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  • SQL Stored Queries - use result of query as boolean based on existence of records

    - by Christian Mann
    Just getting into SQL stored queries right now... anyway, here's my database schema (simplified for YOUR convenience): member ------ id INT PK board ------ id INT PK officer ------ id INT PK If you're into OOP, Officer Inherits Board Inherits Member. In other words, if someone is listed on the officer table, s/he is listed on the board table and the member table. I want to find out the highest privilege level someone has. So far my SP looks like this: DELIMITER // CREATE PROCEDURE GetAuthLevel(IN targetID MEDIUMINT) BEGIN IF SELECT `id` FROM `member` WHERE `id` = targetID; THEN IF SELECT `id` FROM `board` WHERE `id` = targetID; THEN IF SELECT `id` FROM `officer` WHERE `id` = targetID; THEN RETURN 3; /*officer*/ ELSE RETURN 2; /*board member*/ ELSE RETURN 1; /*general member*/ ELSE RETURN 0; /*not a member*/ END // DELIMITER ; The exact text of the error is #1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'SELECT id FROM member WHERE id = targetID; THEN IF SEL' at line 4 I suspect the issue is in the arguments for the IF blocks. What I want to do is return true if the result-set is at least one -- i.e. the id was found in the table. Do any of you guys see anything to do here, or should I reconsider my database design into this:? person ------ id INT PK level SMALLINT

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  • Flex 3 - Scroll bar issue

    - by Emma
    Im currently learning Flex, and Im having the hardest time getting scroll bars to work. In short Im pretty much just making a giant form for users to fill out, contained within a viewstack component, the user will type up information in one view, and it will be displayed in the other. But right now in the first canvas i have components that run of the screen and flex doesnt seem to automate a scroll bar, so i added in 'verticalScrollPolicy="on"' to my canvas, now while it gives me a scroll bar, it gives me an empty scroll bar, I still cannot move it up or down, meaning components are still trapped off the bottom of my screen. Im I missing something amazingly simple? Edit - Sorry, Im using Adobe Flex Builder 3, and the components it lets you drag in. http://img12.imageshack.us/img12/218/problem1f.jpg This is a picture of the problem, and i guess relavent code would be. <mx:Application xmlns:mx="adobe.com/2006/mxml"; layout="absolute" width="830" height="835"> <mx:ViewStack x="10" y="72" id="viewstack1" width="790" height="751" > <mx:Canvas label="Design Mode" width="100%" height="100%" verticalScrollPolicy="on" horizontalScrollPolicy="on" > (Components inside) </mx:Canvas> Sorry if Im using this site wrong, still very new

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  • Hiring a programmer: looking for the "right attitude"

    - by Totophil
    It's actually two questions in one: What is the right attitude for a programmer? How do you (or would you) look for one when interviewing or during hiring process? Please note this question is not about personality or traits of a candidate, it is about their attitude towards what they do for living. This is also not about reverse of programmers pet peeves. The question has been made community wiki, since I am interested in a good answer rather than reputation. I disagree that the question is purely subjective and just a matter of opinion: clearly some attitudes make a better programmer than others. Consecutively, there might quite possibly exist an attitude that is common to the most of the better programmers. Update: After some deliberation I came up with the following attitude measurement scales: identifies themselves with the job ? fully detached perceives code as a collection of concepts ? sees code as a sequence of steps thinks of creating software as an art ? takes 100% rational approach to design and development Answers that include some sort of a comment on the appropriateness of these scales are greatly appreciated. Definition of "attitude": a complex mental state involving beliefs and feelings and values and dispositions to act in certain ways; "he had the attitude that work was fun" The question came as a result of some reflection on the top voted answer to "How do you ensure code quality?" here on Stack Overflow.

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  • chrome extension login security with iframe

    - by Weaver
    I should note, I'm not a chrome extension expert. However, I'm looking for some advice or high level solution to a security concern I have with my chrome extension. I've searched quite a bit but can't seem to find a concrete answer. The situation I have a chrome extension that needs to have the user login to our backend server. However, it was decided for design reasons that the default chrome popup balloon was undesirable. Thus I've used a modal dialog and jquery to make a styled popup that is injected with content scripts. Hence, the popup is injected into the DOM o the page you are visiting. The Problem Everything works, however now that I need to implement login functionality I've noticed a vulnerability: If the site we've injected our popup into knows the password fields ID they could run a script to continuously monitor the password and username field and store that data. Call me paranoid, but I see it as a risk. In fact,I wrote a mockup attack site that can correctly pull the user and password when entered into the given fields. My devised solution I took a look at some other chrome extensions, like Buffer, and noticed what they do is load their popup from their website and, instead, embed an iFrame which contains the popup in it. The popup would interact with the server inside the iframe. My understanding is iframes are subject to same-origin scripting policies as other websites, but I may be mistaken. As such, would doing the same thing be secure? TLDR To simplify, if I embedded an https login form from our server into a given DOM, via a chrome extension, are there security concerns to password sniffing? If this is not the best way to deal with chrome extension logins, do you have suggestions with what is? Perhaps there is a way to declare text fields that javascript can simply not interact with? Not too sure! Thank you so much for your time! I will happily clarify anything required.

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  • Why is an Add method required for { } initialization?

    - by Dan Tao
    To use initialization syntax like this: var contacts = new ContactList { { "Dan", "[email protected]" }, { "Eric", "[email protected]" } }; ...my understanding is that my ContactList type would need to define an Add method that takes two string parameters: public void Add(string name, string email); What's a bit confusing to me about this is that the { } initializer syntax seems most useful when creating read-only or fixed-size collections. After all it is meant to mimic the initialization syntax for an array, right? (OK, so arrays are not read-only; but they are fixed size.) And naturally it can only be used when the collection's contents are known (at least the number of elements) at compile-time. So it would almost seem that the main requirement for using this collection initializer syntax (having an Add method and therefore a mutable collection) is at odds with the typical case in which it would be most useful. I'm sure I haven't put as much thought into this matter as the C# design team; it just seems that there could have been different rules for this syntax that would have meshed better with its typical usage scenarios. Am I way off base here? Is the desire to use the { } syntax to initialize fixed-size collections not as common as I think? What other factors might have influenced the formulation of the requirements for this syntax that I'm simply not thinking of?

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  • Generic function pointers in C

    - by Lucas
    I have a function which takes a block of data and the size of the block and a function pointer as argument. Then it iterates over the data and performes a calculation on each element of the data block. The following is the essential outline of what I am doing: int myfunction(int* data, int size, int (*functionAsPointer)(int)){ //walking through the data and calculating something for (int n = 0; n < size; n++){ data[n] = (*function)(data[n]); } } The functions I am passing as arguments look something like this: int mycalculation(int input){ //doing some math with input //... return input; } This is working well, but now I need to pass an additional variable to my functionpointer. Something along the lines int mynewcalculation(int input, int someVariable){ //e.g. input = input * someVariable; //... return input; } Is there an elegant way to achieve this and at the same time keeping my overall design idea?

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  • Selectively suppress XML comments?

    - by Mike Post
    We deliver a number of assemblies to external customers, but not all of the public APIs are officially supported. For example, due to less than optimal design choices sometimes a type must be publicly exposed from an assembly for the rest of our code to work, but we don't want customers to use that type. One part of communicating the lack of support is not provide any intellisense in the form of XML comments. Is there a way to selectively suppress XML comments? I'm looking for something other than ignoring warning 1591 since it's a long term maintenance issue. Example: I have an assembly with public classes A and B. A is officially supported and should have XML documentation. B is not intended for external use and should not be documented. I could turn on XML documentation and then suppress warning 1591. But when I later add the officially supported class C, I want the compiler to tell me that I've screwed up and failed to add the XML documentation. This wouldn't occur if I had suppressed 1591 at the project level. I suppose I could #pragma across entire classes, but it seems like there should be a better way to do this.

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  • In Ruby, how to implement global behaviour?

    - by Gordon McAllister
    Hi all, I want to implement the concept of a Workspace. This is a global concept - all other code will interact with one instance of this Workspace. The Workspace will be responsible for maintaining the current system state (i.e. interacting with the system model, persisting the system state etc) So what's the best design strategy for my Workspace, bearing in mind this will have to be testable (using RSpec now, but happy to look at alternatives). Having read thru some open source projects out there and I've seen 3 strategies. None of which I can identify as "the best practice". They are: Include the singleton class. But how testable is this? Will the global state of Workspace change between tests? Implemented all behaviour as class methods. Again how do you test this? Implemented all behaviour as module methods. Not sure about this one at all! Which is best? Or is there another way? Thanks, Gordon

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  • checkbox like radiobutton wpf c#

    - by rockenpeace
    i have investigated this problem but this is solved in design view and code-behind. but my problem is little difference: i try to do this as only code-behind because my checkboxes are dynamically created according to database data.In other words, number of my checkboxes is not stable. i want to check only one checkbox in group of checkboxes. when i clicked one checkbox,i want that ischecked property of other checkboxes become false.this is same property in radiobuttons. i take my checkboxes from a stackpanel in xaml side: <StackPanel Margin="4" Orientation="Vertical" Grid.Row="1" Grid.Column="1" Name="companiesContainer"> </StackPanel> my xaml.cs: using (var c = new RSPDbContext()) { var q = (from v in c.Companies select v).ToList(); foreach (var na in q) { CheckBox ch = new CheckBox(); ch.Content = na.Name; ch.Tag = na; companiesContainer.Children.Add(ch); } } foreach (object i in companiesContainer.Children) { CheckBox chk = (CheckBox)i; chk.SetBinding(ToggleButton.IsCheckedProperty, "DataItem.IsChecked"); } how can i provide this property in checkboxes in xaml.cs ? thanks in advance..

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  • How to refresh jasper image without flickering?

    - by Aru
    Hi, I am using jasper reports to generate graph. I am refresheing the graph. But the problem is while refreshing the graph it is flickering. Code is- PrintWriter out = response.getWriter(); response.setContentType("text/html"); JRDataSource dataSource = createReportDataSource(perfArrayListSample.toArray()); ServletContext context = this.getServletConfig().getServletContext(); File reportFile = new File(context.getRealPath("/cpuUsageGraph.jasper")); if (!reportFile.exists()) throw new JRRuntimeException("File cpuUsageGraph.jasper not found. The report design must be compiled first."); JasperReport jasperReport = (JasperReport)JRLoader.loadObject(reportFile.getPath()); JasperPrint print = JasperFillManager.fillReport(jasperReport, new HashMap(), dataSource); JRHtmlExporter exporter = new JRHtmlExporter(); request.getSession().setAttribute(ImageServlet.DEFAULT_JASPER_PRINT_SESSION_ATTRIBUTE, print); exporter.setParameter(JRExporterParameter.JASPER_PRINT, print); exporter.setParameter(JRExporterParameter.OUTPUT_WRITER, out); exporter.setParameter(JRHtmlExporterParameter.IMAGES_URI, "image?ver="+new Date().getTime() +"&image="); exporter.exportReport(); perfArrayListSample.clear(); So how to refresh the graph wihout flickering?

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  • Cooperative/Non-preemptive threading avoiding threadlooks?

    - by Wayne
    Any creative ideas to avoid deadlocks on a yield or sleep with cooperative/non-preemptive multitasking without doing an O/S Thread.Sleep(10)? Typically the yield or sleep call will call back into the scheduler to run other tasks. But this can sometime produce deadlocks. Some background: This application has enormous need for speed and, so far, it's extremely fast as compared to other systems in the same industry. One of the speed techniques is cooperative/non-preemptive threading rather then the cost of a context switch from O/S threads. The high level design a priority manager which calls out to tasks depending on priority and processing time. Each task does one "iteration" of work and returns to wait its turn again in the priority queue. The tricky thing with non-preemptive threading is what to do when you want to a particular task to stop in the middle of work and wait for some other event from a different task before continuing. In this case, we have 3 tasks, A B and C where A is a controller that must synchronize the activity of B and C. First, A starts both B and C. Then B yields so C gets invoked. When C yields, A sees they are both inactive, decides it's time for B to run but not time for C yet. Well B is now stuck in a yield that has called C, so it can never run. Sincerely, Wayne

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  • Designing a fluent Javascript interface to abstract away the asynchronous nature of AJAX

    - by Anurag
    How would I design an API to hide the asynchronous nature of AJAX and HTTP requests, or basically delay it to provide a fluid interface. To show an example from Twitter's new Anywhere API: // get @ded's first 20 statuses, filter only the tweets that // mention photography, and render each into an HTML element T.User.find('ded').timeline().first(20).filter(filterer).each(function(status) { $('div#tweets').append('<p>' + status.text + '</p>'); }); function filterer(status) { return status.text.match(/photography/); } vs this (asynchronous nature of each call is clearly visible) T.User.find('ded', function(user) { user.timeline(function(statuses) { statuses.first(20).filter(filterer).each(function(status) { $('div#tweets').append('<p>' + status.text + '</p>'); }); }); }); It finds the user, gets their tweet timeline, filters only the first 20 tweets, applies a custom filter, and ultimately uses the callback function to process each tweet. I am guessing that a well designed API like this should work like a query builder (think ORMs) where each function call builds the query (HTTP URL in this case), until it hits a looping function such as each/map/etc., the HTTP call is made and the passed in function becomes the callback. An easy development route would be to make each AJAX call synchronous, but that's probably not the best solution. I am interested in figuring out a way to make it asynchronous, and still hide the asynchronous nature of AJAX.

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  • Modalpopupextender - Javascript error

    - by clklachu
    Hi, I just tried creating a simple sample with Modalpopup extender and Caledarextender. My design is like below. <asp:UpdatePanel ID="pnlUpdate" runat="server"> <ContentTemplate> <asp:Panel ID="pnlSample" runat="server" CssClass="frame"> <asp:TextBox ID="txtOSDate" runat="server"></asp:TextBox> <asp:TextBox ID="txtDate" runat="server"></asp:TextBox> <asp:CalendarExtender ID="calDate" runat="server" TargetControlID="txtOSDate"> </asp:CalendarExtender> <asp:CalendarExtender ID="calOSDate" runat="server" TargetControlID="txtDate"> </asp:CalendarExtender> <asp:Button ID="btnCancel" runat="server" Text="Cancel" /> </asp:Panel> <asp:Button ID="btnHiddenSample" runat="server" Style="display: none;" /> <asp:Button ID="btnSample" runat="server" CssClass="Button" Text="New Sample" /> <asp:ModalPopupExtender ID="mpeSample" runat="server" TargetControlID="btnHiddenSample" CancelControlID="btnCancel" PopupControlID="pnlSample" DropShadow="false" BackgroundCssClass="modalBackground"> </asp:ModalPopupExtender> </ContentTemplate> </asp:UpdatePanel> When i run the sample and click the "New Sample" button, i get javascript error as "Error: Sys.InvalidOperationException: Two components with the same id 'ctl00_MainContent_calDate' can't be added to the application.' can't be added to the application." I checked the rendered HTML using DeveloperTools and i still found the asp Panel recreated. Someone please advice me what is the actual problem? PS:When i comment the Calendar Extender, i dont get the error. Regards, Lakxman Kumar C

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  • Function within function in R

    - by frespider
    Can you please explain to me why th code complain saying that Samdat is not found? I am trying to switch between the models as you can see, so i declared a functions that contains these specific models and I just need to call these function as one of the argument in the get.f function where the resampling will change the structure for each design matrix in the model. the code complain the Samdat is not found when it is found. Also, is there a way I can make the condition statement as if(Model == M1()) instead I have to create another argument M to set if(M==1) Can you explain please? dat <- cbind(Y=rnorm(20),rnorm(20),runif(20),rexp(20),rnorm(20),runif(20), rexp(20),rnorm(20),runif(20),rexp(20)) nam <- paste("v",1:9,sep="") colnames(dat) <- c("Y",nam) M1 <- function(){ a1 = cbind(Samdat[,c(2:5,7,9)]) b1 = cbind(Samdat[,c(2:4,6,8,7)]) c1 = b1+a1 list(a1=a1,b1=b1,c1=c1)} M2 <- function(){ a1= cbind(Samdat[,c(2:5,7,9)])+2 b1= cbind(Samdat[,c(2:4,6,8,7)])+2 c1 = a1+b1 list(a1=a1,b1=b1,c1=c1)} M3 <- function(){ a1= cbind(Samdat[,c(2:5,7,9)])+8 b1= cbind(Samdat[,c(2:4,6,8,7)])+8 c1 = a1+b1 list(a1=a1,b1=b1,c1=c1)} ################################################################# get.f <- function(asim,Model,M){ sse <-c() for(i in 1:asim){ set.seed(i) Samdat <- dat[sample(1:nrow(dat),nrow(dat),replace=T),] Y <- Samdat[,1] if(M==1){ a2 <- Model$a1 b2 <- Model$b1 c2 <- Model$c1 s<- a2+b2+c2 fit <- lm(Y~s) cof <- sum(summary(fit)$coef[,1]) coff <-Model$cof sse <-c(sse,coff) } else if(M==2){ a2 <- Model$a1 b2 <- Model$b1 c2 <- Model$c1 s<- c2+12 fit <- lm(Y~s) cof <- sum(summary(fit)$coef[,1]) coff <-Model$cof sse <-c(sse,coff) } else { a2 <- Model$a1 b2 <- Model$b1 c2 <- Model$c1 s<- c2+a2 fit <- lm(Y~s) cof <- sum(summary(fit)$coef[,1]) coff <- Model$cof sse <-c(sse,coff) } } return(sse) } get.f(10,Model=M1(),M=1) get.f(10,Model=M2(),M=2) get.f(10,Model=M3(),M=3)

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  • I need an abstract field !

    - by Jules Olléon
    I know abstract fields do not exist in java. I also read this question but the solutions proposed won't solve my problem. Maybe there is no solution, but it's worth asking :) Problem I have an abstract class that does an operation in the constructor depending on the value of one of its fields. The problem is that the value of this field will change depending on the subclass. How can I do so that the operation is done on the value of the field redefined by the subclass ? If I just "override" the field in the subclass the operation is done on the value of the field in the abstract class. I'm open to any solution that would ensure that the operation will be done during the instantiation of the subclass (ie putting the operation in a method called by each subclass in the constructor is not a valid solution, because someone might extend the abstract class and forget to call the method). Also, I don't want to give the value of the field as an argument of the constructor. Is there any solution to do that, or should I just change my design ?

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  • [ASP.NET] Difficulties using custom control - RichTextEditor

    - by Chris
    I am working on a school project that uses ASP.NET. I found this TextEditor control ( http://blogs.msdn.com/kirti/archive/2007/11/10/rich-text-editor-is-here.aspx ) that I am trying to include but it isn't working. The error I am getting is: Error Rendering Control - TextEditor. An unhandled exception has occurred. Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: index. I see this error when I go Design part of the editor. I just don't understand this error at all. Also I am a lil bit confused as there is no parameter called index. :( What I have done is reference the binary in my project and then on the page I am trying to use it have registered its namespace and assembly with this line: <%@ Register Assembly="RichTextEditor" Namespace="AjaxControls" TagPrefix="rtt" %> I then go ahead and try to add the control to the page with this line of code: <rtt:richtexteditor ID="TextEditor" Theme="Blue" runat="server" /> Any help would be much appreciated. I haven't done anything like add a custom control before.

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  • How to build n-layered web architecture with PHP?

    - by Alex
    I have a description and design of a website and I need to redesign it to allow for new requirements. The website's purpose is the offering of government's contracts and bidding opportunities for different businesses.I'm dealing with the 3-tier architecture PHP website comprising of the user-interface tier(client's web browser),business logic layer(Apache web server with PHP engine in it and a couple of applications running within a web server as well) and a database layer(local mysql database). Now,i need to redesign it to su???rt distributed n-tier architecture and specify how I would go about it.After long hours of research i came to this solution: business logic should be separated into presentation and purely business logic tier to allow for n-layer architecture(user-interface,presentation tier,b.logic and data tier).I have decided to use ??? just for the presentation(since the original existing website is in PHP) and use it within apache web server.In the business logic i want to use J2?? implementation technology instead of implementing it in PHP(i.e using Zend app.server and smarty template) cz J2EE can provide much more essential container services which are essential for business logic,its robustness,maintainability and different critical business operations which will be carried out by the g?v?rnment's website.So,particularly,i want to use J??ss app.server with ?J? business objects in it which would provide all the b.logic in java and would interact with the database and so forth.In order to connect PHP on a web server with java on app.server i'm gonna use PHP/Java bridge API (or maybe Quercus or SOAP is better?).Finally,i have my data tier with mysql which will communicate with b.logic via JD??.Payment system application in ???.server is gonna use S??? to talk with credit card company. From your professional point of view,does it sound like a good way of redesigning the original website to allow for n-tier architecture considering the specifics of the website and the criticality of its operations?(payment system is included in it)or u would personally prefer to use PHP business objects for business logic as well instead of J2EE?If you have any wiser recommendation or some alternative,please let me know what is right or wrong in my current solution. H??? to hear your professional advice very s??n (I'm new to the area of web development) Thanks in advance

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  • Stream Reuse in C#

    - by MikeD
    I've been playing around with what I thought was a simple idea. I want to be able to read in a file from somewhere (website, filesystem, ftp), perform some operations on it (compress, encrypt, etc.) and then save it somewhere (somewhere may be a filesystem, ftp, or whatever). It's a basic pipeline design. What I would like to do is to read in the file and put it onto a MemoryStream, then perform the operations on the data in the MemoryStream, and then save that data in the MemoryStream somewhere. I was thinking I could use the same Stream to do this but run into a couple of problems: Everytime I use a StreamWriter or StreamReader I need to close it and that closes the stream so that I cannot use it anymore. That seems like there must be some way to get around that. Some of these files may be big and so I may run out of memory if I try to read the whole thing in at once. I was hoping to be able to spin up each of the steps as separate threads and have the compression step begin as soon as there is data on the stream, and then as soon as the compression has some compressed data available on the stream I could start saving it (for example). Is anything like this easily possible with the C# Streams? ANyone have thoughts as to how to accomplish this best? Thanks, Mike

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  • How do I detect whether the sample supplied by VideoSink.OnSample() is right-side up?

    - by Ken Smith
    We're currently using the Silverlight VideoSink to capture video from users' local webcams, kinda like so: protected override void OnSample(long sampleTime, long frameDuration, byte[] sampleData) { if (FrameShouldBeSubmitted()) { byte[] resampledData = ResizeFrame(sampleData); mediaController.SetVideoFrame(resampledData); } } Now, on most of the machines that we've tested, the video sample provided in the byte[] sampleData parameter is upside-down, i.e., if you try to take the RGBA data and turn it into, say, a WriteableBitmap, the bitmap will be upside-down. That's odd, but fairly easy to correct, of course -- you just have to reverse the array as you encode it. The problem is that at least on some machines (e.g., the single Macintosh in our test environment), the video sample provided is no longer upside-down, but right-side up, and hence, flipping the image actually results in an image that's received upside-down on the far side. I reported this to MS as a bug, but their (terse) response was that it was "As Designed". Further attempts at clarification have so far been ignored. Now, I'll grant that it's kinda entertaining to imagine the discussions behind this design decision: "OK, just to make it interesting, let's play the video rightside up on a Mac, but let's turn it upside down for Windows!" "Great idea!" "Yeah, that'll keep those developers guessing!" But beyond that, I can't find this, umm, "feature" documented anywhere, nor can I find any documentation on how one is supposed to be able to tell that a given video sample is upside down or rightside up. Any thoughts on how to tell this?

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  • Small-o(n^2) implementation of Polynomial Multiplication

    - by AlanTuring
    I'm having a little trouble with this problem that is listed at the back of my book, i'm currently in the middle of test prep but i can't seem to locate anything regarding this in the book. Anyone got an idea? A real polynomial of degree n is a function of the form f(x)=a(n)x^n+?+a1x+a0, where an,…,a1,a0 are real numbers. In computational situations, such a polynomial is represented by a sequence of its coefficients (a0,a1,…,an). Assuming that any two real numbers can be added/multiplied in O(1) time, design an o(n^2)-time algorithm to compute, given two real polynomials f(x) and g(x) both of degree n, the product h(x)=f(x)g(x). Your algorithm should **not** be based on the Fast Fourier Transform (FFT) technique. Please note it needs to be small-o(n^2), which means it complexity must be sub-quadratic. The obvious solution that i have been finding is indeed the FFT, but of course i can't use that. There is another method that i have found called convolution, where if you take polynomial A to be a signal and polynomial B to be a filter. A passed through B yields a shifted signal that has been "smoothed" by A and the resultant is A*B. This is supposed to work in O(n log n) time. Of course i am completely unsure of implementation. If anyone has any ideas of how to achieve a small-o(n^2) implementation please do share, thanks.

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  • Thread implemented as a Singleton

    - by rocknroll
    Hi all, I have a commercial application made with C,C++/Qt on Linux platform. The app collects data from different sensors and displays them on GUI. Each of the protocol for interfacing with sensors is implemented using singleton pattern and threads from Qt QThreads class. All the protocols except one work fine. Each protocol's run function for thread has following structure: void <ProtocolClassName>::run() { while(!mStop) //check whether screen is closed or not { mutex.lock() while(!waitcondition.wait(&mutex,5)) { if(mStop) return; } //Code for receiving and processing incoming data mutex.unlock(); } //end while } Hierarchy of GUI. 1.Login screen. 2. Screen of action. When a user logs in from login screen, we enter the action screen where all data is displayed and all the thread's for different sensors start. They wait on mStop variable in idle time and when data arrives they jump to receiving and processing data. Incoming data for the problem protocol is 117 bytes. In the main GUI threads there are timers which when timeout, grab the running instance of protocol using <ProtocolName>::instance() function Check the update variable of singleton class if its true and display the data. When the data display is done they reset the update variable in singleton class to false. The problematic protocol has the update time of 1 sec, which is also the frame rate of protocol. When I comment out the display function it runs fine. But when display is activated the application hangs consistently after 6-7 hours. I have asked this question on many forums but haven't received any worthwhile suggestions. I Hope that here I will get some help. Also, I have read a lot of literature on Singleton, multithreading, and found that people always discourage the use of singletons especially in C++. But in my application I can think of no other design for implementation. Thanks in advance A Hapless programmer

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  • Calculate car filled up times

    - by Ivan
    Here is the question: The driving distance between Perth and Adelaide is 1996 miles. On the average, the fuel consumption of a 2.0 litre 4 cylinder car is 8 litres per 100 kilometres. The fuel tank capacity of such a car is 60 litres. Design and implement a JAVA program that prompts for the fuel consumption and fuel tank capacity of the aforementioned car. The program then displays the minimum number of times the car’s fuel tank has to be filled up to drive from Perth to Adelaide. Note that 62 miles is equal to 100 kilometres. What data will you use to test that your algorithm works correctly? Here is what I've done so far: import java.util.Scanner;// public class Ex4{ public static void main( String args[] ){ Scanner input = new Scanner( System.in ); double distance, consumption, capacity, time; distance = Math.sqrt(1996/62*100); consumption = Math.sqrt(8/100); capacity = 60; time = Math.sqrt(distance*consumption/capacity); System.out.println("The car's fuel tank need to be filled up:" + time + "times"); } } I can compile it but the problem is that the result is always 0.0, can anyone help me what's wrong with it ?

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  • Interactive Web Collaboration Platform

    - by user1477586
    I am currently unsatisfied with most, if not all, web-based collaboration tools I've ever used. Examples of what I'm considering a "web-based collaboration tool" are TWiki, WebEx, etc. What I have in mind of developing is to develop my own. The target "market" is for software/hardware developers who will likely be working on separate projects linked by a common goal. Example: You work at a company who is designing a brand new printer. So, one man is working on the ink cartridge, another on the paper feed, one on the circuitry of the printer and one more is working on the drivers. What I would like to make (unless it already exists) is a website that, upon loading, presents the user with a web that has each project within it's own bubble, graphically. These bubbles would all be linked to the central bubble of "[Company Name]". Upon selecting an individual bubble the browser would focus and zoom in on that project bubble and expand more information (in bullets or with more affiliated bubbles) about subprojects, progress, setbacks, etc. Then, at a terminal "node" (i.e. a bubble with no sub-bubbles) a selection would then load a page with information relevant to that node. That's a lot of monologue. In short, I want to know how I might approach this. My background is with algorithmic use of Python and C++. I've never done interactive web design like this; though, I have gone through the W3C tutorials on HTML4/5. I'm willing to learn a new language I'm just wondering which language/set of languages seem(s) most appropriate for this project. Thanks, world, for imparting your knowledge to me. An example of what the start page might look like is:

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  • How do I use Linq-to-sql to iterate db records?

    - by Seth Spearman
    I asked on SO a few days ago what was the simplest quickest way to build a wrapper around a recently completed database. I took the advice and used sqlmetal to build linq classes around my database design. Now I am having two problems. One, I don't know LINQ. And, two, I have been shocked to realize how hard it is to learn. I have a book on LINQ (Linq In Action by Manning) and it has helped some but at the end of the day it is going to take me a couple of weeks to get traction and I need to make some progress on my project today. So, I am looking for some help getting started. Click HERE To see my simple database schema. Click HERE to see the vb class that was generated for the schema. My needs are simple. I have a console app. The main table is the SupplyModel table. Most of the other tables are child tables of the SupplyModel table. I want to iterate through each of Supply Model records. I want to grab the data for a supply model and then DoStuff with the data. And I also need to iterate through the child records, for each supply model, for example the NumberedInventories and DoStuff with that as well. I need help doing this in VB rather than C# if possible. I am not looking for the whole solution...if you can supply a couple of code-snippets to get me on my way that would be great. Thanks for your help. Seth

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  • Sharepoint designer is replacing french characters with &#65533;

    - by chris
    First of all, I'm not a web designer, I'm a programmer, so I'm working a bit out of my knowledge area. However, as the person in my office who has some working knowledge of French, I'm stuck with this issue. The Problem: Sharepoint Designer is replacing all French accented characters with the &#65533; (square box or diamond-? �) character. It doesn't appear to matter if I enter the 'é' character as alt-130 (in either design or source or as &eacute; Everything works fine when editing, but when the file is saved and loaded into a browser, it replaces the characters. When reloading into designer, the file shows the 65533 symbol. EDIT: More info. I use &#233; and save, close SP designer, Reloading SP designer will show the é (instead of the code) in source. Next reload will have replaced it with &#65533; Question 1: (more important) HOW DO I STOP THIS!? Question 2: (more interesting) Why does this happen? Charset is iso-8859-1

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