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• Automatic Generalization

  - by Nick Harrison

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

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• A project idea I've got...

  - by Mr Teeth

  Hi, Next year I will be doing a final year project at Uni. I've already thought of one and was wondering what you guys think of it. I want to create a University Information Search for prospective students who are trying to look for an affordable University to attend. It will depend on the student's family income and the grades they get. They enter in those two parameters (and some more) and it comes up with a list of suitable Unis based on their criteria. This is not about the price of tution fee. It's mostly to do with the cost of living. Stuff like: Rent (if living in a private flat). Student Accomadation. Cost of traveling to your home and back (for holidays). ...and some other stuff stuff I haven't thought about yet. It'll mostly be GUI driven with some textual information. I'm also thinking of using it as a website interface. What do you guys think? Can I program something like this Java? If there's any holes you see in my idea please tell me.

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• xorg-edgers PPA with llvmpipe breaks AMD APU system

  - by linux_RRT

  I've read before where this had happened to another user with the same system... I was running Ubuntu 12.04 LTS with Kernel 3.2.0.29 and decided to give xorg-edgers a try. I purged fglrx* and xorg* before beginning. I upgraded with sudo apt-get upgrade -d The system downloaded and installed 109MB worth of data to the system, including llvmpipe which I am very unfamiliar with, and Kernel 3.5.0.11. The system was then rebooted to finalize the upgrade. The system boots to a black screen and then tells me "The system is running in low-graphics mode". Did I miss a step in the install? Or do the newest open-source drivers just not work with my hardware? I realize this hardware (APU) is some of the newer development. I dropped to command via the fallback menu and attempted to boot lightdm as root, but the system hangs in 'Configuring kernel parameters' at Starting initializes zram swaping. ...and then it just sits there. The other thing that concerns me is the output at the top of the screen that says: could not write bytes: Broken pipe Does llvmpipe work for this type of system? To be clear the system is: MSI x370-206us Laptop Radeon HD 6320 AMD e450 APU 1.67ghz dual-core Any help would be much appreciated. Like I said, I'm pretty sure I followed the right order of operations for the install procedure, but I was curious if anyone with similar hardware had experienced anything similar.

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• How to implment the database for event conditions and item bonuses for a browser based game

  - by Saifis

  I am currently creating a browser based game, and was wondering what was the standard approach in making diverse conditions and status bonuses database wise. Currently considering two cases. Event Conditions Needs min 1000 gold Needs min Lv 10 Needs certain item. Needs fulfillment of another event Status Bonus Reduces damage by 20% +100 attack points Deflects certain type of attack I wish to be able to continually change these parameters during the process of production and operation, so having them hard-coded isn't the best way. All I could come up with are the following two methods. Method 1 Create a table that contains each conditions with needed attributes Have a model named conditions with all the attributes it would need to set them conditions condition_type (level, money_min, money_max item, event_aquired) condition_amount prerequisite_condition_id prerequisite_item_id Method 2 write it in a DSL form that could be interpreted later in the code Perhaps something like yaml, have a text area in the setting form and have the code interpret it. condition_foo: condition_type :level min_level: 10 condition_type :item item_id: 2 At current Method 2 looks to be more practical and flexible for future changes, trade off being that all the flex must be done on the code side. Not to sure how this is supposed to be done, is it supposed to be hard coded? separate config file? Any help would be appreciated. Added For additional info, it will be implemented with Ruby on Rails

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• Data classes: getters and setters or different method design

  - by Frog

  I've been trying to design an interface for a data class I'm writing. This class stores styles for characters, for example whether the character is bold, italic or underlined. But also the font-size and the font-family. So it has different types of member variables. The easiest way to implement this would be to add getters and setters for every member variable, but this just feels wrong to me. It feels way more logical (and more OOP) to call style.format(BOLD, true) instead of style.setBold(true). So to use logical methods insteads of getters/setters. But I am facing two problems while implementing these methods: I would need a big switch statement with all member variables, since you can't access a variable by the contents of a string in C++. Moreover, you can't overload by return type, which means you can't write one getter like style.getFormatting(BOLD) (I know there are some tricks to do this, but these don't allow for parameters, which I would obviously need). However, if I would implement getters and setters, there are also issues. I would have to duplicate quite some code because styles can also have a parent styles, which means the getters have to look not only at the member variables of this style, but also at the variables of the parent styles. Because I wasn't able to figure out how to do this, I decided to ask a question a couple of weeks ago. See Object Oriented Programming: getters/setters or logical names. But in that question I didn't stress it would be just a data object and that I'm not making a text rendering engine, which was the reason one of the people that answered suggested I ask another question while making that clear (because his solution, the decorator pattern, isn't suitable for my problem). So please note that I'm not creating my own text rendering engine, I just use these classes to store data. Because I still haven't been able to find a solution to this problem I'd like to ask this question again: how would you design a styles class like this? And why would you do that? Thanks on forehand!

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• How to write PowerShell code part 2 (Using function)

  - by ybbest

  In the last post, I have showed you how to use external configuration file in your PowerShell script. In this post, I will show you how to create PowerShell function and call external PowerShell script.You can download the script here. 1. In the original script, I create the site directly using New-SPSite command. I will refactor it so that I will create a new function to create the site using New-SPSite. The PowerShell function is quite similar to a C# method. You put your function parameters in () and separate each parameter by a comma (,). Then you put your method body in {}. function add ([int] $num1 , [int] $num2){ $total=$num1+$num2 #Return $total $total } 2. The difference is you do not need semi-colon (;) at the end of each statement and when calling the method you do not need comma (,) to separate each parameter. function add ([int] $num1 , [int] $num2){ $total=$num1+$num2 #Return $total $total } #Calling the function [int] $num1=3 [int] $num2=4 $d= add $num1 $num2 Write-Host $d 3. If you like to return anything from the function, you just need to type in the object you like to return, not need to type return .e.g. $ObjectToReturn not return $ObjectToReturn

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• Failed Project: When to call it?

  - by Dan Ray

  A few months ago my company found itself with its hands around a white-hot emergency of a project, and my entire team of six pulled basically a five week "crunch week". In the 48 hours before go-live, I worked 41 of them, two back to back all-nighters. Deep in the middle of that, I posted what has been my most successful question to date. During all that time there was never any talk of "failure". It was always "get it done, regardless of the pain." Now that the thing is over and we as an organization have had some time to sit back and take stock of what we learned, one question has occurred to me. I can't say I've ever taken part in a project that I'd say had "failed". Plenty that were late or over budget, some disastrously so, but I've always ended up delivering SOMETHING. Yet I hear about "failed IT projects" all the time. I'm wondering about people's experience with that. What were the parameters that defined "failure"? What was the context? In our case, we are a software shop with external clients. Does a project that's internal to a large corporation have more space to "fail"? When do you make that call? What happens when you do? I'm not at all convinced that doing what we did is a smart business move. It wasn't my call (I'm just a code monkey) but I'm wondering if it might have been better to cut our losses, say we're not delivering, and move on. I don't just say that due to the sting of the long hours--the company royally lost its shirt on the project, plus the intangible costs to the company in terms of employee morale and loyalty were large. Factor that against the PR hit of failing to deliver a high profile project like this one was... and I don't know what the right answer is.

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• Social Media APIs and Their C# Counterparts

  Whether it's talking about current events or sharing photos of a family vacation, the world is now addicted to social networks. Businesses recognize this, and these days every business wants social media addressed in their applications. Facebook, Twitter, and other sites provide powerful APIs you can use to harness the power of social networking in your own applications. However, most of these APIs tend to return data formatted in any number of syndication formats that can be quite painful to work with. Luckily, there are many free .NET based libraries that make interacting with these APIs a breeze. Over the next several weeks, I'll be posting some information and examples specific to some of these libraries. Here are a few of them now for your consumption... TweetSharp Twitter exposes its API in the form of three different APIs, two REST APIs and one Streaming API. These APIs can be queried by making HTTP GET/POST requests to a specific URL with some required parameters. Unfortunately, ...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Select (loop) or command not working in shell-script

  - by user208098

  I've been tinkering with Linux and Unix for years but still a novice in my mind and recently find myself trying to be more pro with it as I work in IT. So with that notion I'm studying shell scripting. I've hit a snag in ubuntu using the latest version 13.10 Saucy. When I use the select command in a sh script it doesn't work, depending on how I format the command it will either return Unexpected "do" or Unexpected "done". See the following two examples: This section of code produces an unexpected "do" error: #/bin/bash PS3='Please enter your choice' select opt in option1 option2 option3 quit do case $opt in "option1") echo "you chose choice 1" ;; "option2") echo "you chose choice 2" ;; "option3") echo "you chose choice 3" ;; "quit") break ;; *) echo invalid option ;; esac done This section of code produces an unexpected "done" error. #/bin/bash PS3='Please enter your choice' select opt in option1 option2 option3 quit ; do case $opt in "Option1") echo "you chose choice 1" ;; "Option2") echo "you chose choice 2" ;; "Option3") echo "you chose choice 3" ;; "quit") break ;; *) echo invalid option ;; esac done When I enter these parameters into the command line interactively or manually I get the desired result which is a list of choices to choose from. However when executed from a script I get the before mentioned errors. Also a side note I have tried this in Fedora as a script and it worked perfectly so my question is why isn't it working in Ubuntu, is this a difference between RHL and Debian? Or is it a bug in the latest version of Ubuntu? Thanks in advance for any help! KG

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• Thoughts on type aliases/synonyms?

  - by Rei Miyasaka

  I'm going to try my best to frame this question in a way that doesn't result in a language war or list, because I think there could be a good, technical answer to this question. Different languages support type aliases to varying degrees. C# allows type aliases to be declared at the beginning of each code file, and they're valid only throughout that file. Languages like ML/Haskell use type aliases probably as much as they use type definitions. C/C++ are sort of a Wild West, with typedef and #define often being used seemingly interchangeably to alias types. The upsides of type aliasing don't invoke too much dispute: It makes it convenient to define composite types that are described naturally by the language, e.g. type Coordinate = float * float or type String = [Char]. Long names can be shortened: using DSBA = System.Diagnostics.DebuggerStepBoundaryAttribute. In languages like ML or Haskell, where function parameters often don't have names, type aliases provide a semblance of self-documentation. The downside is a bit more iffy: aliases can proliferate, making it difficult to read and understand code or to learn a platform. The Win32 API is a good example, with its DWORD = int and its HINSTANCE = HANDLE = void* and its LPHANDLE = HANDLE FAR* and such. In all of these cases it hardly makes any sense to distinguish between a HANDLE and a void pointer or a DWORD and an integer etc.. Setting aside the philosophical debate of whether a king should give complete freedom to their subjects and let them be responsible for themselves or whether they should have all of their questionable actions intervened, could there be a happy medium that would allow the benefits of type aliasing while mitigating the risk of its abuse? As an example, the issue of long names can be solved by good autocomplete features. Visual Studio 2010 for instance will alllow you to type DSBA in order to refer Intellisense to System.Diagnostics.DebuggerStepBoundaryAttribute. Could there be other features that would provide the other benefits of type aliasing more safely?

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• Oracle HRMS API – Create Employee State Tax Rule

  - by PRajkumar

  API --  pay_state_tax_rule_api.create_state_tax_rule Example --   DECLARE     lc_dt_ud_mode                     VARCHAR2(100)     := NULL;      ln_assignment_id                 NUMBER                    := 33561;     lb_correction                            BOOLEAN;      lb_update                                 BOOLEAN;      lb_update_override               BOOLEAN;      lb_update_change_insert    BOOLEAN;     ln_emp_state_tax_rule_id   PAY_US_EMP_STATE_TAX_RULES_F.EMP_STATE_TAX_RULE_ID%TYPE;     ln_object_version_number  NUMBER;      ld_effective_start_date          DATE;      ld_effective_end_date           DATE; BEGIN       -- Find Date Track Mode       -- --------------------------------         dt_api.find_dt_upd_modes         (     p_effective_date                  => TO_DATE('12-JUN-2011'),               p_base_table_name            => 'PER_ALL_ASSIGNMENTS_F',               p_base_key_column          => 'ASSIGNMENT_ID',               p_base_key_value              => ln_assignment_id,               -- Output data elements               -- --------------------------------              p_correction                           => lb_correction,              p_update                                => lb_update,              p_update_override              => lb_update_override,              p_update_change_insert   => lb_update_change_insert        );      IF ( lb_update_override = TRUE OR lb_update_change_insert = TRUE )    THEN       -- UPDATE_OVERRIDE       -- ---------------------------------       lc_dt_ud_mode := 'UPDATE_OVERRIDE';    END IF;      IF ( lb_correction = TRUE )    THEN       -- CORRECTION       -- ----------------------       lc_dt_ud_mode := 'CORRECTION';    END IF;      IF ( lb_update = TRUE )    THEN       -- UPDATE       -- --------------       lc_dt_ud_mode := 'UPDATE';    END IF;      -- Create Employee State Tax Rule    -- -----------------------------------------------     pay_state_tax_rule_api.create_state_tax_rule     (    -- Input Parameters          -- --------------------------          p_effective_date                         => TO_DATE('15-JUN-2011'),          p_default_flag                            => 'Y',          p_assignment_id                      => 33561,          p_state_code                               => '05',          -- Output Parameters          -- ----------------------------         p_emp_state_tax_rule_id        => ln_emp_state_tax_rule_id,         p_object_version_number       => ln_object_version_number,         p_effective_start_date               => ld_effective_start_date,         p_effective_end_date                => ld_effective_end_date   );    COMMIT; EXCEPTION           WHEN OTHERS THEN                        ROLLBACK;                         dbms_output.put_line(SQLERRM); END; / SHOW ERR;  

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• Http handler for classic ASP application for introducing a layer between client and server

  - by JPReddy

  I've a huge classic ASP application where in thousands of users manage their company/business data. Currently this is not multi-user so that application users can create users and authorize them to access certain areas in the system. I'm thinking of writing a handler which will act as middle man between client and server and go through every request and find out who the user is and whether he is authorized to access the data he is trying to. For the moment ignore about the part how I'm going to check the authorization and all that stuff. Just want to know whether I can implement a ASP.net handler and use it as middle man for the requests coming for a asp website? I just want to read the url and see what is the page user is trying to access and what are the parameters he is passing in the url the posted data. Is this possible? I read that Asp.net handler cannot be used with asp website and I need to use isapi filter or extensions for that and that can be developed only c/c++. Can anybody through some light on this and guide me whether I'm in the right direction or not?

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• First Shard for SQL Azure and SQL Server

  - by Herve Roggero

  That's it!!!!! It's ready to go and be tested, abused and improved! It requires .NET 4.0 and uses some cool technologies, like caching (the new System.Runtime.Caching) and the Task Parallel Library (System.Threading.Tasks). With this library you can: Define a shard of 1, 2 or 100 SQL databases (a mix of SQL Server and SQL Azure) Read from the shard in parallel or sequentially, and cache resultsets Update, Delete a record from the shard Insert records quickly in the shard with a round-robin load Reset the cache You can download the source code and a sample application here: http://enzosqlshard.codeplex.com/  Note about the breadcrumbs: I had to add a connection GUID in order for the library to know which database a record came from. The GUID is currently calculated on the fly in the library using some of the parameters of the connection string. The GUID is also dynamically added to the result set so the client can pass it back to the library. I am curious to get your feedback on this approach. ** Correction from my previous post: this is a library for a Horizontal Partition Shard (HPS): tables are split across databases horizontally. So in essence, the tables need to have the same schema across the databases.

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• How can i make Brightness Control work?

  - by Semen

  I have Xubuntu 12.04 with latest updates on Toshiba Satellite A210-15K laptop semen@bloknot:~$ uname -a Linux bloknot 3.2.0-24-generic #37-Ubuntu SMP Wed Apr 25 08:43:22 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux ...and I can't adjust LCD brightness (. I tried to use fnfx tool: semen@bloknot:~$ fnfx-client FnFX Client v0.3 (c) 2003, 2004 Timo Hoenig <[email protected]> fatal error: Could not open "/home/semen/.fnfxrc". Please make sure that the default config is accessible. ...and xbacklight: semen@bloknot:~$ xbacklight No outputs have backlight property ...and I tried to add acpi_osi=Linux and acpi_backlight=vendor parameters in GRUB config, but nothing happens. I soppose .fnfxrc file must be available after installation or first fnfx demon lauch. Isn't it? semen@bloknot:~$ cat /sys/class/backlight/toshiba/brightness -5 semen@bloknot:~$ cat /sys/class/backlight/toshiba/max_brightness 7 semen@bloknot:~$ echo 6 | sudo tee /sys/class/backlight/toshiba/brightness [sudo] password for semen: 6 ... ...but brightness is the same. Help, please. P.S. Execuse me for my poor English. UPD. I have spent 2 days to solve this boring problem, but I can't. So. If I wish linux work correctly, I have to choose another distro.

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• Ubuntu Server 11.10 boot, white terminal with garbled black text

  - by SpeedCrazy

  I just installed Ubuntu server 11.10 and the install went fine. This system is running on an Intel Pentium II board with onboard graphics. However when I try to boot into Ubuntu I get a white terminal with garbled black text. I have tried various grub 'fixes' as googling the issue seemed to suggest it was a res or grub related issue. I cannot ssh in so the issue does affect Linux as well. I have had no luck with anything thus far and am at my wits end. This was my first Ubuntu excursion as my friend told me it was better for servers than CentOS because it was easier... Not so much.... Does anyone have any ideas as to what the issue could be? When answering bear in mind I am an Ubuntu noob and Linux novice. As of 1/26/12 I have tried to add the console=ttyl line to the /etc/default/grub and run update-grub. This results in the line in the boot parameters that normally reads: linux /vmlunz-3.0.0-12-generic-pae root=/dev/mapper/dev-root rovt.handoff=7 now reads: linux /vmlunz-3.0.0-12-generic-pae root=/dev/mapper/dev-root ro console=ttyl vt.handoff=7 This does not work. Is there anyway to have console=ttyl inserted on a line by itself? I am at my wits ends, Thanks for all your help, Speed

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• How to sell logistical procedures that require less time to perform but more finesse?

  - by foampile

  I am working with a group where part of the responsibilities is managing a certain set of configuration files which, of course, have the same skeleton/structure across different environments but different values (like server, user, this setting, that setting etc.). Pretty classic scenario... The problem is that everyone just goes and modifies final, environment-specific files and basically repeats the work for every environment. Personally, I am offended to have to peform repeatable, mundane tasks in this day and age when we have technologies to automate it all. So I devised a very simple procedure of abstracting the files into templates, stubbing env-specific values with parameters and then wrote a simple Perl script that, given a template and an environment matrix with env-specific values for each param, produces the final file. So this is nothing special, cutting-edge or revolutionary -- I am pretty sure that 20 years ago efficient places did their CM like that. However, that requires that changes are made at the template level and then distributed across different environments using the script and not making changes in the final environment-specific files. This is where I am encountering resentment as they feel "comfortable" doing it their old, manual, repeated labor way. Personally, I don't have a problem with them working hard rather than smart but the problem is when I have to build on top of someone else's changes, I have to merge their changes into my template from a specific file, which takes time and is grueling. So my question is how to go about selling my method, which makes it so much faster in an environment that is resentful to change and where most things have to be done at the level of the least competent team member?

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• Do all mods simply alter game files? [on hold]

  - by Starkers

  When you install some mods you drag certain files into your game directory and replace the files. Other mods, though, come with an installer where you can set parameters first. Does the installer then go and automatically replace the certain files? At the end of the day, is that all the installation of any mod is? Is the installation of a mod simply the replacement of certain files inside the game's root directory? Do mods exist which don't fit the above statement? That install outside the game's root? Why do they do this? All the mods I can think of do just replace certain files inside the game's root. However, I know Team Fortress was spawned from a multiplayer halflife 1 mod. Do you reckon that mod installed files outside the root to enable multiplayer via a network for a single player game? How rare are these mods? Or do they not even exist? Do even extensive mods make all their changes inside the root?

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• How can I draw crisp per-pixel images with OpenGL ES on Android?

  - by Qasim

  I have made many Android applications and games in Java before, however I am very new to OpenGL ES. Using guides online, I have made simple things in OpenGL ES, including a simple triangle and a cube. I would like to make a 2D game with OpenGL ES, but what I've been doing isn't working quite so well, as the images I draw aren't to scale, and no matter what guide I use, the image is always choppy and not the right size (I'm debugging on my Nexus S). How can I draw crisp, HD images to the screen with GL ES? Here is an example of what happens when I try to do it: And the actual image: Here is how my texture is created: //get id int id = -1; gl.glGenTextures(1, texture, 0); id = texture[0]; //get bitmap Bitmap bitmap = BitmapFactory.decodeResource(context.getResources(), R.drawable.ball); //parameters gl.glBindTexture(GL10.GL_TEXTURE_2D, id); gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MIN_FILTER, GL10.GL_NEAREST); gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MAG_FILTER, GL10.GL_LINEAR); gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_S, GL10.GL_CLAMP_TO_EDGE); gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_T, GL10.GL_CLAMP_TO_EDGE); gl.glTexEnvf(GL10.GL_TEXTURE_ENV, GL10.GL_TEXTURE_ENV_MODE, GL10.GL_REPLACE); GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, bitmap, 0); //crop image mCropWorkspace[0] = 0; mCropWorkspace[1] = height; mCropWorkspace[2] = width; mCropWorkspace[3] = -height; ((GL11) gl).glTexParameteriv(GL10.GL_TEXTURE_2D, GL11Ext.GL_TEXTURE_CROP_RECT_OES, mCropWorkspace, 0);

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• Want Google to index redirect urls

  - by Dave Goten

  I'm having issues with users who think that Google Search is the address bar. Some of the sites that link to my site use user friendly addresses with 301 redirects to pages that have less friendly URLs. So, for example if I enter www.foo.com/bar it goes to www.bar.com/page.php?some-parameters-and-utm-codes-etc usually this is done by a 301 redirect in order to keep the SEO from foo.com on bar.com and so on, which I believe is standard practice. However, lately there have been more and more people searching www.foo.com/bar instead of going to www.foo.com/bar directly and because the page /bar is nothing more than a redirect it has no SEO that I know of. Things I've thought of but haven't been able to test, because Google takes forever to update :) (and I'm lazy like that), include using Google sitemaps and having them enter their redirects as entries there. (I could see this working if they were the top search entry all the time, and it might appear as a sitelink, but I don't know if that'll make the url itself show up in searches) Using Canonical tags on my pages to the redirects they set up. Which is a nightmare in itself because of the nature of my pages. One week the www.foo.com/bar might go to www.bar.com/pageA.php the next it might goto www.bar.com/pageB.php and having to remember to take the canonical tag off of pageA, so that it doesn't get confused with pageB would be a pain. Using 302 redirects -.- So I guess the question here is, does anyone have any experience or knowledge about this? What should I do to make www.foo.com/bar show up when someone 'searches' for this redirect url?

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• Particle trajectory smoothing: where to do the simulation?

  - by nkint

  I have a particle system in which I have particles that are moving to a target and the new targets are received via network. The list of new target are some noisy coordinates of a moving target stored in the server that I want to smooth in the client. For doing the smoothing and the particle I wrote a simple particle engine with standard euler integration model. So, my pseudo code is something like that: # pseudo code class Particle: def update(): # do euler motion model integration: # if the distance to the target is more than a limit # add a new force to the accelleration # seeking the target, # and add the accelleration to velocity # and velocity to the position positionHistory.push_back(position); if history.length > historySize : history.pop_front() class ParticleEngine: particleById = dict() # an associative array # where the keys are the id # and particle istances are sotred as values # this method is called each time a new tcp packet is received and parsed def setNetTarget(int id, Vec2D new_target): particleById[id].setNewTarget(new_target) # this method is called each new frame def draw(): for p in particleById.values: p.update() beginVertex(LINE_STRIP) for v in p.positionHistory: vertex(v.x, v.y) endVertex() The new target that are arriving are noisy but setting some accelleration/velocity parameters let the particle to have a smoothed trajectories. But if a particle trajectory is a circle after a while the particle position converge to the center (a normal behaviour of euler integration model). So I decided to change the simulation and use some other interpolation (spline?) or smooth method (kalman filter?) between the targets. Something like: switch( INTERPOLATION_MODEL ): case EULER_MOTION: ... case HERMITE_INTERPOLATION: ... case SPLINE_INTERPOLATION: ... case KALMAN_FILTER_SMOOTHING: ... Now my question: where to write the motion simulation / trajectory interpolation? In the Particle? So I will have some Particle subclass like ParticleEuler, ParticleSpline, ParticleKalman, etc..? Or in the particle engine?

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• What is a 'good number' of exceptions to implement for my library?

  - by Fuzz

  I've always wondered how many different exception classes I should implement and throw for various pieces of my software. My particular development is usually C++/C#/Java related, but I believe this is a question for all languages. I want to understand what is a good number of different exceptions to throw, and what the developer community expect of a good library. The trade-offs I see include: More exception classes can allow very fine grain levels of error handling for API users (prone to user configuration or data errors, or files not being found) More exception classes allows error specific information to be embedded in the exception, rather than just a string message or error code More exception classes can mean more code maintenance More exception classes can mean the API is less approachable to users The scenarios I wish to understand exception usage in include: During 'configuration' stage, which might include loading files or setting parameters During an 'operation' type phase where the library might be running tasks and doing some work, perhaps in another thread Other patterns of error reporting without using exceptions, or less exceptions (as a comparison) might include: Less exceptions, but embedding an error code that can be used as a lookup Returning error codes and flags directly from functions (sometimes not possible from threads) Implemented an event or callback system upon error (avoids stack unwinding) As developers, what do you prefer to see? If there are MANY exceptions, do you bother error handling them separately anyway? Do you have a preference for error handling types depending on the stage of operation?

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• Questioning one of the arguments for dependency injection: Why is creating an object graph hard?

  - by oberlies

  Dependency injection frameworks like Google Guice give the following motivation for their usage (source): To construct an object, you first build its dependencies. But to build each dependency, you need its dependencies, and so on. So when you build an object, you really need to build an object graph. Building object graphs by hand is labour intensive (...) and makes testing difficult. But I don't buy this argument: Even without dependency injection, I can write classes which are both easy to instantiate and convenient to test. E.g. the example from the Guice motivation page could be rewritten in the following way: class BillingService { private final CreditCardProcessor processor; private final TransactionLog transactionLog; // constructor for tests, taking all collaborators as parameters BillingService(CreditCardProcessor processor, TransactionLog transactionLog) { this.processor = processor; this.transactionLog = transactionLog; } // constructor for production, calling the (productive) constructors of the collaborators public BillingService() { this(new PaypalCreditCardProcessor(), new DatabaseTransactionLog()); } public Receipt chargeOrder(PizzaOrder order, CreditCard creditCard) { ... } } So there may be other arguments for dependency injection (which are out of scope for this question!), but easy creation of testable object graphs is not one of them, is it?

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• preseeded installation keeps asking for confirmation while creating RAID-Partitions on certain hardware-platform

  - by Marc Shennon

  I am aware of the partman-md/confirm_nooverwrite thing, that was the solution to most of this problems in the past. The thing is, that the preseed-file works for almost all hardware-platforms I tested, but only for one (Primergy MX130) it keeps asking for confirmation, before writing the partition-layout to the disks. All machines I tested are running with two SATA Disks, nothing special. I'm not really sure, what information could be needed in order to investigate the cause of this behaviour, but I would of course be willing to provide more information, if someone has an idea. Relevant part of the preseed file is the following: d-i partman-auto/disk string /dev/sda /dev/sdb d-i partman-auto/method string raid d-i partman-md/confirm boolean true d-i partman-partitioning/confirm_write_new_label boolean true d-i partman-md/device_remove_md boolean true d-i partman/choose_partition select finish d-i partman-md/confirm_nooverwrite boolean true # Write the changes to disks? d-i partman/confirm boolean true d-i mdadm/boot_degraded boolean true # RECIPE # Next you need to specify the physical partitions that will be used. d-i partman-auto/expert_recipe string \ multiraid :: \ 500 10000 1000000000 raid $lvmignore{ }\ $primary{ } \ method{ raid } \ . \ 512 1000 786 raid $lvmignore{ }\ $primary{ } \ method{ raid } \ . \ 8192 10240 10240 raid $lvmignore{ }\ method{ raid } \ . # Parameters are: # <raidtype> <devcount> <sparecount> <fstype> <mountpoint> <devices> <sparedevices> d-i partman-auto-raid/recipe string \ 1 2 0 ext4 / /dev/sda1#/dev/sdb1 . \ 1 2 0 ext2 /boot /dev/sda2#/dev/sdb2 . \ 1 2 0 swap - /dev/sda5#/dev/sdb5 .

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• 64kb limit on the size of MSMQ Multicast Messages

  - by John Breakwell

  When Windows 2003 came out, Microsoft introduced the ability to broadcast messages to any machines that were listening back. All you had to do was send out a message on a particular port and IP address and any client that had set up a Multicast queue with matching port and IP address would get a copy. Since its introduction, there have been a couple of security vulnerabilities that needed to be removed: Microsoft Security Bulletin MS06-052 Vulnerability in Pragmatic General Multicast (PGM) Could Allow Remote Code Execution (919007) Microsoft Security Bulletin MS08-036 Vulnerabilities in Pragmatic General Multicast (PGM) could allow denial of service (950762) The second of these, MS08-036, was resolved through an undocumented change in functionality. Basically, a limit of 64kb was put on the maximum size of a message that could be broadcast using the Multicast method. Obviously this has caused a few problems for any existing MSMQ Multicast applications that expected to be able to send larger messages. A hotfix has been developed to resolve this problem. 961605 FIX: Multicast messages larger than 64 kilobytes (KB) are not delivered as expected by using Message Queuing 3.0 after security update MS08-036 is installed A registry change is required: Open the registry with Regedit Navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\RMCAST\Parameters\ Create a DWord called MaxpacketSize Set the value to the desired number of bytes. You can set it to a value between zero and 4MB. If you specify anything above 4MB, it will default to 64K. A reboot is needed after adding this value.

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• Unable to debug an encodded javascript?

  - by miles away

  I’m having some problems debugging an encoded javacscript. This script I’m referring to given in this link over here. The encoding here is simple and it works by shifting the unicodes values to whatever Codekey was use during encoding. The code that does the decoding is given here in plain English below:- <script language="javascript"> function dF(s){ var s1=unescape(s.substr(0,s.length-1)); var t=''; for(i=0;i<s1.length;i++)t+=String.fromCharCode(s1.charCodeAt(i)-s.substr(s.length-1,1)); document.write(unescape(t)); } </script> I’m interested in knowing or understanding the values (e.g s1,t). Like for example when the value of i=0 what values would the following attributes / method would hold s1.charCodeAt(i) and s.substr(s.length-1,1) The reason I’m doing this is to understand as to how a CodeKey function really works. I don’t see anything in the code above which tells it to decode on the basis of codekey value. The only thing I can point in the encoding text is the last character which is set to 1 , 2 ,3 or 4 depending upon the codekey selected during encoding process. One can verify using the link I have given above. However, to debug, I’m using firebug addon with the script running as localhost on my wamp server. I’m able to put a breakpoint on the js using firebug but I’m unable to retrieve any of the user defined parameters or functions I mentioned above. I want to know under this context what would be best way to debug this encoded js.

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