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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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• Where to start with game development?

  - by steven_desu

  I asked this earlier in this thread at stackoverflow.com. One of the early comments redirected me here to gamedev.stackexchange.com, so I'm reposting here. Searching for related questions I found a number of very specific questions, but I'm afraid the specifics have proved fruitless for me and after 4 hours on Google I'm no closer than I started, so I felt reaching out to a community might be in order. First, my goal: I've never made a game before, although I've muddled over the possibility several times. I decided to finally sit down and start learning how to code games, use game engines, etc. All so that one day (hopefully soon) I'll be able to make functional (albeit simple) games. I can start adding complexity later, for now I'd be glad to have a keyboard-controlled camera moving in a 3D world with no interaction beyond that. My background: I've worked in SEVERAL programming languages ranging from PHP to C++ to Java to ASM. I'm not afraid of any challenges that come with learning the new syntax or limitations inherent in a new language. All of my past programming experience, however, has been strictly non-graphical and usually with little or extremely simple interaction during execution. I've created extensive and brilliant algorithms for solving logical and mathematical problems as well as graphing problems. However in every case input was either defined in a file, passed form an HTML form, or typed into the console. Real-time interaction with the user is something with which I have no experience. My question: Where should I start in trying to make games? Better yet- where should I start in trying to create a keyboard-navigable 3D environment? In searching online I've found several resources linking to game engines, graphics engines, and physics engines. Here's a brief summary of my experiences with a few engines I tried: Unreal SDK: The tutorial videos assume that you already have in-depth knowledge of 3D modeling, graphics engines, animations, etc. The "Getting Started" page offers no formal explanation of game development but jumps into how Unreal can streamline processes it assumes you're already familiar with. After downloading the SDK and launching it to see if the tools were as intuitive as they claimed, I was greeted with about 60 buttons and a blank void for my 3D modeling. Clicking on "add volume" (to attempt to add a basic cube) I was met with a menu of 30 options. Panicking, I closed the editor. Crystal Space: The website seemed rather informative, explaining that Crystal Space was just for graphics and the companion software, CEL, provided entity logic for making games. A demo game was provided, which was built using "CELStart", their simple tool for people with no knowledge of game programming. I launched the game to see what I might look forward to creating. It froze several times, the menus were buggy, there were thousands of graphical glitches, enemies didn't respond to damage, and when I closed the game it locked up. Gave up on that engine. IrrLicht: The tutorial assumes I have Visual Studio 6.0 (I have Visual Studio 2010). Following their instructions I was unable to properly import the library into Visual Studio and unable to call any of the functions that they kept using. Manually copying header files, class files, and DLLs into my project's folder - the project failed to properly compile. Clearly I'm not off to a good start and I'm going in circles. Can someone point me in the right direction? Should I start by downloading a program like Blender and learning 3D modeling, or should I be learning how to use a graphics engine? Should I look for an all-inclusive game engine, or is it better to try and code my own game logic? If anyone has actually made their own games, I would prefer to hear how they got their start. Also- taking classes at my school is not an option. Nothing is offered.

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• Where to start with game development?

  - by steven_desu

  Searching for related questions I found a number of very specific questions, but I'm afraid the specifics have proved fruitless for me and after 4 hours on Google I'm no closer than I started, so I felt reaching out to a community might be in order. First, my goal: I've never made a game before, although I've muddled over the possibility several times. I decided to finally sit down and start learning how to code games, use game engines, etc. All so that one day (hopefully soon) I'll be able to make functional (albeit simple) games. I can start adding complexity later, for now I'd be glad to have a keyboard-controlled camera moving in a 3D world with no interaction beyond that. My background: I've worked in SEVERAL programming languages ranging from PHP to C++ to Java to ASM. I'm not afraid of any challenges that come with learning the new syntax or limitations inherent in a new language. All of my past programming experience, however, has been strictly non-graphical and usually with little or extremely simple interaction during execution. I've created extensive and brilliant algorithms for solving logical and mathematical problems. However in every case input was either defined in a file, passed form an HTML form, or typed into the console. Real-time interaction with the user is something with which I have no experience. My question: Where should I start in trying to make games? Better yet- where should I start in trying to create a keyboard-navigable 3D environment? In searching online I've found several resources linking to game engines, graphics engines, and physics engines. Here's a brief summary of my experiences with a few engines I tried: Unreal SDK: The tutorial videos assume that you already have in-depth knowledge of 3D modeling, graphics engines, animations, etc. The "Getting Started" page offers no formal explanation of game development but jumps into how Unreal can streamline processes it assumes you're already familiar with. After downloading the SDK and launching it to see if the tools were as intuitive as they claimed, I was greeted with about 60 buttons and a blank void for my 3D modeling. Clicking on "add volume" (to attempt to add a basic cube) I was met with a menu of 30 options. Panicking, I closed the editor. Crystal Space: The website seemed rather informative, explaining that Crystal Space was just for graphics and the companion software, CEL, provided entity logic for making games. A demo game was provided, which was built using "CELStart", their simple tool for people with no knowledge of game programming. I launched the game to see what I might look forward to creating. It froze several times, the menus were buggy, there were thousands of graphical glitches, enemies didn't respond to damage, and when I closed the game it locked up. Gave up on that engine. IrrLicht: The tutorial assumes I have Visual Studio 6.0 (I have Visual Studio 2010). Following their instructions I was unable to properly import the library into Visual Studio and unable to call any of the functions that they kept using. Manually copying header files, class files, and DLLs into my project's folder - the project failed to properly compile. Clearly I'm not off to a good start and I'm going in circles. Can someone point me in the right direction? Should I start by downloading a program like Blender and learning 3D modeling, or should I be learning how to use a graphics engine? Should I look for an all-inclusive game engine, or is it better to try and code my own game logic? If anyone has actually made their own games, I would prefer to hear how they got their start. Also- taking classes at my school is not an option. Nothing is offered.

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• C# 5 Async, Part 2: Asynchrony Today

  - by Reed

  The .NET Framework has always supported asynchronous operations.  However, different mechanisms for supporting exist throughout the framework.  While there are at least three separate asynchronous patterns used through the framework, only the latest is directly usable with the new Visual Studio Async CTP.  Before delving into details on the new features, I will talk about existing asynchronous code, and demonstrate how to adapt it for use with the new pattern. The first asynchronous pattern used in the .NET framework was the Asynchronous Programming Model (APM).  This pattern was based around callbacks.  A method is used to start the operation.  It typically is named as BeginSomeOperation.  This method is passed a callback defined as an AsyncCallback, and returns an object that implements IAsyncResult.  Later, the IAsyncResult is used in a call to a method named EndSomeOperation, which blocks until completion and returns the value normally directly returned from the synchronous version of the operation.  Often, the EndSomeOperation call would be called from the callback function passed, which allows you to write code that never blocks. While this pattern works perfectly to prevent blocking, it can make quite confusing code, and be difficult to implement.  For example, the sample code provided for FileStream’s BeginRead/EndRead methods is not simple to understand.  In addition, implementing your own asynchronous methods requires creating an entire class just to implement the IAsyncResult. Given the complexity of the APM, other options have been introduced in later versions of the framework.  The next major pattern introduced was the Event-based Asynchronous Pattern (EAP).  This provides a simpler pattern for asynchronous operations.  It works by providing a method typically named SomeOperationAsync, which signals its completion via an event typically named SomeOperationCompleted. The EAP provides a simpler model for asynchronous programming.  It is much easier to understand and use, and far simpler to implement.  Instead of requiring a custom class and callbacks, the standard event mechanism in C# is used directly.  For example, the WebClient class uses this extensively.  A method is used, such as DownloadDataAsync, and the results are returned via the DownloadDataCompleted event. While the EAP is far simpler to understand and use than the APM, it is still not ideal.  By separating your code into method calls and event handlers, the logic of your program gets more complex.  It also typically loses the ability to block until the result is received, which is often useful.  Blocking often requires writing the code to block by hand, which is error prone and adds complexity. As a result, .NET 4 introduced a third major pattern for asynchronous programming.  The Task<T> class introduced a new, simpler concept for asynchrony.  Task and Task<T> effectively represent an operation that will complete at some point in the future.  This is a perfect model for thinking about asynchronous code, and is the preferred model for all new code going forward.  Task and Task<T> provide all of the advantages of both the APM and the EAP models – you have the ability to block on results (via Task.Wait() or Task<T>.Result), and you can stay completely asynchronous via the use of Task Continuations.  In addition, the Task class provides a new model for task composition and error and cancelation handling.  This is a far superior option to the previous asynchronous patterns. The Visual Studio Async CTP extends the Task based asynchronous model, allowing it to be used in a much simpler manner.  However, it requires the use of Task and Task<T> for all operations.

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• Is inconsistent formatting a sign of a sloppy programmer?

  - by dreza

  I understand that everyone has their own style of programming and that you should be able to read other people's styles and accept it for what it is. However, would one be considered a sloppy programmer if one's style of coding was inconsistent across whatever standard they were working against? Some example of inconsistencies might be: Sometimes naming private variables with _ and sometimes not Sometimes having varying indentations within code blocks Not aligning braces up i.e. same column if using start using new line style Spacing not always consistent around operators i.e. p=p+1, p+=1 vs other times p =p+1 or p = p + 1 etc Is this even something that as a programmer I should be concerned with addressing? Or is it such a minor nit picking thing that at the end of the day I should just not worry about it and worry about what the end user sees and whether the code works rather than how it looks while working? Is it sloppy programming or just over obsessive nit picking? EDIT: After some excellent comments I realized I may have left out some information in my question. This question came about after reviewing another colleagues code check-in and noticing some of these things and then realizing that I've seen these kind of in-consistencies in previous check-ins. It then got me thinking about my code and whether I do the same things and noticed that I typically don't etc I'm not suggesting his technique is either bad or good in this question or whether his way of doing things is right or wrong. EDIT: To answer some queries to some more good feed back. The specific instance this review occurred in was using Visual Studio 2010 and programming in c# so I don't think the editor would cause any issues. In fact it should only help I would hope. Sorry if I left that piece of info out and it effects any current answers. I was trying to be a bit more generic in understanding if this would be considered sloppy etc. And to add an even more specific example of a code piece I saw during reading of the check-in: foreach(var block in Blocks) { // .. some other code in here foreach(var movement in movements) { movement.Moved.Zero(); } // the un-formatted brace } Such a minor thing I know, but many small things add up(???), and I did have to double glance at the code at the time to see where everything lined up I guess. Please note this code was formatted appropriately before this check-in. EDIT: After reading some great answers and varying thoughts, the summary I've taken from this was. It's not necessarily a sign of a sloppy programmer however as programmers we have a duty (to ourselves and other programmers) to make the code as readable as possible to assist in further ongoing development. However it can hint at inadequacies which is something that is only possible to review on a case by case (person by person) basis. There are many reasons why this might occur. They should be taken in context and worked through with the person/people involved if reasonable. We have a duty to try and help all programmers become better programmers! In the good old days when development was done using good old notepad (or other simple text editing tool) this occurred much more frequently. However we have the assistance of modern IDE's now so although we shouldn't necessarily become OTT about this, it should still probably be addressed to some degree. We as programmers vary in our standards, styles and approaches to solutions. However it seems that in general we all take PRIDE in our work and as a trait it is something that can stand programmers apart. Making something to the best of our abilities both internal (code) and external (end user result) goes along way to giving us that big fat pat on the back that we may not go looking for but swells our heart with pride. And finally to quote CrazyEddie from his post below. Don't sweat the small stuff

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• Disneyland Inside Out on iPhone and Android

  - by Ryan Cain

  It's hard to believe October was the last time I was over here on my blog.  Ironically after getter the developer phone from Microsoft I have been knee deep in iPhone programming and for the past few weeks Android programming again.  This time I've spent all my non-working hours programming a fun project for my "other" website, Disneyland Inside Out.  Disneyland Inside Out, a vacation planning site for Disneyland in California, has been around in various forms since June 1996.  It has always been a place for me to explore new technologies and learn about some of the new trends on the web.  I recently migrated the site over to DotNetNuke and have been building out custom modules for DNN.  I've also been hacking things together w/ the URLRewrite module in IIS 7.5 to provide strong SEO optimized URLs.  I can't say all that has really stuck within the DNN model of doing things, but it has worked pretty well. As part of my learning process, I spent most of the Fall bringing Disneyland Inside Out to the iPhone.  I will post more details on my development experiences later.  But this project gave me a really great opportunity to get a good feel for Objective-C development.  After 3 months I actually feel somewhat competent in the language and iPhone SDK, instead of just floundering around getting things to work.  The project also gave me a chance to play with some new frameworks on the iPhone and really dig into the Facebook SDK.  I also dug into some of the Gowalla REST api's as well.  We've been live with the app in iTunes for just about 10 days now, and have been sitting in the top 200 of free travel apps for the past few days.  You can get more info and the direct iTunes download link on our site: Disneyland Inside Out for iPhone Since launching the iPhone version I have gotten back into Android development, porting the Disneyland Inside Out app over to Android.  As I said in my first review of iPhone vs. Android, coming from a managed code background, Android is much easier to get going with.  I just about 3 weeks total I will have about 85 - 90% of the functionality up and running in the Android app, that took probably 1.5 - 2x's that time for iPhone.  That isn't a totally fair comparison as I am much more comfortable w/ Xcode and Objective-C today and can get some of the basic stuff done much faster than I could in the fall.  Though I'd say some of the hardest code to debug is still the null pointer issues on objects that were dealloc'd too early in Objective-C.  This isn't too bad with the NSZoombies enabled for synchronous code, but when you have a lot of async, which my app does, it can be hairy at times to track exactly what was causing the issue.   I will post more details later, as I am trying to wrap up a beta of the Android app today.  But in the meantime, if you have an iPhone, iPod Touch or iPad head on over to the site and take a look at my app.

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• Communication between state machines with hidden transitions

  - by slartibartfast

  The question emerged for me in embedded programming but I think it can be applied to quite a number of general networking situations e.g. when a communication partner fails. Assume we have an application logic (a program) running on a computer and a gadget connected to that computer via e.g. a serial interface like RS232. The gadget has a red/green/blue LED and a button which disables the LED. The LEDs color can be driven by software commands over the serial interface and the state (red/green/blue/off) is read back and causes a reaction in the application logic. Asynchronous behaviour of the application logic with regard to the LED color down to a certain delay (depending on the execution cycle of the application) is tolerated. What we essentially have is a resource (the LED) which can not be reserved and handled atomically by software because the (organic) user can at any time press the button to interfere/break the software attempt to switch the LED color. Stripping this example from its physical outfit I dare to say that we have two communicating state machines A (application logic) and G (gadget) where G executes state changes unbeknownst to A (and also the other way round, but this is not significant in our example) and only A can be modified at a reasonable price. A needs to see the reaction and state of G in one piece of information which may be (slightly) outdated but not inconsistent with respect to the short time window when this information was generated on the side of G. What I am looking for is a concise method to handle such a situation in embedded software (i.e. no layer/framework like CORBA etc. available). A programming technique which is able to map the complete behaviour of both participants on classical interfaces of a classical programming language (C in this case). To complicate matters (or rather, to generalize), a simple high frequency communication cycle of A to G and back (IOW: A is rapidly polling G) is out of focus because of technical restrictions (delay of serial com, A not always active, etc.). What I currently see as a general solution is: the application logic A as one thread of execution an adapter object (proxy) PG (presenting G inside the computer), together with the serial driver as another thread a communication object between the two (A and PG) which is transactionally safe to exchange The two execution contexts (threads) on the computer may be multi-core or just interrupt driven or tasks in an RTOS. The com object contains the following data: suspected state (written by A): effectively a member of the power set of states in G (in our case: red, green, blue, off, red_or_green, red_or_blue, red_or_off...etc.) command data (written by A): test_if_off, switch_to_red, switch_to_green, switch_to_blue operation status (written by PG): operation_pending, success, wrong_state, link_broken new state (written by PG): red, green, blue, off The idea of the com object is that A writes whichever (set of) state it thinks G is in, together with a command. (Example: suspected state="red_or_green", command: "switch_to_blue") Notice that the commands issued by A will not work if the user has switched off the LED and A needs to know this. PG will pick up such a com object and try to send the command to G, receive its answer (or a timeout) and set the operation status and new state accordingly. A will take back the oject once it is no longer at operation_pending and can react to the outcome. The com object could be separated of course (into two objects, one for each direction) but I think it is convenient in nearly all instances to have the command close to the result. I would like to have major flaws pointed out or hear an entirely different view on such a situation.

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• Wireless doesn't work on a Broadcom BCM4312

  - by Boderick

  As stated, I've just upgraded to 12.04 and my Dell Inspiron 1545 isn't recognising its wireless card and I was wondering if anybody could help? Edit: Okay, so I found the wireless card by using lspci -vvv and it returned this: 0c:00.0 Network controller: Broadcom Corporation BCM4312 802.11b/g LP-PHY (rev 01) Subsystem: Dell Wireless 1397 WLAN Mini-Card Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx- Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast TAbort- SERR- Kernel modules: ssb lsmod Module Size Used by dm_crypt 22528 0 joydev 17393 0 dell_wmi 12601 0 sparse_keymap 13658 1 dell_wmi dell_laptop 13671 0 dcdbas 14098 1 dell_laptop psmouse 72919 0 uvcvideo 67203 0 serio_raw 13027 0 videodev 86588 1 uvcvideo snd_hda_codec_idt 60251 1 mac_hid 13077 0 snd_hda_intel 32765 5 snd_hda_codec 109562 2 snd_hda_codec_idt,snd_hda_intel snd_hwdep 13276 1 snd_hda_codec parport_pc 32114 0 rfcomm 38139 0 bnep 17830 2 ppdev 12849 0 snd_pcm 80845 3 snd_hda_intel,snd_hda_codec bluetooth 158438 10 rfcomm,bnep snd_seq_midi 13132 0 snd_rawmidi 25424 1 snd_seq_midi snd_seq_midi_event 14475 1 snd_seq_midi snd_seq 51567 2 snd_seq_midi,snd_seq_midi_event snd_timer 28931 2 snd_pcm,snd_seq snd_seq_device 14172 3 snd_seq_midi,snd_rawmidi,snd_seq binfmt_misc 17292 1 snd 62064 18 snd_hda_codec_idt,snd_hda_intel,snd_hda_codec,snd_hwdep,snd_pcm,snd_rawmidi,snd_seq,snd_timer,snd_seq_device soundcore 14635 1 snd snd_page_alloc 14108 2 snd_hda_intel,snd_pcm lp 17455 0 parport 40930 3 parport_pc,ppdev,lp sky2 53628 0 ums_realtek 17920 0 uas 17699 0 i915 414603 3 wmi 18744 1 dell_wmi drm_kms_helper 45466 1 i915 drm 197692 4 i915,drm_kms_helper i2c_algo_bit 13199 1 i915 video 19068 1 i915 usb_storage 39646 1 ums_realtek ifconfig -a eth0 Link encap:Ethernet HWaddr 00:23:ae:24:71:45 inet addr:192.168.1.158 Bcast:192.168.1.255 Mask:255.255.255.0 inet6 addr: fe80::223:aeff:fe24:7145/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:14340 errors:0 dropped:0 overruns:0 frame:0 TX packets:10191 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:15403754 (15.4 MB) TX bytes:1262570 (1.2 MB) Interrupt:18 ham0 Link encap:Ethernet HWaddr 7a:79:05:2d:b0:f7 inet addr:5.45.176.247 Bcast:5.255.255.255 Mask:255.0.0.0 inet6 addr: fe80::7879:5ff:fe2d:b0f7/64 Scope:Link inet6 addr: 2620:9b::52d:b0f7/96 Scope:Global UP BROADCAST RUNNING MULTICAST MTU:1404 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:179 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:500 RX bytes:0 (0.0 B) TX bytes:27480 (27.4 KB) lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:433 errors:0 dropped:0 overruns:0 frame:0 TX packets:433 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:60051 (60.0 KB) TX bytes:60051 (60.0 KB) iwconfig lo no wireless extensions. ham0 no wireless extensions. eth0 no wireless extensions. the results for sudo lshw -class network *-network description: Wireless interface product: BCM4312 802.11b/g LP-PHY vendor: Broadcom Corporation physical id: 0 bus info: pci@0000:0c:00.0 logical name: eth1 version: 01 serial: 00:22:5f:77:1f:e6 width: 64 bits clock: 33MHz capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless configuration: broadcast=yes driver=wl0 driverversion=5.100.82.38 latency=0 multicast=yes wireless=IEEE 802.11bg resources: irq:17 memory:f69fc000-f69fffff *-network description: Ethernet interface product: 88E8040 PCI-E Fast Ethernet Controller vendor: Marvell Technology Group Ltd. physical id: 0 bus info: pci@0000:09:00.0 logical name: eth0 version: 13 serial: 00:23:ae:24:71:45 size: 100Mbit/s capacity: 100Mbit/s width: 64 bits clock: 33MHz capabilities: pm msi pciexpress bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd autonegotiation configuration: autonegotiation=on broadcast=yes driver=sky2 driverversion=1.30 duplex=full firmware=N/A ip=192.168.1.158 latency=0 link=yes multicast=yes port=twisted pair speed=100Mbit/s resources: irq:45 memory:f68fc000-f68fffff ioport:de00(size=256) *-network description: Ethernet interface physical id: 2 logical name: ham0 serial: 7a:79:05:2d:b0:f7 size: 10Mbit/s capabilities: ethernet physical configuration: autonegotiation=off broadcast=yes driver=tun driverversion=1.6 duplex=full firmware=N/A ip=5.45.176.247 link=yes multicast=yes port=twisted pair speed=10Mbit/s and the results of rfkill list all 0: brcmwl-0: Wireless LAN Soft blocked: yes Hard blocked: yes 1: dell-wifi: Wireless LAN Soft blocked: yes Hard blocked: yes

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• Move on and look elsewhere, or confront the boss?

  - by Meister

  Background: I have my Associates in Applied Science (Comp/Info Tech) with a strong focus in programming, and I'm taking University classes to get my Bachelors. I was recently hired at a local company to be a Software Engineer I on a team of about 8, and I've been told they're looking to hire more. This is my first job, and I was offered what I feel to be an extremely generous starting salary ($30/hr essentially + benefits and yearly bonus). What got me hired was my passion for programming and a strong set of personal projects. Problem: I had no prior experience when I interviewed, so I didn't know exactly what to ask them about the company when I was hired. I've spotted a number of warning signs and annoyances since then, such as: Four developers when I started, with everyone talking about "Ben" or "Ryan" leaving. One engineer hired thirty days before me, one hired two weeks after me. Most of the department has been hiring a large number of people since I started. Extremely limited internet access. I understand the idea from an IT point of view, but not only is Facebook blocked, but so it Youtube, Twitter, and Pandora. I've also figured out that they block all access to non-DNS websites (http://xxx.xxx.xxx.xxx/) and strangely enough Miranda-IM. Low cubicles. Which is fine because I like my immediate coworkers, but they put the developers with the customer service, customer training, and QA department in a huge open room. Noise, noise, noise, and people stop to chitchat all day long. Headphones only go so far. Several emails have been sent out by my boss since I started telling us programmers to not talk about non-work-related-things like Video Games at our cubicles, despite us only spending maybe five minutes every few hours doing so. Further digging tells me that this is because someone keeps complaining that the programmers are "slacking off". People are looking over my shoulder all day. I was in the Freenode webchat to get help with a programming issue, and within minutes I had an email from my boss (to all the developers) telling us that we should NOT be connected to any outside chat servers at work. Version control system from 2005 that we must access with IE and keep the Java 1.4 JRE installed to be able to use. I accidentally updated to Java 6 one day and spent the next two days fighting with my PC to undo this "problem". No source control, no comments on anything, no standards, no code review, no unit testing, no common sense. I literally found a problem in how they handle string resource translations that stems from the simple fact that they don't trim excess white spaces, leading to developers doing: getResource("Date: ") instead of: getResource("Date") + ": ", and I was told to just add the excess white spaces back to the database instead of dealing with the issue directly. Some of these things I'd like to try to understand, but I like having IRC open to talk in a few different rooms during the day and keep in touch with friends/family over IM. They don't break my concentration (not NEARLY as much as the lady from QA stopping by to talk about her son), but because people are looking over my shoulder all day as they walk by they complain when they see something that's not "programmer-looking work". I've been told by my boss and QA that I do good, fast work. I should be judged on my work output and quality, not what I have up on my screen for the five seconds you're walking by So, my question is, even though I'm just barely at my 90 days: How do you decide to move on from a job and looking elsewhere, or when you should start working with your boss to resolve these issues? Is it even possible to get the boss to work with me in many of these things? This is the only place I heard back from even though I sent out several resume's a day for several months, and this place does pay well for putting up with their many flaws, but I'm just starting to get so miserable working here already. Should I just put up with it?

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• "The connection has timed out" - Please help!

  - by gon

  I recently installed a fresh Ubuntu 12.04 LTS on a desktop, and the installation itself was successful (other than 'grub rescue' issue that I encountered but fixed) but this connection problem is really giving me a headache. Symptoms: 1. When I open the FireFox browser and try to connect to a website, it just hangs for a while saying "Connecting..." but eventually loads an error page "The connection has timed out". 2. It's not a browser problem (and I tried setting ipv6 thing to "true" at about:config) because running "sudo apt-get install [some-random-package]" at terminal fails ("E: Unable to locate package [package]") too. All other operations that need internet access are not working. 3. I certainly see a wired network (called "eth1") at the Network Manager, and it says "Connection Established" after disconnecting and then connecting again. I have tried almost everything that could be found from google search results still no luck. Their problems slightly differ from mine or the solutions just don't work. By the way it didn't have internet access when installing Ubuntu 12.04. (I ignored the message that I need internet to install Ubuntu) Could this be a problem? I'm sorry I don't remember if internet worked or not on the previous version of Ubuntu. :( I would really appreciate your help... I don't even know what more to do if this fails too.. Thanks!! Thanks for your comment. Here is the result of ifconfig: eth0 Link encap:Ethernet HWaddr 78:ac:c0:3d:b2:b9 inet addr:10.10.65.185 Bcast:10.10.65.255 Mask:255.255.255.0 inet6 addr: fe80::7aac:c0ff:fe3d:b2b9/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:3907 errors:0 dropped:0 overruns:0 frame:0 TX packets:771 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:393118 (393.1 KB) TX bytes:73472 (73.4 KB) Interrupt:16 eth1 Link encap:Ethernet HWaddr 78:ac:c0:3d:b2:b8 UP BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:0 (0.0 B) Interrupt:17 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:4 errors:0 dropped:0 overruns:0 frame:0 TX packets:4 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:204 (204.0 B) TX bytes:204 (204.0 B) route -n: Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 10.10.65.1 0.0.0.0 UG 0 0 0 eth0 10.10.65.0 0.0.0.0 255.255.255.0 U 1 0 0 eth0 169.254.0.0 0.0.0.0 255.255.0.0 U 1000 0 0 eth0 /etc/resolv.conf: # Dynamic resolv.conf(5) file for glibc resolver(3) generated by resolvconf(8) # DO NOT EDIT THIS FILE BY HAND -- YOUR CHANGES WILL BE OVERWRITTEN nameserver 8.8.8.8 nameserver 8.8.4.4 nameserver 10.81.1.8 nameserver 10.1.2.10 nameserver 127.0.0.1 search yamatake.local /etc/network/interfaces: auto lo iface lo inet loopback #auto eth0 #iface eth0 inet dhcp #auto eth1 #iface eth1 inet dhcp And I'll also include the result of 'sudo lshw -C network' in case it might help: *-network description: Ethernet interface product: NetXtreme BCM5764M Gigabit Ethernet PCIe vendor: Broadcom Corporation physical id: 0 bus info: pci@0000:02:00.0 logical name: eth0 version: 10 serial: 78:ac:c0:3d:b2:b9 size: 100Mbit/s capacity: 1Gbit/s width: 64 bits clock: 33MHz capabilities: pm vpd msi pciexpress bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation configuration: autonegotiation=on broadcast=yes driver=tg3 driverversion=3.121 duplex=full firmware=5764m-v3.35 ip=10.10.65.185 latency=0 link=yes multicast=yes port=twisted pair speed=100Mbit/s resources: irq:93 memory:fc000000-fc00ffff *-network description: Ethernet interface product: NetXtreme BCM5764M Gigabit Ethernet PCIe vendor: Broadcom Corporation physical id: 0 bus info: pci@0000:01:00.0 logical name: eth1 version: 10 serial: 78:ac:c0:3d:b2:b8 size: 100Mbit/s capacity: 1Gbit/s width: 64 bits clock: 33MHz capabilities: pm vpd msi pciexpress bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation configuration: autonegotiation=on broadcast=yes driver=tg3 driverversion=3.121 duplex=full firmware=5764m-v3.35 latency=0 link=no multicast=yes port=twisted pair speed=100Mbit/s resources: irq:94 memory:fb000000-fb00ffff

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• Software and/(x)or Hardware Projects for Pre-School Kids

  - by haylem

  I offered to participate at my kid's pre-school for various activities (yes, I'm crazy like that), and one of them is to help them discover extra-curricular (big word for a pre-school, but by lack of a better one... :)) hobbies, which may or may not relate to a professional activity. At first I thought that it wouldn't be really easy to have pre-schoolers relate to programming or the internal workings of a computer system in general (and I'm more used to teaching middle-school to university-level students), but then I thought there must be a way. So I'm trying to figure out ways to introduce very young kids (3yo) to computer systems in a fun and preferably educational way. Of course, I don't expect them to start smashing the stack for fun and profit right away (or at least not voluntarily, though I could use the occasion for some toddler tests...), but I'm confident there must be ways to get them interested in both: using the systems, becoming curious about understanding what they do, interacting with the systems to modify them. I guess this setting is not really relevant after all, it's pretty much the same as if you were aiming to achieve the same for your own kids at home. Ideas Considering we're talking 3yo pre-schoolers here, and that at this age some kids are already quite confident using a mouse (some even a keyboard, if not for typing, at least to press some buttons they've come to associate with actions) while others have not yet had any interaction with computers of any kind, it needs to be: rather basic, demonstrated and played with in less then 5 or 10 minutes, doable in in groups or alone, scalable and extendable in complexity to accommodate their varying abilities. The obvious options are: basic smallish games to play with, interactive systems like LOGO, Kojo, Squeak and clones (possibly even simpler than that), or thngs like Lego Systems. I guess it can be a thing to reflect on both at the software and the hardware levels: it could be done with a desktop or laptop machine, a tablet, a smartphone (or a crap-phone, for that matter, as long as you can modify it), or even get down to building something from scratch (Raspberry Pi and Arduino being popular options at the moment). I can probably be in the form of games, funny visualizations (which are pretty much games) w/ Prototype, virtual worlds to explore. I also thought on the moment (and I hope this won't offend anyone) that some approaches to teaching pets could work (reward systems, haptic feedback and such things could quickly point a kid in the right direction to understanding how things work, in a similar fashion - I'm not suggesting to shock the kids!). Hmm, Is There an Actual Question in There? What type of systems do you think might be a good fit, both in terms of hardware and software? Do you have seen such systems, or have anything in mind to work on? Are you aware of some research in this domain, with tangible results? Any input is welcome. It's not that I don't see options: there are tons, but I have a harder time pinpointing a more concrete and definite type of project/activity, so I figure some have valuable ideas or existing ones. Note: I am not advocating that every kid should learn to program, be interested in computer systems, or that all of them in a class would even care enough to follow such an introduction with more than a blank stare. I don't buy into the "everybody would benefit from learning to program" thing. Wouldn't hurt, but not necessary in any way. But if I can walk out of there with a few of them having smiled using the thing (or heck, cried because others took them away from them), that'd be good enough. Related Questions I've seen and that seem to complement what I'm looking for, but not exactly for the same age groups or with the same goals: Teaching Programming to Kids Recommendations for teaching kids math concepts & skills for programming?

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• What do you need to know to be a world-class master software developer? [closed]

  - by glitch

  I wanted to bring up this question to you folks and see what you think, hopefully advise me on the matter: let's say you had 30 years of learning and practicing software development in front of you, how would you dedicate your time so that you'd get the biggest bang for your buck. What would you both learn and work on to be a world-class software developer that would make a large impact on the industry and leave behind a legacy? I think that most great developers end up being both broad generalists and specialists in one-two areas of interest. I'm thinking Bill Joy, John Carmack, Linus Torvalds, K&R and so on. I'm thinking that perhaps one approach would be to break things down by categories and establish a base minimum of "software development" greatness. I'm thinking: Operating Systems: completely internalize the core concepts of OS, perhaps gain a lot of familiarity with an OSS one such as Linux. Anything from memory management to device drivers has to be complete second nature. Programming Languages: this is one of those topics that imho has to be fully grokked even if it might take many years. I don't think there's quite anything like going through the process of developing your own compiler, understanding language design trade-offs and so on. Programming Language Pragmatics is one of my favorite books actually, I think you want to have that internalized back to back, and that's just the start. You could go significantly deeper, but I think it's time well spent, because it's such a crucial building block. As a subset of that, you want to really understand the different programming paradigms out there. Imperative, declarative, logic, functional and so on. Anything from assembly to LISP should be at the very least comfortable to write in. Contexts: I believe one should have experience working in different contexts to truly be able to appreciate the trade-offs that are being made every day. Embedded, web development, mobile development, UX development, distributed, cloud computing and so on. Hardware: I'm somewhat conflicted about this one. I think you want some understanding of computer architecture at a low level, but I feel like the concepts that will truly matter will be slightly higher level, such as CPU caching / memory hierarchy, ILP, and so on. Networking: we live in a completely network-dependent era. Having a good understanding of the OSI model, knowing how the Web works, how HTTP works and so on is pretty much a pre-requisite these days. Distributed systems: once again, everything's distributed these days, it's getting progressively harder to ignore this reality. Slightly related, perhaps add solid understanding of how browsers work to that, since the world seems to be moving so much to interfacing with everything through a browser. Tools: Have a really broad toolset that you're familiar with, one that continuously expands throughout the years. Communication: I think being a great writer, effective communicator and a phenomenal team player is pretty much a prerequisite for a lot of a software developer's greatness. It can't be overstated. Software engineering: understanding the process of building software, team dynamics, the requirements of the business-side, all the pitfalls. You want to deeply understand where what you're writing fits from the market perspective. The better you understand all of this, the more of your work will actually see the daylight. This is really just a starting list, I'm confident that there's a ton of other material that you need to master. As I mentioned, you most likely end up specializing in a bunch of these areas as you go along, but I was trying to come up with a baseline. Any thoughts, suggestions and words of wisdom from the grizzled veterans out there who would like to share their thoughts and experiences with this? I'd really love to know what you think!

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• Concurrent Affairs

  - by Tony Davis

  I once wrote an editorial, multi-core mania, on the conundrum of ever-increasing numbers of processor cores, but without the concurrent programming techniques to get anywhere near exploiting their performance potential. I came to the.controversial.conclusion that, while the problem loomed for all procedural languages, it was not a big issue for the vast majority of programmers. Two years later, I still think most programmers don't concern themselves overly with this issue, but I do think that's a bigger problem than I originally implied. Firstly, is the performance boost from writing code that can fully exploit all available cores worth the cost of the additional programming complexity? Right now, with quad-core processors that, at best, can make our programs four times faster, the answer is still no for many applications. But what happens in a few years, as the number of cores grows to 100 or even 1000? At this point, it becomes very hard to ignore the potential gains from exploiting concurrency. Possibly, I was optimistic to assume that, by the time we have 100-core processors, and most applications really needed to exploit them, some technology would be around to allow us to do so with relative ease. The ideal solution would be one that allows programmers to forget about the problem, in much the same way that garbage collection removed the need to worry too much about memory allocation. From all I can find on the topic, though, there is only a remote likelihood that we'll ever have a compiler that takes a program written in a single-threaded style and "auto-magically" converts it into an efficient, correct, multi-threaded program. At the same time, it seems clear that what is currently the most common solution, multi-threaded programming with shared memory, is unsustainable. As soon as a piece of state can be changed by a different thread of execution, the potential number of execution paths through your program grows exponentially with the number of threads. If you have two threads, each executing n instructions, then there are 2^n possible "interleavings" of those instructions. Of course, many of those interleavings will have identical behavior, but several won't. Not only does this make understanding how a program works an order of magnitude harder, but it will also result in irreproducible, non-deterministic, bugs. And of course, the problem will be many times worse when you have a hundred or a thousand threads. So what is the answer? All of the possible alternatives require a change in the way we write programs and, currently, seem to be plagued by performance issues. Software transactional memory (STM) applies the ideas of database transactions, and optimistic concurrency control, to memory. However, working out how to break down your program into sufficiently small transactions, so as to avoid contention issues, isn't easy. Another approach is concurrency with actors, where instead of having threads share memory, each thread runs in complete isolation, and communicates with others by passing messages. It simplifies concurrent programs but still has performance issues, if the threads need to operate on the same large piece of data. There are doubtless other possible solutions that I haven't mentioned, and I would love to know to what extent you, as a developer, are considering the problem of multi-core concurrency, what solution you currently favor, and why. Cheers, Tony.

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• RadGrid Custom Filter

  - by Aaron

  I'm trying to add a custom filter to my RadGrid. I have a column, vendNum, which I want to allow users to filter on multiple vendNums with a comma-separated list. Basically, I want the same functionality as an "in" statement in SQL (where vendNum in (X,Y,Z)). I followed the tutorial on this site and came up with the following code to place in my RadGrid1_ItemCommand event. protected void RadGrid1_ItemCommand(object source, GridCommandEventArgs e) { if (e.CommandName == RadGrid.FilterCommandName) { Pair filterPair = (Pair)e.CommandArgument; switch (filterPair.Second.ToString()) { case "vendNum": TextBox tbPattern = (e.Item as GridFilteringItem)["vendNum"].Controls[0] as TextBox; if (tbPattern.Text.Contains(",")) { string[] values = tbPattern.Text.Split(','); if (values.Length >= 2) { e.Canceled = true; StringBuilder newFilter = new StringBuilder(); for (int i = 0; i < values.Length; i++) { if (i == values.Length - 1) newFilter.Append("[vendNum] = " + values[i]); else newFilter.Append("[vendNum] = " + values[i] + " OR "); } if (RadGrid1.MasterTableView.FilterExpression == "") RadGrid1.MasterTableView.FilterExpression = newFilter.ToString(); else RadGrid1.MasterTableView.FilterExpression = "((" + RadGrid1.MasterTableView.FilterExpression + ") AND (" + newFilter.ToString() + "))"; RadGrid1.Rebind(); } } break; default: break; } } } Doing this, though, keeps giving me an error "Expression Expected" when I try to filter with a comma separated list. I'm still able to filter a single vendNum. My FilterExpression does come out as expected. The code is failing on the RadGrid1.Rebind() statement. Has anyone dealt with this before? Any help is greatly appreciated. Thanks, Aaron

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• Android: trouble updating to Android SDK Tools, revision 7.

  - by Arhimed

  Currently I have Android SDK 2.1 (+ tools revision 4). I'd like to upgrade to Android SDK 2.2. When I try to do it I'm informed I need to upgrade Android SDK Tools to revision 7 first. So I agree, the process starts and then I get an error: -= warning! =- A folder failed to be renamed or moved. On Windows this typically means that a program Is using that Folder (for example Windows Explorer or your anti-virus software.) Please momentarily deactivate your anti-virus software. Please also close any running programs that may be accessing the directory 'D:\Install\Programming\android-sdk-working-dir\android-sdk_r04-windows\android-sdk-windows\too!s'. When ready, press YES to try again. Downloading Android SDK Tools, revision 7 Installing Android SDK Tools, revision 7 Failed to rename directory D:\Install\Programming\android-sdk-working-dir\android-sdk_r04-windows\android-sdk-windows\tools to D:\Install\Programming\android-sdk-working-dir\android-sdk_r04-windows\android-sdk-windows\temp\ToolPackage.old01. I am aware of http/https and antivirus issues. So I disactivated my AV. I also closed any application that might hold a handle to the folder. Eclipse is also closed (I start the manager via command line). However I still get the same error. Looks like the only app that can hold a handle to the folder is the manager itself, because its starting directory is the one the error complains about ('\tools'). I am on Win XP Pro + SP3. Does anyone have an idea?

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• How can I validate the result in an ASP.NET MVC editor template?

  - by Morten Christiansen

  I have created an editor template for representing selecting from a dynamic dropdown list and it works as it should except for validation, which I have been unable to figure out. If the model has the [Required] attribute set, I want that to invalidate if the default option is selected. The view model object that must be represented as the dropdown list is Selector: public class Selector { public int SelectedId { get; set; } public IEnumerable<Pair<int, string>> Choices { get; private set; } public string DefaultValue { get; set; } public Selector() { //For binding the object on Post } public Selector(IEnumerable<Pair<int, string>> choices, string defaultValue) { DefaultValue = defaultValue; Choices = choices; } } The editor template looks like this: <%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl" %> <select class="template-selector" id="<%= ViewData.ModelMetadata.PropertyName %>.SelectedId" name="<%= ViewData.ModelMetadata.PropertyName %>.SelectedId"> <% var model = ViewData.ModelMetadata.Model as QASW.Web.Mvc.Selector; if (model != null) { %> <option><%= model.DefaultValue %></option><% foreach (var choice in model.Choices) { %> <option value="<%= choice.Value1 %>"><%= choice.Value2 %></option><% } } %> </select> I sort of got it to work by calling it from the view like this (where Category is a Selector): <%= Html.ValidationMessageFor(n => n.Category.SelectedId)%> But it shows the validation error for not supplying a proper number and it does not care if I set the Required attribute.

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• Newbie, deciding Python or Erlang

  - by Joe

  Hi Guys, I'm a Administrator (unix, Linux and some windows apps such as Exchange) by experience and have never worked on any programming language besides C# and scripting on Bash and lately on powershell. I'm starting out as a service provider and using multiple network/server monitoring tools based on open source (nagios, opennms etc) in order to monitor them. At this moment, being inspired by a design that I came up with, to do more than what is available with the open source at this time, I would like to start programming and test some of these ideas. The requirement is that a server software that captures a stream of data and store them in a database(CouchDB or MongoDB preferably) and the client side (agent installed on a server) would be sending this stream of data on a schedule of every 10 minutes or so. For these two core ideas, I have been reading about Python and Erlang besides ruby. I do plan to use either Amazon or Rackspace where the server platform would run. This gives me the scalability needed when we have more customers with many servers. For that reason alone, I thought Erlang was a better fit(I could be totally wrong, new to this game) and I understand that Erlang has limited support in some ways compared to Ruby or Python. But also I'm totally new to the programming realm of things and any advise would be appreciated grately. Jo

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• Status of VB6/ Best Desktop Application Language with Native Compilation

  - by Sandeep Jindal

  I was looking for a Desktop Application Programming Language with one of the biggest constraint: - “I need to output as native executable”. I explored multiple options: Java is not a very good option for desktop programming, but still you can use it. But Java to Exe is a problem. Only GCJ and Excelsior-Jet provides this. .Net platform does not support native compilation. Only very few expensive tools are available which can do the job. Python is not an option for native compilation. Right? VB6 is the option I am left with. From the above list, if I am correct, VB6 is the only and probably the best option I have. But VB6 itself has issues like: It is no more under development since There are questions on support of VB6 IDE with Vista Thus my questions are: From the list of programming language options, do you want to add any more? If VB6 is good/best option, looking at its development status, would you suggest using VB6 in this era?

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• Binary Trees in Scheme

  - by Javier

  Consider the following BNF defining trees of numbers. Notice that a tree can either be a leaf, a node-1 with one subtrees, or a node-2 with two subtrees. tree ::= (’leaf number) | (’node-1 tree) | (’node-2 tree tree) a. Write a template for recursive procedures on these trees. b. Define the procedure (leaf-count t) that returns the number of leaves in t > (leaf-count ’(leaf 5)) 1 > (leaf-count ’(node-2 (leaf 25) (leaf 17))) 2 > (leaf-count ’(node-1 (node-2 (leaf 4) (node-2 (leaf 2) (leaf 3))))) 3 Here's what I have so far: ;define what a leaf, node-1, and node-2 is (define leaf list) (define node-1 list) (define node-2 list) ;procedure to decide if a list is a leaf or a node (define (leaf? tree) (number? (car tree))) (define (node? tree) (pair? (car tree))) (define (leaf-count tree) (cond ((null? tree) 0) ((number? tree) 0) ((leaf? tree) 1) (else (+ (leaf-count (car tree)) (leaf-count (cdr tree)))))) It looks like it should run just fine, but when I try to run it using a simple test case like (leaf-count '(leaf 5)) I get the following error message: car: expects argument of type pair; given leaf What does this error message mean? I am defining a leaf as a list. But for some reason, it's not seeing that and gives me that error message.

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• Python PyQt Timer Firmata

  - by George Cullins

  Hello. I am pretty new to python and working with firmata I am trying to play around with an arduino . Here is what I want to happen: Set arduino up with an LED as a digital out Set potentiometer to analog 0 Set PyQt timer up to update potentiometer position in application Set a threshold in PyQt to turn LED on (Analog in has 1024bit resolution, so say 800 as the threshold) I am using this firmata library : Link Here is the code that I am having trouble with: import sys from PyQt4 import QtCore, QtGui from firmata import * # Arduino setup self.a = Arduino('COM3') self.a.pin_mode(13, firmata.OUTPUT) # Create timer self.appTimer = QtCore.QTimer(self) self.appTimer.start(100) self.appTimer.event(self.updateAppTimer()) def updateAppTimer(self): self.analogPosition = self.a.analog_read(self, 0) self.ui.lblPositionValue.setNum() I am getting the error message: Traceback (most recent call last): File "D:\Programming\Eclipse\IO Demo\src\control.py", line 138, in myapp = MainWindow() File "D:\Programming\Eclipse\IO Demo\src\control.py", line 56, in init self.appTimer.event(self.updateAppTimer()) File "D:\Programming\Eclipse\IO Demo\src\control.py", line 60, in updateAppTimer self.analogPosition = self.a.analog_read(self, 0) TypeError: analog_read() takes exactly 2 arguments (3 given) If I take 'self' out I get the same error message but that only 1 argument is given What is python doing implicitly that I am not aware of? Blockquote

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• Why is the compiler not selecting my function-template overload in the following example?

  - by Steve Guidi

  Given the following function templates: #include <vector> #include <utility> struct Base { }; struct Derived : Base { }; // #1 template <typename T1, typename T2> void f(const T1& a, const T2& b) { }; // #2 template <typename T1, typename T2> void f(const std::vector<std::pair<T1, T2> >& v, Base* p) { }; Why is it that the following code always invokes overload #1 instead of overload #2? void main() { std::vector<std::pair<int, int> > v; Derived derived; f(100, 200); // clearly calls overload #1 f(v, &derived); // always calls overload #1 } Given that the second parameter of f is a derived type of Base, I was hoping that the compiler would choose overload #2 as it is a better match than the generic type in overload #1. Are there any techniques that I could use to rewrite these functions so that the user can write code as displayed in the main function (i.e., leveraging compiler-deduction of argument types)?

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• Decisions in teaching someone else to program: language selection

  - by Dinah

  My friend would like for me to guide her into learning programming. She's already proven enormous aptitude for thinking like a programmer but is scared of the idea of programming since in her mind it's relegated to some magical realm accessible only to smart people and trained computer scientists (ironically, I am neither but that's beside the point). My main question is the age-old and irritating question: which language should I chose? I've limited it down to these: PHP: dead simple to start with and I remember enough of the language to answer all novice questions. However, I can think of a million reasons why I wouldn't recommend this as a first language. The most diplomatic of which is that there's no desktop app option to which I would feel comfortable subjecting a novice. Python: supposed to be wonderful for beginners and generally everything I've heard about it screams that this is the correct choice. That's the problem: everything I've heard about it. I don't know it yet and have a lot of projects going on right now so I don't feel like learning it yet -- but I'm going to be the tech-support when any little thing goes wrong. I know there are tons of online resources but in the frustration of the moment, it's always going to be just me. C#: this is the language I'm most comfortable with so I know I can be good tech support. I also love this language and its versatility and community. The big drawback here is that I remember when I first learned it after doing mainly PHP, Perl, and JavaScript and I found the experience overwhelming. You are simultaneously learning: programming concepts, C# syntax, strong typing, OOP, and a complex powerful IDE with a bazillion options and buttons all over it.

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• What is the best "forgot my password" method?

  - by Edward Tanguay

  I'm programming a community website. I want to build a "forgot my password" feature. Looking around at different sites, I've found they employ one of three options: send the user an email with a link to a unique, hidden URL that allows him to change his password (Gmail and Amazon) send the user an email with a new, randomly generated password (Wordpress) send the user his current password (www.teach12.com) Option #3 seems the most convenient to the user but since I save passwords as an MD5 hash, I don't see how option #3 would be available to me since MD5 is irreversible. This also seems to be insecure option since it means that the website must be saving the password in clear text somewhere, and at the least the clear-text password is being sent over insecure e-mail to the user. Or am I missing something here? So if I can't do option #1, option #2 seems to be the simplest to program since I just have to change the user's password and send it to him. Although this is somewhat insecure since you have to have a live password being communicated via insecure e-mail. However, this could also be misused by trouble-makers to pester users by typing in random e-mails and constantly changing passwords of various users. Option #1 seems to be the most secure but requires a little extra programming to deal with a hidden URL that expires etc., but it seems to be what the big sites use. What experience have you had using/programming these various options? Are there any options I've missed?

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• Composite key syntax in Boost MultiIndex

  - by Sarah

  Even after studying the examples, I'm having trouble figuring out how to extract ranges using a composite key on a MultiIndex container. typedef multi_index_container< boost::shared_ptr< Host >, indexed_by< hashed_unique< const_mem_fun<Host,int,&Host::getID> >, // ID index ordered_non_unique< const_mem_fun<Host,int,&Host::getAgeInY> >, // Age index ordered_non_unique< const_mem_fun<Host,int,&Host::getHousehold> >, // Household index ordered_non_unique< // Age & eligibility status index composite_key< Host, const_mem_fun<Host,int,&Host::getAgeInY>, const_mem_fun<Host,bool,&Host::isPaired> > > > // end indexed_by > HostContainer; My goal is to get an iterator pointing to the first of the subset of elements in HostContainer hmap that has age partnerAge and returns false to Host::isPaired(): std::pair< hmap::iterator,hmap::iterator > pit = hmap.equal_range(boost::make_tuple( partnerAge, false ) ); I think this is very wrong. How/Where do I specify the iterator index (which should be 3 for age & eligibility)? I will include other composite keys in the future. What exactly are the two iterators in std::pair? (I'm copying syntax from an example that I don't understand.) I would ideally use std::count to calculate the number of elements of age partnerAge that are eligible (return false to Host::isPaired()). What is the syntax for extracting the sorted index that meets these requirements? I'm obviously still learning C++ syntax. Thanks in advance for any help.

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• Implementing arrays using a stack

  - by Zack

  My programming language has no arrays, no lists, no pointers, no eval and no variable variables. All it has: Ordinary variables like you know them from most programming languages: They all have an exact name and a value. One stack. Functions provided are: push (add element to top), pop (remove element from top, get value) and empty (check if stack is empty) My language is turing-complete. (Basic arithmetics, conditional jumps, etc implemented) That means, it must be possible to implement some sort of list or array, right? But I have no idea how... What I want to achieve: Create a function which can retrieve and/or change an element x of the stack. I could easily add this function in the implementation of my language, in the interpreter, but I want to do it in my programming language. "Solution" one (Accessing an element x, counting from the stack top) Create a loop. Pop off the element from the stack top x times. The last element popped of is element number x. I end up with a destroyed stack. Solution two: Do the same as above, but store all popped off values in a second stack. Then you could move all elements back after you are done. But you know what? I don't have a second stack!

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