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  • How to solve such system with given parts of it? (maple)

    - by Kabumbus
    So I had a system #for given koefs k:=3; n:=3; #let us solve system: koefSolution:= solve({ sum(a[i], i = 0 .. k) = 0, sum(a[i], i = 0 .. k)-(sum(b[i], i = 0 .. k)) = 0, sum(i^n*a[i], i = 0 .. k)-(sum(i^(n-1)*b[i], i = 0 .. k)) = 0 }); So I have a vector like koefSolution := { a[0] = 7*a[2]+26*a[3]-b[1]-4*b[2]-9*b[3], a[1] = -8*a[2]-27*a[3]+b[1]+4*b[2]+9*b[3], a[2] = a[2], a[3] = a[3], b[0] = -b[1]-b[2]-b[3], b[1] = b[1], b[2] = b[2], b[3] = b[3]} I have a[0] so I try solve({koefSolution, a[0] = 1}); why it does not solve my system for given a[0]? ( main point here is to fill koefSolution with given a[] and b[] and optimize.)

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  • What is your longest-held programming assumption that turned out to be incorrect?

    - by Demi
    I am doing some research into common errors and poor assumptions made by junior (and perhaps senior) software engineers. What was your longest-held poor assumption that was eventually corrected? For example: I at one point failed to understand that the size of an integer was not a standard (depends on the language and target). A bit embarrassing to state, but there it is. Be frank: what hard-held belief did you have, and roughly how long did you maintain the assumption? It can be about an algorithm, a language, a programming concept, testing, anything under the computer science domain.

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  • importing same module more than once

    - by wallacoloo
    So after a few hours, I discovered the cause of a bug in my application. My app's source is structure like: main/ __init__.py folderA/ __init__.py fileA.py fileB.py Really, there are about 50 more files. But that's not the point. In main/__init__.py, I have this code: from folderA.fileA import * in folderA/__init__.py I have this code: sys.path.append(pathToFolderA) in folderA/fileB.py I have this code: from fileA import * The problem is that fileA gets imported twice. However, I only want to import it once. The obvious way to fix this (to me atleast) is to change certain paths from path to folderA.path But I feel like Python should not even have this error in the first place. What other workarounds are there that don't require each file to know it's absolute location?

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  • Abort a slow flush to disk after write?

    - by Therealstubot
    Is there a way to abort a python write operation in such a way that the OS doesn't feel it's necessary to flush the unwritten data to the disc? I'm writing data to a USB device, typically many megabytes. I'm using 4096 bytes as my block size on the write, but it appears that Linux caches up a bunch of data early on, and write it out to the USB device slowly. If at some point during the write, my user decides to cancel, I want the app to just stop writing immediately. I can see that there's a delay between when the data stops flowing from the application, and the USB activity light stops blinking. Several seconds, up to about 10 seconds typically. I find that the app is holding in the close() method, I'm assuming, waiting for the OS to finish writing the buffered data. I call flush() after every write, but that doesn't appear to have any impact on the delay. I've scoured the python docs for an answer but have found nothing.

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  • Packaging one or two plugins as a standalone RCP application?

    - by Martin Cowie
    I have a handful of Eclipse plugins that I maintain. They are proving useful enough that non Eclipse users have asked for them without the overhead of a full eclipse install. I am certain this is possible, but uncertain how to make this possible. My attempts at creating a standalone RCP app and then including my plugins as dependencies have given me mixed results. More specifically, my perspective tries to instantiate a view from a plugin and fails (silently)... public void createInitialLayout(IPageLayout layout) { layout.addStandaloneView( "myPlugin.ID", false, IPageLayout.LEFT, 0.25f, editorArea); } ... but as the same plugin implements a search extension, it does show up in the standard Eclipse search dialog. Are there any resources that hardened Eclipse tars can point me to, that will help overcome this hurdle? M.

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  • Best calculator software to help programmers

    - by RHaguiuda
    As a embedded systems programmer I always need to make lots of base conversions (dec to hex, hex to bin and so on...), and I must admit: Windows 7 calculator is a good calc, but too limited in my point of view. I work a lot with communications protocols and it`s common to need some base conversion in this field of knowledge. I`m looking for a calculator software (not a hardware one), to help with base conversions, but it must also support scientific calc. Can anyone help on this? Since this subject is intended to help programmers, I did not ask this in SuperUser.com. Thanks.

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  • How to make WordPress "Add/Edit Post" form more Tumblr like?

    - by Eliot Sykes
    Hi, WordPress requires you give each blog post at least two fields: a title and text body content. I'm wondering how to modify WordPress admin so I can sometimes enter a single field for a blog post, in particular a URL, without WordPress requiring a title (related but not the point of this question: a custom theme would then know how to handle a post that only contained a URL, it would treat it like a "Link" post in Tumblr). Ideally it'd be good if the "add/edit post" form could be modified so it only contains this single URL/Link field when this is wanted. I'm guessing this is possible through a plugin but I'm not certain. I'm hoping some smart WordPress devs are here to share and brainstorm ideas for how this could be done. Thanks in advance for any help, Eliot

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  • ASP.NET MVC authorization & permission to use model classes

    - by Tomek
    Hi, This is my first post here, so hello :) Okey, let's get to the point... I am writing my first app in ASP.NET MVC Framework and i have a problem with checking privileges to use instances of model classes (read, edit). Sample code looks like this: // Controller action [CustomAuthorize(Roles="Editor, Admin")] public ActionResult Stats(int id) { User user = userRepository.GetUser(id); if (user == null || !user.Activated || user.Removed) return View("NotFound"); else if (!user.IsCurrentSessionUserOwned) return View("NotAuthorized"); return View(user); } So far authorize attribute protects only controller actions, so my question is: how to make (custom) authorize attribute to check not only user role, usernames but also did i.e. resources instantiated in action methods (above: User class, but there are other ORM objects like News, Photos etc.) All of these object to check have their unique ID's, so user have own ID, News have their ID and UserID field referecned to Users table (i mean these objects are LINQ2SQL classes). How should i resolve that problem?

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  • iphone memory leaks and malloc?

    - by Brodie4598
    Okay so im finally to the point where I am testing my iPad App on an actual iPad... One thing that my app does is display a large (2mb) image in a scroll view. This is causing the iPad to get memory warnings. I run the app in the instruments to check for the leak. When I load the image, a leak is detected and i see the following in the allocations: ALl Allocations: 83.9 MB Malloc 48.55 MB: 48.55 MB Malloc 34.63 MB: 34.63 MB What im trying to understand is how to plug the leak obviously, but also why a 2MB image is causing a malloc of 20x that size I am very new to programming in obj-c so im sure this is an obvious thing, but I just cant figure it out. Here is the code:

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  • How to assign default values and define unique keys in Entity Framework 4 Designer

    - by csharpnoob
    Hello, I've had a look at the Entity Framework 4. While generating code for the SQL Server 2008 I came to the point where I want to define some default values for some fields. how to define in the designer for a Created DateTime Field the DateTime.Now default value? - Error 54: Default value (DateTime.Now) is not valid for DateTime. The value must be in the form 'yyyy-MM-dd HH:mm:ss.fffZ' how to make for code generation a string Field unique. Like E-Mail or Username can exists only once in the table. I've search alot in the internet and also checked my books Pro Entity Framework 4.0 and Programming Entity Framework. But none of them seems to come up with the default value issue, or using sql commands as default values for database generation. Another thing is, how to prevent on database generation always from droping tables? Instead i want to append non existing fields and keep the data. Thanks for any suggestions.

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  • Silverlight error-handling conventions: There is no relationship between onSilverlightError and Repo

    - by rasx
    When I see the call System.Windows.Browser.HtmlPage.Window.Eval (which is evil) in ReportErrorToDOM (in App.xaml.cs) this shows me that it has no relationship to onSilverlightError. So what kind of JavaScript-based scenario calls onSilverlightError? When will onSilverlightError definitely be needed? What are Silverlight error-handling conventions in general? This is a very important comment by Erik Monk but needs more detail: There are 2 kinds of terminal errors in Silverlight. 1) Managed errors (hit the managed Application_UnhandledException method). Note that some errors may not even get to this point. If the managed infrastructure can't be loaded for some reason (out of memory error maybe...), you won't get this kind of error. Still, if you can get it, you can use a web service (or the CLOG project) to communicate it back to the server. 2) Javascript errors.

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  • JMS have javax.jms.InvalidDestinationException when client stop working

    - by Tran
    I use JMS for sending requests from a client to a server. My client sends a request to the server. While the server is working with my request, my client stops (network problem) before the server finishes. When the server is finished, it'll return to the client, but the server can't see the client which sent the request to server, at which point, the server will return an exception in log file. The exception is : javax.jms.InvalidDestinationException: Cannot publish to a deleted Destination: temp-queue://ID:PC0092-49463-1344231871819-0:0:9 [^] My question is: what do I need to do in this case? Can I catch or disable this exception? And how can I do it? (Sorry, If my english is not good.)

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  • If Possible, How Can One Set Either a Background Color on Cells within a Sizer or Gridlines for the

    - by MetaHyperBolic
    I am flailing about with wxWidgets, in particular, the wx.Sizer in wxPython. I have read the documents, I have a copy of wXPython in Action before me, and have set aside the problem to work on other things a better mental model of sizers hopefully gestated within my skull. None of this has worked. I am not grokking, or even getting to the point where I can bang about usefully, how sizers work. In HTML, I could at least set a background color on some div or td, or call forth borders so I could see how things are laid out. Here, I have a grey expanse and no idea which of the nested static box sizers from which it originates. I am giving static box sizers after making a mess out of the grid bag sizers. Either alternative would let me at least get a handle on how these work.

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  • to escape or not to escape: well formed XHTML with diacritics

    - by andresmh
    Say that you have a XHTML document in English but it has accented characters (e.g. meta name="author" content="José"). Let's say you have no control over the HTTP headers. Should the characters be replaced for their corresponding named entities (e.g. &aacute;, etc)? Should the doc type and the xml:lang attribute be set to English? I know I can check the W3C recommendation but I am asking more from a practical point of view.

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  • Global variable life in Javascript - destroyed on a reload?

    - by Paul Nathan
    (I am learning Javascript) Problem: A page I am working on has 2 views, a data entry view with a textbox and a data rendering view. There is a a href src="currentpage#" link that switches between the 2 views. In order to transmit data from view to view, the javascript parses it from the current HTML and pushes it into the correct form for the other view. This is ugly and I want to refactor it out, ideally into some sort of global where it can be neatly rendered down into the view on command (I'm refactoring the code base to a point where I can AJAX it from a server). However, I am not certain about scoping rules and variable life in JS.

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  • Real world example of Unification in First Order Logic?

    - by Sebi
    I know this is only part of a programming question, but at the moment, I'm doing a little bit of logic programming. One thing I still don't understand correctly is Unification in First Order Logic. I read the Wikipedia article and it is more or less clear that the purpose is searching a term that unifies two sentences... There are also examples in this article but I just don't get the point why this should be useful. Can anyone give an example with real world objects instead of A, B, C,, etc.? I hope this will help me to understand. Thanks

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  • Compare GetNextInsertionPosition and GetNextContextPosition in WPF

    - by paradisonoir
    As I enter a character in my RichTextBox, I want to get the next character from the its TextRange. So here is how I do it: TextPointer ptr1= RichTextBox.CaretPosition; char nextChar = GetNextChar(); while (char.IsWhiteSpace(nextChar)) { ptr1= ptr1.GetNextInsertionPosition(LogicalDirection.Forward); nextChar = GetCharacterAt(Ptr1); } then I get the ptr1 of the next character and from the TextPointer, I get the TextRange, and do my changes. So here is the problem? when the next word is spelled correctly, I have no problem, but if it's not spelled properly then ptr1 would not point to the first character of the next word (the second character), and if I use GetNextContextPosition(LogicalDirection.Forward) it would give me the first letter of the next word if it's misspelled. So depending on the spelling only one of them works? I was just wondering if you have any idea about this problem? Is there anything wrong I am doing here?

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  • Getting "Object is read only" error when setting ClientCredentials in WCF

    - by Paul Mrozowski
    I have a proxy object generated by Visual Studio (client side) named ServerClient. I am attempting to set ClientCredentials.UserName.UserName/Password before opening up a new connection using this code: InstanceContext context = new InstanceContext(this); m_client = new ServerClient(context); m_client.ClientCredentials.UserName.UserName = "Sample"; As soon as the code hits the UserName line it fails with an "Object is read-only" error. I know this can happen if the connection is already open or faulted, but at this point I haven't called context.Open() yet. I have configured the Bindings (which uses netTcpBinding) to use Message as it's security mode, and MessageClientCredentialType is set to UserName. Any ideas?

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  • Why is IE7 hiding my overflow when, as far as I can tell, all it's containing elements have overflow

    - by dougoftheabaci
    If you visit the site in question (haddongrant.com) and go to the Artwork section, if you click on an image and view it's stack in Safari, Chrome or Firefox you'll notice the images extend up and down the page, eventually disappearing over the edge. This is what you should be seeing. In Internet Explorer 7, however, the overflow gets cut off at some point before it ever gets to the end of the page. The problem is... I can't tell where! I've had a look and every containing element should show overflow. I don't know why IE7 isn't. Does anyone have any ideas where I might need to add an overflow-y:visible;?

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  • logic of button to be disabled or not in mvc

    - by rod
    Hi All, Here's an excerpt from a book I'm reading about application design with MVC: Ideally, the view is so simple and logic-free as to need virtually no testing. Users (and developers before users) can reasonably test the view by simply looking at the pixels on the screen. Anything else beyond pure graphical rendering should ideally be taken out of the view and placed in the controller and model. This includes, for example, the logic that determines whether a certain button should be enabled or grayed out at some point. what does the bold statement mean to you? what would this look like? thanks, rod.

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  • counter variable not working?

    - by jaycode
    Just like many things in rails, sometimes it works, sometimes it doesn't... Showing app/views/admin/products/_variant.html.erb where line #8 raised: undefined local variable or method `variant_counter' for #<ActionView::Base:0x107f7ae10> I only want to display variant_counter from partial _variant. This was the render caller code: <%= render :partial => '/admin/products/variant', :collection => product.variants %> The funny thing is, I have been using partial counter heaps number of times, somehow now I encountered this issue. Could anybody point me out what are there to find out what may went wrong?

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  • [StructureMap] Xml configuration or Configuration through code?

    - by Amith George
    I personally like the option to configure StructureMap from C# code. From what I understand, one of the advantages of DI, is that we can easily swap in a new concrete instance. But, if the configuration is defined in code, then the concrete instances are hardcoded in the dll. So, practically, its as good as having hard coded the dependencies, right? I know, during testing it makes life easier... My point is, wouldnt it be better to use xml configuration instead? you want to plugin a new concrete instance? simply have your installer overwrite the structuremap.config file with the new one. So, what is the preferred way to configure StructureMap? Extra: Am forced to use C# configuration for the time being because I dont know how to pass the connection string to instance. I can write the connectionstring in the config file, but i would like to reuse the connectionstring defined in app.config.

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  • Can you use the PackageMaker command to create an installer from a list of files?

    - by zekel
    I want to (periodically and automatically) create an installer from various files and folders that are in many places. But, I can't figure out how to supply the packagemaker command with all the paths of the items I want to install. This is for internal development purposes, not for customer distribution. I want the files included to be configureable; it's not really an option to use the GUI to add all the paths because they will change frequently. The best I could do was to use the --watch flag and touch all of the stuff I wanted included in the package. This is very messy and includes other files that happen to be accessed at the same time. There isn't a common scheme to what I want to include, so I can't just --filter the rest out. Is there a better way? Am I missing the point?

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  • Return a dynamic string from std::exception's `what`

    - by Shtééf
    I'm convinced at this point that I should be creating subclasses of std::exception for all my exception throwing needs. Now I'm looking at how to override the what method. The situation that I'm facing, it would be really handy if the string what returns be dynamic. Some pieces of code parse an XML file for example, and adding a position or line number to the error message is useful to me. What I'd like to know: what returns a const char *, which implies any catcher is likely not going to free the string. So I need some other place to store the result, but where would that be? (I need thread-safety.) what also includes throw() in its signature. While I can prevent my what from throwing anything, it seems to me that this method really isn't intended for anything too dynamic. If what is not the right place, then where should I be doing this instead?

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  • Working examples of winform/WPF apps

    - by melody
    I'm a user interface designer. The project I'm working on is a dashboard that will have several interactive and customizable widgets (think Netvibes, etc.). The development group is going to be using either WinForm or WPF to build the dashboard and widgets. I need to understand the capabilities of each technology better and see a sampling of actual working apps to help accomplish this. I can't download and build examples... need live examples somewhere on the web. Can you point me to live, existing apps? Thx.

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