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• Installing Django on Windows

  - by Pranav

  Ever needed to install Django in a Microsoft Windows environment, here is a quick start guide to make that happen: Read through the official Django installation documentation, it might just save you a world of hut down the road. Download Python for your version of Windows. Install Python, my preference here is to put it into the Program Files folder under a folder named Python<Version> Add your chosen Python installation path into your Windows path environment variable. This is an optional step, however it allows you to just type python in the command line and have it fire up the Python interpreter. An easy way of adding it is going into Control Panel, System and into the Environment Variables section. Download Django, you can either download a compressed file or if you’re comfortable with using version control – check it out from the Django Subversion repository. Create a folder named django under your <Python installation directory>\Lib\site-packages\ folder. Using my example above that would have been C:\Program Files\Python25\Lib\site-packages\. If you chose to download the compressed file, open it and extract the contents of the django folder into your newly created folder. If you’d prefer to check it out from Subversion, the normal check out points are http://code.djangoproject.com/svn/django/trunk/ for the latest development copy or a named release which you’ll find under http://code.djangoproject.com/svn/django/tags/releases/. Done, you now have a working Django installation on Windows. At this point, it’d be pertinent to confirm that everything is working properly, which you can do by following the first Django tutorial. The tutorial will make mention of django-admin.py, which is a utility which offers some basic functionality to get you off the ground. The file is located in the bin folder under your Django installation directory. When you need to use it, you can either type in the full path to it or simply add that file path into your environment variables as well. Hope this helps!

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• Where to find common database abbreviations in Spanish

  - by jmh_gr

  I'm doing a little pro bono work for an organization in Central America. I'm ok at Spanish and my contacts are perfectly fluent but are not techincal people. Even if they don't care what I call some fields in a database I still want to make as clean a schema as possible, and I'd like to know what some typical abbreviations are for field / variable names in Spanish. I understand abbreviations and naming conventions are entirely personal. I'm not asking for the "correct" or "best" way to abbreviate database object names. I'm just looking for references to lists of typical abbreviations that would be easily recognizable to a techincally competent native Spanish speaker. I believe I am a decent googler but I've had no luck on this one. For example, in my company (where English is the primary language) 'Date' is always shortened to 'DT', 'Code' to 'CD', 'Item' to 'IT', etc. It's easy for the crowds of IT temp workers who revolve through on various projects to figure out that 'DT' stands for 'Date', 'YR' for 'Year', or 'TN' for 'Transaction' without even having to consult the official abbreviations list.

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• Totem crashes immediately after startup in 12.10

  - by Sakib Hasan

  I did a fresh install of Ubuntu 12.10 and did sudo apt-get update && sudo apt-get update. Then I installed ubuntu-restricted-extras, audacious and vlc from Software Center. After that I tried launch Totem Movie player but in terminal following error comes up: (totem:9295): Gdk-ERROR **: The program 'totem' received an X Window System error. This probably reflects a bug in the program. The error was 'BadDrawable (invalid Pixmap or Window parameter)'. (Details: serial 1808 error_code 9 request_code 152 minor_code 9) (Note to programmers: normally, X errors are reported asynchronously; that is, you will receive the error a while after causing it. To debug your program, run it with the GDK_SYNCHRONIZE environment variable to change this behavior. You can then get a meaningful backtrace from your debugger if you break on the gdk_x_error() function.) Trace/breakpoint trap (core dumped) I tried purge and again install. But the error remains. What should I do?

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• Animating sprites in HTML5 canvas

  - by fnx

  I'm creating a 2D platformer game with HTML5 canvas and javascript. I'm having a bit of a struggle with animations. Currently I animate by getting preloaded images from an array, and the code is really simple, in player.update() I call a function that does this: var animLength = this.animations[id].length; this.counter++; this.counter %= 3; if (this.counter == 2) this.spriteCounter++; this.spriteCounter %= animLength; return this.animations[id][this.spriteCounter]; There are a couple of problems with this one: When the player does 2 actions that require animating at the same time, animation speed doubles. Apparently this.counter++ is working twice at the same time. I imagine that if I start animating multiple sprites with this, the animation speed will multiply by the amount of sprites. Other issue is that I couldn't make the animation run only once instead of looping while key is held down. Someone told me that I should create a function Animation(animation id, isLooped boolean) and the use something like player.sprite = new Animation("explode", false) but I don't know how to make it work. Yes I'm a noob... :)

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• 301 redirect from HTTP to HTTPS - how to be sure Google is fetching the correct information?

  - by user33692

  I'm hoping somebody might be able to provide a bit of advice on an issue I am having. I have one site where we implemented a 301 redirect on the homepage from HTTP to HTTPS. We have links on the homepage to other parts of the site that are not under SSL (in fact there is only one other page under SSL). When I go to our Webmaster Tools account I notice that we are not being provided with any webmaster information (e.g., search queries, backlinks, etc...) related to our homepage under SSL. I performed a Fetch as Google on the homepage and the information it returned is: HTTP/1.1 301 Moved Permanently Date: Fri, 08 Nov 2013 17:26:24 GMT Server: Apache/2.2.16 (Debian) Location: https://mysite.com/ Vary: Accept-Encoding Content-Encoding: gzip Content-Length: 242 Keep-Alive: timeout=15, max=100 Connection: Keep-Alive Content-Type: text/html; charset=iso-8859-1 <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN"> <html><head> <title>301 Moved Permanently</title> </head><body> <h1>Moved Permanently</h1> <p>The document has moved <a href="https://mysite.com/">here</a>.</p> <hr> <address>Apache/2.2.16 (Debian) Server at mysite.com</address> </body></html> I am worried by the fact that Google fetch is not getting the correct Title tags and Meta information from our homepage and that this is hurting our search results. Additionally, I am worried that we need to do something specific with the sitemap to ensure that Google is correctly indexing all our pages and being able to flow from the HTTPS to the HTTP without issues. Does anybody have any advice on how we can correctly set this up or be sure that Google is fetching the correct information?

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• Throwing and catching exceptions in the same function/method

  - by usr

  I've written a function that asks a user for input until user enters a positive integer (a natural number). Somebody said I shouldn't throw and catch exceptions in my function and should let the caller of my function handle them. I wonder what other developers think about this. I'm also probably misusing exceptions in the function. Here's the code in Java: private static int sideInput() { int side = 0; String input; Scanner scanner = new Scanner(System.in); do { System.out.print("Side length: "); input = scanner.nextLine(); try { side = Integer.parseInt(input); if (side <= 0) { // probably a misuse of exceptions throw new NumberFormatException(); } } catch (NumberFormatException numFormExc) { System.out.println("Invalid input. Enter a natural number."); } } while (side <= 0); return side; } I'm interested in two things: Should I let the caller worry about exceptions? The point of the function is that it nags the user until the user enters a natural number. Is the point of the function bad? I'm not talking about UI (user not being able to get out of the loop without proper input), but about looped input with exceptions handled. Would you say the throw statement (in this case) is a misuse of exceptions? I could easily create a flag for checking validity of the number and output the warning message based on that flag. But that would add more lines to the code and I think it's perfectly readable as it is. The thing is I often write a separate input function. If user has to input a number multiple times, I create a separate function for input that handles all formatting exceptions and limitations.

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• Trying to make a game with C++, using lists to store bullets and enemies, but they are not erased

  - by XD_dued

  I've been trying to make a pretty simple space shooter game with C++, and I have been having a lot of trouble trying to use lists to store enemies and bullets. Basically I followed the post here almost exactly to store my bullets: SDL Bullet Movement I've done something similar to store my enemies. However, when I call bullets.erase(it++), for some reason the bullet is not erased. When the bullet movement is run for the next frame, it tries to re delete the bullet and segfaults the program. When I comment out the erase line, it runs fine, but the bullets are then never erased from the list... Is there any reason why the elements of the list aren't being deleted? I also set it up to print the number of elements in the list for every iteration, and it does not go down after deleting. Thanks! EDIT: Here's the specific code I'm using to store my enemies and having them act: std::list<Grunt*> doGrunts(std::list<Grunt*> grunts) { for(std::list<Grunt*>::iterator it = grunts.begin(); it != grunts.end();) { if((*it)->getHull() == 0) { delete * it; grunts.erase(it++); } else { (**it).doUnit(grunts, it); ++it; } } } Grunt is my enemy class, and the list grunts is a global variable. Is that my problem? When I pass the global into the function it becomes local? I assumed lists would be a reference type so thought this wouldn't be a problem. Sorry if this was a dumb question, I'm very new to C++, this is the first major thing I'm working on.

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• Boundary conditions for testing

  - by Loggie

  Ok so in a programming test I was given the following question. Question 1 (1 mark) Spot the potential bug in this section of code: void Class::Update( float dt ) { totalTime += dt; if( totalTime == 3.0f ) { // Do state change m_State++; } } The multiple choice answers for this question were. a) It has a constant floating point number where it should have a named constant variable b) It may not change state with only an equality test c) You don't know what state you are changing to d) The class is named poorly I wrongly answered this with answer C. I eventually received feedback on the answers and the feedback for this question was Correct answer is a. This is about understanding correct boundary conditions for tests. The other answers are arguably valid points, but do not indicate a potential bug in the code. My question here is, what does this have to do with boundary conditions? My understanding of boundary conditions is checking that a value is within a certain range, which isn't the case here. Upon looking over the question, in my opinion, B should be the correct answer when considering the accuracy issues of using floating point values.

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• More efficient in range checking

  - by Mob

  I am going to use a specific example in my question, but overall it is pretty general. I use java and libgdx. I have a ship that moves through space. In space there is debris that the ship can tractor beam in and and harvest. Debris is stored in a list, and the object contains it own x and y values. So currently there is no way to to find the debris's location without first looking at the debris object. Now at any given time there can be a huge (1000+) amount of debris in space, and I figure that calculating the distance between the ship and every single piece of debris and comparing it to maximum tractor beam length is rather inefficient. I have thought of dividing space into sectors, and have each sector contain a list of every object in it. This way I could only check nearby sectors. However this essentially doubles memory for the list. (I would reference the same object so it wouldn't double overall. I am not CS major, but I doubt this would be hugely significant.) This also means anytime an object moves it has to calculate which sector it is in, again not a huge problem. I also don't know if I can use some sort of 2D MAP that uses x and y values as keys. But since I am using float locations this sounds more trouble than its worth. I am kind of new to programming games, and I imagined there would be some eloquent solution to this issue.

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• What’s ‘default’ for?

  - by Strenium

  Sometimes there's a need to communicate explicitly that value variable is yet to be "initialized" or in other words - we’ve never changed it from its' default value. Perhaps "initialized" is not the right word since a value type will always have some sort of value (even a nullable one) but it's just that - how do we tell? Of course an 'int' would be 0, an 'enum' would the first defined value of a given enum and so on – we sure can make this kind of check "by hand" but eventually it would get a bit messy. There's a more elegant way with a use of little-known functionality of: 'default'Let’s just say we have a simple Enum: Simple Enum namespace xxx.Common.Domain{    public enum SimpleEnum    {        White = 1,         Black = 2,         Red = 3    }}   In case below we set the value of the enum to ‘White’ which happens to be a first and therefore default value for the enum. So the snippet below will set value of the ‘isDefault’ Boolean to ‘true’. 'True' Case SimpleEnum simpleEnum = SimpleEnum.White;bool isDefault; /* btw this one is 'false' by default */ isDefault = simpleEnum == default(SimpleEnum) ? true : false; /* default value 'white' */   Here we set the value to ‘Red’ and ‘default’ will tell us whether or not this the default value for this enum type. In this case: ‘false’. 'False' Case simpleEnum = SimpleEnum.Red; /* change from default */isDefault = simpleEnum == default(SimpleEnum) ? true : false; /* value is not default any longer */ Same 'default' functionality can also be applied to DateTimes, value types and other custom types as well. Sweet ‘n Short. Happy Coding!

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• Designing communications for extensibility

  - by Thomas S.

  I am working on the design stages of an application that will a) collect data from various sources (in my case that's scientific data from serial ports), keeping track of the age of the data, b) generate real-time statistics (e.g. running averages) c) display, record, and otherwise handle the data (and statistics). I anticipate that I will be adding both data producers and consumers over time, and would like to design this application abstractly so that I will be able to trivially add functionality with a small amount of interface code. What I'm stumbling on is deciding what communication infrastructure I should use to handle the interfaces. In particular, how should I make the processed data and statistics available to multiple consumers? Some things I've considered: Writing to several named pipes (variable number). Each consumer reads from one of them. Using FUSE to make a userspace filesystem where a read() returns the latest line of data even if another process has already read it. Making a TCP server, and having consumers connect and request data individually. Simply writing the consumers as part of the same program that aggregates the data. So I would like to hear your all's advice on deciding how to interface these functions in the best way to keep them separate and allow room for extenstions.

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• How do I reconstruct depth in deferred rendering using an orthographic projection?

  - by Jeremie

  I've been trying to get my world space position of my pixel but I4m missing something. I'm using a orthographic view for a 2.5d game. My depth is linear and this is my code. float3 lightPos = lightPosition; float2 texCoord = PostProjToScreen(PSIn.lightPosition)+halfPixel; float depth = tex2D(depthMap, texCoord); float4 position; position.x = texCoord.x *2-1; position.y = (1-texCoord.y)*2-1; position.z = depth.r; position.w = 1; position = mul(position, inViewProjection); //position.xyz/=position.w; // I comment it but even without it it doesn't work float4 normal = (tex2D(normalMap, texCoord)-.5f) * 2; normal = normalize(normal); float3 lightDirection = normalize(lightPos-position); float att = saturate(1.0f - length(lightDirection) /attenuation); float lightning = saturate (dot(normal, lightDirection)); lightning*= brightness; return float4(lightColor* lightning*att, 1); I'm using a sphere but it's not working the way I want. I reproject the texture properly onto the sphere but the light coordinates in the pixel shader seems to be stuck at zero even if when I move the light volume update properly.

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• XNA- Transforming children

  - by user1806687

  So, I have a Model stored in MyModel, that is made from three meshes. If you loop thrue MyModel.Meshes the first two are children of the third one. And was just wondering, if anyone could tell me where is the problem with my code. This method is called whenever I want to programmaticly change the position of a whole model: public void ChangePosition(Vector3 newPos) { Position = newPos; MyModel.Root.Transform = Matrix.CreateScale(VectorMathHelper.VectorMath(CurrentSize, DefaultSize, '/')) * Matrix.CreateFromAxisAngle(MyModel.Root.Transform.Up, MathHelper.ToRadians(Rotation.Y)) * Matrix.CreateFromAxisAngle(MyModel.Root.Transform.Right, MathHelper.ToRadians(Rotation.X)) * Matrix.CreateFromAxisAngle(MyModel.Root.Transform.Forward, MathHelper.ToRadians(Rotation.Z)) * Matrix.CreateTranslation(Position); Matrix[] transforms = new Matrix[MyModel.Bones.Count]; MyModel.CopyAbsoluteBoneTransformsTo(transforms); int count = transforms.Length - 1; foreach (ModelMesh mesh in MyModel.Meshes) { mesh.ParentBone.Transform = transforms[count]; count--; } } This is the draw method: foreach (ModelMesh mesh in MyModel.Meshes) { foreach (BasicEffect effect in mesh.Effects) { effect.View = camera.view; effect.Projection = camera.projection; effect.World = mesh.ParentBone.Transform; effect.EnableDefaultLighting(); } mesh.Draw(); } The thing is when I call ChangePosition() the first time everything works perfectlly, but as soon as I call it again and again. The first two meshes(children meshes) start to move away from the parent mesh. Another thing I wanted to ask, if I change the scale/rotation/position of a children mesh, and then do CopyAbsoluteBoneTransforms() will children meshes be positioned properlly(at the proper distance) or would achieving that require more math/methods? Thanks in advance

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• Most efficient Implementation a Tree in C++

  - by Topo

  I need to write a tree where each element may have any number of child elements, and because of this each branch of the tree may have any length. The tree is only going to receive elements at first and then it is going to use exclusively for iterating though it's branches in no specific order. The tree will have several million elements and must be fast but also memory efficient. My plan makes a node class to store the elements and the pointers to its children. When the tree is fully constructed, it would be transformed it to an array or something faster and if possible, loaded to the processor's cache. Construction and the search on the tree are two different problems. Can I focus on how to solve each problem on the best way individually? The construction of has to be as fast as possible but it can use memory as it pleases. Then the transformation into a format that give us speed when iterating the tree's branches. This should preferably be an array to avoid going back and forth from RAM to cache in each element of the tree. So the real question is which is the structure to implement a tree to maximize insert speed, how can I transform it to a structure that gives me the best speed and memory?

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• Proper way to encapsulate a Shader into different modules

  - by y7haar

  I am planning to build a Shader system which can be accessed through different components/modules in C++. Each component has its own functionality like transform-relevated stuff (handle the MVP matrix, ...), texture handler, light calculation, etc... So here's an example: I would like to display an object which has a texture and a toon shading material applied and it should be moveable. So I could write ONE shading program that handles all 3 functionalities and they are accessed through 3 different components (texture-handler, toon-shading, transform). This means I have to take care of feeding a GLSL shader with different uniforms/attributes. This implies to know all necessary uniform locations and attribute locations, that the GLSL shader owns. And it would also necessary to provide different algorithms to calculate the value for each input variable. Similar functions would be grouped together in one component. A possible way would be, to wrap all shaders in a own definition file written in JSON/XML and parse that file in C++ to get all input members and create and compile the resulting GLSL. But maybe there is another way that is not so complex? So I'm searching for a way to build a system like that, but I'm not sure yet which is the best approach.

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• What is the standard technique for shifting the frames of a sprite according to user input?

  - by virtual__

  From my own experience, I developed two techniques for changing the sprites of a character that's reacting to user input -- this in the context of a classic 2D platformer. The first one is to store all character's pixmaps in a list, putting the index of the currently used pixmap in an ordinary variable. This way, every time the player presses a key -- say the right arrow for moving the character forward -- the graphics engine sees what's the next pixmap to draw, draws it, and increments the index counter. That's a pretty common approach I believe, the problem is that in this case the animation's quality depends not only on the number of sprites available but also on how often your engine listens to user input. The second technique is to actually play an animation every key press event. For this you can use any sort of animation framework you want. It's only necessary to set the timer, the animation steps and to call the animation's play() method on your key press event handler. The problem with that approach is that is lacks responsiveness, since the character won't react to any input while the current animation is still being played. What I want to know is whether you are using one of these techniques -- or something similar -- in your games, or whether there's a standard method for animating sprites out there that's widely known by everybody but me.

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• Getting Center and Radius of Irregural Object

  - by Moaz ELdeen

  I have drawn an asteroid object manually , and would like to get its center/radius by a specific equation. I think I can get them by calculated and hard-coded values. The code to draw the asteroid: void Asteroid::Draw() { float ratio = app::getWindowWidth()/app::getWindowHeight(); gl::pushMatrices(); gl::translate(m_Pos*ratio); gl::scale(3.5*ratio,3.5*ratio,3.5*ratio); gl::color(ci::Color(1,1,1)); gl::drawLine(Vec2f(-15,0),Vec2f(-10,-5)); gl::drawLine(Vec2f(-10,-5),Vec2f(-5,-5)); gl::drawLine(Vec2f(-5,-5),Vec2f(-5,-8)); gl::drawLine(Vec2f(-5,-8),Vec2f(5,-8)); gl::drawLine(Vec2f(5,-8),Vec2f(5,-5)); gl::drawLine(Vec2f(5,-5),Vec2f(10,-5)); gl::drawLine(Vec2f(10,-5),Vec2f(15,0)); gl::drawLine(Vec2f(15,0),Vec2f(10,5)); gl::drawLine(Vec2f(10,5),Vec2f(-10,5)); gl::drawLine(Vec2f(-10,5),Vec2f(-10,5)); gl::drawLine(Vec2f(-15,0),Vec2f(-10,5)); gl::popMatrices(); } According to the answer I have written that code to calculate the radius, is it correct or not ? cinder::Vec2f Asteroid::getCenter() { return ci::Vec2f(m_Pos.x, m_Pos.y); } double Asteroid::getRadius() { ci::Vec2f _vec = (getCenter()- Vec2f(15,5)); return _vec.length()*0.3f; }

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• Finite Numbers and ExplorerCanvas

  - by PhubarBaz

  I was working on my online mathematical graphing application, CloudGraph, and trying to make it work in IE. The app uses the HTML5 canvas element to draw graphs. Since IE doesn't support canvas yet I use ExplorerCanvas to provide that support for IE. However, it seems that when using excanvas, if you try to moveTo or drawTo a point that is not finite it loses it's mind and stops drawing anything else after that. I had no such problems in Firefox or Chrome so it took me awhile to figure out what was going on. Next I discovered that I needed a way to check if a variable was NaN or Inifinity or any other non-finite value so I could avoid calling moveTo() in that case. I started writing a long if statement, then I thought there has to be a better way. Sure enough there was. There just happens to be an isFinite() function built into Javascript just for this purpose. Who knew! It works great. Another difference I discovered with excanvas is that you must specify a starting point using a moveTo() when beginning a drawing path. Again, Chrome and Firefox are a lot more forgiving in this area so it took me a while to figure out why my lines weren't drawing. But, all is happy now and I'm a little wiser to the ways of the canvas.

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• 7 drived classes with one common base class

  - by user144905

  i have written the following code, //main.cpp #include<iostream> #include<string> #include"human.h" #include"computer.h" #include"referee.h" #include"RandomComputer.h" #include"Avalanche.h" #include"Bureaucrat.h" #include"Toolbox.h" #include"Crescendo.h" #include"PaperDoll.h" #include"FistfullODollors.h" using namespace std; int main() { Avalanche pla1; Avalanche pla2; referee f; pla1.disp(); for (int i=0;i<5;i++) { cout<<pla2.mov[i]; } return 0; } in this program all included classes except referee.h and human.h are drived from computer.h. each drived calls has a char array variable which is initialized when a member of a drived class is declared. the problem is that when i declare tow diffrent drived class memebers lets say Avalache and ToolBox. upon printing the char array for one of them using for loop it prints nothing. However if i declare only one of them in main.cpp the it works properly. and the file for computer.h is as such: #ifndef COMPUTER_H #define COMPUTER_H class computer { public: int nump; char mov[]; void disp(); }; #endif ToolBox.h is like this: #ifndef TOOLBOX_H #define TOOLBOX_H #include"computer.h" class Toolbox: public computer { public: Toolbox(); }; #endif finally Avalanche.h is as following: #ifndef AVALANCHE_H #define AVALANCHE_H #include"computer.h" class Avalanche: public computer { public: Avalanche(); }; #endif

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• How to input data into user defined variables into MySql query

  - by user292791

  Simple Shell script echo "Enter 1 for month of March" echo "Enter 2 for month of April" echo "Enter 3 for month of May" read Month case "$Month" in 1) echo "enter establishment name" read a; mysql -u root -p $a < "March.sql";; 2) echo "enter establishment name" read b; mysql -u root -p $b < "April.sql";; 3) echo "enter establishment name" read c; mysql -u root -p $c < "May.sql";; esac done In this i have three other query files March.sql, April.sql, May.sql. i'm linking this in shell script . Example of .sql file: SELECT DISTINCT substr( a.case_no, 3, 2 ), b.case_type, b.type_name, a.case_no into outfile '/tmp/April.csv' FIELDS TERMINATED BY ',' ENCLOSED BY '"' LINES TERMINATED BY '\r\n' FROM Civil_t AS a, Case_type_t AS b, disposal_proc AS c WHERE substr( a.case_no, 3, 2 ) = b.case_type AND a.date_of_decision BETWEEN '2014-04-01' AND '2014-04-30' AND a.case_no = c.case_no AND a.court_no =1; I have to alter the .sql script every time. Is there any method to read the variables from shell script and use it in mysql. For example:- echo "enter date" read a #input date Now i have read a "date" and i want to use it in March.sql query in where clause. Is there is any method of using this variable in .sql query.

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• CUDA 4.1 Update

  - by N0xus

  I'm currently working on porting a particle system to update on the GPU via the use of CUDA. With CUDA, I've already passed over the required data I need to the GPU and allocated and copied the date via the host. When I build the project, it all runs fine, but when I run it, the project says I need to allocate my h_position pointer. This pointer is my host pointer and is meant to hold the data. I know I need to pass in the current particle position to the required cudaMemcpy call and they are currently stored in a list with a for loop being created and interated for each particle calling the following line of code: m_particleList[i].positionY = m_particleList[i].positionY - (m_particleList[i].velocity * frameTime * 0.001f); My current host side cuda code looks like this: float* h_position; // Your host pointer. This holds the data (I assume it's already filled with the data.) float* d_position; // Your device pointer, we will allocate and fill this float* d_velocity; float* d_time; int threads_per_block = 128; // You should play with this value int blocks = m_maxParticles/threads_per_block + ( (m_maxParticles%threads_per_block)?1:0 ); const int N = 10; size_t size = N * sizeof(float); cudaMalloc( (void**)&d_position, m_maxParticles * sizeof(float) ); cudaMemcpy( d_position, h_position, m_maxParticles * sizeof(float), cudaMemcpyHostToDevice); Both of which were / can be found inside my UpdateParticle() method. I had originally thought it would be a simple case of changing the h_position variable in the cudaMemcpy to m_particleList[i] but then I get the following error: no suitable conversion function from "ParticleSystemClass::ParticleType" to "const void *" exists I've probably messed up somewhere, but could someone please help fix the issues I'm facing. Everything else seems to running fine, it's just when I try to run the program that certain things hit the fan.

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• Should I always encapsulate an internal data structure entirely?

  - by Prog

  Please consider this class: class ClassA{ private Thing[] things; // stores data // stuff omitted public Thing[] getThings(){ return things; } } This class exposes the array it uses to store data, to any client code interested. I did this in an app I'm working on. I had a ChordProgression class that stores a sequence of Chords (and does some other things). It had a Chord[] getChords() method that returned the array of chords. When the data structure had to change (from an array to an ArrayList), all client code broke. This made me think - maybe the following approach is better: class ClassA{ private Thing[] things; // stores data // stuff omitted public Thing[] getThing(int index){ return things[index]; } public int getDataSize(){ return things.length; } public void setThing(int index, Thing thing){ things[index] = thing; } } Instead of exposing the data structure itself, all of the operations offered by the data structure are now offered directly by the class enclosing it, using public methods that delegate to the data structure. When the data structure changes, only these methods have to change - but after they do, all client code still works. Note that collections more complex than arrays might require the enclosing class to implement even more than three methods just to access the internal data structure. Is this approach common? What do you think of this? What downsides does it have other? Is it reasonable to have the enclosing class implement at least three public methods just to delegate to the inner data structure?

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• why does array initialization in function other than main is temporary? [on hold]

  - by shafeeq

  This is the code in which i initialize array "turn[20]" in main as well as in function "checkCollisionOrFood()",the four values turn[0],turn[1],turn[2],turn[3] are initialized to zero in main function,rest are being intialized in "checkCollisionOrFood()".This is where fault starts.when i initialize turn[4]=0 in "checkCollisionOrFood()" and then access it anywhere,it remains 0 in any function,but! when i initialize next turn[] i.e turn[5],the value of turn[4] gets depleted .i.e turn[4] have garbage value.turn[20] is global variable,its index"head" is also global.I'm stuck.Plz help me get out of it.Ishall be highly obliged for this act of kindness.This is my excerpt of code unsigned short checkCollisionOrFood(){ head=(head+1)%20; if(turn[head-1]==0){ turn[head]=0; /this is where turn[] is iniliazized and if i access turn[head] here i.e just after iniliazition then it gives correct value but if i access its previous value means turn[head-1]then it gives garbage value/ rowHead=(rowHead+1)%8; if(!(address[colHead]&(1<<rowHead)))return 1; else if((address[colHead]&(1<<rowHead))&& (!((colHead==foody)&&(rowHead==foodx))))gameOver(); else return 0; } if(turn[head-1]==1){ turn[head]=1; colHead=(colHead+1)%8; if(!(address[colHead]&(1<<rowHead)))return 1; else if((address[colHead]&(1<<rowHead))&& (!((colHead==foody)&&(rowHead==foodx))))gameOver(); else return 0; } } void main(void) { turn[0]=0;turn[1]=0;turn[2]=0;turn[3]=0; /these values of turn[] are not changed irrespective of where they are accessed./ while (1) { if(checkCollisionOrFood()) { PORTB=(address[colHead] |=1<<rowHead); turnOffTail(); blink(); } else { PORTB=address[colHead]; createFood(); blink(); } } } Plz help me.

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• Rendering multiple squares fast?

  - by Sam

  so I'm doing my first steps with openGL development on android and I'm kinda stuck at some serious performance issues... What I'm trying to do is render a whole grid of single colored squares on to the screen and I'm getting framerates of ~7FPS. The squares are 9px in size right now with one pixel border in between, so I get a few thousand of them. I have a class "Square" and the Renderer iterates over all Squares every frame and calls the draw() method of each (just the iteration is fast enough, with no openGL code the whole thing runs smootlhy at 60FPS). Right now the draw() method looks like this: // Prepare the square coordinate data GLES20.glVertexAttribPointer(mPositionHandle, COORDS_PER_VERTEX, GLES20.GL_FLOAT, false, vertexStride, vertexBuffer); // Set color for drawing the square GLES20.glUniform4fv(mColorHandle, 1, color, 0); // Draw the square GLES20.glDrawElements(GLES20.GL_TRIANGLES, drawOrder.length, GLES20.GL_UNSIGNED_SHORT, drawListBuffer); So its actually only 3 openGL calls. Everything else (loading shaders, filling buffers, getting appropriate handles, etc.) is done in the Constructor and things like the Program and the handles are also static attributes. What am I missing here, why is it rendering so slow? I've also tried loading the buffer data into VBOs, but this is actually slower... Maybe I did something wrong though. Any help greatly appreciated! :)

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• Is application-specific data required for good unit testing?

  - by stinkycheeseman

  I am writing unit tests for a fairly simple function that depends on a fairly complicated set of data. Essentially, the object I am manipulating represents a graph and this function determines whether to chart a line, bar, or pie chart based on the data that came back from the server. This is a simplified version, using jQuery: setDefaultChartType: function (graphObject) { var prop1 = graphObject.properties.key; var numCols = 0; $.each(graphObject.columns, function (colIndex, column) { numCols++; }); if ( numCols > 6 || ( prop1 > 1 && graphObject.data.length == 1) ) { graphObject.setChartType("line"); } else if ( numCols <=6 && prop1 == 1 ) { graphObject.setChartType("bar"); } else if ( numCols <=6 && prop1 > 1 ) { graphObject.setChartType("pie"); } } My question is, should I use mock data that is procured from the actual database? Or can I just fabricate data that fits the different cases? I'm afraid that fabricating data will not expose bugs arising from changes in the database, but on the other hand, it would require a lot more effort to keep the test data up-to-date that I'm not sure is necessary.

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