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  • ArchBeat Link-o-Rama for 2012-09-06

    - by Bob Rhubart
    Oracle Technology Network Architect Day - Boston, MA - 9/12/2012 Sure, you could ask a voodoo priestess for help in improving your solution architecture skills. But there's the whole snake thing, and the zombie thing, and other complications. So why not keep it simple and register for Oracle Technology Network Architect Day in Boston, MA. There's no magic, just a full day of technical sessions covering Cloud, SOA, Engineered Systems, and more. Registration is free, but seating is limited. You'll curse yourself if you miss this one. Register now. Adding a runtime LOV for a taskflow parameter in WebCenter | Yannick Ongena Oracle ACE Yannick Ongena illustrates how to customize the parameters tab for a taskflow in WebCenter. Tips on Migrating from AquaLogic .NET Accelerator to WebCenter WSRP Producer for .NET | Scott Nelson "It has been a very winding path and this blog entry is intended to share both the lessons learned and relevant approaches that led to those learnings," says Scott Nelson. "Like most journeys of discovery, it was not a direct path, and there are notes to let you know when it is practical to skip a section if you are in a hurry to get from here to there." Using FMAP and AnalyticsRes in a Oracle BI High Availability Implementation | Christian Screen "The fmap syntax has been used for a long time in Oracle BI / Siebel Analytics when referencing images inherent in the application as well as custom images," says Oracle ACE Christian Screen. "This syntax is used on Analysis requests an dashboards." More on Embedded Business Intelligence | David Haimes David Haimes give an example of Timeliness as "one of the three key attributes required for BI to be considered embedded BI." Thought for the Day "Architect: Someone who knows the difference between that which could be done and that which should be done. " — Larry McVoy Source: Quotes for Software Engineers

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  • Virtualization or Raw Metal?

    - by THE
    Normal 0 21 false false false DE X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-fareast-language:EN-US;} With the growing number of customers who want to run the Oracles EPM/BI (or other Fusion Middleware Software) in a virtualized environment, we face a growing number of people asking if running Oracle Software within VMware is supported or not. Two KM articles reflect Oracles policy towards the use of VMware: 249212.1 and 475484.1 . The bottom line is: “you may use it at your own risk, but Oracle does not recommend it”. So far we have seen few problems with the use of VMware (other than performance and the usual limitations) but Oracle does not certify its software for the use in VMware (and specifically for RAC Software actively refuses any support) and any issue that may occur will be fixed for the native OS only. It is on the customer to prove that the issue is NOT due to VMware in case that an issue is encountered. See: “Oracle Fusion Middleware Supported System Configurations page” And also “Supported Virtualization and Partitioning Technologies for Oracle Fusion Middleware”

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  • Collision Detection with SAT: False Collision for Diagonal Movement Towards Vertical Tile-Walls?

    - by Macks
    Edit: Problem solved! Big thanks to Jonathan who pointed me in the right direction. Sean describes the method I used in a different thread. Also big thanks to him! :) Here is how I solved my problem: If a collision is registered by my SAT-method, only fire the collision-event on my character if there are no neighbouring solid tiles in the direction of the returned minimum translation vector. I'm developing my first tile-based 2D-game with Javascript. To learn the basics, I decided to write my own "game engine". I have successfully implemented collision detection using the separating axis theorem, but I've run into a problem that I can't quite wrap my head around. If I press the [up] and [left] arrow-keys simultaneously, my character moves diagonally towards the upper left. If he hits a horizontal wall, he'll just keep moving in x-direction. The same goes for [up] and [left] as well as downward-diagonal movements, it works as intended: http://i.stack.imgur.com/aiZjI.png Diagonal movement works fine for horizontal walls, for both left and right-movement However: this does not work for vertical walls. Instead of keeping movement in y-direction, he'll just stop as soon as he "enters" a new tile on the y-axis. So for some reason SAT thinks my character is colliding vertically with tiles from vertical walls: http://i.stack.imgur.com/XBEKR.png My character stops because he thinks that he is colliding vertically with tiles from the wall on the right. This only occurs, when: Moving into top-right direction towards the right wall Moving into top-left direction towards the left wall Bottom-right and bottom-left movement work: the character keeps moving in y-direction as intended. Is this inherited from the way SAT works or is there a problem with my implementation? What can I do to solve my problem? Oh yeah, my character is displayed as a circle but he's actually a rectangular polygon for the collision detection. Thank you very much for your help.

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  • Acceptable placement of the composition root using dependency injection and inversion of control containers

    - by Lumirris
    I've read in several sources including Mark Seemann's 'Ploeh' blog about how the appropriate placement of the composition root of an IoC container is as close as possible to the entry point of an application. In the .NET world, these applications seem to be commonly thought of as Web projects, WPF projects, console applications, things with a typical UI (read: not library projects). Is it really going against this sage advice to place the composition root at the entry point of a library project, when it represents the logical entry point of a group of library projects, and the client of a project group such as this is someone else's work, whose author can't or won't add the composition root to their project (a UI project or yet another library project, even)? I'm familiar with Ninject as an IoC container implementation, but I imagine many others work the same way in that they can scan for a module containing all the necessary binding configurations. This means I could put a binding module in its own library project to compile with my main library project's output, and if the client wanted to change the configuration (an unlikely scenario in my case), they could drop in a replacement dll to replace the library with the binding module. This seems to avoid the most common clients having to deal with dependency injection and composition roots at all, and would make for the cleanest API for the library project group. Yet this seems to fly in the face of conventional wisdom on the issue. Is it just that most of the advice out there makes the assumption that the developer has some coordination with the development of the UI project(s) as well, rather than my case, in which I'm just developing libraries for others to use?

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  • Android Card Game Database for Deck Building

    - by Singularity222
    I am making a card game for Android where a player can choose from a selection of cards to build a deck that would contain around 60 cards. Currently, I have the entire database of cards created that the user can browse. The next step is allowing the user to select cards and create a deck with whatever cards they would like. I have a form where the user can search for specific cards based off a few different attributes. The search results are displayed in a List Activity. My thought about deck creation is to add the primary key of each card the user selects to a SQLite Database table with the amount they would like in the deck. This way as the user performs searches for cards they can see the state of the deck. Once the user decides to save the deck. I'll export the card list to XML and wipe the contents of the table. If the user wanted to make changes to the deck, they would load it, it would be parsed back into the table so they could make the changes. A similar situation would occur when the eventually load the deck to play a game. I'm just curious what the rest of you may think of this method. Currently, this is a personal project and I am the only one working on it. If I can figure out the best implementation before I even begin coding I'm hoping to save myself some time and trouble.

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  • I want to be a programmer, work in corporate environment, earn well, learn fast and eventually become a great programmer [on hold]

    - by Shin San
    I'll try to keep this simple: I'm 29, been dabbling with computers for the past 10 years, had entry level jobs in tech support for different apps, been fixing computers for a while and now want to specialize in something. I'm not 100% stranger to programming but haven't gone past if/then/else with anything. A bit of JavaScript, PHP, Python and currently checking out the "SELECT" statement in SQL :)) I'm curious about programming, I enjoy it and I'm thinking of making a living out of it. So, while I'm at it, why not earn a bit more than the average Joe? So, that's why I'm checking what the best solution, the best learning path and the most useful languages are considering: a) how easy/fast can you find a job by knowing it b) how much would I be able to earn c) how fast can I learn it By reading 10-20 articles online I've come up with an example, but I'm here for some expert advice. Example: * ratings from a) and b) point of view #1 sql ; #2 java ; #3 html (please don't start the markup language debate) ; #4 javascript From this ratings, I'd say a good way to go is learn html/css/(javascript or php) for the web part of apps, some SQL/MySQL/whateverSQL for holding data and loads of Java for the program itself. Please let me know if this is a good idea and if so, what should be the order for learning all of the above. Else, please let me know a better way and why it would be better. Many thanks for taking the time to read my question. Best wishes to you guys Edit: if I think Java + SQL + HTML&JavaScript is the way to go, does the order I'm learning them in matter? Or can I try to learn them all at once?

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  • Priority Manager&ndash;Part 1- Laying out the plan

    - by Patrick Liekhus
    Now that we have shown the EDMX with XPO/XAF and how use SpecFlow and BDD to run EasyTest scripts, let’s put it all together and show the evolution of a project using all the tools combined. I have a simple project that I use to track my priorities throughout the day.  It uses some of Stephen Covey’s principles from The 7 Habits of Highly Effective People.  The idea is to write down all your priorities the night before and rank them.  This way when you get started tomorrow you will have your list of priorities.  Now it’s not that new things won’t appear tomorrow and reprioritize your list, but at least now you can track them.  My idea is to create a project that will allow you manage your list from your desktop, a web browser or your mobile device.  This way your list is never too far away.  I will layout the data model and the additional concepts as time progresses. My goal is to show the power of all of these tools combined and I thought the best way would be to build a project in sequence.  I have had this idea for quite some time so let’s get it completed with the outline below. Here is the outline of the series of post in the near future: Part 2 – Modeling the Business Objects Part 3 – Changing XAF Default Properties Part 4 – Advanced Settings within Liekhus EDMX/XAF Tool Part 5 – Custom Business Rules Part 6 – Unit Testing Our Implementation Part 7 – Behavior Driven Development (BDD) and SpecFlow Tests Part 8 – Using the Windows Application Part 9 – Using the Web Application Part 10 – Exposing OData from our Project Part 11 – Consuming OData with Excel PowerPivot Part 12 – Consuming OData with iOS Part 13 – Consuming OData with Android Part 14 – What’s Next I hope this helps outline what to expect.  I anticipate that I will have additional topics mixed in there but I plan on getting this outline completed within the next several weeks.  Thanks

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  • Complexity of defense AI

    - by Fredrik Johansson
    I have a non-released game, and currently it's only possible to play with another human being. As the game rules are made up by me, I think it would be great if new players could learn basic game play by playing against an AI opponent. I mean it's not like Tennis, where the majority knows at least the fundamental rules. On the other hand, I'm a bit concerned that this AI implementation can be quite complex. I hope you can help me with an complexity estimation. I've tried to summarize the gameplay below. Is this defense AI very hard to do? Basic Defense Game Play Player Defender can move within his land, i.e. inside a random, non-convex, polygon. This land will also contain obstacles modeled as polygons, that Defender has to move around. Player Attacker has also a land, modeled as another such polygon. Assume that Defender shall defend against Attacker. Attacker will then throw a thingy towards Defender's land. To be rewarded, Attacker wants to hit Defender's land, and Defender will want to strike away the thingy from his land before it stops to prevent Attacker from scoring. To feint Defender, Attacker might run around within his land before the throw, and based on these attacker movements Defender shall then continuously move to the best defense position within his land.

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  • BPM Solution Catalogue–promote your process templates

    - by JuergenKress
    Oracle’s BPM Solution Catalogue showcasing our solutions with partners is now live. Take a look at the initial entries here. We are planning to use this catalogue not only to publish and highlight successful BPM implementations but also will be running campaigns in industry verticals with your solutions. If you have delivered a successful implementation in BPM and think it could be reused and applied again in a similar scenario in the same industry or in a similar environment, then we are keen to know about it and will add it to the solution catalogue. The solution catalogue will showcase successful BPM solutions both inside and outside Oracle. Be in touch with us on this via this e-mail id and we will make sure to add your solution. For more information you can also read the article “Leading-Edge BPM Benefits Without Bleeding-Edge Pain” SOA & BPM Partner Community For regular information on Oracle SOA Suite become a member in the SOA & BPM Partner Community for registration please visit  www.oracle.com/goto/emea/soa (OPN account required) If you need support with your account please contact the Oracle Partner Business Center. Blog Twitter LinkedIn Mix Forum Technorati Tags: BPM,Solution Catalogue,process templates,BPM Suite,SOA Community,Oracle SOA,Oracle BPM,Community,OPN,Jürgen Kress

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  • ArchBeat Link-o-Rama for December 4, 2012

    - by Bob Rhubart
    Exalogic 2.0.1 Tea Break Snippets - Creating and using Distribution Groups | The Old Toxophilist "Although in many cases we, as Cloud Users, may not be to worried how the Virtualisation Algorithm decides where to place our vServers," says The Old Toxopholist, "there are cases where it is extremely important that vServers run on distinct physical compute nodes." There's plenty more on the subject in his blog post. Oracle Endeca (2.3) Record Level Security | Adam Seed Adam Sneed's blog post covers "the basics of security within Endeca Information Discovery, as these basic security objects are required in order to explain the implementation of record level security." ODI Handling DQ | Gurcan Orhan Oracle ACE Director Gurcan Orhan suggests you have fun with these scripts for Oracle Data Integrator. Parleys Testimonial at GlassFish Community Event - JavaOne 2012 Video of Parley's webmaster Stephan Janssen's presentation at the GlassFish Community Event at JavaOne 2012, in which he explains why Parley's moved from Tomcat to GlassFish. Java Spotlight Episode 109: Pete Muir on CDI 1.1 This edition of Roger Brinkley's Java Spotlight Podcast features an interview with CDI 1.1 spec lead Pete Muir of JBoss/Red Hat. Muir talks about the features in CDI 1.1 and what to expect in the future. Webcast: Java Management Extensions with Oracle WebLogic Server 12c Dr. Frank Munz and Dave Cabelus do the talking in this on-demand webcast focused on Oracle WebLogic Server 12c with Java Management Extensions (JMX). Using the Coherence API to get Portable Object Format bytes | Bruno Borges Bruno Borges shares a code snippet that illustrates how easy it is to use the Coherence API. Thought for the Day "Experience is something you don't get until just after you need it." — Anonymous Source: SoftwareQuotes.com

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  • Partner Training for Oracle Business Intelligence Applications 4-Day Bootcamp

    - by Mike.Hallett(at)Oracle-BI&EPM
    Partners 4-Day training from 15th - 18th October 2012, at Oracle Reading (UK) The Oracle Business Intelligence Applications provide pre-built Operational BI solutions for eBusiness Suite, Peoplesoft, Siebel, JDE and SAP; offering out-of-the-box integration. This FREE for Partners 4-Day training will provide attendees with an in-depth working understanding of the architecture, the technical and the functional content of the Oracle Business Intelligence Applications, whilst also providing an understanding of their installation, configuration and extension. The course will cover the following topics: Overview of Oracle Business Intelligence Applications Oracle BI Applications Fundamentals and Features Configuring BI Applications for Oracle E-Business Suite Understanding BI Applications Architecture Fundamentals of BI Applications Security   REGISTER HERE NOW    (acceptance is subject to availability and your place will be confirmed within two weeks: for help see the Partner Registration Guide) Location: Bray Room, at Oracle Corporation UK Ltd Oracle Parkway Thames Valley Park Reading, Berkshire RG6 1RA 15th - 18th October 2012, 4-Days :  9:30 am – 5:00 pm BST Audience The seminar is aimed at BI Consultants and Implementation Consultants within Oracle's Gold and Platinum Partners. Good understanding of basic data warehousing concepts Hands on experience in Oracle Business Intelligence Enterprise Edition Hands on experience in Informatica Some understanding of  Oracle BI Applications is required (See Sales & Technical Tutorials for OBI, BI-Apps and Hyperion EPM)  Good understanding of any of the following Oracle EBS modules: General Ledger, Accounts Receivables, Accounts Payables Please note that attendees are required to bring a laptop: 4GB RAM Windows 64 bits 80GB free space in Hard drive or External Device CPU Core 2 Duo or Higher Windows 7, Windows XP, Windows 2003 NOT ALLOWED with Windows Vista An Administrator User For more information please contact [email protected].

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  • Should you create a class within a method?

    - by Amndeep7
    I have made a program using Java that is an implementation of this project: http://nifty.stanford.edu/2009/stone-random-art/sml/index.html. Essentially, you create a mathematical expression and, using the pixel coordinate as input, make a picture. After I initially implemented this in serial, I then implemented it in parallel due to the fact that if the picture size is too large or if the mathematical expression is too complex (especially considering the fact that I made the expression recursively), it takes a really long time. During this process, I realized that I needed two classes which implemented the Runnable interface as I had to put in parameters for the run method, which you aren't allowed to do directly. One of these classes ended up being a medium sized static inner class (not large enough to make an independent class file for it though). The other though, just needed a few parameters to determine some indexes and the size of the for loop that I was making run in parallel - here it is: class DataConversionRunnable implements Runnable { int jj, kk, w; DataConversionRunnable(int column, int matrix, int wid) { jj = column; kk = matrix; w = wid; } public void run() { for(int i = 0; i < w; i++) colorvals[kk][jj][i] = (int) ((raw[kk][jj][i] + 1.0) * 255 / 2.0); increaseCounter(); } } My question is should I make it a static inner class or can I just create it in a method? What is the general programming convention followed in this case?

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  • Does purposely linking to an invalid URL and then using 301 affect SEO?

    - by Mike
    On a section of my site, I am currently using .htaccess rewrites to put the ID as part of the URL instead of in the query, like so: RewriteRule ^([a-z_]+)?/?tours/([0-9]+)/(.*) /tours/tour_text.php?lang=$1&id=$2&urlstr=$3 [L] For example, if someone goes to /en/tours/12/some-text-here it will rewrite it to /tours/tour_text.php?lang=en&id=12&urlstr=some-text-here. However I don't want the users to be able to put just any text, so if they type in the wrong some-text-here part it will 301 redirect them to the right page. This works perfectly, but I can see a potential problem potential arising when localizing the website, so I just wanted to make sure it's not actually a problem. How it is now, if someone goes to /en/tours/12/some-text-here, the anchor to the Spanish version of that page will be /es/tours/12/some-text-here (i.e. only changing the "en" to "es"), and then the script will then 301 them to the correct Spanish text (something like /es/tours/12/algun-texto-aqui). And the reverse will also be the same. The anchor on the Spanish version to the English version would be /en/tours/12/algun-texto-aqui and then they will be forwarded with 301 back to /en/tours/12/some-text-here. Basically, the anchor changes the language and the 301 changes the string at the end. So I have two questions: Does purposely and permanently having invalid URLs on your site that get 301'ed to the correct ones have any effect on SEO? I could make it just show the correct URL to begin with, but this is a significant amount of work due to how I am handling the translations, so I would prefer just to 301 them. Will the invalid URLs that are contained in the links be added to the search engine indexes even if they get 301'ed to another page?

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  • Social-network, online community, company and job reviews, salaries statistics and much more.. Do we have it? Do we need it?

    - by Vlad Lazarenko
    I have many friends from Ukraine who are programmers. So I found out that they have a web site that collects, organizes and analyzing information about IT companies, which includes location, feedbacks, company reviews from current and former employees etc. They also collect programming salaries and organize them by language, region etc. That web site is ran by programmers and for programmers, all information is absolutely public and free. Plus, web site has forums, and people can discuss (more or less social than specific programming stuff) things, publish articles, news etc. I personally think that is useful, especially for those who are new in this industry. For example, you may do a small research and find out that, for example, Java programmers getting paid more than PHP programmers but demand is lower. Or you get an offer from the company, is about to accept it, but read reviews and find out that they don't even provide internet access at work and if you need to download something, you have to ask your manager to do it for you, and managers share a single computer that has internet connection to get that stuff for you (there is only one such company in Kiev, Ukraine, called SMK, for Software Mac Kiev, a big shame). So the question is - do we have something like it in US? Or at least, say, for New York region? Or state? All information I managed to find online is inaccurate or not full. Forums are very specific. If we don't have it, would you be interested in creating such a portal? Thanks!

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  • Getting Started with GlassFish 4 and OEPE

    - by gstachni
    Oracle Enterprise Pack for Eclipse 12.1.1.2.2 introduces new support for GlassFish 4.0, the reference implementation of Java EE7.  Getting started with GlassFish 4.0 in Eclipse couldn't be easier. Follow these short steps to get GlassFish 4.0 setup so you can start developing, deploying, and debugging your Java EE7 applications. Prerequisites GlassFish 4.0 Oracle Enterprise Pack for Eclipse 12.1.1.2.2+ from OTN or Eclipse Marketplace Setting up the server connection In the Servers view, click to add a New > Server . Select GlassFish 4.0 from the list of supported server configurations. Pick your GlassFish installation directory (usually <glassfish 4>/glassfish) and select your domain. After you click Finish you should now be setup to launch Glassfish 4.0 in normal and debug mode within Eclipse as well as associate projects for deployment through the Add and Remove wizard. Using GlassFish tools in Eclipse GlassFish server tools provide some useful information about your running GlassFish 4.0 environment. Resources displays current resources deployed in the domain including your JDBC Connection Pool and JDBC Resource names. I find this extra bit of information useful when working with JPA. Deployed Applications shows the current active deployments in GlassFish which can be undeployed as needed from within Eclipse. Deployed Web Services provides information about SOAP-based web services deployed in this domain. Also with the running server are quick launch links to open the Administrative Console, Server Logs, and the GlassFish Community Site all within Eclipse's embedded browser.

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  • Which opcodes are faster at the CPU level?

    - by Geotarget
    In every programming language there are sets of opcodes that are recommended over others. I've tried to list them here, in order of speed. Bitwise Integer Addition / Subtraction Integer Multiplication / Division Comparison Control flow Float Addition / Subtraction Float Multiplication / Division Where you need high-performance code, C++ can be hand optimized in assembly, to use SIMD instructions or more efficient control flow, data types, etc. So I'm trying to understand if the data type (int32 / float32 / float64) or the operation used (*, +, &) affects performance at the CPU level. Is a single multiply slower on the CPU than an addition? In MCU theory you learn that speed of opcodes is determined by the number of CPU cycles it takes to execute. So does it mean that multiply takes 4 cycles and add takes 2? Exactly what are the speed characteristics of the basic math and control flow opcodes? If two opcodes take the same number of cycles to execute, then both can be used interchangeably without any performance gain / loss? Any other technical details you can share regarding x86 CPU performance is appreciated

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  • Which forum software has the most advanced community/GetSatisfaction type features?

    - by Gaia
    I need to assemble a GetSatisfaction/Lithium/Jive type support forum/community. The first is not available in the desired language and the last two are priced for the enterprise market. I did research some other options (open source or SaaS) but they all seem to be either: kind of dead (open source options) too focused in gathering ideas/feedback (uservoice) strictly support without the community/voting features (zendesk) I need an open forum (people powered support/UGC with community/voting features). Therefore I will have to do some of the work on my own. I want to piece things (plugins/mods/etc) on top of a standard forum platform to give it the features I need. For this purpose, I want to use a mature product with widespread userbase, active community and lots of plugin options. I believe most will agree that my options therefore are: vBulletin phpBB SMF Here are the questions: Which one of the three above offers the easier path towards the desired goal? Which one of the three above has the most advanced features related to the desired goal? Of course I dont expect anyone to know these answers cut and dry. I am hoping to hear some experiences and see some examples. Also, it would be great if both those questions had the same answer, but I am not going to get my hopes up... PS: I wish I could add the tags "phpbb" and "smf" ;)

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  • Website Ethics / legal issues, image copyrights

    - by RailsN00b
    Ignoring the technical implementation of a website for a second, assume a website that is similar to twitter but with pictures. A user say something and puts a picture of whatever they said. As the nature of the internet, the images will most likely not be his/hers image. There are 2 options that I see for dealing with this: 1. The user will post a URL of the picture and the website will pull the picture from that URL everytime someone enters that page 2. The website will save the image in its own database of images and display the image to the visitors 'locally' The problem with option #1, while it saved storage, I see an issue with 'stealing' other websites bandwidth and if my website has many many visitors it could cost the image-hosting websites a lot and possible even crash it if the server can't handle the load. The problem with opion #2, while it saves the load to other websites, it practically takes pictures that could have copyright on them. Which option is better to implement in terms of legal issues and ethics? When do I need to contact another website to request permission to use the images from that site? Does anyone really care about that anymore. Where can I read about this?

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  • Floating point undesireable in highly critical code?

    - by Kirt Undercoffer
    Question 11 in the Software Quality section of "IEEE Computer Society Real-World Software Engineering Problems", Naveda, Seidman, lists fp computation as undesirable because "the accuracy of the computations cannot be guaranteed". This is in the context of computing acceleration for an emergency braking system for a high speed train. This thinking seems to be invoking possible errors in small differences between measurements of a moving object but small differences at slow speeds aren't a problem (or shouldn't be), small differences between two measurements at high speed are irrelevant - can there be a problem with small roundoff errors during deceleration for an emergency braking system? This problem has been observed with airplane braking systems resulting in hydroplaning but could this actually happen in the context of a high speed train? The concern about fp errors seems to not be well-founded in this context. Any insight? The fp is used for acceleration so perhaps the concern is inching over a speed limit? But fp should be just fine if they use a double in whatever implementation language. The actual problem in the text states: During the inspection of the code for the emergency braking system of a new high speed train (a highly critical, real-time application), the review team identifies several characteristics of the code. Which of these characteristics are generally viewed as undesirable? The code contains three recursive functions (well that one is obvious). The computation of acceleration uses floating point arithmetic. All other computations use integer arithmetic. The code contains one linked list that uses dynamic memory allocation (second obvious problem). All inputs are checked to determine that they are within expected bounds before they are used.

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  • Go/Obj-C style interfaces with ability to extend compiled objects after initial release

    - by Skrylar
    I have a conceptual model for an object system which involves combining Go/Obj-C interfaces/protocols with being able to add virtual methods from any unit, not just the one which defines a class. The idea of this is to allow Ruby-ish open classes so you can take a minimalist approach to library development, and attach on small pieces of functionality as is actually needed by the whole program. Implementation of this involves a table of methods marked virtual in an RTTI table, which system functions are allowed to add to during module initialization. Upon typecasting an object to an interface, a Go-style lookup is done to create a vtable for that particular mapping and pass it off so you can have comparable performance to C/C++. In this case, methods may be added /afterwards/ which were not previously known and these new methods allow newer interfaces to be satisfied; while I like this idea because it seems like it would be very flexible (disregarding the potential for spaghetti code, which can happen with just about any model you use regardless). By wrapping the system calls for binding methods up in a set of clean C-compatible calls, one would also be able to integrate code with shared libraries and retain a decent amount of performance (Go does not do shared linking, and Objective-C does a dynamic lookup on each call.) Is there a valid use-case for this model that would make it worth the extra background plumbing? As much as this Dylan-style extensibility would be nice to have access to, I can't quite bring myself to a use case that would justify the overhead other than "it could make some kinds of code more extensible in future scenarios."

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  • C++ and system exceptions

    - by Abyx
    Why standard C++ doesn't respect system (foreign or hardware) exceptions? E.g. when null pointer dereference occurs, stack isn't unwound, destructors aren't called, and RAII doesn't work. The common advice is "to use system API". But on certain systems, specifically Win32, this doesn't work. To enable stack unwinding for this C++ code // class Foo; // void bar(const Foo&); bar(Foo(1, 2)); one should generate something like this C code Foo tempFoo; Foo_ctor(&tempFoo); __try { bar(&tempFoo); } __finally { Foo_dtor(&tempFoo); } Foo_dtor(&tempFoo); and it's impossible to implement this as C++ library. Upd: Standard doesn't forbid handling system exceptions. But it seems that popular compilers like g++ doesn't respect system exceptions on any platforms just because standard doesn't require this. The only thing that I want - is to use RAII to make code readable and program reliable. I don't want to put hand-crafted try\finally around every call to unknown code. For example in this reusable code, AbstractA::foo is such unknown code: void func(AbstractA* a, AbstractB* b) { TempFile file; a->foo(b, file); } Maybe one will pass to func such implementation of AbstractA, which every Friday will not check if b is NULL, so access violation will happen, application will terminate and temporary file will not be deleted. How many months uses will suffer because of this issue, until either author of func or author of AbstractA will do something with it? Related: Is `catch(...) { throw; }` a bad practice?

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  • Should I use an interface when methods are only similar?

    - by Joshua Harris
    I was posed with the idea of creating an object that checks if a point will collide with a line: public class PointAndLineSegmentCollisionDetector { public void Collides(Point p, LineSegment s) { // ... } } This made me think that if I decided to create a Box object, then I would need a PointAndBoxCollisionDetector and a LineSegmentAndBoxCollisionDetector. I might even realize that I should have a BoxAndBoxCollisionDetector and a LineSegmentAndLineSegmentCollisionDetector. And, when I add new objects that can collide I would need to add even more of these. But, they all have a Collides method, so everything I learned about abstraction is telling me, "Make an interface." public interface CollisionDetector { public void Collides(Spatial s1, Spatial s2); } But now I have a function that only detects some abstract class or interface that is used by Point, LineSegment, Box, etc.. So if I did this then each implementation would have to to a type check to make sure that the types are the appropriate type because the collision algorithm is different for each different type match up. Another solution could be this: public class CollisionDetector { public void Collides(Point p, LineSegment s) { ... } public void Collides(LineSegment s, Box b) { ... } public void Collides(Point p, Box b) { ... } // ... } But, this could end up being a huge class that seems unwieldy, although it would have simplicity in that it is only a bunch of Collide methods. This is similar to C#'s Convert class. Which is nice because it is large, but it is simple to understand how it works. This seems to be the better solution, but I thought I should open it for discussion as a wiki to get other opinions.

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  • Why is there no facility to overload static properties in PHP?

    - by Jon
    Intro PHP allows you to overload method calls and property accesses by declaring magic methods in classes. This enables code such as: class Foo { public function __get($name) { return 42; } } $foo = new Foo; echo $foo->missingProperty; // prints "42" Apart from overloading instance properties and methods, since PHP 5.3.0 we can also overload static methods calls by overriding the magic method __callStatic. Something missing What is conspicuously missing from the available functionality is the ability to overload static properties, for example: echo Foo::$missingProperty; // fatal error: access to undeclared static property This limitation is clearly documented: Property overloading only works in object context. These magic methods will not be triggered in static context. Therefore these methods should not be declared static. As of PHP 5.3.0, a warning is issued if one of the magic overloading methods is declared static. But why? My questions are: Is there a technical reason that this functionality is not currently supported? Or perhaps a (shudder) political reason? Have there been any aborted attempts to add this functionality in the past? Most importantly, the question is not "how can I have dynamic static properties in userland PHP?". That said, if you know of an especially cute implementation based on __callStatic that you want to share then by all means do so.

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  • Suggestions to start a cross-platform project

    - by Gabriele
    I have a big project in my head, it should be cross-platform (Win, Max and Linux), online (Client - Server) and with 3D graphics. I would like some suggestions to start with the right things. Currently I'm a PHP/MySQL coder, I used to code in C and Pascal on DOS ages (Borland Times ;)), my C knowlegde need a refresh but it's ok. I guess C++ it's the right language. What platform and what i should use to code? I can choose from all three platforms. My idea was to use Visual Studio 2010 C++, but i'm not sure if it support Native code. What kind of libraries should i use? I guessed OpenSSL for the login, OpenGL for graphics part. For the Audio or the GUI? Any other suggestions are well accepted. I know it's a "BIG DEAL" but I have no rush and it'll be a free-time project, only for my pleasure. Thank you in advance.

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  • Understanding Asynchronous Programming with .NET Reflector

    - by Nick Harrison
    When trying to understand and learn the .NET framework, there is no substitute for being able to see what is going on behind at the scenes inside even the most confusing assemblies, and .NET Reflector makes this possible. Personally, I never fully understood connection pooling until I was able to poke around in key classes in the System.Data assembly. All of a sudden, integrating with third party components was much simpler, even without vendor documentation!With a team devoted to developing and extending Reflector, Red Gate have made it possible for us to step into and actually debug assemblies such as System.Data as though the source code was part of our solution. This maybe doesn’t sound like much, but it dramatically improves the way you can relate to and understand code that isn’t your own.Now that Microsoft has officially launched Visual Studio 2012, Reflector is also fully integrated with the new IDE, and supports the most complex language feature currently at our command: Asynchronous processing.Without understanding what is going on behind the scenes in the .NET Framework, it is difficult to appreciate what asynchronocity actually bring to the table and, without Reflector, we would never know the Arthur C. Clarke Magicthat the compiler does on our behalf.Join me as we explore the new asynchronous processing model, as well as review the often misunderstood and underappreciated yield keyword (you’ll see the connection when we dive into how the CLR handles async).Read more here

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