRatio > screenAspectRatio) { // Viewport is wider than screen, fit on X } else if (viewAspectRatio < screenAspectRatio) { // Screen is wider than viewport, fit on Y } else // window aspect ratio matches view aspect ratio { tempViewport.height = 1; tempViewport.width = 1; tempViewport.left = 0; tempViewport.top = 0; } viewport = tempViewport; camera.setViewport(viewport); gameWindow.setView(camera); } The problem is I'm having trouble with the logic to determine the properties of the viewport.

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• Importing tab delimited file into array in Visual Basic 2013 [migrated]

  - by JaceG

  I am needing to import a tab delimited text file that has 11 columns and an unknown number of rows (always minimum 3 rows). I would like to import this text file as an array and be able to call data from it as needed, throughout my project. And then, to make things more difficult, I need to replace items in the array, and even add more rows to it as the project goes on (all at runtime). Hopefully someone can suggest code corrections or useful methods. I'm hoping to use something like the array style sMyStrings(3,2), which I believe would be the easiest way to control my data. Any help is gladly appreciated, and worthy of a slab of beer. Here's the coding I have so far: Imports System.IO Imports Microsoft.VisualBasic.FileIO Public Class Main Dim strReadLine As String Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load Dim sReader As IO.StreamReader = Nothing Dim sRawString As String = Nothing Dim sMyStrings() As String = Nothing Dim intCount As Integer = -1 Dim intFullLoop As Integer = 0 If IO.File.Exists("C:\MyProject\Hardware.txt") Then ' Make sure the file exists sReader = New IO.StreamReader("C:\MyProject\Hardware.txt") Else MsgBox("File doesn't exist.", MsgBoxStyle.Critical, "Error") End End If Do While sReader.Peek >= 0 ' Make sure you can read beyond the current position sRawString = sReader.ReadLine() ' Read the current line sMyStrings = sRawString.Split(New Char() {Chr(9)}) ' Separate values and store in a string array For Each s As String In sMyStrings ' Loop through the string array intCount = intCount + 1 ' Increment If TextBox1.Text <> "" Then TextBox1.Text = TextBox1.Text & vbCrLf ' Add line feed TextBox1.Text = TextBox1.Text & s ' Add line to debug textbox If intFullLoop > 14 And intCount > -1 And CBool((intCount - 0) / 11 Mod 0) Then cmbSelectHinge.Items.Add(sMyStrings(intCount)) End If Next intCount = -1 intFullLoop = intFullLoop + 1 Loop End Sub

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• Is goto to improve DRY-ness OK?

  - by Marco Scannadinari

  My code has many checks to detect errors in various cases (many conditions would result in the same error), inside a function returning an error struct. Instead of looking like this: err_struct myfunc(...) { err_struct error = { .error = false }; ... if(something) { error.error = true; error.description = "invalid input"; return error; } ... case 1024: error.error = true; error.description = "invalid input"; // same error, but different detection scenario return error; break; // don't comment on this break please (EDIT: pun unintended) ... Is use of goto in the following context considered better than the previous example? err_struct myfunc(...) { err_struct error = { .error = false }; ... if(something) goto invalid_input; ... case 1024: goto invalid_input; break; return error; invalid_input: error.error = true; error.description = "invalid input"; return error;

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• Common practice in handling bounce message

  - by foodil

  At now I mainly create a mail account separately (with different domain name [email protected]) and i add this mail as one return path. So the bounce message will only go to that mailbox and i parse the mail message one by one to check the failure receipent and the error code, then i convert the error code to the actual error message. Finally, the error message and the fail receipent's mail are post to my system and let my system user check the bounce information. Is it a common practice? Since i am worry about the mail other from bounce message have sent to my mail box, that would be a disaster if i parse them without filter them out, but how can i filter out between bounce message and normal mail? Thank you for any kind of help.

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• Any good reason open files in text mode?

  - by Tinctorius

  (Almost-)POSIX-compliant operating systems and Windows are known to distinguish between 'binary mode' and 'text mode' file I/O. While the former mode doesn't transform any data between the actual file or stream and the application, the latter 'translates' the contents to some standard format in a platform-specific manner: line endings are transparently translated to '\n' in C, and some platforms (CP/M, DOS and Windows) cut off a file when a byte with value 0x1A is found. These transformations seem a little useless to me. People share files between computers with different operating systems. Text mode would cause some data to be handled differently across some platforms, so when this matters, one would probably use binary mode instead. As an example: while Windows uses the sequence CR LF to end a line in text mode, UNIX text mode will not treat CR as part of the line ending sequence. Applications would have to filter that noise themselves. Older Mac versions only use CR in text mode as line endings, so neither UNIX nor Windows would understand its files. If this matters, a portable application would probably implement the parsing by itself instead of using text mode. Implementing newline interpretation in the parser might also remove some overhead of using text mode, as buffers would need to be rewritten (and possibly resized) before returning to the application, while this may be less efficient than when it would happen in the application instead. So, my question is: is there any good reason to still rely on the host OS to translate line endings and file truncation?

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• Where should I handle fatal exceptions

  - by Puckl

  For example, I have a controller that loads a file and hands it over to the processing. Should I handle the exception in the file loader and return Null if something is wrong, or should I throw the exception and handle it in the controller? Without the file the rest of the program can´t work. Where should I handle a exception that shuts down the program properly? I want to shut down an Android application properly.

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• Handling cameras in a large scale game engine

  - by Hannesh

  What is the correct, or most elegant, way to manage cameras in large game engines? Or should I ask, how does everybody else do it? The methods I can think of are: Binding cameras straight to the engine; if someone needs to render something, they bind their own camera to the graphics engine which is in use until another camera is bound. A camera stack; a small task can push its own camera onto the stack, and pop it off at the end to return to the "main" camera. Attaching a camera to a shader; Every shader has exactly one camera bound to it, and when the shader is used, that camera is set by the engine when the shader is in use. This allows me to implement a bunch of optimizations on the engine side. Are there other ways to do it?

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• Handling & processing credit card payments

  - by Bob Jansen

  I'm working on program that charges customers on a pay as you go per month modal. This means that instead of the customers paying their invoices at the start of the month, they will have to pay at the end of the month. In order to secure the payments I want my customers credit card information stored so that they can be charged automatically at the end of the month. I do not have the resources, time, or risk to handle and store my customers credit card information on my servers and am looking for a third party solution. I'm a tad overwhelmed by all the different options and services that are out there and was wondering if anyone with experience have any recommendations and tips. I'm having difficulty finding services that allow me to to store my customers credit card information and charge them automatically. Most of them seem to offer an invoice styled approach.

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• I've been told that Exceptions should only be used in exceptional cases. How do I know if my case is exceptional?

  - by tieTYT

  My specific case here is that the user can pass in a string into the application, the application parses it and assigns it to structured objects. Sometimes the user may type in something invalid. For example, their input may describe a person but they may say their age is "apple". Correct behavior in that case is roll back the transaction and to tell the user an error occurred and they'll have to try again. There may be a requirement to report on every error we can find in the input, not just the first. In this case, I argued we should throw an exception. He disagreed, saying, "Exceptions should be exceptional: It's expected that the user may input invalid data, so this isn't an exceptional case" I didn't really know how to argue that point, because by definition of the word, he seems to be right. But, it's my understanding that this is why Exceptions were invented in the first place. It used to be you had to inspect the result to see if an error occurred. If you failed to check, bad things could happen without you noticing. Without exceptions every level of the stack needs to check the result of the methods they call and if a programmer forgets to check in one of these levels, the code could accidentally proceed and save invalid data (for example). Seems more error prone that way. Anyway, feel free to correct anything I've said here. My main question is if someone says Exceptions should be exceptional, how do I know if my case is exceptional?

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• Criteria for selecting timeout value?

  - by stijn

  Situation: a piece of software reads frames of data from a file in a seperate thread and puts it on a queue, emptied by another thread. That second thread periodically checks on the queue and fails rather gracefully, by showing an error message stating the read timed out, if no data is available within a certain amount of time. Initially this timeout was set to 200mSec. There was no real reasoning behind that constant though, but it worked fine. We measured on a couple of machines and for large data frames, larger than what would be used by customers, a read took like 20mSec whith no other load on the machine. However one customer now gets timeout errors now and then (on the second try all is fine, probably the file is in cache or the virus scanner leaves it alone). The programmers are like 'well, yeah, but that customer's machine is full of cruft, virus scanners, tons of unneeded background processes etc'. Of course the customer is like 'hey this should just work, shouldn't it'? While the programers have a point, since the software is heavy enough to validate the need for a dedicated machine, that does not make the customer happy. Increasing the timeout to 2 seconds, for example, solves the problem. But I'd like to make a proper decision now instead of just randomly pick some magic constant that is probably ok in 99% of cases. What criteria should be used for that? We could just pick a large number, but that feels wrong. (and then we end up with a program that has the horrible bahaviour of hanging when trying to read from a disconnected drive for instance, whereas we'd rather make it show an error right away). Or we could make the timeout value a user setting, but then we need to ducument it clearly and even then not all customers are tech savy enough to really understand what it does. Or we could try and wait until another customer reports timeouts and increase the value again. And again. Until we find something ok for 99.99% of the cases.. Any good practice for this type of situation?

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• Handling buildings in isometric tile based games

  - by MustSeeMelons

  A simple question, to which i couldn't find a definitive answer - how to manage buildings on a tiled map? Should the building be sliced in to tiles or one big image? EDIT: The game is being built from scratch using C++/SDL 2.0, it will be a turn based strategy, something like Fallout 1 & 2 without the hex grid, a simple square grid, where the Y axis is squished by 50%. Buildings can span multiple tiles, the characters move tile by tile. For now, the terrain is completely flat. Some basic functionality is in place, so I'm aiming to advancing the terrain and levels them selves - adding buildings, gates, cliffs, not sure about the elevation.

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• SSIS 2008 Configuration Settings Handling Logic for Variables Visualized

  - by Compudicted

  There are many articles discussing the specifics of how the configuration settings are applied including the differences between SSIS 2005 and 2008 version implementations, however this topic keeps resurfacing on MSDN’s SSIS Forum. I thought it could be useful to cover the logic aspect visually. Below is a diagram explaining the basic flow of a variable setting for a case when no parent package is involved.   As you can see the run time stage ignores any command line flags for variables already set in the config file, I realize this is not stressed enough in many publications. Besides, another interesting fact is that the command line dtexec tool is case sensitive for the portion following the package keyword, I mean if you specify your flag to set a new value for a variable like dtexec /f Package.dtsx -set \package.variables[varPkgMyDate].value;02/01/2011 (notice the lover case v in .value) You will get errors. By capitalizing the keyword the package runs successfully.

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• Effective handling of variables in non-object oriented programming

  - by srnka

  What is the best method to use and share variables between functions in non object-oriented program languages? Let's say that I use 10 parameters from DB, ID and 9 other values linked to it. I need to work with all 10 parameters in many functions. I can do it next ways: 1. call functions only with using ID and in every function get the other parameters from DB. Advantage: local variables are clear visible, there is only one input parameter to function Disadvantage: it's slow and there are the same rows for getting parameters in every function, which makes function longer and not so clear 2. call functions with all 10 parameters Advantage: working with local variables, clear function code Disadvantage: many input parameters, what is not nice 3. getting parameters as global variables once and using them everywhere Advantage - clearer code, shorter functions, faster processing Disadvantage - global variables - loosing control of them, possibility of unwanted overwriting (Especially when some functions should change their values) Maybe there is some another way how to implement this and make program cleaner and more effective. Can you say which way is the best for solving this issue?

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• Handling player/background movements in 2D games

  - by lukeluke

  Suppose you have your animated character controlled by the player and a 2D world (like the old 2D side-scrolling games). When the user press right on the keyboard, the background is moved to the right. If the path is always horizontal, this is simple to do (incrementation/decrementation of the x-coordinate). But suppose that the path is instead a polygonal chain. My questions are: How do you move the background? How do you move the background if the game objects are managed with a physics engine like box2D?

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• "t-sql" tool for csv files?

  - by adolf garlic

  Is there a tool that allows to query files based on the following criteria, and change them? creation date filenames (e.g. filetypeA_YYYYMMDD_data2.blah) file content For the example, the workflow could be the following one: Get all files created between date x and date y, where the filename contains z and the file itself contains value x under column zzz. Update it to be a different value/another column.

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• Is possible to write too many asserts?

  - by Lex Fridman

  I am a big fan of writing assert checks in C++ code as a way to catch cases during development that cannot possibly happen but do happen because of logic bugs in my program. This is a good practice in general. However, I've noticed that some functions I write (which are part of a complex class) have 5+ asserts which feels like it could potentially be a bad programming practice, in terms of readability and maintainability. I think it's still great, as each one requires me to think about pre- and post-conditions of functions and they really do help catch bugs. However, I just wanted to put this out there to ask if there is a better paradigms for catching logic errors in cases when a large number of checks is necessary.

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• Handling array passed to object at creation

  - by cecilli0n

  When creating my object I pass it an array of a row from my database. (everything in the array we will need, disregarding unnecessary elements at sql query level) When I need to access certain array elements from within my class, I do so like $this->row['element'] However, As I continue development, I sometimes forget what exactly is in this passed array.(this itself doesn't seem good) I am wondering if their is a professional approach to dealing with this, Or am I the only one who has these "I wonder whats in the array" thoughts. One approach to tackling this could be that when we originally pass the array, in the constructor, we assign each element of the array to its own variable, but is this considered professional practice? Additionally by doing this, we could make those variables constants, in a attempt at immutability. Overall I am trying to adhere to good software craftsmanship. Regards.

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• Handling Types for Real and Complex Matrices in a BLAS Wrapper

  - by mga

  I come from a C background and I'm now learning OOP with C++. As an exercise (so please don't just say "this already exists"), I want to implement a wrapper for BLAS that will let the user write matrix algebra in an intuitive way (e.g. similar to MATLAB) e.g.: A = B*C*D.Inverse() + E.Transpose(); My problem is how to go about dealing with real (R) and complex (C) matrices, because of C++'s "curse" of letting you do the same thing in N different ways. I do have a clear idea of what it should look like to the user: s/he should be able to define the two separately, but operations would return a type depending on the types of the operands (R*R = R, C*C = C, R*C = C*R = C). Additionally R can be cast into C and vice versa (just by setting the imaginary parts to 0). I have considered the following options: As a real number is a special case of a complex number, inherit CMatrix from RMatrix. I quickly dismissed this as the two would have to return different types for the same getter function. Inherit RMatrix and CMatrix from Matrix. However, I can't really think of any common code that would go into Matrix (because of the different return types). Templates. Declare Matrix<T> and declare the getter function as T Get(int i, int j), and operator functions as Matrix *(Matrix RHS). Then specialize Matrix<double> and Matrix<complex>, and overload the functions. Then I couldn't really see what I would gain with templates, so why not just define RMatrix and CMatrix separately from each other, and then overload functions as necessary? Although this last option makes sense to me, there's an annoying voice inside my head saying this is not elegant, because the two are clearly related. Perhaps I'm missing an appropriate design pattern? So I guess what I'm looking for is either absolution for doing this, or advice on how to do better.

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• Handling bugs, quirks, or annoyances in vendor-supplied headers

  - by supercat

  If the header file supplied by a vendor of something with whom one's code must interact is deficient in some way, in what cases is it better to: Work around the header's deficiencies in the main code Copy the header file to the local project and fix it Fix the header file in the spot where it's stored as a vendor-supplied tool Fix the header file in the central spot, but also make a local copy and try to always have the two match Do something else As an example, the header file supplied by ST Micro for the STM320LF series contains the lines: typedef struct { __IO uint32_t MODER; __IO uint16_t OTYPER; uint16_t RESERVED0; .... __IO uint16_t BSRRL; /* BSRR register is split to 2 * 16-bit fields BSRRL */ __IO uint16_t BSRRH; /* BSRR register is split to 2 * 16-bit fields BSRRH */ .... } GPIO_TypeDef; In the hardware, and in the hardware documentation, BSRR is described as a single 32-bit register. About 98% of the time one wants to write to BSRR, one will only be interested in writing the upper half or the lower half; it is thus convenient to be able to use BSSRH and BSSRL as a means of writing half the register. On the other hand, there are occasions when it is necessary that the entire 32-bit register be written as a single atomic operation. The "optimal" way to write it (setting aside white-spacing issues) would be: typedef struct { __IO uint32_t MODER; __IO uint16_t OTYPER; uint16_t RESERVED0; .... union // Allow BSRR access as 32-bit register or two 16-bit registers { __IO uint32_t BSRR; // 32-bit BSSR register as a whole struct { __IO uint16_t BSRRL, BSRRH; };// Two 16-bit parts }; .... } GPIO_TypeDef; If the struct were defined that way, code could use BSRR when necessary to write all 32 bits, or BSRRH/BSRRL when writing 16 bits. Given that the header isn't that way, would better practice be to use the header as-is, but apply an icky typecast in the main code writing what would be idiomatically written as thePort->BSRR = 0x12345678; as *((uint32_t)&(thePort->BSSRH)) = 0x12345678;, or would be be better to use a patched header file? If the latter, where should the patched file me stored and how should it be managed?

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• 3D physics engine for accurate collision handling on desktop/laptop computers (non-console)

  - by Georges Oates Larsen

  What are your suggestions for a physics engine that satisfies the following criteria? Capable of calculating collisions between multiple concave mesh-based colliders Handles many collisions going on at once (for instance one mesh being wedged between two others, which themselves may be wedged between two meshes) Does not allow for collider passthrough, even at high speeds. For instance, if I am applying force to a programmatically hinged object that makes it spin, I do not want it to pass through another rigidbody that it collides with while spinning. I have this problem using PhysX As implied before, reacts well to hinged objects, preferably has its own implementation of a hinge, but I am willing to program my own. The important part is that it has some sort of interface that guarantees accurate collision tracking even when dealing with these things Platform independent -- runs on mac as well as PC, also not tied down to specific graphics cards I think that's the best way to explain what I am looking for. Basically, I need SUPER reliable collisions. Something that can't be accomplished with a simple ray casting approach that sends a ray from the last position of the object to the current position (as this object may be potentially large and colliding with small objects via rotation) Bonus points for also including an OPEN SOURCE engine.

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• Efficient way to check for changes to the contents of folders

  - by MrVimes

  I am creating an application that maintains a database of files of a certain type in a given folder (and all subfolders) Initially the program will recurse the folders and add any file it finds of that type to the database. I want the application to have the ability to re-scan the folder and add any files that were not there the last time the folders were scanned. It can't use the date created property of the file because there is a high chance of a file being added to the folders that isn't a new file. I am wondering what the most efficient way of doing this is, and if there is a way that doesn't involve checking each file is in the database already (which, if there are 5000 files would mean 5000 queries of a list 5000 items in size, or 25 million 'checks' for the sql engine to perform) I suppose a more specific question to acheive the same goal would be - is there a property of a file (in Microsoft Windows) that will reliably tell you when that file arrived in that folder.

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• Handling deleted users - separate or same table?

  - by Alan Beats

  The scenario is that I've got an expanding set of users, and as time goes by, users will cancel their accounts which we currently mark as 'deleted' (with a flag) in the same table. If users with the same email address (that's how users log in) wish to create a new account, they can signup again, but a NEW account is created. (We have unique ids for every account, so email addresses can be duplicated amongst live and deleted ones). What I've noticed is that all across our system, in the normal course of things we constantly query the users table checking the user is not deleted, whereas what I'm thinking is that we dont need to do that at all...! [Clarification1: by 'constantly querying', I meant that we have queries which are like: '... FROM users WHERE isdeleted="0" AND ...'. For example, we may need to fetch all users registered for all meetings on a particular date, so in THAT query, we also have FROM users WHERE isdeleted="0" - does this make my point clearer?] (1) continue keeping deleted users in the 'main' users table (2) keep deleted users in a separate table (mostly required for historical book-keeping) What are the pros and cons of either approach?

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