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• Memory limiting solutions for greedy applications that can crash OS?

  - by Hooked

  I use my computer for scientific programming. It has a healthy 8GB of RAM and 12GB of swap space. Often, as my problems have gotten larger, I exceed all of the available RAM. Rather than crashing (which would be preferred), it seems Ubuntu starts loading everything into swap, including Unity and any open terminals. If I don't catch a run-away program in time, there is nothing I can do but wait - it takes 4-5 minutes to switch to a command prompt eg. Ctrl-Alt-F2 where I can kill the offending process. Since my own stupidity is out of scope of this forum, how can I prevent Ubuntu from crashing via thrashing when I use up all of the available memory from a single offending program? At-home experiment*! Open a terminal, launch python and if you have numpy installed try this: >>> import numpy >>> [numpy.zeros((10**4, 10**4)) for _ in xrange(50)] * Warning: may have adverse effects, monitor the process via iotop or top to kill it in time. If not, I'll see you after your reboot.

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• How do I get my programs to communicate with each other

  - by Benjamin Lindqvist

  I'm basically just getting started with programming. The problem I have with progressing is that I have a hard time learning stuff just for the sake of knowing them - I do better when there's a problem to be solved or a task to be completed so I can learn 'on the job'. So I'm interested in starting some interesting project. I know the basics of Python, Java, Matlab and some C++ aswell and I know enough about microcontrollers to make LED blink etc. The type of stuff I'm looking for is for example scraping some weather forecast site (with Python) and outputting the chance of rain to a LCD display, or a program that makes chrome open and log in to facebook if I say "HAL, time for facebook", or more generally, a program that reads serial/USB input, looks for certain sequences and sends instructions to some other program if it finds one. Do you open some kind of shared stream in which one program reads and one writes? What do I need to read up on to do accomplish this myself? I have no experience with linux or the linux terminal, but looking over peoples shoulders makes me suspect that's what people use. Is that correct?

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• What are some efficient ways to set up my environment when working on a remote site?

  - by Prefix

  Hello fellow Programmers, I am still a relatively new programmer and have recently gotten my first on-campus programming position. I am the sole dev responsible for 8 domains as well as 3 small sized PHP web apps. The campus has its web environment divided into staging and live servers -- we develop on the staging via SFTP and then push the updates to the live server through a web GUI. I use Sublime Text 2 and the Sublime SFTP plugin currently for all my dev work (its my preferred editor). If I am just making an edit to a page I'll open that individual file via the ftp browser. If I am working on the PHP web app projects, I have the app directory mapped to a local folder so that when I save locally the file is auto-uploaded through Sublime SFTP. I feel like this workflow is slow and sub-optimal. How can I improve my workflow for working with remote content? I'd love to set up a local environment on my machine as that would eliminate the constant SFTP upload/download, but as I said there are many sites and the space required for a local copy of the entire domain would be quite large and complex; not to mention keeping it updated with whatever the latest on the staging server is would be a nightmare. Anyone know how I can improve my general web dev workflow from what I've described? I'd really like to cut out constantly editing over FTP but I'm not sure where to start other than ripping the entire directory and dumping it into XAMP.

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• Is a big name computer science degree worth the cost?

  - by Serplat

  I'm currently in High School and trying to look into what I want to do after I graduate. I know that I will be going to college, and that I want a degree in Computer Science, however, I'm not entirely sure where I want to go (I haven't started the application process yet). I already have built up a decent amount of experience in programming (over the summers I have been hired to program at a local university), and I'm pretty capable of teaching myself most of the material I've come across through either books or web documentation. I'm interested in whether it is worth it to get a degree from a major, big-name computer science university for $50,000 each year, as opposed to going to a local state school for only $20,000. For my Bachelor's degree alone, this would be $120,000 more than the state school. I've also heard that where you get your Bachelor's doesn't matter much if you plan to get a Master's degree. Many people recommend going somewhere like a state school for your Bachelor's, and then try to get into a more major school for your Master's. Has anybody found any truth in this? Basically, is going to a big name computer science school for a Bachelor's degree really worth the added expense?

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• Secure Coding Practices in .NET

  - by SoftwareSecurity

  Thanks to everyone who helped pack the room at the Fox Valley Day of .NET.   This presentation was designed to help developers understand why secure coding is important, what areas to focus on and additional resources.  You can find the slides here. Remember to understand what you are really trying to protect within your application.  This needs to be a conversation between the application owner, developer and architect.  Understand what data (or Asset) needs to be protected.  This could be passwords, credit cards, Social Security Numbers.   This also may be business specific information like business confidential data etc.  Performing a Risk and Privacy Assessment & Threat Model on your applications even in a small way can help you organize this process. These are the areas to pay attention to when coding: Authentication & Authorization Logging & Auditing Event Handling Session and State Management Encryption Links requested Slides Books The Security Development Lifecycle: SDL: A Process for Developing Demonstrably More Secure Software Threat Modeling Writing Secure Code The Web Application Hackers Handbook  Secure Programming with Static Analysis   Other Resources: OWASP OWASP Top 10 OWASP WebScarab OWASP WebGoat Internet Storm Center Web Application Security Consortium Events: OWASP AppSec 2011 in Minneapolis

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• Html 5 clock, part ii - CSS marker classes and getElementsByClassName

  - by Norgean

  The clock I made in part i displays the time in "long" - "It's a quarter to ten" (but in Norwegian). To save space, some letters are shared, "sevenineight" is four letters shorter than "seven nine eight". We only want to highlight the "correct" parts of this, for example "sevenineight". When I started programming the clock, each letter had its own unique ID, and my script would "get" each element individually, and highlight / hide each element according to some obscure logic. I quickly realized, despite being in a post surgery haze, …this is a stupid way to do it. And, to paraphrase NPH, if you find yourself doing something stupid, stop, and be awesome instead. We want an easy way to get all the items we want to highlight. Perhaps we can use the new getElementsByClassName function? Try to mark each element with a classname or two. So in "sevenineight": 's' is marked as 'h7', and the first 'n' is marked with both 'h7' and 'h9' (h for hour). <div class='h7 h9'>N</div><div class='h9'>I</div> getElementsByClassName('h9') will return the four letters of "nine". Notice that these classes are not backed by any CSS, they only appear directly in html (and are used in javascript). I have not seen classes used this way elsewhere, and have chosen to call them "marker classes" - similar to marker interfaces - until somebody comes up with a better name.

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• Algorithm to match timestamped events from two sources

  - by urza.cc

  I have two different physical devices (one is camera, one is other device) that observe the same scene and mark when a specified event occures. (record timestamp) So they each produce a serie of timestamps "when the event was observed". Theoretically the recorded timestamps should be very well aligned: Visualized ideal situation on two time lines "s" and "r" as recorded from the two devices: but more likely they will not be so nicely aligned and there might be missing events from timeline s or r: I am looking for algorithm to match events from "s" and "r" like this: So that the result will be something like: (s1,null); (s2,r1); (s3,null); (s4,r2); (s5,r3); (null,r4); (s6,r5); Or something similar. Maybe with some "confidence" rating. I have some ideas, but I feel that this might be probably a well known problem, that has some good known solutions, but I don't know the right terminology. I am a little bit out of my element here, this is not my primary area of programming.. Any helps, suggestions etc will be appreciated.

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• Learning OO for a C Programmer

  - by Holysmoke

  I've been programming professionally in C, and only C, for around 10 years in a variety of roles. As would be normal to expect, I understand the idioms of the language fairly well and beyond that also some of the design nuances - which APIs to make public, who calls what, who does what, what is supposed to reentrant and so on. I grew up reading 'Writing Solid Code', it's early C edition, not the one based on C++. However, I've never ever programmed in an OO language. Now, I want to migrate to writing applications for iPhone (maybe android), so want to learn to use Objective-C and use it with a degree of competence fitting a professional programmer. How do I wrap my head around the OO stuff? What would be your smallest reading list suggestion to me. Is there a book that carries some sort of relatively real world example OO design Objective-C? Besides, the reading what source code would you recommend me to go through. How to learn OO paradigm using Objective-C?

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• Virtual Developer Day - EMEA-friendly time

  - by Tori Wieldt

  OTN's Virtual Developer Day lets you learn about the latest technical improvements in Java without leaving your desk/couch/park bench. Watch informative tutorials on your laptop and improve your Java programming expertise and engage in live chat sessions with Java experts, all for FREE.  OTN Virtual Developer Day: Java Europe/Africa/Middle East - June 25 09:00 to 13:00 BST / 10:00 to 14:00 CEST / 13:30 to 17:30 IST / 12:00 to 16:00 MSK / 08:00 to 12:00 Corresponding UTC (GMT) After a short keynote, you can dive into one of these three tracks:  Java SE 8 Track Learn about the features scheduled for Java SE 8, including Lambda expressions, extension methods for interfaces and a new Date and Time API. Learn how to create basic apps with JavaFX.  Java EE Track Take a close look at the new functionality in Java EE 7. Get presentations and demos on JSON, WebSockets, Batch, Concurrency, JAX-RS 2, JMS 2,  Java Embedded Track Provides an introductions to the Raspberry Pi, the Keil board, ARM architecture, and how to make it all work with Java Embedded. You know Java, now really know Java. Register now!

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• December 2012 OTN Member Offers

  - by Cassandra Clark - OTN

  Our partners have answered the special offer call just in time for you to either shop for the tech professional in your life or share the list below with someone who keeps asking you what you want for the holidays.  Go right to the Oracle Technology Network Member Discount Page or read on for more details. Oracle  Store has extended their 10% Savings through December 31st 2012.Oracle Press - Oracle Technology Network members get 40% off the latest Oracle Press book by Oracle ACE Directors Ben Prusinski and Gustavo Gonzalez, Oracle E-Business Suite Financials Handbook, Third Edition in print and ebook format. CRC Press - Has added 3 NEW titles!  Get 20% off the below title at checkout. Secure Java: For Web Application Development Open Source Data Warehousing and Business Intelligence Developing Essbase Applications: Advanced Techniques for Finance and IT Professional Oracle Embedded Programming and Application Development Packt Publishing - Get 25% off the print books and get 35% off the eBooks listed below. You will need to be logged in for the discounts to apply at checkout and codes expire December 31st 2012. Getting Started with Oracle Data Integrator 11g: A Hands-On Tutorial Oracle Business Intelligence Enterprise Edition 11g: A Hands-On Tutorial Oracle Certified Associate, Java SE 7 Programmer Study Guide Safari Online-  Give the Gift of Knowledge This Holiday SeasonGive your friends and colleagues the gift of Safari Books Online! With an ever-expanding library of books and videos from more than 100 publishers (including Oracle Press), a subscription to Safari Books Online is the gift that always fits, helping your friends learn new skills and stay current. Starting at $42.99, gift subscriptions are available for 1, 3, 6 and 12 months. Get all of this and more at the Oracle Technology Network Member Discount Page!

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• Abstract Factory Method and Polymorphism

  - by Scotty C.

  Being a PHP programmer for the last couple of years, I'm just starting to get into advanced programming styles and using polymorphic patterns. I was watching a video on polymorphism the other day, and the guy giving the lecture said that if at all possible, you should get rid of if statements in your code, and that a switch is almost always a sign that polymorphism is needed. At this point I was quite inspired and immediately went off to try out these new concepts, so I decided to make a small caching module using a factory method. Of course the very first thing I have to do is create a switch to decide what file encoding to choose. DANG! class Main { public static function methodA($parameter='') { switch ($parameter) { case 'a': $object = new \name\space\object1(); break; case 'b': $object = new \name\space\object2(); break; case 'c': $object = new \name\space\object3(); break; default: $object = new \name\space\object1(); } return (sekretInterface $object); } } At this point I'm not really sure what to do. As far as I can tell, I either have to use a different pattern and have separate methods for each object instance, or accept that a switch is necessary to "switch" between them. What do you guys think?

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• For those of you who are senior developers what do you look for in a new company and development team?

  - by Amy P

  As I move forward in my career new jobs become more difficult to choose between. When I was starting out and for the first 8 years of my career I took the jobs that I could get that would keep me programming on the general technological path that I was on. I am a job hopper, I only stay with a company for between 2 - 3 years. I think that I do this because after 2 years I get bored and unless there are new projects to keep my busy I no longer find work interesting. Now that I am becoming more experienced it is more important for me to only apply for jobs that are interesting and will move my career and my skill set forward. My problem now is that I keep finding jobs where the projects appear to be interesting during the interview but once I get in the company I find the development environment is sub-par and the development team is disjointed. I feel like I am asking the wrong questions during the interview process and don't know what to look for to make sure that the environment I will be working in will be a good one. Now my question: For those of you who are senior developers what do you look for in a new company and development team? I am looking for the key qualities in a company and development team that you look for when interviewing with a company. These qualities are the ones that would give you hints that the company will be a good one to work for.

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• Pause and Resume and get the value of a countdown timer by savedInstanceState [closed]

  - by Catherine grace Balauro

  I have developed a countdown timer and I am not sure how to pause and resume the timer as the TextView for the timer is being clicked. Click to start then click again to pause and to resume, click again the timer's text view. This is my code: Timer = (TextView)this.findViewById(R.id.time); //TIMER Timer.setOnClickListener(TimerClickListener); counter = new MyCount(600000, 1000); }//end of create private OnClickListener TimerClickListener = new OnClickListener() { public void onClick(View v) { updateTimeTask(); } private void updateTimeTask() { if (decision==0){ counter.start(); decision=1;} else if(decision==2){ counter.onResume1(); decision=1; } else{ counter.onPause1(); decision=2; }//end if }; }; class MyCount extends CountDownTimer { public MyCount(long millisInFuture, long countDownInterval) { super(millisInFuture, countDownInterval); }//MyCount public void onResume1(){ onResume(); } public void onPause1() { onPause();} public void onFinish() { Timer.setText("00:00"); p1++; if (p1<=4){ TextView PScore = (TextView) findViewById(R.id.pscore); PScore.setText(p1 + ""); }//end if }//finish public void onTick(long millisUntilFinished) { Integer milisec = new Integer(new Double(millisUntilFinished).intValue()); Integer cd_secs = milisec / 1000; Integer minutes = (cd_secs % 3600) / 60; Integer seconds = (cd_secs % 3600) % 60; Timer.setText(String.format("%02d", minutes) + ":" + String.format("%02d", seconds)); //long timeLeft = millisUntilFinished / 1000; }//on tick }//class MyCount protected void onResume() { super.onResume(); //handler.removeCallbacks(updateTimeTask); //handler.postDelayed(updateTimeTask, 1000); }//onResume @Override protected void onPause() { super.onPause(); //do stuff }//onPause I am only beginner in android programming and I don't know how to get the value of the countdown timer using savedInstanceState. How do I do this?

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• Dynamic model interactions

  - by Richard

  I am just curious as to how in many games (namely games like arkham asylum/city, manhunt, hitman) do they make it so that your character can "grab" a character in front of you and do stuff to them. I know this may sound very confusing but for an example go to youtube and search "hitman executions", and the first video is an example of what i'm asking. Basically I'm wondering how they make your model dynamically interact with whatever other model you come across, so in hitman when you come up behind some one with the fibre wire you strangle the other character or if you have the anesthetic you come up behind some person and put your hand over there mouth while they struggle and slowly go to the floor where you lay them down. I am confused as to whether it was animated to use two models using specific bone/skeletal identifiers, if it is just two completely separate animations that are played at the correct time to make it look like they are actually interacting or something else all together. I am not an animator so i assume most of what i just said is not right but i hope that some one can understand what i mean and provide an answer. PS) I am a programmer and I am in the process of building a hitmanesque game, just because i love that style of game and I want to increase my skills on something fun, so if you do know what i'm talking about have some examples with involving both models and programming (i use c++ and mainly Ogre3D at the moment but i am getting into unity and XNA) i would greatly appreciate it. Thanks.

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• Automatic Generalization

  - by Nick Harrison

  I have been interested in functional programming since college. I played around a little with LISP back then, but I have not had an opportunity since then. Now that F# ships standard with VS 2010, I figured now is my chance. So, I was reading up on it a little over the weekend when I came across a very interesting topic. F# includes a concept called "Automatic Generalization". As I understand it, the compiler will look at your method and analyze how you are using parameters. It will automatically switch to a generic parameter if it is possible based on your usage. Wow! I am looking forward to playing with this. I have long been an advocate of using the most generic types possible especially when developing library classes. Use the highest level base class that you can get away with. Use an interface instead of a specific implementation. I don't advocate passing object around, but you get the idea. Tools like resharper, fxCop, and most static code analysis tools provide guidance to help you identify when a more generalized type is possible, but this is the first time I have heard about the compiler taking matters into its own hands. I like the sound of this. We'll see if it is a good idea or not. What are your thoughts? Am I missing the mark on what Automatic Generalization does in F#? How would this work in C#? Do you see any problems with this?

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• Experienced programmer, beginner at web design, tools for effective maintainable web design? [closed]

  - by Clinton

  I do quite a bit of programming in my work, which I'm comfortable with, but recently I've being trying to do some web-design for non-work related reasons. I've got a Drupal site up and running, and added some content. But they all look fairly basic. Header with some content. It doesn't look particularly polished. Anyway, as an example, what I wanted to do was make some "bubbles", each with some text in them. From a programmers point of view, say: bubble(question_text, answer_text) might expand to a box with some border, with "Question: " + question_text then "Answer: " + answer_text. Of course I'd have lots of these bubbles, but I'd like to change their look and feel in one place, so simple HTML would be a maintainable nightmare. I also want to lay them out on the screen in some fashion. I was thinking a mixture of javascript and CSS, or possibly use PHP which Drupal uses. On the other hand, I fear I might be taking a 1990s approach to this, and that there's actually tools available now that make this process a lot easier. I'm just wondering what the best approach to this sort of task is? Should I be using offline web design software and copying the code to Drupal, and if so, any recommendations? I'm sorry if my question is a bit vague, because I'm not really sure what question I should be asking. I'd appreciate if you answer and comment, and I'll try my best to be more specific as I understand more.

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• MSDN Live 2010 &ndash; Delivered : 24 sessions (4 x 6) on Visual Studio and Team Foundation Server

  - by terje

  We (Mikael Nitell and me) got a whole track on the Norwegian MSDN Live tour this year.  We did these as a pair, and covered 4 cities over 4 days, 6 sessions per day, taking 8 hours to come through it.  The Islandic volcano made the travels a bit rough, but we managed 6 flights out of 8. The first one had to go by van instead, 7-8 hour drive each way together with other MSDN Live presenters – a memorable tour! Oslo was the absolute top point.  We had to change hall to a bigger one. People were crowding, and even the big hall was packed!  The presentations were mostly based on demos, but we had a few slides as well.  They have been uploaded to my SkyDrive.  Info to aliens – some of the text may be Norwegian. The sessions were as follows: Overview of news in Visual Studio and Team Foundation server 2010 Ensuring Quality with VS/TFS 2010 Releasing products with VS/TFS 2010 No More No Repro with VS/TFS 2010 Performance Testing and Parallel Programming with VS/TFS 2010 Migrating to VS/TFS 2010 Tips, tricks, news and some best practices with VS/TFS 2010   In the coming days, I will post up examples from the demos too, with explanations of how they are intended to work. These entries will also contain stuff we had to remove from the actual presentations due to the time constraints. We managed to create recordings of two of the sessions, which will be uploaded to Channel 9 by Microsoft, afaik.   I will update this blog with information about exact locations when that is done. Also note we’re (read:Osiris Data AS) running both Upgrade and Deep Dive courses  on VS/TFS 2010 now in May.  Please look here for more info. If you want to be informed, follow me on Twitter.  All blog entries will be announced on twitter.

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• Does Agile force developers to work more?

  - by Shooshpanchick

  Looking at common Agile practices it seems to me that they (intentionally or unintentionally?) force developer to spend more time actually working as opposed to reading blogs/articles, chatting, coffee breaks and just plain procrastinating. In particular: 1) Pair programming - the biggest work-forcer, just because it is inconvenient to do all that procrastination when there are two of you sitting together. 2) Short stories - when you have a HUGE chunk of work that must be done in e.g. a month, it is pretty common to slack off in the first three weeks and switch to OMG DEADLINE mode for the last one. And with the little chunks (that must be done in a day or less) it is exact opposite - you feel that time is tight, there is no space for maneuvering, and you will be held accountable for the task pretty soon, so you start working immediately. 3) Team communication and cohesion - when you underperform in a slow, distanced and silent environment it may feel ok, but when at the end of the day at Scrum meeting everyone boasts what they have accomplished and you have nothing to say you may actually feel ashamed. 4) Testing and feedback - again, it prevents you from keeping tasks "99% ready" (when it's actually around 20%) until the deadline suddenly happens. Do you feel that under Agile you work more than under "conventional" methodologies? Is this pressure compensated by the more comfortable environment and by the feeling of actually getting right things done quickly?

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• Tomcat + Spring + CI workflow

  - by ex3v

  We're starting our very first project with Spring and java web stack. This project will be mainly about rewriting quite large ERP/CRM from Zend Framework to Java. Important factor in my question is that I come from php territory, where things (in terms of quality) tend to look different than in java world. Fatcs: there will be 2-3 developers, at least one of developers uses Windows, rest uses Linux, there is one remote linux-based machine, which should handle test and production instances, after struggling with buggy legacy code, we want to introduce good programming and development practices (CI, tests, clean code and so on) client: internal, frequent business logic changes, scrum, daily deployments What I want to achieve is good workflow on as many development stages as possible (coding - commiting - testing - deploying). The problem is that I've never done this before, so I don't know what are best practices to do this. What I have so far is: developers code locally, there is vagrant instance on every development machine, managed by puppet. It contains the same linux, jenkins and tomcat versions as production machine, while coding, developer deploys to vagrant machine, after local merge to test branch, jenkins on vagrant handles tests, when everything is fine, developer pushes commits and merges jenkins on remote machine pulls commit from test branch, runs tests and so on, if everything looks green, jenkins deploys to test tomcat instance Deployment to production is manual (altough it can be done using helping scripts) when business logic is tested by other divisions and everything looks fine to client. Now, the real question: does above make any sense? Things that I'm not sure about: Remote machine: won't there be any problems with two (or even three, as jenkins might need one) instances of same app on tomcat? Using vagrant to develop on php environment is just vise. Isn't this overkill while using Tomcat? I mean, is there higher probability that tomcat will act the same on every machine? Is there sense of having local jenkins on vagrant?

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• How to change careers

  - by Jack Black

  For the past 4 years I have worked in c# doing web development. I have really enjoyed it, learnt a lot and have a worked hard to get to a position where I am earning good money and enjoy the work. However lately - I have wanted a change. What with the "native renaissance" I would like to change my career from being high level application and web development to more down to the metal native development. I haven't done any c or c++ since Uni over 4 years ago and so I have begun reading text books and websites to brush up. However - one major issue I have is that I have no practical experience with C++ and although I am brushing up on it, there will be a lot I don't know. Most of the jobs I have seen in native code around me all require native experience. The only positions I can find that don't explicitly ask for native experience are junior level positions. In my current role I am a mid level developer and although there would be a lot to learn in a c++ position, I wouldn't class myself as a junior. I guess my question is, how do people solve this issue when changing programming languages for their profession and / or how would you approach this hurdle? Like I said, I would really like to try out native development professionally but I wouldn't want to move back to a junior role. Would employers consider years of managed development and native hobby projects enough experience?

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• How to shift a vector based on the rotation of another vector?

  - by bpierre

  I’m learning 2D programming, so excuse my approximations, and please, don’t hesitate to correct me. I am just trying to fire a bullet from a player. I’m using HTML canvas (top left origin). Here is a representation of my problem: The black vector represent the position of the player (the grey square). The green vector represent its direction. The red disc represents the target. The red vector represents the direction of a bullet, which will move in the direction of the target (red and dotted line). The blue cross represents the point from where I really want to fire the bullet (and the blue and dotted line represents its movement). This is how I draw the player (this is the player object. Position, direction and dimensions are 2D vectors): ctx.save(); ctx.translate(this.position.x, this.position.y); ctx.rotate(this.direction.getAngle()); ctx.drawImage(this.image, Math.round(-this.dimensions.x/2), Math.round(-this.dimensions.y/2), this.dimensions.x, this.dimensions.y); ctx.restore(); This is how I instanciate a new bullet: var bulletPosition = playerPosition.clone(); // Copy of the player position var bulletDirection = Vector2D.substract(targetPosition, playerPosition).normalize(); // Difference between the player and the target, normalized new Bullet(bulletPosition, bulletDirection); This is how I move the bullet (this is the bullet object): var speed = 5; this.position.add(Vector2D.multiply(this.direction, speed)); And this is how I draw the bullet (this is the bullet object): ctx.save(); ctx.translate(this.position.x, this.position.y); ctx.rotate(this.direction.getAngle()); ctx.fillRect(0, 0, 3, 3); ctx.restore(); How can I change the direction and position vectors of the bullet to ensure it is on the blue dotted line? I think I should represent the shift with a vector, but I can’t see how to use it.

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• Genetic Algorithm new generation exponentially increasing

  - by Rdz

  I'm programming Genetic Algorithm in C++ and after searching all kind of ways of doing GA'a operators (selection, crossover, mutation) I came up with a doubt. Let's say I have an initial population of 500. My selection will consist in getting the top 20% of 500(based on best fitness). So I get 100 individuals to mate. When I do the crossover I'll get 2 children where both together have 50% of surviving. So far so good. I start the mutation, and everything's ok.. Now when I start choosing the Next generation, I see that I have a big number of children (in this case, 4950 if you wanna know). Now the thing is, every time I run GA, if I send all the children to the next generation, the number of individuals per generation will increase exponentially. So there must be a way of choosing the children to fulfill a new generation without getting out of this range of the initial population. What I'm asking here is if there is anyway of choosing the children to fill the new generations OR should I choose somehow (and maybe reduce) the parents to mate so I don't get so many children in the end. Thanks :)

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• SQL language drawbacks, The Third Manifesto

  - by David Portabella

  Sometime ago I read about SQL language drawbacks (the basic language specification, not vendor specific), and one of the drawbacks was that the language does not allow to create a set of tuples that don't come from a table. For instance, SELECT firstName, lastName from people; this creates a set of tuples coming from the table people. Now, if I don't have this table people, and I want to return a constant, I'd need something like this to return a set of two tuples (this would not require to have a table): SELECT VALUES('james', 'dean'), ('tom', 'cruisse'); Why I would need that? Because of the same reasons that we can define constants (not only basic types, but objects and arrays also) in any advanced programming language. Workarounds, Yes, I could create a temporal table, fill the data, and SELECT from that table. This is a hack, to overcome the drawbacks of the poor SQL language. I think that I read about this somewhere in "The Third Manifesto", but I don't find the paragraph/example talking about this concrete drawback anymore. Do you know a reference about it?

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• Removing ocurrances of characters in a string

  - by DmainEvent

  I am reading this book, programming Interviews exposed by John Wiley and sons and in chapter 6 they are discussing removing all instances of characters in a src string using a removal string... so removeChars(string str, string remove) In there writeup they sey the steps to accomplish this are to have a boolean lookup array with all values initially set to false, then loop through each character in remove setting the corresponding value in the lookup array to true (note: this could also be a hash if the possible character set where huge like Unicode-16 or something like that or if str and remove are both relatively small... < 100 characters I suppose). You then iterate through the str with a source and destination index, copying each character only if its corresponding value in the lookup array is false... Which makes sense... I don't understand the code that they use however... They have for(src = 0; src < len; ++src){ flags[r[src]] == true; } which is turning the flag value at the remove string indexed at src to true... so if you start out with PLEASE HELP as your str and LEA as your remove you will be setting in your flag table at 0,1,2... t|t|t but after that you will get an out of bounds exception because r doesn't have have anything greater than 2 in it... even using there example you get an out of bounds exception... Am is there code example unworkable?

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• Advanced PHP book [closed]

  - by Aaditi Sharma

  I've gone and stumbled across a lot of recommendations for PHP books, including on SO, however could not find a reasonable & convincible answer for this. Is there a really good advanced book for PHP. Background: I've done almost 8 months in PHP. I know the basics. I go through php.net very often. I've played around with Codeigniter, amongst other frameworks. I've been doing JavaScript for almost 2 years, and specifically thank Douglas Crockford for this, I completely changed the way I code JavaScript. I spend a lot of time travelling, and would love to read a book about PHP, that includes the awesome parts and even when something doesn't quite work in PHP. (As a note a lot of previous answers on SO and programmers give varied results.) I have to place an order through a library which has it's limitations. One book that some of experienced PHP programmers could recommend would be helpful. I have gone through http://stackoverflow.com/questions/1711/what-is-the-single-most-influential-book-every-programmer-should-read and http://stackoverflow.com/questions/194812/list-of-freely-available-programming-books, which do NOT have books related to PHP.

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