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  • Un développeur donne son avis sur la conception d'OpenGL et explique pourquoi OpenGL est en retard par rapport à DirectX 12 ou Mantle

    Un développeur donne son point de vue sur la conception d'OpenGL Et explique pourquoi OpenGL est en retard par rapport à DirectX 12 ou MantleRich Geldreich, développeur chez Valve écrit sur un blog ses opinions personnelles (donc, à ne pas lier avec Valve) sur OpenGL. Son opinion est intéressante, notamment car Rich a été développeur sur le premier moteur utilisant la technique de rendu différé (pour Shrek, sur Xbox), ensuite il a aussi créé une bibliothèque de compression avancée pour le DXTc,...

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  • How to write files in specific order?

    - by Bernie
    Okay, here's a weird problem -- My wife just bought a 2014 Nissan Altima. So, I took her iTunes library and converted the .m4a files to .mp3, since the car audio system only supports .mp3 and .wma. So far so good. Then I copied the files to a DOS FAT-32 formatted USB thumb drive, and connected the drive to the car's USB port, only to find all of the tracks were out of sequence. All tracks begin with a two digit numeric prefix, i.e., 01, 02, 03, etc. So you would think they would be in order. So I called Nissan Connect support and the rep told me that there is a known problem with reading files in the correct order. He said the files are read in the same order they are written. So, I manually copied a few albums with the tracks in a predetermined order, and sure enough he was correct. So I copied about 6 albums for testing, then changed to the top level directory and did a "find . music.txt". Then I passed this file to rsync like this: rsync -av --files-from=music.txt . ../Marys\ Music\ Sequenced/ The files looked like they were copied in order, but when I listed the files in order of modified time, they were in the same sequence as the original files: ../Marys Music Sequenced/Air Supply/Air Supply Greatest Hits ls -1rt 01 Lost In Love.mp3 04 Every Woman In The World.mp3 03 Chances.mp3 02 All Out Of Love.mp3 06 Here I Am (Just When I Thought I Was Over You).mp3 05 The One That You Love.mp3 08 I Want To Give It All.mp3 07 Sweet Dreams.mp3 11 Young Love.mp3 So the question is, how can I copy files listed in a file named music.txt, and copy them to a destination, and ensure the modification times are in the same sequence as the files are listed?

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  • Output current with Teensy++ 2.0 (arduino-based hardware)

    - by omtinez
    I am working on a project with a Teensy++ 2.0 for testing, eventually the goal is to use a Teensy 2.0 (info on both available here) and mount it onto a robot R/C car along with a Raspberry Pi. I have been able to use and test one of the very cheap distance sensors that use ultrasound, which requires very little current. I was trying to power a motor, I don't know exactly what kind of motor but I assume a very low-power one which is what comes with the R/C car cheapo, but nothing is happening. When I plug the motor to GROUND and +5V it runs fine, but when I use GROUND and one of the GPIO pins then nothing happens with the motor. The same GPIO pins were tested to successfully power and run the ultrasound sensor, so the board is fine. My suspicion is that the GPIO pins don't output enough current to power the motor, but my knowledge of electronics is rather scarce (I am a computer scientist, not an electrical engineer). So please forgive me if I am asking something obvious or plain stupid, but does the board not have enough power to power the motor? If so, I could try to use a second power supply that would go straight into the motor and use the GPIO as a gate to turn that power on and off; would such thing work? Is there a better design that could be used?

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  • Fluent NHibernate - subclasses with shared reference

    - by ollie
    Edit: changed class names. I'm using Fluent NHibernate (v 1.0.0.614) automapping on the following set of classes (where Entity is the base class provided in the S#arp Architecture framework): public class Car : Entity { public virtual int ModelYear { get; set; } public virtual Company Manufacturer { get; set; } } public class Sedan : Car { public virtual bool WonSedanOfYear { get; set; } } public class Company : Entity { public virtual IList<Sedan> Sedans { get; set; } } This results in the following Configuration (as written to hbm.xml): <class name="Company" table="Companies"> <id name="Id" type="System.Int32" unsaved-value="0"> <column name="`ID`" /> <generator class="identity" /> </id> <bag cascade="all" inverse="true" name="Sedans" mutable="true"> <key> <column name="`CompanyID`" /> </key> <one-to-many class="Sedan" /> </bag> </class> <class name="Car" table="Cars"> <id name="Id" type="System.Int32" unsaved-value="0"> <column name="`ID`" /> <generator class="identity" /> </id> <property name="ModelYear" type="System.Int32"> <column name="`ModelYear`" /> </property> <many-to-one cascade="save-update" class="Company" name="Manufacturer"> <column name="`CompanyID`" /> </many-to-one> <joined-subclass name="Sedan"> <key> <column name="`CarID`" /> </key> <property name="WonSedanOfYear" type="System.Boolean"> <column name="`WonSedanOfYear`" /> </property> </joined-subclass> </class> So far so good! But now comes the ugly part. The generated database tables: Table: Companies Columns: ID (PK, int, not null) Table: Cars Columns: ID (PK, int, not null) ModelYear (int, null) CompanyID (FK, int, null) Table: Sedan Columns: CarID (PK, FK, int, not null) WonSedanOfYear (bit, null) CompanyID (FK, int, null) Instead of one FK for Company, I get two! How can I ensure I only get one FK for Company? Override the automapping? Put a convention in place? Or is this a bug? Your thoughts are appreciated.

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  • XML and XSD - use element name as replacement of xsi:type for polymorphism

    - by disown
    Taking the W3C vehicle XSD as an example: <schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="http://cars.example.com/schema" xmlns:target="http://cars.example.com/schema"> <complexType name="Vehicle" abstract="true"/> <complexType name="Car"> <complexContent> <extension base="target:Vehicle"/> ... </complexContent> </complexType> <complexType name="Plane"> <complexContent> <extension base="target:Vehicle"/> <sequence> <element name="wingspan" type="integer"/> </sequence> </complexContent> </complexType> </schema> , and the following definition of 'meansOfTravel': <complexType name="MeansOfTravel"> <complexContent> <sequence> <element name="transport" type="target:Vehicle"/> </sequence> </complexContent> </complexType> <element name="meansOfTravel" type="target:MeansOfTravel"/> With this definition you need to specify the type of your instance using xsi:type, like this: <meansOfTravel> <transport xsi:type="Plane"> <wingspan>3</wingspan> </transport> </meansOfTravel> I would just like to acheive a 'name of type' - 'name of element' mapping so that this could be replaced with just <meansOfTravel> <plane> <wingspan>3</wingspan> </plane> </meansOfTravel> The only way I could do this until now is by making it explicit: <complexType name="MeansOfTravel"> <sequence> <choice> <element name="plane" type="target:Plane"/> <element name="car" type="target:Car"/> </choice> </sequence> </complexType> <element name="meansOfTravel" type="target:MeansOfTravel"/> But this means that I have to list all possible sub-types in the 'MeansOfTravel' complex type. Is there no way of making the XML parser assume that you mean a 'Plane' if you call the element 'plane'? Or do I have to make the choice explicit? I would just like to keep my design DRY - if you have any other suggestions (like groups or so) - i would love to hear them.

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  • I’m a Phoenix… and I’m miffed

    - by Stan Spotts
    For personal reasons, almost 30 years ago I left school to enter the workforce. I decided late 2008 to go back to school and finish my degree. After the expected loss of credits for a transfer, from Temple University to University of Phoenix, I'm now about 75% done. The experience has been interesting. Classes are time compressed, only 5 weeks each. Because I have a family and a full time job, I'm taking one at a time. Even so, I've written more papers in these classes than I ever wrote at Temple. My own papers are one thing, but the team papers give me heartburn since I can't completely control what goes into them. Not a big deal except that they make up 30% of our grade. In any case, most of the class facilitators have been great. I had great ones for Accounting, Finance, and frankly most others. I've had a few (4, maybe) cases where I was less than 2 points from an A, and asked the facilitator if I could get any of my work reviewed to see if I could get those extra points. I figured it was worth a shot, and there were no extenuating circumstances to help make my case. I think that only one facilitator decided after a review of one paper that my interpretation was good, just not what he expected, and gave me another point, which gave me an A. So while none are pushovers, they've all been open to discussion, which is as much as I should expect. Overall, good experience. That is, until my last class. On the second week, the day I was due to hand in my personal assignment for the week, I was in an accident. An SUV creamed my little Ford Focus, and totaled it (estimated repair over $11K). I was pretty banged up, especially my left shoulder. I was scheduled for rotator cuff surgery for two weeks later, and getting hit against the door really made it worse. After dealing with the police, the EMT, the tow truck, and the Percocet and Flexeril for the pain, I crashed for the night and didn't get to upload my paper until the next day. The instructor took 30% off for it being late, even after I supplied photos of the car, my arm (huge bruises), and offered to supply the police report number. I figured I'd be okay since that's 2.7 points, and I could lose up to 5 before jeopardizing an A grade. Well, that wasn't the case as we lost more points than I expected on our team paper in Week 5. I ended up with a 94.3. Yes, 7/10 of a point from an A. Of course I asked the instructor to review the issue with the accident and give me just the 0.7 points I needed for the A. That got me a short response of "I have received your emails and review your work over the last five weeks. Your current grade will stand. If you would like to dispute your grade then please feel free to contact your academic advisor. I wish you much success in your professional and academic career." Brrrr….! So I asked my academic advisor to file a dispute. If it wasn't that a pretty bad car accident was the cause, I wouldn't have. Without the grade reduction, I would have had a 97 for the class, so I'll argue that I was performing at the A level throughout the class. Why her purported "review" of my work didn't then warrant such a minor adjustment, I don't know. An A- drops my GPA, and this ticked me off. Now I have to wait and see what the school says about the grade dispute.

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  • Google Chrome OS

    - by Piet
    It’s about time someone took this initiative: Google Chrome OS I especially like the following: Speed, simplicity and security are the key aspects of Google Chrome OS. We’re designing the OS to be fast and lightweight, to start up and get you onto the web in a few seconds. The user interface is minimal to stay out of your way, and most of the user experience takes place on the web. And as we did for the Google Chrome browser, we are going back to the basics and completely redesigning the underlying security architecture of the OS so that users don’t have to deal with viruses, malware and security updates. It should just work. I recently had the ‘pleasure’ witnessing several 60+ yr old friends and family (all respect for everyone in their 2nd or 3rd youth) buying their first pc, taking their first steps using a pc and the net. Have you ever seen the gazillions of little ‘useful’ tools that are installed on a new standard Vista pc or laptop ? This is like learning to drive a new car and being placed in an airplane cockpit. And all the messages one gets about virus/security checks, fingerprint nog being enrolled, trial period expiring (because half those really useful tools come with a trial period), … If I was in their shoes, being confronted with this as a total newbie, I guess I’d just give up pretty soon. As a matter of fact, I actually gave up on Vista on my work-laptop, it was driving me crazy. Thank god I was allowed to install XP. I’m a Linux user at home, and Vista was such a frustrating experience that Windows XP actually felt like breath of fresh air. And what are those people using? Email, browsing…. and maybe writing a little letter now and then or storing their photo’s if they have a digital camera. Actually (side note), I get the impression that hearing about facebook is a major motivator for the digital newbies to finally take the plunge, buy a pc and get on-line. And OK, we’ve seen initiatives like this before, but Google is a brand everyone knows… unlike Ubuntu, Debain or Mandriva. Google = God. If I was Microsoft I’d be wetting my pants knowing Google was about to release their own OS, without a doubt fully optimized to use their own on-line office suit. On the other hand, the old adage ‘no one ever got fired for choosing Microsoft’ still holds a lot of truth. I hope I’ll be able to give it a big thumbs up if a would-be pc-user asks me what kind of pc/OS they should go for in the near future. On the other hand, if I’d do that, I’m pretty sure a couple of weeks later I’d get a call asking how to install this game or photo editing tool they got from one of their Windows using friends… or that nifty photo-printer they just bought. But then, I also get those questions now from newbie Windows users. It takes a couple of years before Newbie pc users understand that some things just don’t work and aren’t worth the time trying to fix them. I’d just wish they’d go back to the shop when something doesn’t work. You also don’t let you mechanic friend try to fix a problem with your brand new car. But that’s another story… Wait and see…

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  • F1 Pit Pragmatics

    - by mikef
    "I hate computers. No, really, I hate them. I love the communications they facilitate, I love the conveniences they provide to my life. but I actually hate the computers themselves." - Scott Merrill, 'I hate computers: confessions of a Sysadmin' If Scott's goal was to polarize opinion and trigger raging arguments over the 'real reasons why computers suck', then he certainly succeeded. Impassioned vitriol sits side-by-side with rational debate. Yet Scott's fundamental point is absolutely on the money - Computers are a means to an end. The IT industry is finally starting to put weight behind the notion that good User Experience is an absolutely crucial goal, a cause championed by the likes of Microsoft's Bill Buxton, and which Apple's increasingly ubiquitous touch screen interface exemplifies. However, that doesn't change the fact that, occasionally, you just have to man up and deal with complex systems. In fact, sometimes you just need to sacrifice everything else in the name of performance. You'll find a perfect example of this Faustian bargain in Trevor Clarke's fascinating look into the (diabolical) IT infrastructure of modern F1 racing - high performance, high availability. high everything. To paraphrase, each car has up to 100 sensors, transmitting around 30Gb of data over the course of a race (70% in real-time). This data is then processed by no less than 3 servers (per car) so that the engineers in the pit have access to telemetry, strategy information, timing feeds, a connection back to the operations room in the team's home base - the list goes on. All of this while the servers are exposed "to carbon dust, oil, vibration, rain, heat, [and] variable power". Now, this is admittedly an extreme context where there's no real choice but to use complex systems where ease-of-use is, at best, a secondary concern. The flip-side is seen in small-scale personal computing such as that seen in Apple's iDevices, which are incredibly intuitive but limited in their scope. In terms of what kinds of systems they prefer to use, I suspect that most SysAdmins find themselves somewhere along this axis of Power vs. Usability, and which end of this axis you resonate with also hints at where you think the IT industry should focus its energy. Do you see yourself in the F1 pit, making split-second decisions, wrestling with information flows and reticent hardware to bend them to your will? If so, I imagine you feel that computers are subtle tools which need to be tuned and honed, using the advanced knowledge possessed only by responsible SysAdmins (If you have an iPhone, I suspect it's jail-broken). If the machines throw enigmatic errors, it's the price of flexibility and raw power. Alternatively, would you prefer to have your role more accessible, with users empowered by knowledge, spreading the load of managing IT environments? In that case, then you want hardware and software to have User Experience as their primary focus, and are of the "means to an end" school of thought (you're probably also fed up with users not listening to you when you try and help). At its heart, the dichotomy is between raw power (which might be difficult to use) and ease-of-use (which might have some limitations, but you can be up and running immediately). Of course, the ultimate goal is a fusion of flexibility, power and usability all in one system. It's achievable in specific software environments, and Red Gate considers it a target worth aiming for, but in other cases it's a goal right up there with cold fusion. I think it'll be a long time before we see it become ubiquitous. In the meantime, are you Power-Hungry or a Champion of Usability? Cheers, Michael Francis Simple Talk SysAdmin Editor

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  • Developer Profile: Marcelo Quinta

    - by Tori Wieldt
    As the Java developer community lead for Oracle, the best part of my job is going to conferences and meeting Java developers. I’ve had the pleasure to meet men and women who are smart, fun and passionate about Java—they make the Java community happen. The current issue of Java Magazine provides profiles of other young Java developers around the world. Subscribe to read them! Marcelo Quinta Age: 24Occupation: Professor, Federal University of GoiasLocation: Goias, Brazil Twitter: @mrquinta Marcelo (white polo shirt, center) and class OTN: When did you realize that you were good at programming? When I was in graduate school, I developed a Java system that displayed worked out the logics of getting the maximum coverage using the fewest resources (for example, the minimum number of soldiers [and positions] needed for a battlefield. It may seems not difficult, but it's a hard problem to solve, mathematically. Here I was, a freshman, who came up with an app  "solving" it. Some Master's students use my software today. It was then I began to believe in what I could do.OTN: What most inspires you about programming?I'm really inspired by the challenges and tension that comes from solving a complicated problems. Lately, I've been doing a new system focused on education and digital inclusion and was very gratifying to see it working and the results. I felt useful for the community. OTN: What are some things you would like to accomplish using Java?Java is a very strong platform and that gives us power to develop applications for different devices and purposes, from home automation with little microcontrollers to systems in big servers. I would like to build more systems that integrate the people life or different business contexts, from PCs to cell phones and tablets, ubiquitously. I think IT has reached a level where the current challenge is to make systems that leverage existing technologies that are present in daily life. Java gives us a very interesting set of options to put it into practice, especially in systems that require more strength.OTN: What technical insights into Java technology have been most important to you?I have really enjoyed the way that Java has evolved with Oracle, with new features added, many of them which were suggested by the community. Java 7 came with substantial improvements in the language syntax and it seems that Java 8 takes it even further. I also made some applications in JavaFX and liked the new version. The Java GUI is on a higher level than is offered out there. I saw some JavaFX prototypes running in modern tablets and I got excited. OTN: What would you like to be doing 10 years from now?I want my work to make a difference for individuals or an institution. It would be interesting to be improving one of the systems that I am making today. Recently I've been mixing my hobbies and work, playing with Arduino and home automation. The JHome project, winner of the Duke's Choice Award in 2011, is very interesting to me.OTN: Do you listen to music when you write code? If so, what kind?Absolutely! I usually listen to electronic music (Prodigy, Fatboy Slim and Paul Oakenfold), rock (Metallica, Strokes, The Black Keys) and a bit of local alternative music. I live in Goiânia, "The Brazilian Seattle" and I profit from it very well. OTN: What do you do when you're not programming?I like to play guitar and to fish. Last year I sold my economy car and bought a old jeep. Some people called me crazy, but since then I've been having a great time and having adventures on the backroads of Brazil. Once I broke my glasses in a funny game involving my car's suspension and the airbags. OTN: Does your girlfriend think you are crazy?Crazy is someone who doesn't have courage to do strange things! My girlfriend likes my style. =D Subscribe to the free Java Magazine to read profiles of other young Java developers. Visit the Java channel on YouTube to see a video of Marcelo in action.

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  • Cloud Computing Pricing - It's like a Hotel

    - by BuckWoody
    I normally don't go into the economics or pricing side of Distributed Computing, but I've had a few friends that have been surprised by a bill lately and I wanted to quickly address at least one aspect of it. Most folks are used to buying software and owning it outright - like buying a car. We pay a lot for the car, and then we use it whenever we want. We think of the "cloud" services as a taxi - we'll just pay for the ride we take an no more. But it's not quite like that. It's actually more like a hotel. When you subscribe to Azure using a free offering like the MSDN subscription, you don't have to pay anything for the service. But when you create an instance of a Web or Compute Role, Storage, that sort of thing, you can think of the idea of checking into a hotel room. You get the key, you pay for the room. For Azure, using bandwidth, CPU and so on is billed just like it states in the Azure Portal. so in effect there is a cost for the service and then a cost to use it, like water or power or any other utility. Where this bit some folks is that they created an instance, played around with it, and then left it running. No one was using it, no one was on - so they thought they wouldn't be charged. But they were. It wasn't much, but it was a surprise.They had the hotel room key, but they weren't in the room, so to speak. To add to their frustration, they had to talk to someone on the phone to cancel the account. I understand the frustration. Although we have all this spelled out in the sign up area, not everyone has the time to read through all that. I get that. So why not make this easier? As an explanation, we bill for that time because the instance is still running, and we have to tie up resources to be available the second you want them, and that costs money. As far as being able to cancel from the portal, that's also something that needs to be clearer. You may not be aware that you can spin up instances using code - and so cancelling from the Portal would allow you to do the same thing. Since a mistake in code could erase all of your instances and the account, we make you call to make sure you're you and you really want to take it down. Not a perfect system by any means, but we'll evolve this as time goes on. For now, I wanted to make sure you're aware of what you should do. By the way, you don't have to cancel your whole account not to be billed. Just delete the instance from the portal and you won't be charged. You don't have to call anyone for that. And just FYI - you can download the SDK for Azure and never even hit the online version at all for learning and playing around. No sign-up, no credit card, PO, nothing like that. In fact, that's how I demo Azure all the time. Everything runs right on your laptop in an emulated environment.  

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  • What Counts For a DBA – Depth

    - by Louis Davidson
    SQL Server offers very simple interfaces to many of its features. Most people could open up SSMS, connect to a server, write a simple query and see the results. Even several of the core DBA tasks are deceptively straightforward. It doesn’t take a rocket scientist to perform a basic database backup or run a trace (even using the newfangled Extended Events!). However, appearances can be deceptive, and often times it is really important that a DBA understands not just the basics of how to perform a task, but why we do a task, and how that task works. As an analogy, consider a child walking into a darkened room. Most would know that they need to turn on the light, and how to do it, so they flick the switch. But what happens if light fails to shine forth. Most would immediately tell you that you need to consider changing the light bulb. So you hop in the car and take them to the local home store and instruct them to buy a replacement. Confronted with a 40 foot display of light bulbs, how will they decide which of the hundreds of types of bulbs, of different types, fittings, shapes, colors, power and efficiency ratings, is the right choice? Obviously the main lesson the child is going to learn this day is how to use their cell phone as a flashlight so they don’t have to ask for help the next time. Likewise, when the metaphorical toddlers who use your database server have issues, they will instinctively know something is wrong, and may even have some idea what caused it, but will have no depth of knowledge to figure out the right solution. That is where the DBA comes in and attempts to save the day. However, when one looks beneath the shiny UI, SQL Server has its own “40 foot display of light bulbs”, in the form of the tremendous number of tools and the often-bewildering amount of information they can present to the DBA, to help us find issues. Unfortunately, resorting to guesswork, to trying different “bulbs” over and over, hoping to stumble on the answer. This is where the right depth of knowledge goes a long way. If we need to write a SELECT statement, then knowing the syntax and where to find the data is not enough. Knowledge of indexes and query plans is essential. Without it, we might hit on a query that “works”, but we are basically still a user, not a programmer, because we have no real control over our platform. Is that level of knowledge deep enough? Probably not, since knowledge of the underlying metadata and structures would be very useful in helping us make sense of any query plan. Understanding the structure of an index makes the “key lookup” operator not sound like what you do when someone tapes your car key to the ceiling. So is even this level of understanding deep enough? Do we need to understand the memory architecture used to process the query? It might be a comforting level of knowledge, and will doubtless come in handy at some point, but is not strictly necessary in most cases. Beyond that lies (more or less) full knowledge of SQL language and the intricacies of every step the SQL Server engine takes to process our query. My personal theory is that, as a professional, our knowledge of a given task should extend, at a minimum, one level deeper than is strictly necessary to perform the task. Anything deeper can be left to the ridiculously smart, or obsessive, or both. As an example. tasked with storing an integer value between 0 and 99999999, it’s essential that I know that choosing an Integer over Decimal(8,0) will likely offer performance benefits. It is then useful that I also understand the value of adding a CHECK constraint, to make sure the values are valid to the desired range; and comforting that I know a little about the underlying processors, registers and computer math. Anything further, I leave to the likes of Joe Chang, whose recent blog post on the topic offers depth by the bucketful!  

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  • UiModeManager - NightMode (FroYo)

    - by Kaloer
    Hi there, I have been trying to turn off the buttons' light in my application using the UiModeManager's nightmode function. The default Desk Clock application (Nexus One) turns off the buttons' light when it is dimmed, and I want to do this as well. I've tried using the following code: UiModeManager mgr = (UiModeManager) getSystemService(UI_MODE_SERVICE); mgr.setNightMode(UiModeManager.MODE_NIGHT_YES); The UiModeManager.setNightMode(int mode) documentation says this: Sets the night mode. Changes to the night mode are only effective when the car or desk mode is enabled on a device. Does that mean that the device has to be physically in a desk dock? I can set the device to car mode using the UiModeManager.enableCarMode(int flags) method. This works fine, but it doesn't turn off the lights, it only dims the screen's backlight. Is there a way to set the device into desk mode without using a physical desk dock? As the FroYo source code is not yet released, I cannot look at the build-in Desk Clock application. Thanks in advantage.

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  • Scheme Depth-first search of a graph function

    - by John Retallack
    This is a homework question,I'm trying to do a Depth-first search function in Scheme,Here's the code I've written so far: (define explore (?(node visited) (let* ([neighbors (force (cdr node))] [next (nextNode visited neighbors)] [is-visited (member? node visited)]) (cond ;if I have no unvisited neighbours print current node and go up one level [(equal? next #f) (begin (display (car node)) (display " "))] ;if current node is not visited and I have unvisited neighbors ;print current node,mark as visited and visit it's neighbors [(and (equal? is-visited #f) (not (equal? next #f))) (begin (display (car node)) (display " ") (explore next (cons node visited)))]) ;go and visit the next neighbor (if (not (equal? (nextNode (cons next visited) neighbors) #f )) (explore (nextNode (cons next visited) neighbors) (cons node visited)))))) 'node' is the current node 'visited' is a list in witch I keep track of the nodes I visited 'nextNode' is a function that returns the first unvisited neighbor if any or #f otherwise 'member?' test's if a node is in the visited list The Graph representation is using adjacent made using references to nodes with letrec so that's why I use force in 'neighbors': Eg: (letrec ([node1 (list "NY" (delay (list node2 node3)))],where node2 and node3 are defined as node1 The problem witch I'm dealing with is that my visited lists looses track of some of the nodes I visited when I come out of recursion,How can I fix this ?

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  • The subsets-sum problem and the solvability of NP-complete problems

    - by G.E.M.
    I was reading about the subset-sums problem when I came up with what appears to be a general-purpose algorithm for solving it: (defun subset-contains-sum (set sum) (let ((subsets) (new-subset) (new-sum)) (dolist (element set) (dolist (subset-sum subsets) (setf new-subset (cons element (car subset-sum))) (setf new-sum (+ element (cdr subset-sum))) (if (= new-sum sum) (return-from subset-contains-sum new-subset)) (setf subsets (cons (cons new-subset new-sum) subsets))) (setf subsets (cons (cons element element) subsets))))) "set" is a list not containing duplicates and "sum" is the sum to search subsets for. "subsets" is a list of cons cells where the "car" is a subset list and the "cdr" is the sum of that subset. New subsets are created from old ones in O(1) time by just cons'ing the element to the front. I am not sure what the runtime complexity of it is, but appears that with each element "sum" grows by, the size of "subsets" doubles, plus one, so it appears to me to at least be quadratic. I am posting this because my impression before was that NP-complete problems tend to be intractable and that the best one can usually hope for is a heuristic, but this appears to be a general-purpose solution that will, assuming you have the CPU cycles, always give you the correct answer. How many other NP-complete problems can be solved like this one?

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  • Bibliography behaves strange in lyx.

    - by Orjanp
    Hi! I have created a Bibliography section in my document written in lyx. It uses a book layout. For some reason it did start over again when I added some more entries. The new entries was made some time later than the first ones. I just went down to key-27 and hit enter. Then it started on key-1 again. Does anyone know why it behaves like this? The lyx code is below. \begin{thebibliography}{34} \bibitem{key-6}Lego mindstorms, http://mindstorms.lego.com/en-us/default.aspx \bibitem{key-7}C.A.R. Hoare. Communicating sequential processes. Communications of the ACM, 21(8):666-677, pages 666\textendash{}677, August 1978. \bibitem{key-8}C.A.R. Hoare. Communicating sequential processes. Prentice-Hall, 1985. \bibitem{key-9}CSPBuilder, http://code.google.com/p/cspbuilder/ \bibitem{key-10}Rune Møllegård Friborg and Brian Vinter. CSPBuilder - CSP baset Scientific Workflow Modelling, 2008. \bibitem{key-11}Labview, http://www.ni.com/labview \bibitem{key-12}Robolab, http://www.lego.com/eng/education/mindstorms/home.asp?pagename=robolab \bibitem{key-13}http://code.google.com/p/pycsp/ \bibitem{key-14}Paparazzi, http://paparazzi.enac.fr \bibitem{key-15}Debian, http://www.debian.org \bibitem{key-16}Ubuntu, http://www.ubuntu.com \bibitem{key-17}GNU, http://www.gnu.org \bibitem{key-18}IVY, http://www2.tls.cena.fr/products/ivy/ \bibitem{key-19}Tkinter, http://wiki.python.org/moin/TkInter \bibitem{key-20}pyGKT, http://www.pygtk.org/ \bibitem{key-21}pyQT4, http://wiki.python.org/moin/PyQt4 \bibitem{key-22}wxWidgets, http://www.wxwidgets.org/ \bibitem{key-23}wxPython GUI toolkit, http://www.wxPython.org \bibitem{key-24}Python programming language, http://www.python.org \bibitem{key-25}wxGlade, http://wxglade.sourceforge.net/ \bibitem{key-26}http://numpy.scipy.org/ \bibitem{key-27}http://www.w3.org/XML/ \bibitem{key-1}IVY software bus, http://www2.tls.cena.fr/products/ivy/ \bibitem{key-2}sdas \bibitem{key-3}sad \bibitem{key-4}sad \bibitem{key-5}fsa \bibitem{key-6}sad \bibitem{key-7} \end{thebibliography}

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  • Question about registering COM server and Add Reference to it in a C# project

    - by smwikipedia
    I build a COM server in raw C++, here is the procedure: (1) write an IDL file to define the interface and library. (2) use msidl.exe to compile the IDL file to necessary .h, .c, .tlb files. (3) implement the COM server in C++ and build a .dll file. (4) add the following registry entris: [HKEY_CLASSES_ROOT\RawComCarLib.ComCar.1\CurVer] @="RawComCarLib.ComCar.1" ;CLSID [HKEY_CLASSES_ROOT\CLSID{6CC26343-167B-4CF2-9EDF-99368A62E91C}] @="RawComCarLib.ComCar.1" [HKEY_CLASSES_ROOT\CLSID{6CC26343-167B-4CF2-9EDF-99368A62E91C}\InprocServer32] @="D:\com\Project01.dll" [HKEY_CLASSES_ROOT\CLSID{6CC26343-167B-4CF2-9EDF-99368A62E91C}\ProgID] @="RawComCarLib.ComCar.1" [HKEY_CLASSES_ROOT\CLSID{6CC26343-167B-4CF2-9EDF-99368A62E91C}\TypeLib] @="{E5C0EE8F-8806-4FE3-BC0E-3A56CFB38BEE}" ;TypeLib [HKEY_CLASSES_ROOT\TypeLib{E5C0EE8F-8806-4FE3-BC0E-3A56CFB38BEE}] [HKEY_CLASSES_ROOT\TypeLib{E5C0EE8F-8806-4FE3-BC0E-3A56CFB38BEE}\1.0] @="Car Server Type Lib" [HKEY_CLASSES_ROOT\TypeLib{E5C0EE8F-8806-4FE3-BC0E-3A56CFB38BEE}\1.0\0] [HKEY_CLASSES_ROOT\TypeLib{E5C0EE8F-8806-4FE3-BC0E-3A56CFB38BEE}\1.0\0\win32] @="D:\com\Project01.tlb" [HKEY_CLASSES_ROOT\TypeLib{E5C0EE8F-8806-4FE3-BC0E-3A56CFB38BEE}\1.0\FLAGS] @="0" [HKEY_LOCAL_MACHINE\SOFTWARE\Classes\TypeLib{E5C0EE8F-8806-4FE3-BC0E-3A56CFB38BEE}\1.0\0\win32] @="C:\Windows\System32\msdatsrc.tlb" (5) I try to add reference to the COM by click the Add Reference in the C# project. (6) In the COM tab, I saw my "Car Server Type Lib", it's ok until now. I try to use the Object Browser to browse my COM lib, but the Visual Studio said "the following components could not be browsed", and I noticed that there's no new reference added to the list in the C# project Reference. I can use the tlbimp.exe to generate a interop.CarCom.dll, and then use the COM through this interop dll, but I want this interop assembly to be generated automatically when I just add reference to the COM. Could someone tell me what's wrong? Many thanks.

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  • EF4 and multiple abstract levels

    - by Cedric
    I need to use inheritance with EF4 and the TPH model created from DB. I created a new projet to test simples classes. There is my class model: There is my table in SQL SERVER 2008 : VEHICLE ID : int PK Owner : varchar(50) Consumption : float FirstCirculationDate : date Type : varchar(50) Discriminator : varchar(10) I added a condition in my EDMX on the Discriminator field to differentiate the Scooter, Car, Motorbike and Bike entities. MotorizedVehicle and Vehicle are Abstract. But when I compile, this error appears : Error 3032: Problem in mapping fragments starting at lines 78, 85:EntityTypes EF4InheritanceModel.Scooter, EF4InheritanceModel.Motorbike, EF4InheritanceModel.Car, EF4InheritanceModel.Bike are being mapped to the same rows in table Vehicle. Mapping conditions can be used to distinguish the rows that these types are mapped to. Edit : To Ladislav : I try it and error change to become it for all of my entities : Error 3034: Problem in mapping fragments starting at lines 72, 86:An entity is mapped to different rows within the same table. Ensure these two mapping fragments do not map two groups of entities with overlapping keys to two distinct groups of rows. To Henk (with Ladislay suggestion) : There are all of mappings details : What's wrong ? Thanks

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  • C# naming convention for enum and matching property

    - by Serge - appTranslator
    Hi All, I often find myself implementing a class maintaining some kind of own status property as an enum: I have a Status enum and ONE Status property of Status type. How should I solve this name conflict? public class Car { public enum Status { Off, Starting, Moving }; Status status = Status.Off; public Status Status // <===== Won't compile ===== { get { return status; } set { status = value; DoSomething(); } } } If the Status enum were common to different types, I'd put it outside the class and the problem would be solved. But Status applies to Car only hence it doesn't make sense to declare the enum outside the class. What naming convention do you use in this case? NB: This question was partially debated in comments of an answer of this question. Since it wasn't the main question, it didn't get much visibility. EDIT: Filip Ekberg suggests an IMO excellent workaround for the specific case of 'Status'. Yet I'd be interesting to read about solutions where the name of the enum/property is different, as in Michael Prewecki's answer. EDIT2 (May 2010): My favorite solution is to pluralize the enum type name, as suggested by Chris S. According to MS guidelines, this should be used for flag enums only. But I've come to like it more and more. I now use it for regular enums as well.

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  • Using clases in PHP to store function

    - by Artur
    Hello! I need some advise on my PHP code organisation. I need classes where I can store different functions, and I need access to those classes in different parts of my project. Making an object of this classes each time is too sadly, so I've found a two ways have to solve it. First is to use static methods, like class car { public static $wheels_count = 4; public static function change_wheels_count($new_count) { car::$wheels_count = $new_count; } } Second is to use singleton pattern: class Example { // Hold an instance of the class private static $instance; // The singleton method public static function singleton() { if (!isset(self::$instance)) { $c = __CLASS__; self::$instance = new $c; } return self::$instance; } } But author of the article about singletons said, that if I have too much singletons in my code I should reconstruct it. But I need a lot of such classes. Can anybody explain prons and cons of each way? Which is mostly used? Are there more beautiful ways?

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  • How to read XML using XPath in Java

    - by kaibuki
    Hi guys, I want to read XML data using XPath in Java, so for the information I have gathered I am not able to parse XML according to my requirement. here is what I want to do: Get XML file from online via its URL, then use XPath to parse it, I want to create two methods in it. One is in which I enter a specific node attribute id, and I get all the child nodes as result, and second is suppose I just want to get a specific child node value only <?xml version="1.0"?><howto> <topic name="Java"> <url>http://www.rgagnonjavahowto.htm</url> <car>taxi</car> </topic> <topic ame="PowerBuilder"> <url>http://www.rgagnon/pbhowto.htm</url> <url>http://www.rgagnon/pbhowtonew.htm</url> </topic> <topic name="Javascript"> <url>http://www.rgagnon/jshowto.htm</url> </topic> <topic name="VBScript"> <url>http://www.rgagnon/vbshowto.htm</url> </topic></howto> In above example I want to read all the elements if I search via @name and also one function in which I just want the url from @name 'Javascript' only return one node element. I hope I cleared my question :) Thanks. Kai

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  • Restart list numbering in word for each new list created

    - by Feena
    Hi, I am exporting content from a jsp page into MS Word using javascript. When the user is in Word there is a table with 10 rows and 2 columns, A & B. The user creates an ordered list in row 1, column A like this: 1 dog 2 cat 3 mouse if the user then creates a second list in row 1 column B is turns out like this: 4 car 5 truck 6 bike instead of: 1 car 2 truck 3 bike Word is set up to continue the numbering in lists from prior lists automatically. I know this can be reset easily but the users dont want to have to do this. They want the numbering of any potential lists created to restarted at 1. when the document is exported into Word and opened in front of them. So this must be set up in the javasctipt code or using a style or something prior to getting into Word. This is what I dont know how to do. Any help is much appreciated. Thanks, Feena.

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  • Advantages of Using Linux as primary developer desktop

    - by Nick N
    I want to get some input on some of the advantages of why developers should and need to use Linux as their primary development desktop on a daily basic as opposed to using Windows. This is particulary helpful when your Dev, QA, and Production environments are Linux. The current analogy that I keep coming back to is. If I build my demo car as a Ford Escort, but my project car is a Ford Mustang, it doesn't make sense at all. I'm currently at an IT department that allows dual boot with Windows and Linux, but some run Linux while the vast majority use Windows. Here's several advantages that I've came up with since using Linux as a primary desktop. Same Exact operating system as Dev, QA, and Production Same Scripts (.sh) instead of maintaining (.bat and *.sh). Somewhat mitigated by using cygwin, but still a bit different. Team learns simple commands such as: cd, ls, cat, top Team learns Advanced commands like: pkill, pgrep, chmod, su, sudo, ssh, scp Full access to installs typically for Linux, such as RPM, DEB installs just like the target environments. The list could go on and on, but I want to get some feedback of anything that I may have missed, or even any disadvantages (of course there are some). To me it makes sense to migrate an entire team over to using Linux, and using Virtual Box, running Windows XP VM's to test functional items that 95% of most of the world uses. This is similar but a little different thread going on here as well. link text

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  • Create associative multi-dimensional array

    - by Mike
    Hi, I have 3 variables, each one holding a different information and send values from a text file dynamicaly. I want to put them in a Associative multi-dimensional array. let's say : $product sends car, truck, train, etc. $price sends 1000, 3000, 1500, etc. $year sends 1997, 1980, 2008, etc. How to create a function which generates an array as follow, when i execute print_r(myarray): Array ( [0] => Array ( [product] => car [price] => 1000 [year] => 1997 ) [1] => Array ( [product] => truck [price] => 3000 [year] => 1980 ) [2] => Array ( [product] => train [price] => 1500 [year] => 2008 )) and so on. Does anyone know how to do this? Many thanks, Mike,

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  • array_splice() - Numerical Offsets of Associative Arrays

    - by Alix Axel
    I'm trying to do something but I can't find any solution, I'm also having some trouble putting it into works so here is a sample code, maybe it'll be enough to demonstrate what I'm aiming for: $input = array ( 'who' => 'me', 'what' => 'car', 'more' => 'car', 'when' => 'today', ); Now, I want to use array_splice() to remove (and return) one element from the array: $spliced = key(array_splice($input, 2, 1)); // I'm only interested in the key... The above will remove and return 1 element (third argument) from $input (first argument), at offset 2 (second argument), so $spliced will hold the value more. I'll be iterating over $input with a foreach loop, I know the key to be spliced but the problem is I don't know its numerical offset and since array_splice only accepts integers I don't know what to do. A very dull example: $result = array(); foreach ($input as $key => $value) { if ($key == 'more') { // Remove the index "more" from $input and add it to $result. $result[] = key(array_splice($input, 2 /* How do I know its 2? */, 1)); } } I first though of using array_search() but it's pointless since it'll return the associative index.... How do I determine the numerical offset of a associative index?

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