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• Triggering Data Changes in N-Tier

  - by Ryan Kinal

  I've been studying n-tier architectures as of late, particularly in VB.NET with Entity Framework and/or LINQ to SQL. I understand the basic concepts, but have been wondering about best practices in regard to triggering CRUD-type operations from user input/action. So, the arcitecture looks something like the following: [presentation layer] - [business layer] - [data layer] - (database) Getting information from the database into the presentation layer is simple and abstracted. It's just a matter of instantiating a new object from the business layer, which in turn uses the data layer to get at the correct information. However, saving (updating and inserting), and deleting seem to require particular APIs on the relevant business objects. I have to assume this is standard practice, unless a business object will save itself on various operations (which seems inefficient), or on disposal (which seems like it just wouldn't work, or may be unwieldy and unreliable). Should my "savable" business objects all implement a particular "ISavable" or "IDatabaseObject" interface? Is this a recognized (anti-)pattern? Are there other, better patterns I should be using that I'm just unaware of? The TLDR question, I suppose, is How does the presentation layer trigger database changes?

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• What's so great about Clojure?

  - by marco-fiset

  I've been taking a look at Clojure lately and I stumbled upon this post on Stackoverflow that indicates some projects following best practices, and overall good Clojure code. I wanted to get my head around the language after reading some basic tutorials so I took a look at some "real-world" projects. After looking at ClojureScript and Compojure (two the the aforementioned "good" projects), I just feel like Clojure is a joke. I don't understand why someone would pick Clojure over say, Ruby or Python, two languages that I love and have such a clean syntax and are very easy to pick up whereas Clojure uses so much parenthesis and symbols everywhere that it ruins the readability for me. I think that Ruby and Python are beautiful, readable and elegant. They are easy to read even for someone who does not know the language inside out. However, Clojure is opaque to me and I feel like I must know every tiny detail about the language implementation in order to be able to understand any code. So please, enlighten me! What is so good about Clojure? What is the absolute minimum that I should know about the language in order to appreciate it?

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• How do I stop color changes when quitting vi from a terminal emulator?

  - by Michael Warhol

  I have a problem with colors when using vi under Ubuntu 12.04. I'm connecting to my Ubuntu server from a PC, using PowerTerm terminal emulation software. I have PowerTerm set up to display black text on a grey background. When I connect to the Ubuntu box, the screen is fine. When I open a file with vi, the screen is fine. The text is black on a gray background, which is normal for my PowerTerm setup. However, if the file is less than a full screen long, the remainder of the screen is a black background. When I quit vi, the entire background turns black, and the text becomes white. I have to do a Terminal Reset to restore my normal text and background colors. What I want is for there to be no change at all when I use vi. The text should be black and the background grey. I have another server loaded with RedHat 9, and that acts normally; colors don’t change when using vi. Here is my .vimrc file: set compatible syntax off let g:loaded_matchparen=1 set nocp set noincsearch set nohlsearch set noshowmatch set bg=dark I've tried set bg=dark and set bg=light. It makes no difference. Is there some other set command that would clear this up for me, or some TERM setting (my TERM is set to linux)?

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• Are Java's public fields just a tragic historical design flaw at this point?

  - by Avi Flax

  It seems to be Java orthodoxy at this point that one should basically never use public fields for object state. (I don't necessarily agree, but that's not relevant to my question.) Given that, would it be right to say that from where we are today, it's clear that Java's public fields were a mistake/flaw of the language design? Or is there a rational argument that they're a useful and important part of the language, even today? Thanks! Update: I know about the more elegant approaches, such as in C#, Python, Groovy, etc. I'm not directly looking for those examples. I'm really just wondering if there's still someone deep in a bunker, muttering about how wonderful public fields really are, and how the masses are all just sheep, etc. Update 2: Clearly static final public fields are the standard way to create public constants. I was referring more to using public fields for object state (even immutable state). I'm thinking that it does seem like a design flaw that one should use public fields for constants, but not for state… a language's rules should be enforced naturally, by syntax, not by guidelines.

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• Emulate Historical Figures i.e. Einstein - Is this possible using linguistic logic for my http://www.ustimeline.com Education System

  - by Johnnylight

  After hearing about the success of IBM's Watson I started thinking perhaps emulating human language is now possible? My goal is to create Virtual Historical characters to represent the main characters in my Adventur-Cation The Great American Adventure program such as Einstein or Crazy Horse. The goal is to build an intelligent system capable of indexing the internet and storing the data using a schema using modern knowledge on linguistic theory (phonemes, morphemes, syntax) to build a system capable to returning a semantically sound response very similar to the response made by the same person if still alive today. The goal would be to use the same engine/system for all characters. Each characters would have their own digital representation and voice, and would organize data differently based on tags/keywords stored about the individual. Imagine a Max Headroom Einstein. Based on the success of Watson, I believe something like this may now be possible. Would be an interesting way to study history and would be a vehicle of entertainment as well. Can anyone confirm if this has already been attempted? Is anyone interested in exploring this using Cognitive Science, Psychology, Artificial Intelligence, Historical data captured on the internet, and Linguistic theory?

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• Getting the total number of processors a computer has (c#)

  - by mbcrump

  Here is a code snippet for getting the total number of processors a computer has without using Environment.ProcessorCount. I found out that Environment.ProcessorCount is not necessary returning the correct value on some Intel based CPU’s.   using System; usingSystem.Collections.Generic; usingSystem.Linq; usingSystem.Text; usingSystem.Globalization; usingSystem.Runtime.InteropServices; namespaceConsoleApplication4 {     classProgram    {         static voidMain(string[] args)         {             int c = ProcessorCount;             Console.WriteLine("The computer has {0} processors", c);             Console.ReadLine();         }         private static classNativeMethods        {             [StructLayout(LayoutKind.Sequential)]             internal struct SYSTEM_INFO            {                 public ushort wProcessorArchitecture;                 public ushort wReserved;                 public uint dwPageSize;                 publicIntPtr lpMinimumApplicationAddress;                 publicIntPtr lpMaximumApplicationAddress;                 publicUIntPtr dwActiveProcessorMask;                 public uint dwNumberOfProcessors;                 public uint dwProcessorType;                 public uint dwAllocationGranularity;                 public ushort wProcessorLevel;                 public ushort wProcessorRevision;             }             [DllImport("kernel32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]             internal static extern voidGetNativeSystemInfo(refSYSTEM_INFOlpSystemInfo);         }         public static int ProcessorCount         {             get            {                 NativeMethods.SYSTEM_INFOlpSystemInfo = newNativeMethods.SYSTEM_INFO();                 NativeMethods.GetNativeSystemInfo(reflpSystemInfo);                 return(int)lpSystemInfo.dwNumberOfProcessors;             }         }     } }

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• Free Webinar: A faster, cheaper, better IT Department with Azure

  - by Herve Roggero

  Join me for a free Webinar on Wednesday October 17th at 1:30PM, Eastern Time. I will discuss the benefits of cloud computing with the Azure platform. There isn’t a company out there that would say “No” to reduced IT costs and unlimited scaling bandwidth. This webinar will focus on the specific benefits of the Microsoft Azure cloud platform and will convince you on the sound business rationale behind moving to the cloud. From Infrastructure as a Service (Iaas) to Platform as a Service (Paas), Azure supports quick deployments, virtual machines, native SQL Databases and much more. Topics that will be discussed: - Why use Azure for your Cloud Computing needs - Iaas and Paas Offerings - Differing project approaches to Cloud computing - How Azure’s agility and reduced costs lead to better solutions Attendees of this webinar will also be eligible to receive the following: Free Two Hour Consultation which can include: - Review of Your Cloud Strategy - Cloud Roadmap Review - Review of Data-mart strategies - Review of Mobility Strategies Click Here to Register Now. About Herve Roggero Hervé Roggero, Azure MVP, is the founder of Blue Syntax Consulting, a company specialized in cloud computing products and services. Hervé's experience includes software development, architecture, database administration and senior management with both global corporations and startup companies. Hervé holds multiple certifications, including an MCDBA, MCSE, MCSD. He also holds a Master's degree in Business Administration from Indiana University. Hervé is the co-author of "PRO SQL Azure" from Apress. For more information, visit www.bluesyntax.net.

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• c# vocabulary

  - by foxjazz

  I have probably seen and used the word Encapsulation 4 times in my 20 years of programming.I now know what it is again, after an interview for a c# job. Even though I have used the public, private, and protected key words in classes for as long as c# was invented. I can sill remember coming across the string.IndexOf function and thinking, why didn't they call it IndexAt.Now with all the new items like Lambda and Rx, Linq, map and pmap etc, etc. I think the more choices there is to do 1 or 2 things 10 or 15 differing ways, the more programmers think to stay with what works and try and leverage the new stuff only when it really becomes beneficial.For many, the new stuff is harder to read, because programmers aren't use to seeing declarative notation.I mean I have probably used yield break, twice in my project where it may have been possible to use it many more times. Or the using statement ( not the declaration of namespace references) but inline using. I never really saw a big advantage to this, other than confusion. It is another form of local encapsulation (oh there 5 times used in my programming career) but who's counting?  THE COMPUTERS ARE COUNTING!In business logic most programming is about displaying lists, selecting items in a list, and sending those choices to some other system or database to keep track of those selections. What makes this difficult is how these items relate to one, each other, and two externally listed items.Well I probably need to go back to school and learn c# certification so I can say I am an expert in c#. Apparently using all aspects of c# (even unsafe code) in my programming life, doesn't make me certified, just certifiable.This is a good time to sign off:Fox-jazzy

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• About the new Microsoft Innovation Center (MIC) in Miami

  - by Herve Roggero

  Originally posted on: http://geekswithblogs.net/hroggero/archive/2014/08/21/about-the-new-microsoft-innovation-center-mic-in-miami.aspxLast night I attended a meeting at the new MIC in Miami, run by Blain Barton (@blainbar), Sr IT Pro Evangelist at Microsoft. The meeting was well attended and is meant to be run as a user group format in a casual setting. Many of the local Microsoft MVPs and group leaders were in attendance as well, which allows technical folks to connect with community leaders in the area. If you live in South Florida, I highly recommend to look out for future meetings at the MIC; most meetings will be about the Microsoft Azure platform, either IT Pro or Dev topics. For more information on the MIC, check out this announcement:  http://www.microsoft.com/en-us/news/press/2014/may14/05-02miamiinnovationpr.aspx. About Herve Roggero Herve Roggero, Microsoft Azure MVP, @hroggero, is the founder of Blue Syntax Consulting (http://www.bluesyntaxconsulting.com). Herve's experience includes software development, architecture, database administration and senior management with both global corporations and startup companies. Herve holds multiple certifications, including an MCDBA, MCSE, MCSD. He also holds a Master's degree in Business Administration from Indiana University. Herve is the co-author of "PRO SQL Azure" and “PRO SQL Server 2012 Practices” from Apress, a PluralSight author, and runs the Azure Florida Association.

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• JAVA Gui on Hello World [closed]

  - by user58892

  I am designing, implementing, testing, and debuging a GUI-based version of a “Hello, World!” program in a JFrame that includes a JLabel that reads “Hello, World!” and I am trying to use a layout manager, and an Exit button to close the program. Here's what I have so far, I would really apreciate if you could help on it syntax. I am 90% done but tried hard and it couldn't run. import java.awt.*; // Needed for flow layout manager import javax.swing.*; //All swing components live in the javax.swing package import javax.swing.JButton; //to recognize buttons import javax.swing.JFrame; import javax.swing.JPanel; import javax.swing.JTextField; public class HelloWorld { public static void main(String[] args) { //creates the label. The JLabel constructor //takes an optional argument which set the text of the label /* The text will be aligned with the center of the frame * otherwise it will align on the left. */ JLabel label= new JLabel("Hello World!"); new FlowWindow(); label.setHorizontalAlignment (SwingConstants.CENTER); JFrame frame = new JFrame("Hello"); //create exit button JButton button1 = new JButton("Exit"); //Add exit button to the content pane. add(button1); frame.add(label); frame.setSize(300, 300); frame.setVisible(true); frame.setLocationRelativeTo(null); frame.toFront(); } public static void FlowWindow() { //Add a new FlowLayout()); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); } }

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• What to learn after standard C++?

  - by Luca Cerone

  I switched to C++ a few months ago, learning its syntax, the main features of the STL and what you can usually find in a "learn C++" manual. Now I would like to go further. What would be your recommendations? I would like to know what to learn next (not only about the language, but also debugging, frameworks etc. etc.) I know probably the answer depends on the specific needs of each user, so here is a list of mine: Cross Platform development Developing GUI for my programs Develop extendible software, allowing the use of plugins Use of scientific libraries Interact with databases (mainly MySQL) Having server/client functionalities (I'd like users of my programs to interact through internet.. as you might have guessed I am not a programmer by training so I might have used the wrong terms.. if so I apologize for that). Of course I know it takes time, but I would like to have a good list of references and resources to start (both books and websites are ok). Thanks a lot for your help!

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• Am I missing something about these considerations about Leaderboard's database's schema?

  - by misiMe

  I just finished to develop a mobile game, now I want to implement an online leaerboard using mysql. I'm wondering about the database's schema, I thought about some possibilities: (I didn't got in detail with syntax because my question is just about the logic of it) Name: string; Score: integer I thought to ask the name just the first time. If, in the future, you will modify that, it will call just an update to the name associated with your id. Leaderboard(ID, Name, Score) ID: integer autoincrement, PrimaryKey With this kind of idea maybe the db will grow fast because if you choose everytime a different name for the score, it will add a new entry. Leaderboard(PhoneId, Name, Score) Here PhoneId will be the unique identifier of the phone, PrimaryKey. A con of this choice is that if you want to play with your friends' phone, you can't put a different name for the score. Leaderboard(Name, Score) Here Name is PrimaryKey. With that, if you enter a name that already exists, you will be prompted to choose another one. Do you agree with this considerations? What will you do? Am I missing something?

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• Problem with SAT collision detection overlap checking code

  - by handyface

  I'm trying to implement a script that detects whether two rotated rectangles collide for my game, using SAT (Separating Axis Theorem). I used the method explained in the following article for my implementation in Google Dart. 2D Rotated Rectangle Collision I tried to implement this code into my game. Basically from what I understood was that I have two rectangles, these two rectangles can produce four axis (two per rectangle) by subtracting adjacent corner coordinates. Then all the corners from both rectangles need to be projected onto each axis, then multiplying the coordinates of the projection by the axis coordinates (point.x*axis.x+point.y*axis.y) to make a scalar value and checking whether the range of both the rectangle's projections overlap. When all the axis have overlapping projections, there's a collision. First of all, I'm wondering whether my comprehension about this algorithm is correct. If so I'd like to get some pointers in where my implementation (written in Dart, which is very readable for people comfortable with C-syntax) goes wrong. Thanks! EDIT: The question has been solved. For those interested in the working implementation: Click here

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• SQL to XML open data made simple

  - by drrwebber

  The perennial question for people is how to easily generate XML from SQL table content?  The latest CAM Editor release really tackles this head on by providing a powerful and simple toolset.  Firstly you can visually browse your SQL tables and then drag and drop from columns and tables into the XML structure editor.   This gives you a code-free method of describing the transformation you require.  So you do not need to know about the vagaries of XML and XSD schema syntax. Second you can map directly into existing industry domain XML exchange structures in the XML visual editor, again no need to wrestle with XSD schema, you have WYSIWYG visual control over what your output will look like. If you do not have a target XML structure and need to build one from scratch, then the CAM Editor makes this simple.  Switch the SQL viewer into designer mode, then take your existing SQL table and drag and drop it into the XML structure editor.  Automatically the XML wizard tool will take your SQL column names and definitions and create equivalent XML for you and insert the mappings. Simply save the structure template, and run the Open Data generator menu option, and your XML is built for you. Completely code-free template driven development. To see this in action, see our video demonstration links and then download the tools and samples and try it yourself.

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• Two components offering the same functionality, required by different dependencies

  - by kander

  I'm building an application in PHP, using Zend Framework 1 and Doctrine2 as the ORM layer. All is going well. Now, I happened to notice that both ZF1 and Doctrine2 come with, and rely on, their own caching implementation. I've evaluated both, and while each has its own pro's and cons, neither of them stand out as superior to the other for my simple needs. Both libraries also seem to be written against their respective interfaces, not their implementations. Reasons why I feel this is an issue is that during the bootstrapping of my application, I have to configure two caching drivers - each with its own syntax. A mismatch is easily created this way, and it feels inefficient to set up two connections to the caching backend because of this. I'm trying to determine what the best way forward is, and would welcome any insights you may be able to offer. What I've thought up so far are four options: Do nothing, accept that two classes offering caching functionality are present. Create a Facade class to stick Zend's interface onto Doctrine's caching implementation. Option 2, the other way around - create a Facade to map Doctrine's interface on a Zend Framework backend. Use multiple-interface-inheritance to create one interface to rule them all, and pray that there aren't any overlaps (ie: if both have a "save" method, they'll need to accept params in the same order due to PHP's lack of proper polymorphism). What option is best, or is there a "None of the above" variant that I'm not aware of?

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• is wisdom of what happens 'behind scenes' (in compiler, external DLLs etc.) important?

  - by I_Question_Things_Deeply

  I have been a computer-fanatic for almost a decade now. I've always loved and wondered how computers work, even from the purest, lowest hardware level to the very smallest pixel on the screen, and all the software around that. That seems to be my problem though ... as I try to write code (I'm pretty fluent at C++) I always sit there enormous amounts of time in front of a text-editor wondering how every line, statement, datum, function, etc. will correspond to every Assembly and machine instruction performed to do absolutely everything necessary for the kernel to allocate memory to run my compiled program, and all of the other hardware being used as well. For example ... I would write cout << "Before memory changed" << endl; and run the debugger to get the Assembly for this, and then try and reverse disassemble the Assembly to machine code based on my ISA, and then research every .dll, library file, linked library, linking process, linker source code of the program, the make file, the kernel I'm using's steps of processing this compilation, the hardware's part aside from the processor (e.g. video card, sound card, chipset, cache latency, byte-sized registers, calling convention use, DDR3 RAM and disk drive, filesystem functioning and so many other things). Am I going about programming wrong? I mean I feel I should know everything that goes on underneath English syntax on a computer program. But the problem is that the more I research every little thing the less I actually accomplish at all. I can never finish anything because of this mentality, yet I feel compelled to know everything... what should I do?

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• Understanding interfaces [closed]

  - by user985482

  Possible Duplicate: When to use abstract classes instead of interfaces and extension methods in C#? Why are interfaces useful? What is the point of an interface? What other reasons are there to write interfaces rather than abstract classes? What is the point of having every service class have an interface? Is it bad habit not using interfaces? I am reading Microsoft Visual C# 2010 Step by Step which I feel it is a very good book on introducing you to the C# language. I have just finished reading a chapter on interfaces and although I understood the syntax of creating and using interfaces I have trouble of understanding the point on why should I use them? Correct me If I am wrong but in an interface you can only declare methods names and parameters.The body of the method should be declared in the class that inherits the interface. So in this case why should I declare an interface if I am going to declare the entire method in the class that inherits that interface? What is the point? Does this have something to do with the fact that a class can inherit multiple interfaces?

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• Is looking for code examples constantly a sign of a bad developer?

  - by Newly Insecure

  I am a comp sci student with several years of experience in C and C++, and for the last few years I've been constantly working with Java/Objective C doing app dev and now I have switched to web dev and am mainly focused on ruby on rails and I came to the realization that (as with app dev, really) I reference other code wayyyy too much. I constantly google functionality for lots of things I imagine I should be able to do from scratch and it's really cracked my confidence a bit. Basic fundamentals are not an issue, I hate to use this as an example but I can run through javabat in both java/python at a sprint - obviously not an accomplishment and but what I mean to say is I have a strong base for the fundamentals I think? I know what I need to use typically but reference syntax constantly. Would love some advice and input on this, as it has been holding me back pretty solidly in terms of looking for work in this field even though I'm finishing my degree. My main reason for asking is not really about employment, but more that I don't want to be the only guy at a hackathon not hammering out nonstop code and sitting there with 20 google/github tabs open, and I have refrained from attending any due to a slight lack of confidence... Is a person a bad developer by constantly looking to code examples for moderate to complex tasks?

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• Is constantly looking for code examples a sign of a bad developer?

  - by Newly Insecure

  I am a CS student with several years of experience in C and C++, and for the last few years I've been constantly working with Java/Objective C doing app development and now I have switched to web development and am mainly focused on ruby on rails and I came to the realization that (as with app development , really) I reference other code way too much. I constantly Google functionality for lots of things I imagine I should be able to do from scratch and it's really cracked my confidence a bit. Basic fundamentals are not an issue, I hate to use this as an example but I can run through javabat in both java/python at a sprint - obviously not an accomplishment and but what I mean to say is I have a strong base for the fundamentals I think? I know what I need to use typically but reference syntax constantly. Would love some advice and input on this, as it has been holding me back pretty solidly in terms of looking for work in this field even though I'm finishing my degree. My main reason for asking is not really about employment, but more that I don't want to be the only guy at a hackathon not hammering out nonstop code and sitting there with 20 Google/github tabs open, and I have refrained from attending any due to a slight lack of confidence... Is a person a bad developer by constantly looking to code examples for moderate to complex tasks?

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• Anyone can suggest some Game Frameworks for GNU/Linux? [closed]

  - by dysoco

  So I've been developing a little bit with XNA + C# in Windows, not really much: just some 2D stuff, but I've found that XNA is a really good framework. I'm a GNU/Linux user, and I'm definitely migrating my desktop to Gentoo Linux (I've been using Arch in my laptop for a while now). But, of course, I need a C# + XNA alternative... I'm not really an expert in any language, so I can really pick up anything (except, maybe, Functional ones), I prefer C-Like languages like Java or Ruby, I tried Python but found the Whitespace syntax confusing. I would like to hear some of you'r suggestions, I'm not asking for "the best", but for "some suggestions", so I think this is objective enough. Probably you're going to suggest C++ + SDL, but I would prefer something more "High Level" like XNA, but I'm open to discuss anything. So... any ideas ? Note: I think this questions meets the guidelines for this site, if it doesn't: please not only downvote this question, but comment on what can I do to improve it. Thanks. PS: 2D Games, not 3D

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• What are some good ways for an intermediate programmer to build skills?

  - by Jordan

  Preface: I work mostly in Python, and Web Dev languages (HTML, CSS, Javascript and Jquery, PHP) I'm proficient at coding but I want to get better. In larger more advanced projects my programming skills break down. The more code there is the more trouble I have fitting all the pieces together. I understand syntax well, and I can catch and correct errors fairly easier. But the more advanced it gets the more I struggle. I believe I have a good understand of the basic and nuts and bolts of programming and I understand what's going on, but when it comes to larger projects, especially ones with heavy math involved my confidence flags and I start making mistakes. It's not that I can't do it, I'm just not used to doing it. Does anyone have any advice for someone who knows programming, but wants to get better? The only tutorials I can really find are beginner basic type stuff. Basically what I'm saying is I want to be confident when I'm tackling advanced projects, but I can't because I have little experience dealing with difficult situations.

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• How do i impress employers with my resume?

  - by acidzombie24

  I built a entire website from scratch in 10days which looks and feels professional with the site being unique. The site has features like logging in, sending activation emails, tag/content search (lucence.net), syntax highlighting (prettify) and a diff (one of the js diffs), markup for comments all on this site and autocomplete in a textbox (remember, 10days). I wrote i have 5+ years of C# experience (i could lie and say more but smart employers will know its only 8 years old and 1.1 is very different from what we use now). I had employers REPEATEDLY say they are looking for someone who has more C# experience... wtf. Maybe they don't read my CV, maybe they dont believe it or ignore me because i am not yet a graduate. I laughed when i first read Steve Yegge The Five Essential Phone Screen Questions as i knew all of that (although i still never used graph datastruct nor know much about it). I'm pretty sure competency wise i can do the job. I am also positive no one noticed i have markup, a diff, autocomplete nor email activation/forget password (i offer a test user account). So maybe my site/example work isnt impressive bc you dont realize what is in it. In short i dont think they read my CV or notice my site. How do i impress employers? PS: The problem is i dont get to the interview. I had one and ruined it by speaking too technical to the PM because i was nervous. The other 25+ jobs either didnt contact me or was kind enough to send a rejection email.

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• Using ConcurrentQueue for thread-safe Performance Bookkeeping.

  - by Strenium

  Just a small tidbit that's sprung up today. I had to book-keep and emit diagnostics for the average thread performance in a highly-threaded code over a period of last X number of calls and no more. Need of the day: a thread-safe, self-managing stats container. Since .NET 4.0 introduced new thread-safe 'Collections.Concurrent' objects and I've been using them frequently - the one in particular seemed like a good fit for storing each threads' performance data - ConcurrentQueue. But I wanted to store only the most recent X# of calls and since the ConcurrentQueue currently does not support size constraint I had to come up with my own generic version which attempts to restrict usage to numeric types only: unfortunately there is no IArithmetic-like interface which constrains to only numeric types – so the constraints here here aren't as elegant as they could be. (Note the use of the Average() method, of course you can use others as well as make your own).   FIFO FixedSizedConcurrentQueue using System;using System.Collections.Concurrent;using System.Linq; namespace xxxxx.Data.Infrastructure{    [Serializable]    public class FixedSizedConcurrentQueue<T> where T : struct, IConvertible, IComparable<T>    {        private FixedSizedConcurrentQueue() { }         public FixedSizedConcurrentQueue(ConcurrentQueue<T> queue)        {            _queue = queue;        }         ConcurrentQueue<T> _queue = new ConcurrentQueue<T>();         public int Size { get { return _queue.Count; } }        public double Average { get { return _queue.Average(arg => Convert.ToInt32(arg)); } }         public int Limit { get; set; }        public void Enqueue(T obj)        {            _queue.Enqueue(obj);            lock (this)            {                T @out;                while (_queue.Count > Limit) _queue.TryDequeue(out @out);            }        }    } }   The usage case is straight-forward, in this case I’m using a FIFO queue of maximum size of 200 to store doubles to which I simply Enqueue() the calculated rates: Usage var RateQueue = new FixedSizedConcurrentQueue<double>(new ConcurrentQueue<double>()) { Limit = 200 }; /* greater size == longer history */   That’s about it. Happy coding!

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• Language Design: Are languages like Python and CoffeeScript really more comprehensible?

  - by kittensatplay

  The "Verbally Readable !== Quicker Comprehension" argument on http://ryanflorence.com/2011/case-against-coffeescript/ is really potent and interesting. I and I'm sure others would be very interested in evidence arguing against this. There's clear evidence for this and I believe it. People naturally think in images, not words, so we should be designing languages that aren't similar to human language like English, French, whatever. Being "readable" is quicker comprehension. Most articles on Wikipedia are not readable as they are long, boring, dry, sluggish and very very wordy. Because Wikipedia documents a ton of info, it is not especially helpful when compared to sites with more practical, useful and relevant info. Languages like Python and CoffeScript are "verbally readable" in that they are closer to English syntax. Having programmed firstly and mainly in Python, I'm not so sure this is really a good thing. The second interesting argument is that CoffeeScript is an intermediator, a step between two ends, which may increase the chance of bugs. While CoffeeScript has other practical benefits, this question specifically requests evidence showing support for the counter-case of language "readability"

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• How to handle multi-processing of libraries which already spawn sub-processes?

  - by exhuma

  I am having some trouble coming up with a good solution to limit sub-processes in a script which uses a multi-processed library and the script itself is also multi-processed. Both, the library and script are modifiable by us. I believe the question is more about design than actual code, but for what it's worth, it's written in Python. The goal of the library is to hide implementation details of various internet routers. For that reason, the library has a "Proxy" factory method which takes the IP of a router as parameter. The factory then probes the device using a set of possible proxies. Usually, there is one proxy which immediately knows that is is able to send commands to this device. All others usually take some time to return (given a timeout). One thought was already to simply query the device for an identifier, and then select the proper proxy using that, but in order to do so, you would already need to know how to query the device. Abstracting this knowledge is one of the main purposes of the library, so that becomes a little bit of a "circular-requirement"/deadlock: To connect to a device, you need to know what proxy to use, and to know what proxy to create, you need to connect to a device. So probing the device is - as we can see - the best solution so far, apart from keeping a lookup-table somewhere. The library currently kills all remaining processes once a valid proxy has been found. And yes, there is always only one good proxy per device. Currently there are about 12 proxies. So if one create a proxy instance using the factory, 12 sub-processes are spawned. So far, this has been really useful and worked very well. But recently someone else wanted to use this library to "broadcast" a command to all devices. So he took the library, and wrote his own multi-processed script. This obviously spawned 12 * n processes where n is the number of IPs to which he broadcasted. This has given us two problems: The host on which the command was executed slowed down to a near halt. Aborting the script with CTRL+C ground the system to a total halt. Not even the hardware console responded anymore! This may be due to some Python strangeness which still needs to be investigated. Maybe related to http://bugs.python.org/issue8296 The big underlying question, is how to design a library which does multi-processing, so other applications which use this library and want to be multi-processed themselves do not run into system limitations. My first thought was to require a pool to be passed to the library, and execute all tasks in that pool. In that way, the person using the library has control over the usage of system resources. But my gut tells me that there must be a better solution. Disclaimer: My experience with multiprocessing is fairly limited. I have implemented a few straightforward which did not require access control to resources. So I have not yet any practical experience with semaphores or mutexes. p.s.: In the future, we may have enough information to do this without the probing. But the database which would contain the proper information is not yet operational. Also, the design about multiprocessing a multiprocessed library intrigues me :)

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