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• How to use boost normal distribution classes?

  - by David Alfonso

  Hi all, I'm trying to use boost::normal_distribution in order to generate a normal distribution with mean 0 and sigma 1. The following code uses boost normal classes. Am I using them correctly? #include <boost/random.hpp> #include <boost/random/normal_distribution.hpp> int main() { boost::mt19937 rng; // I don't seed it on purpouse (it's not relevant) boost::normal_distribution<> nd(0.0, 1.0); boost::variate_generator<boost::mt19937&, boost::normal_distribution<> > var_nor(rng, nd); int i = 0; for (; i < 10; ++i) { double d = var_nor(); std::cout << d << std::endl; } } The result on my machine is: 0.213436 -0.49558 1.57538 -1.0592 1.83927 1.88577 0.604675 -0.365983 -0.578264 -0.634376 As you can see all values are not between -1 and 1. Thank you all in advance!

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• Which is better? OpenCyc or ConceptNet?

  - by Daniel Loureiro

  Hi, I'm doing a NLP project where I need to recognise concepts in sentences to find other similar concepts. I do this to infer word valences from a list I already have. I started using WordNet, but it gave many contradictory results. By contradictory results I mean word expansions that had contradictory valences. So now I'm looking into ConceptNet and OpenCyc. I've already implemented ConceptNet and it was all very easy and I love it. Problem is that OpenCyc appears to have a much larger and more logically rigid database, which is important when I found so many "contradictions" on WordNet... But I wouldn't know because I haven't tried it. Could someone tell me if it's worth going through the (considerable, for me) effort to implement OpenCyc, or is ConceptNet good enough to infer word valences? Are they that different? I'll be happy to explain myself further, if needed. Trying to keep it short for now! Thanks!

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• Does ASP.NET need to be configured for Full Trust to implement 'PageHandlerFactory' ?

  - by Kev

  Our hosting platform (running IIS6/ASP.NET 2.0) is configured to run under partial trust. In the machine wide web.config file we set the ASP.NET trust level to Medium (and lock to prevent overrides) and use a modified policy file. When trying to add a custom HttpHandler to handle .aspx requests for a website running in this configuration I get the following security exception: Security Exception Description: The application attempted to perform an operation not allowed by the security policy. To grant this application the required permission please contact your system administrator or change the application's trust level in the configuration file. Exception Details: System.Security.SecurityException: Request failed. Source Error: An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below. Stack Trace: [SecurityException: Request failed.] System.Reflection.Assembly._GetType(String name, Boolean throwOnError, Boolean ignoreCase) +0 System.Reflection.Assembly.GetType(String name, Boolean throwOnError, Boolean ignoreCase) +42 System.Web.Compilation.CompilationUtil.GetTypeFromAssemblies(AssemblyCollection assembliesCollection, String typeName, Boolean ignoreCase) +172 System.Web.Compilation.BuildManager.GetType(String typeName, Boolean throwOnError, Boolean ignoreCase) +291 System.Web.Configuration.ConfigUtil.GetType(String typeName, String propertyName, ConfigurationElement configElement, XmlNode node, Boolean checkAptcaBit, Boolean ignoreCase) +52 I'm using a class derived from PageHandlerFactory, for example: public class MyPageHandlerFactory : PageHandlerFactory { public override System.Web.IHttpHandler GetHandler(System.Web.HttpContext context, string requestType, string virtualPath, string path) { // CustomPageHandler derives from System.Web.UI.Page return new CustomPageHandler(); } } My web.config httpHandler configuration is as follow: <httpHandlers> <add verb="*" path="*.aspx" type="MyPageHandler.MyPageHandlerFactory" /> </httpHandlers> The documentation for PageHandlerFactory shows that PageHandlerFactory is decorated with the following attributes: [PermissionSetAttribute(SecurityAction.LinkDemand, Unrestricted = true)] [PermissionSetAttribute(SecurityAction.InheritanceDemand, Unrestricted = true)] public class PageHandlerFactory : IHttpHandlerFactory Does this mean that I need to set ASP.NET to run at Full Trust to be able to create my own PageHandlerFactory classes?

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• Using JSF, PrimeFaces and JPA: Create Basic WebApp without using Generated CRUD Classes, Forms, etc

  - by user2774489

  I am trying to build a basic CRUD application with NetBeans 7.4, JSF, PrimeFaces and JPA using MySQL. I have successfully done this by using the NetBeans wizards. I want to do this from scratch, no wizards. There seems to be a lack of support for the combo of JSF, PrimeFaces and JPA. When I say "lack", I mean a full example (I might be asking too much), without using the CRUD auto-gen templates/classes AND shows actual queries coded and passed to the datatables(primefaces). YouTube is full of non-English speaking examples using Hibernate (not JPA) and other examples that show flashy GUI's with no code. So far I understand you need an @Entity class (provides the physical build of the tables), a Controller (serializable) and the .xhtml web page to show the datatable.. what else? Also, I'm not seeing any posts or examples where queries are using with JPA/JSF and how they are tied together (in one place). I need to connect the dots here so that I can leverage JSF/JPA to create simple queries to populate my PF DataTables. I've read the blogs and I've googled the intranets until I'm blue in the face. Sending me a list of URL's to read to learn about each product is something I've already done. I get what they do independently, but am looking for the "How do they all connect" answer with maybe some basic code examples!! :)

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• Reading a Wordpress function description

  - by Casebash

  I want to be able to understand the standard function description that is provided for Wordpress functions. In particular, could someone explain the following example from here: Usage <?php wp_list_categories( $args ); ?> Default Usage <?php $args = array( 'show_option_all' => , 'orderby' => 'name', 'order' => 'ASC', 'show_last_update' => 0, 'style' => 'list', 'show_count' => 0, 'hide_empty' => 1, 'use_desc_for_title' => 1, 'child_of' => 0, 'feed' => , 'feed_type' => , 'feed_image' => , 'exclude' => , 'exclude_tree' => , 'include' => , 'current_category' => 0, 'hierarchical' => true, 'title_li' => __( 'Categories' ), 'number' => NULL, 'echo' => 1, 'depth' => 0 ); ?> I can guess most of it, but in particular I can't guess: What does blank after the comma mean? Empty string? What is the __? How do I call the function? Keyword like python, positional arguments or do I have to pass an array? Is there anything else about Wordpress function descriptions which isn't covered in this example? Thanks, Chris

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• Dealing with expired session for a partially filled form?

  - by aaronls

  I have a large webform, and would like to prompt the user to login if their session expires, or have them login when they submit the form. It seems that having them login when they submit the form creates alot of challenges because they get redirected to the login page and then the postback data for the original form submission is lost. So I'm thinking about how to prompt them to login asynchrounsly when the session expires. So that they stay on the original form page, have a panel appear telling them the session has expired and they need to login, it submits the login asynchronously, the login panel disapears, and the user is still on the original partially filled form and can submit it. Is this easily doable using the existing ASP.NET Membership controls? When they submit the form will I need to worry about the session key? I mean, I am wondering if the session key the form submits will be the original one from before the session expired which won't match the new one generated after logging in again asynchrounously(I still do not understand the details of how ASP.NET tracks authentication/session IDs). Edit: Yes I am actually concerned about authentication expiration. The user must be authenticated for the submitted data to be considered valid.

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• Using SHFileOperation: What errors are occuring

  - by Sascha

  Hello I am using the function SHFileOperation() to send a file to the recycling bin. And I am getting 2 errors that I do not know what they mean because with this function the error codes are not GetLastError() values. Now when the function SHFileOperation() fails the return values are 0x57 (decimal 87) & 0x2 (decimal 2). Can you help me discover the definitions of these errors (expecially when you consider with this function, the errors are not part of the GetLastError() codes). Some important information: • I am using Windows 7 (& I know that MSDN says to use IFileOperation instead of SHFileOperation but I want to make my app backwards compatable which is why I am using SHFileOperation). If the error is occuring because I am using SHFileOperation on Windows 7 what solution could I use to make this work on all versions of windows from 2000 & up? • I have debugged extensively & as far as I know my SHFILEOPSTRUCT is correct (correct flags used, .pFrom is a double-null ended string). One thing I know for sure is that my path to the file is correct (leads to a real file & it correctly formatted). • About 2/5 times the SHFileOperation() works, meaning it sends the file to the recycle bin & does not returns an error BOOL result; SHFILEOPSTRUCT fileStruct; fileStruct.hwnd = hwnd; fileStruct.wFunc = FO_DELETE; fileStruct.pFrom = dest.c_str(); fileStruct.fFlags = FOF_FILESONLY; // FOF_ALLOWUNDO fileStruct.fAnyOperationsAborted = result; // Call operation(delete file) int success = SHFileOperation( &fileStruct ); // if delete was successful if ( success != 0 ) { printf( "%s \t %X %d \n", dest.c_str(), success, success ); cout << result << endl; MessageBox( hwnd, "Failed to delete file", "Error", MB_OK|MB_ICONERROR ); return; }

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• Linear regression confidence intervals in SQL

  - by Matt Howells

  I'm using some fairly straight-forward SQL code to calculate the coefficients of regression (intercept and slope) of some (x,y) data points, using least-squares. This gives me a nice best-fit line through the data. However we would like to be able to see the 95% and 5% confidence intervals for the line of best-fit (the curves below). What these mean is that the true line has 95% probability of being below the upper curve and 95% probability of being above the lower curve. How can I calculate these curves? I have already read wikipedia etc. and done some googling but I haven't found understandable mathematical equations to be able to calculate this. Edit: here is the essence of what I have right now. --sample data create table #lr (x real not null, y real not null) insert into #lr values (0,1) insert into #lr values (4,9) insert into #lr values (2,5) insert into #lr values (3,7) declare @slope real declare @intercept real --calculate slope and intercept select @slope = ((count(*) * sum(x*y)) - (sum(x)*sum(y)))/ ((count(*) * sum(Power(x,2)))-Power(Sum(x),2)), @intercept = avg(y) - ((count(*) * sum(x*y)) - (sum(x)*sum(y)))/ ((count(*) * sum(Power(x,2)))-Power(Sum(x),2)) * avg(x) from #lr Thank you in advance.

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• Groovy / Scala / Java under the hood

  - by Jack

  I used Java for like 6-7 years, then some months ago I discovered Groovy and started to save a lot of typing.. then I wondered how certain things worked under the hood (because groovy performance is really poor) and understood that to give you dynamic typing every Groovy object is a MetaClass object that handles all the things that the JVM couldn't handle by itself. Of course this introduces a layer in the middle between what you write and what you execute that slows down everything. Then somedays ago I started getting some infos about Scala. How these two languages compare in their byte code translations? How much things they add to the normal structure that it would be obtained by plain Java code? I mean, Scala is static typed so wrapper of Java classes should be lighter, since many things are checked during compile time but I'm not sure about the real differences of what's going inside. (I'm not talking about the functional aspect of Scala compared to the other ones, that's a different thing) Can someone enlighten me? From WizardOfOdds it seems like that the only way to get less typing and same performance would be to write an intermediate translator that translates something in Java code (letting javac compile it) without alterating how things are executed, just adding synctatic sugar withour caring about other fallbacks of the language itself.

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• Is there a language with native pass-by-reference/pass-by-name semantics, which could be used in mod

  - by Bubba88

  Hi! This is a reopened question. I look for a language and supporting platform for it, where the language could have pass-by-reference or pass-by-name semantics by default. I know the history a little, that there were Algol, Fortran and there still is C++ which could make it possible; but, basically, what I look for is something more modern and where the mentioned value pass methodology is preferred and by default (implicitly assumed). I ask this question, because, to my mind, some of the advantages of pass-by-ref/name seem kind of obvious. For example when it is used in a standalone agent, where copyiong of values is not necessary (to some extent) and performance wouldn't be downgraded much in that case. So, I could employ it in e.g. rich client app or some game-style or standalone service-kind application. The main advantage to me is the clear separation between identity of a symbol, and its current value. I mean when there is no reduntant copying, you know that you're working with the exact symbol/path you have queried/received. And intristing boxing of values will not interfere with the actual logic of program. I know that there is C# ref keyword, but it's something not so intristic, though acceptable. Equally, I realize that pass-by-reference semantics could be simulated in virtually any language (Java as an instant example) and so on.. not sure about pass by name :) What would you recommend - create a something like DSL for such needs wherever it be appropriate; or use some languages that I already know? Maybe, there is something that I'm missing? Thank you!

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• Understanding Symbols In Ruby

  - by Kezzer

  Despite reading this article, I'm still confused as to the representation of the data in memory when it comes to using symbols. If a symbol, two of them contained in different objects, exist in the same memory location, then how is it that they contain different values? I'd have expected the same memory location to contain the same value. As a quote from the link: Unlike strings, symbols of the same name are initialized and exist in memory only once during a session of ruby I just don't understand how it manages to differentiate the values contained in the same memory location. EDIT So let's consider the example: patient1 = { :ruby => "red" } patient2 = { :ruby => "programming" } patient1.each_key {|key| puts key.object_id.to_s} 3918094 patient2.each_key {|key| puts key.object_id.to_s} 3918094 patient1 and patient2 are both hashes, that's fine. :ruby however is a symbol. If we were to output the following: patient1.each_key {|key| puts key.to_s} Then what will be output? "red", or "programming"? FURTHER EDIT I'm still really quite confused. I'm thinking a symbol is a pointer to a value. Let's forget hashes for a second. The questions I have are; can you assign a value to a symbol? Is a symbol just a pointer to a variable with a value in it? If symbols are global, does that mean a symbol always points to one thing?

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• Execute function without sending 'self' to it

  - by Sergey

  Is that possible to define a function without referencing to self this way? def myfunc(var_a,var_b) But so that it could also get sender data, like if I defined it like this: def myfunc(self, var_a,var_b) That self is always the same so it looks a little redundant here always to run a function this way: myfunc(self,'data_a','data_b'). Then I would like to get its data in the function like this sender.fields. UPDATE: Here is some code to understand better what I mean. The class below is used to show a page based on Jinja2 templates engine for users to sign up. class SignupHandler(webapp.RequestHandler): def get(self, *args, **kwargs): utils.render_template(self, 'signup.html') And this code below is a render_template that I created as wrapper to Jinja2 functions to use it more conveniently in my project: def render_template(response, template_name, vars=dict(), is_string=False): template_dirs = [os.path.join(root(), 'templates')] logging.info(template_dirs[0]) env = Environment(loader=FileSystemLoader(template_dirs)) try: template = env.get_template(template_name) except TemplateNotFound: raise TemplateNotFound(template_name) content = template.render(vars) if is_string: return content else: response.response.out.write(content) As I use this function render_template very often in my project and usually the same way, just with different template files, I wondered if there was a way to get rid of having to call it like I do it now, with self as the first argument but still having access to that object.

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• C Run-Time library part 2

  - by b-gen-jack-o-neill

  Hi, I was suggested when I have some further questions on my older ones, to create newer Question and reffer to old one. So, this is the original question: What is the C runtime library? OK, from your answers, I now get thet statically linked libraries are Microsoft implementation of C standart functions. Now: If I get it right, the scheme would be as follow: I want to use printf(), so I must include which just tels compiler there us functio printf() with these parameters. Now, when I compile code, becouse printf() is defined in C Standart Library, and becouse Microsoft decided to name it C Run Time library, it gets automatically statically linked from libcmt.lib (if libcmt.lib is set in compiler) at compile time. I ask, becouse on wikipedia, in article about runtime library there is that runtime library is linked in runtime, but .lib files are linked at compile time, am I right? Now, what confuses me. There is .dll version of C standart library. But I thought that to link .dll file, you must actually call winapi program to load that library. So, how can be these functions dynamically linked, if there is no static library to provide code to tell Windows to load desired functions from dll? And really last question on this subject - are C Standart library functions also calls to winapi even they are not .dll files like more advanced WinAPI functions? I mean, in the end to access framebuffer and print something you must tell Windows to do it, since OS cannot let you directly manipulate HW. I think of it like the OS must be written to support all C standart library functions same way across similiar versions, since they are statically linked, and can differently support more complex WinAPI calls becouse new version of OS can have adjustements in the .dll file.

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• Task predecessor/dependencies logic for task management application

  - by Serge

  Hey guys, I'm trying to figure out the logic for creating tasks that have dependencies. In short I'm building a dynamic task management system and each tasks has several options one of them is to have the task start after a predecessor. Users can add/remove/re-order (by drag&drop) tasks so I'm wondering how can I make the predecessors dynamic, here's an example of what I mean Task 1 Task 2 Task 3 - dependent of task 2 Task 4 - dependent of task 2 Tasks get renamed on delete and/or re-order. If task 1 gets deleted then 3 and 4 should become dependent of task 1 (which is the old task 2). I've been banging my head for the past few hours trying to figure out how to do that. I'm using jQuery right now and each task is contained in a div with an incremental id (ie id="task1") that gets renamed whenever a task is removed or re-ordered and I'm using a dynamically populated drop down for selecting a predecessor. What would be the easiest way to get this done?? by the way, I'm not necessarily asking for code, just trying to figure out the best way to tackle this

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• Tablet interface for the physically disabled?

  - by Glenn

  My sister has Cerebral Palsy, which in her case means she has only gross motor control and her speech is slurred. Implications should be obvious: traditional computer/phone/tablet interfaces won't work for her and she can't speak clearly enough for speech recognition software to help her at all. She enjoys reading but has difficulty holding the book and/or turning a page. There are a few options for helping her use a computer, but nothing for tablets or eReaders. That's where you come in. I would like to make (or buy, if such a thing exists) a better interface to an Android tablet that would work for someone with little to no physical dexterity or speech ability. I'd also be interested in work on the Kindle or iPad, but I'm most familiar with Android so I'm starting there. I know Android has Bluetooth capability. Is it possible to interface a joystick to control the Android device? By "control", I mean the entire operating system - selecting an app, launching it, controlling the menus, etc. I want to give her control over the whole thing, not just a specific app. On a PC this can be accomplished by creating a generic USB HID interface and an arcade joystick to move the mouse over the screen and click on thigns. Is it possible to do something like that in Android? Any help you can offer would be greatly appreciated. Thanks!

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• Reducing the opacity on a div without reducing the opacity of the contents

  - by user352744

  Want to reduce the opacity of page contents container background without reducing the opacity of the contents. <div id="container"> <div id="page contents"> page contents goes here, like amazing articles and all that. </div> </div> Needs to be able to expand with the content, thus can't have a fixed height. Absolute positioning it underneath the content will mean there will be no relationship between the two divs and it wont expand with the contents, so I think this is a dead end, feel free to say otherwise. Can't use Jquery as could be too laggy and not instant. Other options preferred please. May have to use 'png' background images but were hoping not to as it is a template and needs to be able to change colour based on colour schemes. Could generate images on demand but not ideal. Oh and to top it off cant use CSS3 as wont work in IE! of course! Any suggestions?

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• Strongly Typed Controls in .NET

  - by Tigraine

  I am working on a Windows Forms app for quite some time now, and I really find myself doing more typecasts in the GUI code than I ever did in my underlying business code. What I mean becomes apparent if you watch the ComboBox control that accepts some vague "object" as it's item. Then you go off and may display some DisplayMember and a ValueMember and so on. If I want to retrieve that value later I need to typecast my object back to what it was. Like with strings getting the value takes string value = (string)combobox1.SelectedItem; Since there are generics in the Framework for quite some time now, I still wonder why in the Hell not one control from the standard toolbox is generic. I also find myself using the .Tag property on ListViewItems all the time to keep the displayed domain object. But everytime I need to access that object I then need another typecast. Why cant I just create a ComboBox or ListView with items of type ListViewItem Am I missing something here or is this just another example of not perfectly well thought through controls?

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• how to apply iddata into calculation?

  - by Sam

  I am trying to figure out how to combine the input and output data into the ARX model and then apply it into the BIC (Bayesian Information Criterion) formula. Below is the code that I am currently working on: for i=1:30; %% Set Model Order data=iddata(output,input,1); model = arx(data,[8 9 i]); yp = predict(model,data); ye = regress(data,yp{1,1}(1:4018,1)); M(i) = var(yp); BIC(i)=(N+i*(log(N)-1))/(N-i)*log(M(i)); end But it does not work. It keep on giving me an error something like below: "The syntax "Data{...}" is not supported. Use the "getexp" command to extract individual experiments from an IDDATA object." I did not understand what does that mean. Can someone explain it to me and where do I do wrong on my piece of code? Thanks in advance. Sam.

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• how to pause and stop a changing ImageView

  - by user270811

  hi, i have an ImageView in which the picture switches every 5s, i am trying to add a pause and resume button that can stop and restart the action. i am using a Handler, Runnable, and postDelay() for image switch, and i put the code on onResume. i am thinking about using wait and notify for the pause and resume, but that would mean creating an extra thread. so far for the thread, i have this: class RecipeDisplayThread extends Thread { boolean pleaseWait = false; // This method is called when the thread runs public void run() { while (true) { // Do work // Check if should wait synchronized (this) { while (pleaseWait) { try { wait(); } catch (Exception e) { } } } // Do work } } } and in the main activity's onCreate(): Button pauseButton = (Button) findViewById(R.id.pause); pauseButton.setOnClickListener(new View.OnClickListener() { public void onClick(View view) { while (true) { synchronized (thread) { thread.pleaseWait = true; } } } }); Button resumeButton = (Button) findViewById(R.id.resume); resumeButton.setOnClickListener(new View.OnClickListener() { public void onClick(View view) { while (true) { // Resume the thread synchronized (thread) { thread.pleaseWait = false; thread.notify(); } } } }); the pause button seems to work, but then after that i can't press any other button, such as the resume button. thanks.

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• 'Bank Switching' Sprites on old NES applications

  - by Jeffrey Kern

  I'm currently writing in C# what could basically be called my own interpretation of the NES hardware for an old-school looking game that I'm developing. I've fired up FCE and have been observing how the NES displayed and rendered graphics. In a nutshell, the NES could hold two bitmaps worth of graphical information, each with the dimensions of 128x128. These are called the PPU tables. One was for BG tiles and the other was for sprites. The data had to be in this memory for it to be drawn on-screen. Now, if a game had more graphical data then these two banks, it could write portions of this new information to these banks -overwriting what was there - at the end of each frame, and use it from the next frame onward. So, in old games how did the programmers 'bank switch'? I mean, within the level design, how did they know which graphic set to load? I've noticed that Mega Man 2 bankswitches when the screen programatically scrolls from one portion of the stage to the next. But how did they store this information in the level - what sprites to copy over into the PPU tables, and where to write them at? Another example would be hitting pause in MM2. BG tiles get over-written during pause, and then get restored when the player unpauses. How did they remember which tiles they replaced and how to restore them? If I was lazy, I could just make one huge static bitmap and just grab values that way. But I'm forcing myself to limit these values to create a more authentic experience. I've read the amazing guide on how M.C. Kids was made, and I'm trying to be barebones about how I program this game. It still just boggles my mind how these programmers accomplisehd what they did with what they had. EDIT: The only solution I can think of would be to hold separate tables that state what tiles should be in the PPU at what time, but I think that would be a huge memory resource that the NES wouldn't be able to handle.

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• Concatenate CLOB-rows with PL/SQL

  - by david K

  Hi, I've got a table which has an id and a clob content like: Create Table v_example_l ( nip number, xmlcontent clob ); We insert our data: Insert into V_EXAMPLE_L (NIP,XMLCONTENT) Values (17852,'<section><block><name>delta</name><content>548484646846484</content></block></section>'); Insert into V_EXAMPLE_L (NIP,XMLCONTENT) Values (17852,'<section><block><name>omega</name><content>545648468484</content></block></section>'); Insert into V_EXAMPLE_L (NIP,XMLCONTENT) Values (17852,'<section><block><name>gamma</name><content>54564846qsdqsdqsdqsd8484</content></block></section>'); I'm trying to do a function that concatenates the rows of the clob that gone be the result of a select, i mean without having to give multiple parameter about the name of table or such, i should only give here the column that contain the clobs, and it should handle the rest. CREATE OR REPLACE function assemble_clob(q varchar2) return clob is v_clob clob; tmp_lob clob; hold VARCHAR2(4000); --cursor c2 is select xmlcontent from V_EXAMPLE_L where id=17852 cur sys_refcursor; begin OPEN cur FOR q; LOOP FETCH cur INTO tmp_lob; EXIT WHEN cur%NOTFOUND; --v_clob := v_clob || XMLTYPE.getClobVal(tmp_lob.xmlcontent); v_clob := v_clob || tmp_lob; END LOOP; return (v_clob); --return (dbms_xmlquery.getXml( dbms_xmlquery.set_context("Select 1 from dual")) ) end assemble_clob; The function is broken... (if anybody could give me a help, thanks a lot, and i'm noob in sql so ....). Thanks!

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• Password hashing, salt and storage of hashed values

  - by Jonathan Leffler

  Suppose you were at liberty to decide how hashed passwords were to be stored in a DBMS. Are there obvious weaknesses in a scheme like this one? To create the hash value stored in the DBMS, take: A value that is unique to the DBMS server instance as part of the salt, And the username as a second part of the salt, And create the concatenation of the salt with the actual password, And hash the whole string using the SHA-256 algorithm, And store the result in the DBMS. This would mean that anyone wanting to come up with a collision should have to do the work separately for each user name and each DBMS server instance separately. I'd plan to keep the actual hash mechanism somewhat flexible to allow for the use of the new NIST standard hash algorithm (SHA-3) that is still being worked on. The 'value that is unique to the DBMS server instance' need not be secret - though it wouldn't be divulged casually. The intention is to ensure that if someone uses the same password in different DBMS server instances, the recorded hashes would be different. Likewise, the user name would not be secret - just the password proper. Would there be any advantage to having the password first and the user name and 'unique value' second, or any other permutation of the three sources of data? Or what about interleaving the strings? Do I need to add (and record) a random salt value (per password) as well as the information above? (Advantage: the user can re-use a password and still, probably, get a different hash recorded in the database. Disadvantage: the salt has to be recorded. I suspect the advantage considerably outweighs the disadvantage.) There are quite a lot of related SO questions - this list is unlikely to be comprehensive: Encrypting/Hashing plain text passwords in database Secure hash and salt for PHP passwords The necessity of hiding the salt for a hash Clients-side MD5 hash with time salt Simple password encryption Salt generation and Open Source software I think that the answers to these questions support my algorithm (though if you simply use a random salt, then the 'unique value per server' and username components are less important).

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• Javascript functions Math.round(num) vs num.toFixed(0) and browser inconsistencies

  - by eft

  Edit: To clarify, the problem is how to round a number to the nearest integer. i.e. 0.5 should round to 1 and 2.5 shoud round to 3. Consider the following code: <html><head></head><body style="font-family:courier"> <script> for (var i=0;i<3;i++){ var num = i + 0.50; var output = num + " " + Math.round(num) + " " + num.toFixed(0); var node = document.createTextNode(output); var pElement = document.createElement("p"); pElement.appendChild(node); document.body.appendChild(pElement); } </script> </body></html> In Opera 9.63 I get: 0.5 1 0 1.5 2 2 2.5 3 2 In FF 3.03 I get: 0.5 1 1 1.5 2 2 2.5 3 3 In IE 7 I get: 0.5 1 0 1.5 2 2 2.5 3 3 Note the bolded results. Does this mean that toFixed(0) should be avoided?

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• Good practice to create extension methods that apply to System.Object?

  - by Christian

  Hello, I'm wondering whether I should create extension methods that apply on the object level or whether they should be located at a lower point in the class hierarchy. What I mean is something along the lines of: public static string SafeToString(this Object o) { if (o == null || o is System.DBNull) return ""; else { if (o is string) return (string)o; else return ""; } } public static int SafeToInt(this Object o) { if (o == null || o is System.DBNull) return 0; else { if (o.IsNumeric()) return Convert.ToInt32(o); else return 0; } } //same for double.. etc I wrote those methods since I have to deal a lot with database data (From the OleDbDataReader) that can be null (shouldn't, though) since the underlying database is unfortunately very liberal with columns that may be null. And to make my life a little easier, I came up with those extension methods. What I'd like to know is whether this is good style, acceptable style or bad style. I kinda have my worries about it since it kinda "pollutes" the Object-class. Thank you in advance & Best Regards :) Christian P.S. I didn't tag it as "subjective" intentionally.

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• What exactly does entitlemets.plist do ?

  - by sagar

  To execute my application in iPhone first of all I have to add provisioning profile in to my iPhone. Good. But I don't understand the reason behind adding a entitlements.plist in iphone application in xCode under resources. What does that entitlements.plist file do actually ? Why that .plist file have only single Boolean in it ? (get-task-allow) Can't we add that Boolean variable to application-info.plist ? I mean, I can't find the reason behind storing a single Boolean variable in separate plist file. Instead application-info.plist already contains many many application settings. Can't we just add this Boolean variable to application-info.plist. Ok, any way. I know - it won't be possible. Because we have to follow - what apple says. But, here main intention behind all these was "what is the basic need of entitlements.plist ?" or "what is the functionality of entitlements.plist ?" "How provisioning profile, entitlements.plist, application-info.plist & iPhone application compile all together & make verification on iPhone & execute it on iPhone ? "

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