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• Android/ iOS how to determine small changes in distance using sensors?

  - by Tom

  I have been doing a bit of research, but I cannot seem to find a way to determine small distances (centimeters and meters) using the sensors in Android or iOS devices. Bluetooth appears too inaccurate and require more than one device, GPS only works over larger variations in distance, and small variations in rotation seem to make using the accelerometer nearly impossible. Is there a method that I am unaware of that would allow me to do such a thing? I am familiar with Calculus, so using Integrals to determine distance based on changes in time and velocity/ acceleration is not a problem for me, I just do not know how to determine those things. Thank you.

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• How can I add floats together in different orders, and always get the same total?

  - by splicer

  Let's say I have three 32-bit floating point values, a, b, and c, such that (a + b) + c != a + (b + c). Is there summation algorithm, perhaps similar to Kahan summation, that guarantees that these values can be summed in any order and always arrive at the exact same (fairly accurate) total? I'm looking for the general case (i.e. not a solution that only deals with 3 numbers). Is arbitrary precision arithmetic the only way to go? I'm dealing with very large data sets, so I'd like to avoid the overhead of using arbitrary precision arithmetic if possible. Thanks!

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• When (and why) is {} undefined in a JavaScript console?

  - by JS_Riddler

  In the console of both FF and Chrome, {} is considered undefined until explicitly evaluated: {}; // undefined ({}); // ? Object Actually, it's a bit less defined than undefined -- it's apparently bad syntax: {} === undefined; // SyntaxError: Unexpected token === {}.constructor; // SyntaxError: Unexpected token . But not if it's on the other side, in which case it's fine: "[object Object]" == {}.toString(); // true Or if it's not the first expression: undefined + undefined; // NaN {} + undefined; // NaN undefined + {}; // "undefined[object Object]" What gives?

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• Rails passenger production cache definition

  - by mark

  Hi I'm having a bit of a problem with storing data in rails cache under production. What I currently have is this, though I have been trying to work this out for hours already: #production.rb config.cache_store = :mem_cache_store if defined?(PhusionPassenger) PhusionPassenger.on_event(:starting_worker_process) do |forked| if forked Rails.cache.instance_variable_get(:@data).reset end end end I am using a cron job to (try to) save remote data to the cache for display. It is logged as being written to the cache but reportedly null. If anyone could point me toward a decent current tutorial on the subject or offer guidance I'd be extremely grateful. This is really, really frustrating me. :(

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• How do I profile memory usage in my project

  - by Gacek

  Are there any good, free tools to profile memory usage in C# ? Details: I have a visualization project that uses quite large collections. I would like to check which parts of this project - on the data-processing side, or on the visualization side - use most of the memory, so I could optimize it. I know that when it comes to computing size of the collection the case is quite simple and I can do it on my own. But there are also certain elements for which I cannot estimate the memory usage so easily. The memory usage is quite big, for example processing a file of size 35 MB my program uses a little bit more than 250 MB of RAM.

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• Vector of objects

  - by Paul

  I've got a abstract class class A { public: virtual void somefunction() = ; }; and some different classes that inherit this class: class Ab { public: void somefunction(); }; etc. I want to make a vector containing some objects of these classes (how many depends on input parameters) so I can access these easily later. However I'm a bit lost on how to do this. My best idea is vector<A> *objectsVector; Ab AbObject; objectsVector.push_back(AbObject); However this gives me a huge amout of errors from various .h files in /usr/include/c++ How should i solve this?

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• Store data in Ruby on Rails without Database

  - by snowmaninthesun

  I have a few data values that I need to store on my rails app and wanted to know if there are any alternatives to creating a database table just to do this simple task. Background: I'm writing some analytics and dashboard tools for my ruby on rails app and i'm hoping to speed up the dashboard by caching results that will never change. Right now I pull all users for the last 30 days, and re arange them so I can see the number of new users per day. It works great but takes quite a long time, in reality I should only need to calculate the most recent day and just store the rest of the array somewhere else. Where is the best way to store this array? Creating a database table seems a bit overkill, and i'm not sure that global variables are the correct answer. Is there a best practice for persisting data like this? If anyone has done anything like this before let me know what you did and how it turned out.

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• App disappears from Win7's ALT-TAB list sometimes

  - by Mason Wheeler

  I've been having some trouble with one of my Delphi 2010 projects lately. It seems that sometimes, when I have a form open as a modal dialog, the app stops showing up in the ALT-TAB list until I close the dialog. It's still in the Taskbar, but not in ALT-TAB, which means I can't switch to it without using the mouse. Running under Windows 7, 64-bit. Has anyone seen this before? Any idea what causes it and how to fix it?

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• Printing python tkinter output

  - by Eric

  I am trying to print the contents of a python tkinter canvas. I have tried using the postscript method of canvas to create a postscript file, but I get a blank page. I know this is because I have embedded widgets, and these do not get rendered by the postscript method. Before I rewrite my program to create a more printer-friendly layout, can someone suggest a way to approach this problem? All of the programming books I have ever read approach the problem of sending output to a printer with a bit of hand-waving, something along the lines of: "It's a difficult problem that depends on interacting with the operating system." I also have a hard time finding resources about this because of all the pages related to printing to the screen. I am using Python 2.6, on Ubuntu 9.04.

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• Git svn - no changes, no branches (except master), rebase/info is not working

  - by ex3v

  I know that similar questions were asked before, but I think my is a little bit different, so please don't point me to existing threads. I'm migrating our old svn repo to git. I did git svn clone path --authors-file abc.txt and everything seemend legit to me. Then I did git remote add origin xyz and git push --all origin and it also worked. I created this repo as test one, with only me having access to both local repo and origin. No changes were made in project held on this repo, nothing to commit, no pushing and so on. There is also only one branch, because someone initialized svn years ago without creating proper folder structure (branches, trunk, tags). Meanwhile someone pushed their work to svn, so I tried to git svn fetch (which worked), and git svn rebase which didn't, giving me error: Unable to determine upstream SVN information from working tree history Is there any reason why git svn decided to stop working?

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• [Qt] How to make another window pop up that extends QWidget as opposed to QDialog?

  - by Graphics Noob

  So far I've only had my main window pop up other windows that were QDialogs and I'm not getting it to work with a QWidget. The other window I want to display was designed with the Form Editor, then wrapped in a class called ResultViewer which extends QWidget (as opposed to QDialog). What I want is to have the ResultViewer show its ui in a seperate window. Now when I try to display it the ResultViewer ui just pops up in the main window on top of the mainwindow ui. The code I'm using to display it is this (in my mainwindow.cpp file) ResultViewer * rv = new ResultView(this); rv->show(); The constructor for the ResultViewer looks like this ResultViewer::ResultViewer(QWidget * parent) : QWidget(parent), ui(new Ui::ResultViewer) { ui->setupUi(this); } I've looked through the QWidget documentation a bit but the only thing I can find that may be related is the QWidget::window() function, but the explanation isn't very clear, it just gives an example of changing the title of a window.

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• Adding behaviour to a set of classes

  - by devoured elysium

  I have defined an Event class: Event and all the following classes inherit from Event: SportEventType1 SportEventType2 SportEventType3 SportEventType4 Right now I will only have SportEvents but I don't know if in the future I'll want some other kind of events that doesn't even have anything to do with Sports. Later, I will want to draw some graphics with info taken from Events, and the drawing logic can be a bit complex. But, for the moment, I think I shouldn't think of how the drawing will be done and I believe that maybe it'd be better if that drawing part was not put as an integral part of the Event/SportEventX class chain. I am looking for solutions for this problem. I know I could just make Event have an instance variable(attribute, for the java crowds) pointing to something as an IDrawInterface, but that would make the Event class "assume" it will be later used for drawing. I would like to make the Event class oblivious to this if possible. Thanks!

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• How to inplement a nightly process in .NET?

  - by Abe Miessler

  I have a set of tasks that I would like to execute every night. These tasks include querying a database, moving and renaming some images and lastly updating a database table. My first thought had been to create a SQL Server job and use xp_cmdshell to move the files but after a bit of research i decided against it. My question now is what is the best way to implement this as a .NET application? Should I create a Windows service? A console application that is scheduled to run once per night? Some other cool way that I don't even know about?

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• Creating a System.Windows.Controls.Image throws an exception - how do I use the dispatcher to instan

  - by Scott Whitlock

  I'm running my unit tests on a piece of code that does the following in the test: Assert.IsNotNull(target.Icon); Inside the getter for the Icon property, I'm doing this: System.Windows.Controls.Image img = new System.Windows.Controls.Image(); That's throwing this exception: System.InvalidOperationException : The calling thread must be STA, because many UI components require this. I understand what that means, and I understand that I need to use the Dispatcher, but I'm a bit confused about how or why... this is a property of my ViewModel and I don't get any of these exceptions when running the application. Other info: this only started failing when I upgraded to .NET 4.

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• Capture IP packets on Dialup connection - Windows 7

  - by Assaf Levy

  Our product utilizes (the wonderful) Winpcap to capture ip packets from all devices with an IP address and analyze them in real time. Unfortunately, we discovered that it does NOT capture any packets on dialup (e.g. PPP) connections on Windows 7, and that there are no near-term plans for enabling this (1). So we need something else. Microsoft Network Monitor and Windows Packet Filter are two options that surfaced during a bit of googling, but before delving into research I wanted to ask the experienced: what are out options, given the following requirements: Capture all in/outbound IP packets on the machine. Complete background processing - no UI should be involved. Support Windows Vista / 7. Performance (user should not feel the difference). Thanks in advance.

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• Med-PC Programing Language

  - by mknuii

  There's this programing language called Med-PC that works with animal behavior. I'm trying to learn a bit about it, but i can't seem to find any kind of books or material about it. I've "google it" but all i seem to find are some references about it and a PDF explaining the installing of the program itself and sensors(for the experiments), not actual programing instructions. I'm looking for some kind of guidance, documents or books, some kind of reference where i can improve and learn about this language, or if it is based on some other language. I just need some reference about it. So i've resorted to StackOverFlow to see if anybody has worked, knows about it or can point me some links/books about it.

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• Using SVN alone or in small workgroups - workflow approach?

  - by Industrial

  Hi everybody, I have spent some months working on a web application and we're come close to production stage. It's soon time to expand the development group with 1-3 people on this project. I have not too much experience on working with SVN, but It's obviously the choice for a big part of the larger companies out there, so I am guessing that the pros of SVN without a doubt outweights the time spent on commit/check ins / check outs etc. The workflow seems to become a bit more complicated with SVN, and even though I have read Version Control with Subversion by O'Reilly Media and I am not sure yet if it's overkill to use SVN for any reasons besides backup when developing alone or in a small (1-3 people) workgroup? How do you do it? What's your workflow with version control while working alone or in small workgroups? Thanks!

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• How to prompt for username and password entry in C# / SQL ASP.NET web app?

  - by salvationishere

  How do I prompt for username and password in my C#/SQL web application? This was developed in VS 2008 on a 32-bit XP. The current connection string I'm using in my web.config file is: <add name="AdventureWorksConnectionString2" connectionString="Data Source=SIDEKICK;Initial Catalog=AdventureWorks;Persist Security Info=false; " providerName="System.Data.SqlClient" /> When I select Basic Authentication it pops up the warning: "The authentication option you have chosen results in passwords being sent over the network without data encryption..." How do I choose this authentication method and still send passwords over securely? So essentially I am looking for the most secure authentication method but that still requires users to input password?

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• XPath 1.0 to find if an element's value is in a list of values

  - by user364902

  Is there a way to construct an XPath that evaluates whether an element's value is in a predefined list of values? Something akin to this: /Location/Addr[State='TX or AL or MA'] Which would match nodes whith State elements for Texas, Alabama, or Massachusetts? I know that I can unpack the expression: /Location/Addr[State='TX] or /Location/Addr[State='AL'], etc... But this is a bit cumbersome since the xpaths are quite long, as is the list of values. My google-fu isn't turning up much on the issue...

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• Javascript: parseInt() with trailing characters

  - by chris_l

  parseInt("7em", 10); returns 7 in all browsers I tested [*]. But can I rely on this? The reason I ask is, that I want to perform some calculations based on em, like /* elem1.style.top uses em units */ elem2.style.top = parseInt(elem1.style.top, 10) + 1 + "em"; I could do this with regular expressions, but parseInt is easier to use, and probably a bit faster. Or is there another solution (maybe using jQuery)? [*] Tested so far on: IE 6, IE 8, Safari 4, Firefox 3.6, Opera 10.5

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• GDI+ DrawImage function

  - by ET

  There is something I am missing. Say I have the following code: private Bitmap source = new Bitmap (some_stream); Bitmap bmp = new Bitmap(100,100); Rectangle newRect = new Rectangle(0, 0, bmp.Width, bmp.Height); Rectangle toZoom= new Rectangle(0, 0, 10, 10); Graphics g = Graphics.FromImage(bmp); g.DrawImage(source, newRect, toZoom, GraphicsUnit.Pixel); My goal is to zoom-in the 10x10 pixels on the top left corner of the source picture. After I created the graphics object g and called DrawImage: the requested rectangle (toZoom) will be copied to bmp, or will it be displayed on the screen? I am a bit confused, can somebody please clarify?

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• Can Visual Studio exclude certain folders when searching for header files?

  - by identitycrisisuk

  I'm having trouble with a library that we are using, which has two copies of header files that are needed - one which we are modifying and building from and another which is automatically created during the build process. I don't fully know why or really want to change this but it can cause a bit of annoyance when on random occasions the go to definition function takes you to the auto created header instead of the one used to build. Usually you can spot it but sometimes you don't and make changes to the auto created one, which are then overwritten or sometimes stay around for a while so that something works on your machine but breaks on other peoples. I don't know if there is any way around this as the auto created folder is in the additional include directories of some of the projects in the solution but I just thought I would ask if there was any good way of reducing the chance of this annoying situation cropping up.

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• version control projects in eclipse

  - by Stan

  Say I have eclipse installed in office and home. Both eclipse are 3.5 but may have slightly difference, like plugins version. I'd like to commit the code to online repo when get off work and then checkout at home. What would be a possible solution? github? sourceforge? Are they free? Would those slightly difference in eclipse cause any problem? Since I might commit whole project folder which consist some configurations. Can the community explain a bit or suggest some keyword? I will look up more online. Thanks.

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• Learning to work with audio in C++

  - by Skilldrick

  My degree was in audio engineering, but I'm fairly new to programming. I'd like to learn how to work with audio in a programming environment, partly so I can learn C++ better through interesting projects. First off, is C++ the right language for this? Is there any reason I shouldn't be using it? I've heard of Soundfile and some other libraries - what would you recommend? Finally, does anyone know of any good tutorials in this subject? I've learnt the basics of DSP - I just want to program it! EDIT: I use Windows. I'd like to play about with real-time stuff, a bit like Max/MSP but with more control.

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• Change web service url for a suds client on runtime (keeping the wsdl)

  - by patanpatan

  Hi. First of all, my question is similar to this one But it's a little bit different. What we have is a series of environments, with the same set of services. For some environments (the local ones) we can get access to the wsdl, and thus generating the suds client. For external environment, we cannot access the wsdl. But being the same, I was hoping I can change just the URL without regenerating the client. I've tried cloning the client, but it doesn't work.

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