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  • General List of Common Programming Errors

    - by javamonkey79
    As one journey's from apprentice to journeyman to master I've noticed that one accumulates a list of best practices for things they've been bitten by. Personally, I write most of my stuff in java & SQL so my list tends to be slated towards them. I've accumulated the following: When doing list removal, always reverse iterate Avoid adding items to a list you are currently iterating on Watch out for NullPointerExceptions Now, I know there are language specific "common errors" links out there like this one. And I'm also aware of the pragmatic programmer tips, Martin Fowler's "code smells". Does anyone know of any good lists out there of things like I've listed above (re: list removal, adding items, etc). My guess is that there are some good QA folks out there that can probably throw me a bone here. I'm not looking for things the compiler can catch - I'm looking for common things that cause bugs. In the event that there isn't a list out there already then I welcome posting your own findings here. Thanks in advance!

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  • I need an approach to the problem of preventing inserting duplicate records into the database

    - by Maurice
    Apologies is this question is asked on the incorrect "stack" A webservice that I call returns a list of data. The data from the webservice is updated periodically, so a call to the webservice done in one hour could return the same data as a call done in an hour. Also, the data is returned based on a start and end date. We have multiple users that can run the webservice search, and duplicate data is most likely to be returned (especially for historical data). However I don't want to insert this duplicate data in the database. I've created a db table in which the data is stored (most important columns are) Id int autoincrement PK Date date not null --The date to which the data set belongs. LastUpdate date not null --The date the data set was last updated. UserName varchar(50) --The name of the user doing the search. I use sql server 2008 express with c# 4.0 and visual studio 2010. Entity Framework is used as the ORM. If stored procedures could be avoided in the proposed solution, then that will be a plus. Another way of looking interpreting what I'm asking a solution for is as follows: I have a million unique records in my table. A user does a new search. The search results from the user contains around 300k of the data that is already in the db. An efficient solution to finding an inserting only the unique records is needed.

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  • What are the options for retraining formally as a software engineer?

    - by Matt Harrison
    I'm a self-taught programmer. I have a good undergraduate degree in Architecture (building, not software). I was always a science/maths kid and got consistency good grades in these subjects. However I became indecisive at undergraduate level and switched between Physics, Chemistry, Art and finally stuck with Architecture mainly out of the desperate need to finish any degree. As soon as I graduated, I ditched architecture and started writing code again professionally. I've been a programmer now for 3 years and I've progressed very quickly. I'm ambitious and I want to work for the top companies in this field at some point and I've realised I need a Computer Science education to be taken seriously (based on job ads for the big tech firms). I've applied for a few MSc programs in Computer Science but they've all rejected me because of my BA. It's just not an option for me to quit my job and go back and do another 3 year undergraduate degree in CS. I know I can study at this level because I've read most of the books on the reading lists for CS courses in the UK that I can find and I have this knowledge now, it's just I can't prove it on an application form. What options are available to me?

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  • How to charge in agile iterative approach?

    - by user1620696
    I have a doubt about budgeting when working with agile iterative approach. If I understood well, in agile at the end of each iteration we have usable product, so we have some of the requirements met and then some part of the software will be already working. How do we charge for our work in this methodology? Do we charge per iteration, i.e. charge per major requirements being met, or just charge the customer when the software is indeed finished and then receive for everything at once?

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  • Designing exceptions for conversion failures

    - by Mr.C64
    Suppose there are some methods to convert from "X" to "Y" and vice versa; the conversion may fail in some cases, and exceptions are used to signal conversion errors in those cases. Which would be the best option for defining exception classes in this context? A single XYConversionException class, with an attribute (e.g. an enum) specifying the direction of the conversion (e.g. ConversionFromXToY, ConversionFromYToX). A XYConversionException class, with two derived classes ConversionFromXToYException and ConversionFromYToXException. ConversionFromXToYException and ConversionFromYToXException classes without a common base class.

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  • How to handle monetary values in PHP and MySql?

    - by Songo
    I've inherited a huge pile of legacy code written in PHP on top of a MySQL database. The thing I noticed is that the application uses doubles for storage and manipulation of data. Now I came across of numerous posts mentioning how double are not suited for monetary operations because of the rounding errors. However, I have yet to come across a complete solution to how monetary values should be handled in PHP code and stored in a MySQL database. Is there a best practice when it comes to handling money specifically in PHP? Things I'm looking for are: How should the data be stored in the database? column type? size? How should the data be handling in normal addition, subtraction. multiplication or division? When should I round the values? How much rounding is acceptable if any? Is there a difference between handling large monetary values and low ones? Note: A VERY simplified sample code of how I might encounter money values in everyday life: $a= $_POST['price_in_dollars']; //-->(ex: 25.06) will be read as a string should it be cast to double? $b= $_POST['discount_rate'];//-->(ex: 0.35) value will always be less than 1 $valueToBeStored= $a * $b; //--> any hint here is welcomed $valueFromDatabase= $row['price']; //--> price column in database could be double, decimal,...etc. $priceToPrint=$valueFromDatabase * 0.25; //again cast needed or not? I hope you use this sample code as a means to bring out more use cases and not to take it literally of course. Bonus Question If I'm to use an ORM such as Doctrine or PROPEL, how different will it be to use money in my code.

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  • Hover alternatve for touch devices [migrated]

    - by Joshua Frank
    I'm building a standard infographic where you mouse over a region and the image changes as you move. For instance, imagine a map of the world, and when you mouse over a country, that country glows and a panel shows statistics about that country. The implementation is to have a separate image for the glowing country, and a div element with the statistics, and the code shows these additional elements on a hover over the country. The question is: what should this do on a tablet, where there's no hover event? What's a good alternative navigation metaphor for this kind of situation on touch-only devices?

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  • Implementation of a Rules Engine in Your Business Applicaitons

    - by enonu
    I'm for an experience driven answer from a few software engineers who have implemented a rules engine in their internal business applications. How has it affected your business in the following ways: Ability to launch and iterate over business driven logic Ability to have "business users" perform the actual modification of those rules rather than developers. Ability to comprehend the business rules in general. Quality of the software releases. More or less bugs from the end-user's POV? Speed of the applications. If you had to do it all over again, what would you do differently? Lastly, I'm looking for a qualification of your answer w/ respect to the architecture. Would you do the same thing if you were deploying to a 1-machine setup vs. your architecture vs. a multi-tier cloud-based distributed architecture using 1000s of machines? How would it be different? Thanks!

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  • PHPForm Data Generate PDF & Send to Email?

    - by tom
    I'm a beginner in PHP I was wondering if this is easy to do or if i'd have to outsource this to a programmer - Basically when a user fills in the PHP Form and submits it I need this to generate as a PDF (with all the labels etc) which will then email/attach to MY email and NOT the user who submitted this form. I have looked at tcpdf, fpdi but i dont think any of those scripts allow me to do this specifically as from what i heard it generates a download link for the user, and that is not what i need. If anyone can help me it would be greatly appreciated. Regards Tom

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  • Are long methods always bad?

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

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  • Why is web app development path in Java this much confusing? [closed]

    - by Farshid
    I'm currently a .net web developer and I really like to switch to Java. I've used JSP about 7 years ago to develop and deploy a small web application on a JRUN app server. But after 7 years that I like to return back to Java, I can't find the clue. There are many web development frameworks that exist in Java world and each of them has fans that recommand it. There are extensions that sit above jvm for web development (like jRuby i think). I am confused and I do not know where to start the path of learning java web development. I do not want to focus on custom tailor-made approaches and want to remain on the basic path of developing with standard tools and methods and deploy them into standard app servers. (For example some says do not use EJBs, some says focus on MVC facilities like JSF. I'm confused and I do not know the path that i should go on)

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  • Witchcraft! Php [migrated]

    - by Steve Green
    This is madness, hoping someone can explain. $dir = getcwd(); $a = "/bla/httpdocs/ble"; $b = "/bla/httpdocs/meh"; if( ($dir == $a) || ($dir == $b) ){ $dirlist = glob("../images2/spinner/*.jpg"); }else{ $dirlist = glob("images2/spinner/*.jpg"); } works fine but $dir = getcwd(); if( ($dir == "/bla/httpdocs/ble") || ($dir == "/bla/httpdocs/meh") ){ $dirlist = glob("../images2/spinner/*.jpg"); }else{ $dirlist = glob("images2/spinner/*.jpg"); } doesn't. (By doesn't work I mean it returns false, I also tried === ) Wondered if strings were being null terminated so tried: print_r(str_split($a)); //$a has been set to the string below for this. print_r(str_split("/bla/httpdocs/ble")); they returned identical arrays Array ( [0] => / [1] => b [2] => l [3] => a [4] => / [5] => h [6] => t [7] => t [8] => p [9] => d [10] => o [11] => c [12] => s [13] => / [14] => b [15] => l [16] => e ) Array ( [0] => / [1] => b [2] => l [3] => a [4] => / [5] => h [6] => t [7] => t [8] => p [9] => d [10] => o [11] => c [12] => s [13] => / [14] => b [15] => l [16] => e ) Anyone?

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  • Is there a name for this issue?

    - by Epicmaster
    I was just talking to my partner about how hard it is to personally judge how good your product is after a while because you use it so often. You literally spend hours on your computer doing nothing but work on this Consumer Facing application, and you start to feel a little fatigue of using it over and over and over, at least a hundred times a day. You get scared this fatigue may mean the product you are building may have the same effect on the users and might mean you are doing something wrong. All i'm asking is, is there a name for this in product development? For the fact that as a designer+ programmer+everything else, your product might not suck as much as you think simply because you spend way to much time with it, or a variation of this?

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  • why write-enable ring

    - by SpashHit
    Here's an "interview question" that while ostensibly about hardware really does inform a software design principal as well. Computers used to (still do I guess, somewhere) use magnetic tape reels to store data. There was a plastic accessory you could attach to a tape reel called a "write-enable ring". If the tape had such a ring, the tape drive allowed writing to the tape... if not, it only allowed read access. Why was the choice to design the system in this way? Why not have a "write protect ring" instead, with the opposite effect?

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  • As the current draft stands, what is the most significant change the "National Strategy for Trusted Identities in Cyberspace" will provoke?

    - by mfg
    A current draft of the "National Strategy for Trusted Identities in Cyberspace" has been posted by the Department of Homeland Security. This question is not asking about privacy or constitutionality, but about how this act will impact developers' business models and development strategies. When the post was made I was reminded of Jeff's November blog post regarding an internet driver's license. Whether that is a perfect model or not, both approaches are attempting to handle a shared problem (of both developers and end users): How do we establish an online identity? The question I ask here is, with respect to the various burdens that would be imposed on developers and users, what are some of the major, foreseeable implementation issues that will arise from the current U.S. Government's proposed solution? For a quick primer on the setup, jump to page 12 for infrastructure components, here are two stand-outs: An Identity Provider (IDP) is responsible for the processes associated with enrolling a subject, and establishing and maintaining the digital identity associated with an individual or NPE. These processes include identity vetting and proofing, as well as revocation, suspension, and recovery of the digital identity. The IDP is responsible for issuing a credential, the information object or device used during a transaction to provide evidence of the subject’s identity; it may also provide linkage to authority, roles, rights, privileges, and other attributes. The credential can be stored on an identity medium, which is a device or object (physical or virtual) used for storing one or more credentials, claims, or attributes related to a subject. Identity media are widely available in many formats, such as smart cards, security chips embedded in PCs, cell phones, software based certificates, and USB devices. Selection of the appropriate credential is implementation specific and dependent on the risk tolerance of the participating entities. Here are the first considered actionable components of the draft: Action 1: Designate a Federal Agency to Lead the Public/Private Sector Efforts Associated with Achieving the Goals of the Strategy Action 2: Develop a Shared, Comprehensive Public/Private Sector Implementation Plan Action 3:Accelerate the Expansion of Federal Services, Pilots, and Policies that Align with the Identity Ecosystem Action 4:Work Among the Public/Private Sectors to Implement Enhanced Privacy Protections Action 5:Coordinate the Development and Refinement of Risk Models and Interoperability Standards Action 6: Address the Liability Concerns of Service Providers and Individuals Action 7: Perform Outreach and Awareness Across all Stakeholders Action 8: Continue Collaborating in International Efforts Action 9: Identify Other Means to Drive Adoption of the Identity Ecosystem across the Nation

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  • Is wikipedia a valuable resource for studying data structures? (can we call it complete?)

    - by Amir Nasr
    Can I depend on wikipedia to learn data structures fully using the list of data structures http://en.wikipedia.org/wiki/List_of_data_structures and the links they refer to? The same question for algorithms http://en.wikipedia.org/wiki/List_of_algorithm_general_topics ?... What's after learning algorithms and data structures? Specializing in a certain field of algorithms such as computer graohics, memory management...etc? or what could be the plan for mastering programming after knowing the language syntax and the background about program design and programming logic? I asked about wikipedia because i would like to find a complete resource or are least a resource which would be enough for the field of data structures instead of searching for separate articles in different places in other words an alternative to books which may even be more complete.

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  • Etiquette when asking questions in an IRC channel

    - by Zarkonnen
    Many larger OSS projects maintain IRC channels to discuss their usage or development. When I get stuck on using a project, having tried and failed to find information on the web, one of the ways I try to figure out what to do is to go into the IRC channel and ask. But my questions are invariably completely ignored by the people in the channel. If there was silence when I entered, there will still be silence. If there is an ongoing conversation, it carries on unperturbed. I leave the channel open for a few hours, hoping that maybe someone will eventually engage me, but nothing happens. So I worry that I'm being rude in some way I don't understand, or breaking some unspoken rule and being ignored for it. I try to make my questions polite, to the point, and grammatical, and try to indicate that I've tried the obvious solutions and why they didn't work. I understand that I'm obviously a complete stranger to the people on the channel, but I'm not sure how to fix this. Should I just lurk in the channel, saying nothing, for a week? That seems absurd too. A typical message I send might be "Hello all - I've been trying to get Foo to work, but I keep on getting a BarException. I tried resetting the Quux, but this doesn't seem to do anything. Does anyone have a suggestion on what I could try?"

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  • Arguments for or against using Try/Catch as logical operators

    - by James P. Wright
    I just discovered some lovely code in our companies app that uses Try-Catch blocks as logical operators. Meaning, "do some code, if that throws this error, do this code, but if that throws this error do this 3rd thing instead". It uses "Finally" as the "else" statement it appears. I know that this is wrong inherently, but before I go picking a fight I was hoping for some well thought out arguments. And hey, if you have arguments FOR the use of Try-Catch in this manner, please do tell. EDIT For any who are wondering, the language is C# and the code in question is about 30+ lines and is looking for specific exceptions, it is not handling ALL exceptions.

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  • Modern OpenGL context failure [migrated]

    - by user209347
    OK, I managed to create an OpenGL context with wglcreatecontextattribARB with version 3.2 in my attrib struct (So I have initialized a 3.2 opengl context). It works, but the strange thing is, when I use glBindBuffer e,g. I still get unreferenced linker error, shouldn't a newer context prevent this? I'm on windows BTW, Linux doesn't have to deal with older and newer contexts (it directly supports the core of its version). The code: PIXELFORMATDESCRIPTOR pfd; HGLRC tmpRC; int iFormat; if (!(hDC = GetDC(hWnd))) { CMsgBox("Unable to create a device context. Program will now close.", "Error"); return false; } ZeroMemory(&pfd, sizeof(pfd)); pfd.nSize = sizeof(pfd); pfd.nVersion = 1; pfd.dwFlags = PFD_DRAW_TO_WINDOW | PFD_SUPPORT_OPENGL | PFD_DOUBLEBUFFER; pfd.iPixelType = PFD_TYPE_RGBA; pfd.cColorBits = attribs->colorbits; pfd.cDepthBits = attribs->depthbits; pfd.iLayerType = PFD_MAIN_PLANE; if (!(iFormat = ChoosePixelFormat(hDC, &pfd))) { CMsgBox("Unable to find a suitable pixel format. Program will now close.", "Error"); return false; } if (!SetPixelFormat(hDC, iFormat, &pfd)) { CMsgBox("Unable to initialize the pixel formats. Program will now close.", "Error"); return false; } if (!(tmpRC=wglCreateContext(hDC))) { CMsgBox("Unable to create a rendering context. Program will now close.", "Error"); return false; } if (!wglMakeCurrent(hDC, tmpRC)) { CMsgBox("Unable to activate the rendering context. Program will now close.", "Error"); return false; } strncpy(vers, (char*)glGetString(GL_VERSION), 3); vers[3] = '\0'; if (sscanf(vers, "%i.%i", &glv, &glsubv) != 2) { CMsgBox("Unable to retrieve the OpenGL version. Program will now close.", "Error"); return false; } hRC = NULL; if (glv > 2) // Have OpenGL 3.+ support { if ((wglCreateContextAttribsARB = (PFNWGLCREATECONTEXTATTRIBSARBPROC)wglGetProcAddress("wglCreateContextAttribsARB"))) { int attribs[] = {WGL_CONTEXT_MAJOR_VERSION_ARB, glv, WGL_CONTEXT_MINOR_VERSION_ARB, glsubv,WGL_CONTEXT_FLAGS_ARB, 0,0}; hRC = wglCreateContextAttribsARB(hDC, 0, attribs); wglMakeCurrent(NULL, NULL); wglDeleteContext(tmpRC); if (!wglMakeCurrent(hDC, hRC)) { CMsgBox("Unable to activate the rendering context. Program will now close.", "Error"); return false; } moderncontext = true; } } if (hRC == NULL) { hRC = tmpRC; moderncontext = false; }

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  • How to get lookahead symbol when constructing LR(1) NFA for parser?

    - by greenoldman
    I am reading an explanation (awesome "Parsing Techniques" by D.Grune and C.J.H.Jacobs; p.292 in the 2nd edition) about how to construct an LR(1) parser, and I am at the stage of building the initial NFA. What I don't understand is how to get/compute a lookahead symbol. Here is the example from the book, the grammar: S -> E E -> E - T E -> T T -> ( E ) T -> n n is terminal. The "weird" transitions for me are is the sequence: 1) S -> . E eof 2) E -> . E - T eof 3) E -> . E - T - 4) E -> E . - T - 5) E -> E - . T - (Note: In the above table, the state numbers are in front and the lookahead symbol is at the end.) What puzzles me is that transition from (4) to (5) means reading - token, right? So how is it that - is still a lookahead symbol and even more important why is it that eof is no longer a lookahead symbol? After all in an input such as n - n eof there is only one - symbol. My naive thinking tells me (5) should be written as: 5) E -> E - . T - eof And another thing -- n is terminal. Why it is not used at all as a lookahead symbol? I mean -- we expect to see - or (, it is ok, but lack of n means we are sure it won't appear in input? Update: after more reading I am only more confused ;-) I.e. what is really a lookahead? Because I see such state as (p.292, 2nd column, 2nd row): E -> E . - T eof Lookahead says eof but the incoming input says -. Isn't it a contradiction? And it is not only in this book.

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  • Resources for creating a turn-by-turn navigation system

    - by benwad
    I'm trying to create a kind of turn-by-turn satellite navigation system using the iOS SDK. I get the directions from the server and draw them on the map, then I keep getting location updates from the iPhone's GPS chip. Currently I start by finding the nearest turning point then, each time the user comes within a certain distance of the next turning point, a verbal cue is given and the turning point index is incremented. This is a delicate system and I'd like to make it more robust so I can tell when the user is going the wrong direction etc. Basically I'm looking for some literature about turn-by-turn navigation, in terms of tracking the user's progress and whether they're going the right direction. I'd have thought there's a lot of research out there but I can't seem to find anything apart from simple tutorials on how to use a given SDK or directions API. Can anyone direct me to a good run-through of the various techniques used in software such as TomTom or Google Maps Navigation?

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  • Queuing rpc calls

    - by alfa64
    i'm designing a system wich listen to json rpc calls from clients, piles it up inside a list, and if it gets full it should store them in a DB and keep recieving calls. My original plan is to listen to the rpc calls from Perl with the json-rpc and put them in the array. The clients do some long polling in another server to get responses as they appear. What is this blocking/noblocking thing? Should i do a script for node.js to listen to the calls? What do you think is a good practice in this case? The objective is to listen as much calls as possible.

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  • Should you salary reflect how much work there is for you or does that not matter? [closed]

    - by Kevin Simper
    I am working in a consulting company, where the company mostly do IT support. The website is also only focused on IT support, and we do not therefore capture leads for the Web Department. We aim for Small busniess, which needs new computers and firewalls. We were having a performance conversation and talked about salary and my employer told that he was not impressed by the revenue I was generating. I told that I did not have enough work and I would like to get more tasks and project so that i could reach the goal, but that i did not think it was my fault that there was not enough work. He said that it was not his fault either, but he could not pay me more. Is he right that I should not get paid more just because my employee can not get enough Web projects, or should i be paid what i am worth not based on the work amount the sales generate?

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  • Ranking players depending on decision making during a game

    - by tabchas
    How would I go about a ranking system for players that play a game? Basically, looking at video games, players throughout the game make critical decisions that ultimately impact the end game result. Is there a way or how would I go about a way to translate some of those factors (leveling up certain skills, purchasing certain items, etc.) into something like a curve that can be plotted on a graph? This game that I would like to implement this is League of Legends. Example: Player is Level 1 in the beginning. Gets a kill very early in the game (he gets gold because of the kill and it increases his "power curve"), and purchases attack damage (gives him more damage which also increases his "power curve". However, the player that he killed (Player 2), buys armor (counters attack damage). This slightly increases Player 2's own power curve, and reduces Player 1's power curve. There's many factors I would like to take into account. These relative factors (example: BECAUSE Player 2 built armor, and I am mainly attack damage, it lowers my OWN power curve) seem the hardest to implement. My question is this: Is there a certain way to approach this task? Are there similar theoretical concepts behind ranking systems that I should read up on? I've seen the ELO system, but it doesn't seem what I want since it simply takes into account wins and losses.

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  • How to manage/control software versions?

    - by Zwie
    I'm facing a problem to create a version control outline for several already existing software parts for my company. Until now no one - expect for the developers - knows that there are different versions, which is the reason for the outline. In fact, I'm supposed to set up the future version control and communicate all this with our management... So, the question is how to create such a outline. Are there principles to follow to make software versioning easier or even a good program to map all versions and there compatibility? And are there generally good approaches to control software versions?

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