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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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  • Serialization Performance and Google Android

    - by Jomanscool2
    I'm looking for advice to speed up serialization performance, specifically when using the Google Android. For a project I am working on, I am trying to relay a couple hundred objects from a server to the Android app, and am going through various stages to get the performance I need. First I tried a terrible XML parser that I hacked together using Scanner specifically for this project, and that caused unbelievably slow performance when loading the objects (~5 minutes for a 300KB file). I then moved away from that and made my classes implement Serializable and wrote the ArrayList of objects I had to a file. Reading that file into the objects the Android, with the file already downloaded mind you, was taking ~15-30 seconds for the ~100KB serialized file. I still find this completely unacceptable for an Android app, as my app requires loading the data when starting the application. I have read briefly about Externalizable and how it can increase performance, but I am not sure as to how one implements it with nested classes. Right now, I am trying to store an ArrayList of the following class, with the nested classes below it. public class MealMenu implements Serializable{ private String commonsName; private long startMillis, endMillis, modMillis; private ArrayList<Venue> venues; private String mealName; } And the Venue class: public class Venue implements Serializable{ private String name; private ArrayList<FoodItem> foodItems; } And the FoodItem class: public class FoodItem implements Serializable{ private String name; private boolean vegan; private boolean vegetarian; } IF Externalizable is the way to go to increase performance, is there any information as to how java calls the methods in the objects when you try to write it out? I am not sure if I need to implement it in the parent class, nor how I would go about serializing the nested objects within each object.

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  • std::vector iterator or index access speed question

    - by Simone Margaritelli
    Just a stupid question . I have a std::vector<SomeClass *> v; in my code and i need to access its elements very often in the program, looping them forward and backward . Which is the fastest access type between those two ? Iterator access std::vector<SomeClass *> v; std::vector<SomeClass *>::iterator i; std::vector<SomeClass *>::reverse_iterator j; // i loops forward, j loops backward for( i = v.begin(), j = v.rbegin(); i != v.end() && j != v.rend(); i++, j++ ){ // some operations on v items } Subscript access (by index) std::vector<SomeClass *> v; unsigned int i, j, size = v.size(); // i loops forward, j loops backward for( i = 0, j = size - 1; i < size && j >= 0; i++, j-- ){ // some operations on v items } And, does const_iterator offer a faster way to access vector elements in case i do not have to modify them? Thank you in advantage.

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  • Managing lots of callback recursion in Nodejs

    - by Maciek
    In Nodejs, there are virtually no blocking I/O operations. This means that almost all nodejs IO code involves many callbacks. This applies to reading and writing to/from databases, files, processes, etc. A typical example of this is the following: var useFile = function(filename,callback){ posix.stat(filename).addCallback(function (stats) { posix.open(filename, process.O_RDONLY, 0666).addCallback(function (fd) { posix.read(fd, stats.size, 0).addCallback(function(contents){ callback(contents); }); }); }); }; ... useFile("test.data",function(data){ // use data.. }); I am anticipating writing code that will make many IO operations, so I expect to be writing many callbacks. I'm quite comfortable with using callbacks, but I'm worried about all the recursion. Am I in danger of running into too much recursion and blowing through a stack somewhere? If I make thousands of individual writes to my key-value store with thousands of callbacks, will my program eventually crash? Am I misunderstanding or underestimating the impact? If not, is there a way to get around this while still using Nodejs' callback coding style?

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  • How to Write to a User.Config file through ConfigurationManager?

    - by Josh G
    I'm trying to persist user settings to a configuration file using ConfigurationManager. I want to scope these settings to the user only, because application changes can't be saved on Vista/Win 7 without admin privileges. This seems to get me the user's configuration, which appears to be saved here in Win 7 ([Drive]:\Users\[Username]\AppData\Local\[ApplicationName]\[AssemblyName][hash]\[Version\) Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.PerUserRoamingAndLocal); Whenever I try to save any changes at all to this config I get this exception: InnerException: System.InvalidOperationException Message="ConfigurationSection properties cannot be edited when locked." Source="System.Configuration" StackTrace: at System.Configuration.SectionInformation.VerifyIsEditable() at System.Configuration.MgmtConfigurationRecord.GetConfigDefinitionUpdates(Boolean requireUpdates, ConfigurationSaveMode saveMode, Boolean forceSaveAll, ConfigDefinitionUpdates& definitionUpdates, ArrayList& configSourceUpdates) I have tried adding a custom ConfigurationSection to this config. I have tried adding to the AppSettingsSection. Whenever I call config.Save() it throws the exception above. Any ideas? I tried using the ApplicationSettingsBase class through the Project-Settings designer, but it doesn't appear that you can save custom types with this. I want similar functionality with the ability to save custom types. Thanks.

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  • Are there some cases where Python threads can safely manipulate shared state?

    - by erikg
    Some discussion in another question has encouraged me to to better understand cases where locking is required in multithreaded Python programs. Per this article on threading in Python, I have several solid, testable examples of pitfalls that can occur when multiple threads access shared state. The example race condition provided on this page involves races between threads reading and manipulating a shared variable stored in a dictionary. I think the case for a race here is very obvious, and fortunately is eminently testable. However, I have been unable to evoke a race condition with atomic operations such as list appends or variable increments. This test exhaustively attempts to demonstrate such a race: from threading import Thread, Lock import operator def contains_all_ints(l, n): l.sort() for i in xrange(0, n): if l[i] != i: return False return True def test(ntests): results = [] threads = [] def lockless_append(i): results.append(i) for i in xrange(0, ntests): threads.append(Thread(target=lockless_append, args=(i,))) threads[i].start() for i in xrange(0, ntests): threads[i].join() if len(results) != ntests or not contains_all_ints(results, ntests): return False else: return True for i in range(0,100): if test(100000): print "OK", i else: print "appending to a list without locks *is* unsafe" exit() I have run the test above without failure (100x 100k multithreaded appends). Can anyone get it to fail? Is there another class of object which can be made to misbehave via atomic, incremental, modification by threads? Do these implicitly 'atomic' semantics apply to other operations in Python? Is this directly related to the GIL?

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  • C# Help: Adding a complexType to the main XmlSchema

    - by G33kKahuna
    I need to create program that creates a XML schema like below using System.Xml.XmlSchema namespace I'm using the XmlSchemaComplexType to MyString and MyInteger but I can't seem to find a way to set the extension to base string and int respectively. Any guidance is much appreciated ... thanks <?xml version="1.0" encoding="utf-8" ?> <xs:schema elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema"> <xs:complexType name="MyString"> <xs:simpleContent> <xs:extension base="xs:string"> <xs:attribute name="modified" type="xs:boolean" /> </xs:extension> </xs:simpleContent> </xs:complexType> <xs:complexType name="MyInteger"> <xs:simpleContent> <xs:extension base="xs:int"> <xs:attribute name="modified" type="xs:boolean" /> </xs:extension> </xs:simpleContent> </xs:complexType> <xs:element name="data"> <xs:complexType> <xs:sequence> <xs:element name="row"> <xs:complexType> <xs:sequence> <xs:element name="order_id" type="MyInteger" /> <xs:element name="order_status" type="MyString" /> </xs:sequence> </xs:complexType> </xs:element> </xs:sequence> </xs:complexType> </xs:element> </xs:schema>

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  • Clear UITextField when standard number pad is pressed

    - by Manu
    Hi all, I'm sorry if I didn't explain my problem well enough in the title. In my application, I'm using a small subview to create a very basic calculator on the top side of the screen (I just have an UITextField to show the operations and two buttons). Instead of using a custom keyboard for it, I want to use the standard iPhone number pad. My problem is that after doing an operation (e.g. adding two numbers) and showing the result, I cannot figure out how to clear the screen when the user enters a new number. So, for example: User enters "6" - Number 6 is shown in UITextField User selects "+" - UITextField is cleared to make room for the next number User enters "10" - Number 10 is shown in UITextField User selects "+" - 16 is shown as the result of the previous operation, and should stay there until another number is pressed (he wants to continue adding more numbers) User enters "5" At this point, if I was using a custom keyboard, I could clear the UITextField as soon as the button "5" is pressed by the user, but I cannot figure out how to do so when using the standard number pad. So, the result I get at the moment is "165". Is there a way to detect when a key is pressed in the standard number pad so that I can clear the UITextField before the new number appears? I thought there may be a NSNotification for that, but I couldn't find it. I'm aware that I could solve my problem if I created a custom keyboard or if I used two separated UITextFields (one for the operations and another one for the total), but I would like to use the standard number pad if it's possible. Thanks very much!

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  • Control 'ctl00_TextBox1' of type 'TextBox' must be placed inside a form tag with runat=server.

    - by Hiru
    When a form with a run at server is added there will be two forms with runat server and another error occurs. Can some one give me an idea. Thankx in advance. The details of the error are as follows. Control 'ctl00_TextBox1' of type 'TextBox' must be placed inside a form tag with runat=server. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.Web.HttpException: Control 'ctl00_TextBox1' of type 'TextBox' must be placed inside a form tag with runat=server. 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: [HttpException (0x80004005): Control 'ctl00_TextBox1' of type 'TextBox' must be placed inside a form tag with runat=server.] System.Web.UI.Page.VerifyRenderingInServerForm(Control control) +2052287 System.Web.UI.WebControls.TextBox.AddAttributesToRender(HtmlTextWriter writer) +49 System.Web.UI.WebControls.WebControl.RenderBeginTag(HtmlTextWriter writer) +17 System.Web.UI.WebControls.TextBox.Render(HtmlTextWriter writer) +17 System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +25 System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +121 System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +22 System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +199 System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +20 System.Web.UI.Control.Render(HtmlTextWriter writer) +7 System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +25 System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +121 System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +22 System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +199 System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +20 System.Web.UI.Page.Render(HtmlTextWriter writer) +26 System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +25 System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +121 System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +22 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2558 Version Information: Microsoft .NET Framework Version:2.0.50727.1873; ASP.NET Version:2.0.50727.1433

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  • priority queue with limited space: looking for a good algorithm

    - by SigTerm
    This is not a homework. I'm using a small "priority queue" (implemented as array at the moment) for storing last N items with smallest value. This is a bit slow - O(N) item insertion time. Current implementation keeps track of largest item in array and discards any items that wouldn't fit into array, but I still would like to reduce number of operations further. looking for a priority queue algorithm that matches following requirements: queue can be implemented as array, which has fixed size and _cannot_ grow. Dynamic memory allocation during any queue operation is strictly forbidden. Anything that doesn't fit into array is discarded, but queue keeps all smallest elements ever encountered. O(log(N)) insertion time (i.e. adding element into queue should take up to O(log(N))). (optional) O(1) access for *largest* item in queue (queue stores *smallest* items, so the largest item will be discarded first and I'll need them to reduce number of operations) Easy to implement/understand. Ideally - something similar to binary search - once you understand it, you remember it forever. Elements need not to be sorted in any way. I just need to keep N smallest value ever encountered. When I'll need them, I'll access all of them at once. So technically it doesn't have to be a queue, I just need N last smallest values to be stored. I initially thought about using binary heaps (they can be easily implemented via arrays), but apparently they don't behave well when array can't grow anymore. Linked lists and arrays will require extra time for moving things around. stl priority queue grows and uses dynamic allocation (I may be wrong about it, though). So, any other ideas?

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  • KendoUI Mobile switch and datasource

    - by OnaBai
    I'm trying to have a list of items displayed using a listview, something like: <div data-role="view" data-model="my_model"> <ul data-role="listview" data-bind="source: ds" data-template="list-tmpl"></ul> </div> Where I have a view using a model called my_model and a listview where the source is bound to ds. My model is something like: var my_model = kendo.observable({ ds: new kendo.data.DataSource({ transport: { read: readData, update: updateData, create: updateData, remove: updateData }, pageSize: 10, schema: { model: { id: "id", fields: { id: { type: "number" }, name: { type: "string" }, active: { type: "boolean" } } } } }) }); Each item includes an id, a name (that is a string) and a boolean named active. The template used to render each element is: <script id="list-tmpl" type="text/kendo-tmpl"> <span>#= name # : #= active #</span> <input data-role="switch" data-bind="checked: active"/> </script> Where I display the name and (for debugging) the value of active. In addition, I render a switch bound to active. You should see something like: The problems observed are: If you click on a switch you will see that the value of active next to the name changes its value (as expected) but if then, you pick another switch, the value (neither next to name nor in the DataSource) is not updated (despite the value of the switch is correctly updated). The update handler in the DataSource is never invoked (not even for the first chosen switch and despite the DataSource for that first toggled switch is updated). You can check it in JSFiddle: http://jsfiddle.net/OnaBai/K7wEC/ How do I make that the DataSource gets updated and update handler invoked?

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  • find(:all) and then add data from another table to the object

    - by Koning Baard XIV
    I have two tables: create_table "friendships", :force => true do |t| t.integer "user1_id" t.integer "user2_id" t.boolean "hasaccepted" t.datetime "created_at" t.datetime "updated_at" end and create_table "users", :force => true do |t| t.string "email" t.string "password" t.string "phone" t.boolean "gender" t.datetime "created_at" t.datetime "updated_at" t.string "firstname" t.string "lastname" t.date "birthday" end I need to show the user a list of Friendrequests, so I use this method in my controller: def getfriendrequests respond_to do |format| case params[:id] when "to_me" @friendrequests = Friendship.find(:all, :conditions => { :user2_id => session[:user], :hasaccepted => false }) when "from_me" @friendrequests = Friendship.find(:all, :conditions => { :user1_id => session[:user], :hasaccepted => false }) end format.xml { render :xml => @friendrequests } format.json { render :json => @friendrequests } end end I do nearly everything using AJAX, so to fetch the First and Last name of the user with UID user2_id (the to_me param comes later, don't worry right now), I need a for loop which make multiple AJAX calls. This sucks and costs much bandwidth. So I'd rather like that getfriendrequests also returns the First and Last name of the corresponding users, so, e.g. the JSON response would not be: [ { "friendship": { "created_at": "2010-02-19T13:51:31Z", "user1_id": 2, "updated_at": "2010-02-19T13:51:31Z", "hasaccepted": false, "id": 11, "user2_id": 3 } }, { "friendship": { "created_at": "2010-02-19T16:31:23Z", "user1_id": 2, "updated_at": "2010-02-19T16:31:23Z", "hasaccepted": false, "id": 12, "user2_id": 4 } } ] but rather: [ { "friendship": { "created_at": "2010-02-19T13:51:31Z", "user1_id": 2, "updated_at": "2010-02-19T13:51:31Z", "hasaccepted": false, "id": 11, "user2_id": 3, "firstname": "Jon", "lastname": "Skeet" } }, { "friendship": { "created_at": "2010-02-19T16:31:23Z", "user1_id": 2, "updated_at": "2010-02-19T16:31:23Z", "hasaccepted": false, "id": 12, "user2_id": 4, "firstname": "Mark", "lastname": "Gravell" } } ] I thought of a for loop in the getfriendrequests method, but I don't know how to implement this, and maybe there is an easier way. It must also work for XML. Can anyone help me? Thanks

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  • Custom Html Helper is not working in asp.net MVC 2.0

    - by chobo2
    Hey I was using this custom html helper in asp.net mvc 1.0 but now I am trying to use it in a 2.0 project and it crashes http://blog.pagedesigners.co.nz/archive/2009/07/15/asp.net-mvc-ndash-validation-summary-with-2-forms-amp-1.aspx This is the error I get. System.MissingMethodException was unhandled by user code Message=Method not found: 'System.String System.Web.Mvc.Html.ValidationExtensions.ValidationSummary(System.Web.Mvc.HtmlHelper)'. Source=CustomHtmlHelpers StackTrace: at CustomHtmlHelpers.ActionValidationSummaryHelper.ActionValidationSummary(HtmlHelper html, String action) at ASP.views_signin_signin_aspx.__RenderContent2(HtmlTextWriter __w, Control parameterContainer) in SignIn.aspx:line 23 at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) at System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) at System.Web.UI.Control.Render(HtmlTextWriter writer) at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) at System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) at System.Web.UI.Control.RenderControl(HtmlTextWriter writer) at ASP.views_shared_site_master.__Render__control1(HtmlTextWriter __w, Control parameterContainer) Site.Master:line 64 at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) at System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) at System.Web.UI.Control.Render(HtmlTextWriter writer) at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) at System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) at System.Web.UI.Control.RenderControl(HtmlTextWriter writer) at System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) at System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) at System.Web.UI.Page.Render(HtmlTextWriter writer) at System.Web.Mvc.ViewPage.Render(HtmlTextWriter writer) at System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) at System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) at System.Web.UI.Control.RenderControl(HtmlTextWriter writer) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) InnerException: My other html helpers in the same library do work. I added the namespace into the webconfig.

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  • Deserializing XML to Objects in C#

    - by Justin Bozonier
    So I have xml that looks like this: <todo-list> <id type="integer">#{id}</id> <name>#{name}</name> <description>#{description}</description> <project-id type="integer">#{project_id}</project-id> <milestone-id type="integer">#{milestone_id}</milestone-id> <position type="integer">#{position}</position> <!-- if user can see private lists --> <private type="boolean">#{private}</private> <!-- if the account supports time tracking --> <tracked type="boolean">#{tracked}</tracked> <!-- if todo-items are included in the response --> <todo-items type="array"> <todo-item> ... </todo-item> <todo-item> ... </todo-item> ... </todo-items> </todo-list> How would I go about using .NET's serialization library to deserialize this into C# objects? Currently I'm using reflection and I map between the xml and my objects using the naming conventions.

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  • Retactoring advanced has_many example

    - by atmorell
    Hello, My user model has three relations for the same message model, and is using raw SQL :/ Is there a better more rails way to achieve the same result? Could the foreign key be changed dynamically? e.g User.messages.sent (foreign key = author_id) and User.messages.received (foreign key = recipient ) I have been trying to move some of the logic into scopes in the message model, but the user.id is not available from the message model... Any thoughts? Table layout: create_table "messages", :force => true do |t| t.string "subject" t.text "body" t.datetime "created_at" t.datetime "updated_at" t.integer "author_id" t.integer "recipient_id" t.boolean "author_deleted", :default => false t.boolean "recipient_deleted", :default => false end This is my relations for my user model: has_many :messages_received, :foreign_key => "recipient_id", :class_name => "Message", :conditions => ['recipient_deleted = ?', false] has_many :messages_sent, :foreign_key => "author_id", :class_name => "Message", :conditions => ['author_deleted = ?', false] has_many :messages_deleted, :class_name => "Message", :finder_sql => 'SELECT * FROM Messages WHERE author_id = #{self.id} AND author_deleted = true OR recipient_id = #{self.id} AND recipient_deleted = true' Best regards. Asbjørn Morell

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  • Using Qt signals/slots instead of a worker thread

    - by Rob
    I am using Qt and wish to write a class that will perform some network-type operations, similar to FTP/HTTP. The class needs to connect to lots of machines, one after the other but I need the applications UI to stay (relatively) responsive during this process, so the user can cancel the operation, exit the application, etc. My first thought was to use a separate thread for network stuff but the built-in Qt FTP/HTTP (and other) classes apparently avoid using threads and instead rely on signals and slots. So, I'd like to do something similar and was hoping I could do something like this: class Foo : public QObject { Q_OBJECT public: void start(); signals: void next(); private slots: void nextJob(); }; void Foo::start() { ... connect(this, SIGNAL(next()), this, SLOT(nextJob())); emit next(); } void Foo::nextJob() { // Process next 'chunk' if (workLeftToDo) { emit next(); } } void Bar::StartOperation() { Foo* foo = new Foo; foo->start(); } However, this doesn't work and UI freezes until all operations have completed. I was hoping that emitting signals wouldn't actually call the slots immediately but would somehow be queued up by Qt, allowing the main UI to still operate. So what do I need to do in order to make this work? How does Qt achieve this with the multitude of built-in classes that appear to perform lengthy tasks on a single thread?

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  • Can I compare a template variable to an integer in App Engine templates?

    - by matt b
    Using Django templates in Google App Engine (on Python), is it possible to compare a template variable to an integer in an {% if %} block? views.py: class MyHandler(webapp.RequestHandler): def get(self): foo_list = db.GqlQuery(...) ... template_values['foos'] = foo_list template_values['foo_count'] = len(foo_list) handler.response.out.write(template.render(...)) My template: {% if foo_count == 1 %} There is one foo. {% endif %} This blows up with 'if' statement improperly formatted. What I was attempting to do in my template was build a simple if/elif/else tree to be grammatically correct to be able to state #foo_count == 0: There are no foos. #foo_count == 1: There is one foo. #else: There are {{ foos|length }} foos. Browsing the Django template documents (this link provided in the GAE documentation appears to be for versions of Django far newer than what is supported on GAE), it appears as if I can only actually use boolean operators (if in fact boolean operators are supported in this older version of Django) with strings or other template variables. Is it not possible to compare variables to integers or non-strings with Django templates? I'm sure there is an easy way to workaround this - built up the message string on the Python side rather than within the template - but this seems like such a simple operation you ought to be able to handle in a template. It sounds like I should be switching to a more advanced templating engine, but as I am new to Django (templates or any part of it), I'd just like some confirmation first.

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  • Dynamically created operators

    - by Gero
    I created a program using dev-cpp and wxwidgets which solves a puzzle. The user must fill the operations blocks and the results blocks, and the program will solve it. Im solving it using bruteforce, i generate all non repeated 9 length number combinations using a recursive algorithm. It does it pretty fast. Up to here all is great! But the problem is when my program operates depending the character on the blocks. Its extremely slow (it never gets the answer), because of the chars comparation against +, -, *, etc. Im doing a CASE. Is there some way or some programming language wich allows dinamic creation of operators? So i can define the operator ROW1COL2 to be a +, and the same way to all other operations. I leave a screenshot of the app, so its easier to understand how the puzzle works. http://www.imageshare.web.id/images/9gg5cev8vyokp8rhlot9.png PD: The algorithm works, i tryed it with a trivial puzzle, and solved it in a second.

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  • Merging k sorted linked lists - analysis

    - by Kotti
    Hi! I am thinking about different solutions for one problem. Assume we have K sorted linked lists and we are merging them into one. All these lists together have N elements. The well known solution is to use priority queue and pop / push first elements from every lists and I can understand why it takes O(N log K) time. But let's take a look at another approach. Suppose we have some MERGE_LISTS(LIST1, LIST2) procedure, that merges two sorted lists and it would take O(T1 + T2) time, where T1 and T2 stand for LIST1 and LIST2 sizes. What we do now generally means pairing these lists and merging them pair-by-pair (if the number is odd, last list, for example, could be ignored at first steps). This generally means we have to make the following "tree" of merge operations: N1, N2, N3... stand for LIST1, LIST2, LIST3 sizes O(N1 + N2) + O(N3 + N4) + O(N5 + N6) + ... O(N1 + N2 + N3 + N4) + O(N5 + N6 + N7 + N8) + ... O(N1 + N2 + N3 + N4 + .... + NK) It looks obvious that there will be log(K) of these rows, each of them implementing O(N) operations, so time for MERGE(LIST1, LIST2, ... , LISTK) operation would actually equal O(N log K). My friend told me (two days ago) it would take O(K N) time. So, the question is - did I f%ck up somewhere or is he actually wrong about this? And if I am right, why doesn't this 'divide&conquer' approach can't be used instead of priority queue approach?

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  • Random String Generator creates same string on multiple calls

    - by rockinthesixstring
    Hi there. I've build a random string generator but I'm having a problem whereby if I call the function multiple times say in a Page_Load method, the function returns the same string twice. here's the code ''' <summary>' ''' Generates a Random String' ''' </summary>' ''' <param name="n">number of characters the method should generate</param>' ''' <param name="UseSpecial">should the method include special characters? IE: # ,$, !, etc.</param>' ''' <param name="SpecialOnly">should the method include only the special characters and excludes alpha numeric</param>' ''' <returns>a random string n characters long</returns>' Public Function GenerateRandom(ByVal n As Integer, Optional ByVal UseSpecial As Boolean = True, Optional ByVal SpecialOnly As Boolean = False) As String Dim chars As String() ' a character array to use when generating a random string' Dim ichars As Integer = 74 'number of characters to use out of the chars string' Dim schars As Integer = 0 ' number of characters to skip out of the characters string' chars = { _ "A", "B", "C", "D", "E", "F", _ "G", "H", "I", "J", "K", "L", _ "M", "N", "O", "P", "Q", "R", _ "S", "T", "U", "V", "W", "X", _ "Y", "Z", "0", "1", "2", "3", _ "4", "5", "6", "7", "8", "9", _ "a", "b", "c", "d", "e", "f", _ "g", "h", "i", "j", "k", "l", _ "m", "n", "o", "p", "q", "r", _ "s", "t", "u", "v", "w", "x", _ "y", "z", "!", "@", "#", "$", _ "%", "^", "&", "*", "(", ")", _ "-", "+"} If Not UseSpecial Then ichars = 62 ' only use the alpha numeric characters out of "char"' If SpecialOnly Then schars = 62 : ichars = 74 ' skip the alpha numeric characters out of "char"' Dim rnd As New Random() Dim random As String = String.Empty Dim i As Integer = 0 While i < n random += chars(rnd.[Next](schars, ichars)) System.Math.Max(System.Threading.Interlocked.Increment(i), i - 1) End While rnd = Nothing Return random End Function but if I call something like this Dim str1 As String = GenerateRandom(5) Dim str2 As String = GenerateRandom(5) the response will be something like this g*3Jq g*3Jq and the second time I call it, it will be 3QM0$ 3QM0$ What am I missing? I'd like every random string to be generated as unique.

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  • Rails undefined method 'generated_methods' for nil:NilClass

    - by mike
    Okay so I was just starting this rails app and generated my first model ruby script/generate model Grid req:string class:string ctitle:string credits:float grade:string pass:boolean created my table rake db:migrate (in C:/Users/Michael/InstantRails/rails_apps/studentGrid) == CreateGrids: migrating ==================================================== -- create_table(:grids) - 0.0150s == CreateGrids: migrated (0.0150s) =========================================== and went to the console to add some data to my table Grid = Grid(id: integer, req: string, class: string, ctitle: string, credits: float, grade: string, pass: boolean, created_at: datetime, updated_at: datetime) Grid.create(:req="Math Elective", :class="Math 111", :ctitle="Calculus I", :credits=3.0) Pretty standard I thought, but then I get this error and I don't understand why NoMethodError: undefined method 'generated_methods' for nil:NilClass from C:/Users/Michael/InstantRails/ruby/lib/ruby/gems/1.8/gems/activesup port-2.3.5/lib/active_support/whiny_nil.rb:52:inmethod_missing' from C:/Users/Michael/InstantRails/ruby/lib/ruby/gems/1.8/gems/activerec ord-2.3.5/lib/active_record/attribute_methods.rb:352:in respond_to?' from C:/Users/Michael/InstantRails/ruby/lib/ruby/gems/1.8/gems/activerec ord-2.3.5/lib/active_record/base.rb:2746:inattributes=' from C:/Users/Michael/InstantRails/ruby/lib/ruby/gems/1.8/gems/activerec ord-2.3.5/lib/active_record/base.rb:2742:in each' from C:/Users/Michael/InstantRails/ruby/lib/ruby/gems/1.8/gems/activerec ord-2.3.5/lib/active_record/base.rb:2742:inattributes=' from C:/Users/Michael/InstantRails/ruby/lib/ruby/gems/1.8/gems/activerec ord-2.3.5/lib/active_record/base.rb:2438:in initialize' from C:/Users/Michael/InstantRails/ruby/lib/ruby/gems/1.8/gems/activerec ord-2.3.5/lib/active_record/base.rb:721:innew' from C:/Users/Michael/InstantRails/ruby/lib/ruby/gems/1.8/gems/activerec ord-2.3.5/lib/active_record/base.rb:721:in `create' from (irb):2 from :0

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  • Bind SQLiteDataReader to GridView in ASP.NET

    - by Charles Gargent
    Hi, this is all rather new to me, but I have searched for a good while and cant find any idea why I cant get this to work, dr looks like it is populated but I get this nullreferenceexeception when I try to bind to the gridview Thanks code SQLiteConnection cnn = new SQLiteConnection(@"Data Source=c:\log.db"); cnn.Open(); SQLiteCommand cmd = new SQLiteCommand(@"SELECT * FROM evtlog", cnn); SQLiteDataReader dr = cmd.ExecuteReader(); GridView1.DataSource = dr; GridView1.DataBind(); dr.Close(); cnn.Close(); Codebehind <asp:ContentPlaceHolder ID="MainContent" runat="server"> <asp:GridView ID="GridView1" runat="server"> </asp:GridView> </asp:ContentPlaceHolder> error Object reference not set to an instance of an object. at WPKG_Report.SiteMaster.Button1_Click(Object sender, EventArgs e) in C:\Projects\Report\Site.Master.cs:line 32 at System.Web.UI.WebControls.Button.OnClick(EventArgs e) at System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) at System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) at System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) at System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

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  • .net c# cannot find img resources when open with exe

    - by okuryazar
    Hello, My exe processes text documents and I want to be able to right click on documents, select open with and point to my exe file. I can double click on my exe and choose a file to process with OpenFileDialog and it works fine. However, when I do open with, I get FileNotFound error. Here is the error log: System.IO.FileNotFoundException: attention.jpg at System.Drawing.Image.FromFile(String filename, Boolean useEmbeddedColorManagement) at System.Drawing.Image.FromFile(String filename) at ImzaDogrulamaUygulamasi.frmCertificate.FillTreeView() in D:\VSS\SOURCE\VS2008\EGA\ImzaDogrulamaUygulamasi\ImzaDogrulamaUygulamasi\frmCertificate.cs:line 76 at ImzaDogrulamaUygulamasi.frmCertificate.Form2_Load(Object sender, EventArgs e) in D:\VSS\SOURCE\VS2008\EGA\ImzaDogrulamaUygulamasi\ImzaDogrulamaUygulamasi\frmCertificate.cs:line 244 at System.Windows.Forms.Form.OnLoad(EventArgs e) at System.Windows.Forms.Form.OnCreateControl() at System.Windows.Forms.Control.CreateControl(Boolean fIgnoreVisible) at System.Windows.Forms.Control.CreateControl() at System.Windows.Forms.Control.WmShowWindow(Message& m) at System.Windows.Forms.Control.WndProc(Message& m) at System.Windows.Forms.ScrollableControl.WndProc(Message& m) at System.Windows.Forms.ContainerControl.WndProc(Message& m) at System.Windows.Forms.Form.WmShowWindow(Message& m) at System.Windows.Forms.Form.WndProc(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m) and this is how I add my images in my code, all resources are in the same directory with the exe file: ImageList myImageList = new ImageList(); myImageList.Images.Add(Image.FromFile("attention.jpg")); myImageList.Images.Add(Image.FromFile("sandglass.jpg")); myImageList.Images.Add(Image.FromFile("11.JPG")); myImageList.Images.Add(Image.FromFile("checkGif.jpg")); treeView1.ImageList = myImageList; Any help is much appreciated. Thanks

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  • How does this code break the Law of Demeter?

    - by Dave Jarvis
    The following code breaks the Law of Demeter: public class Student extends Person { private Grades grades; public Student() { } /** Must never return null; throw an appropriately named exception, instead. */ private synchronized Grades getGrades() throws GradesException { if( this.grades == null ) { this.grades = createGrades(); } return this.grades; } /** Create a new instance of grades for this student. */ protected Grades createGrades() throws GradesException { // Reads the grades from the database, if needed. // return new Grades(); } /** Answers if this student was graded by a teacher with the given name. */ public boolean isTeacher( int year, String name ) throws GradesException, TeacherException { // The method only knows about Teacher instances. // return getTeacher( year ).nameEquals( name ); } private Grades getGradesForYear( int year ) throws GradesException { // The method only knows about Grades instances. // return getGrades().getForYear( year ); } private Teacher getTeacher( int year ) throws GradesException, TeacherException { // This method knows about Grades and Teacher instances. A mistake? // return getGradesForYear( year ).getTeacher(); } } public class Teacher extends Person { public Teacher() { } /** * This method will take into consideration first name, * last name, middle initial, case sensitivity, and * eventually it could answer true to wild cards and * regular expressions. */ public boolean nameEquals( String name ) { return getName().equalsIgnoreCase( name ); } /** Never returns null. */ private synchronized String getName() { if( this.name == null ) { this.name == ""; } return this.name; } } Questions How is the LoD broken? Where is the code breaking the LoD? How should the code be written to uphold the LoD?

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  • Flex - Increase timeout on a PHP service function call

    - by Travesty3
    I'm using Flash Builder 4 Beta 2. I have it connecting to a PHP service. The way I set this up was using the wizard, so I didn't actually write the code to connect to it. The service looks like this: package services.flash { import mx.rpc.AsyncToken; import com.adobe.fiber.core.model_internal; import mx.rpc.AbstractOperation; import valueObjects.CustomDatatype8; import valueObjects.NewUsageData; import mx.collections.ItemResponder; import mx.rpc.remoting.RemoteObject; import mx.rpc.remoting.Operation; import com.adobe.fiber.services.wrapper.RemoteObjectServiceWrapper; import com.adobe.fiber.valueobjects.AvailablePropertyIterator; import com.adobe.serializers.utility.TypeUtility; [ExcludeClass] internal class _Super_FLASH extends RemoteObjectServiceWrapper { // Constructor public function _Super_FLASH() { // initialize service control _serviceControl = new RemoteObject(); var operations:Object = new Object(); var operation:Operation; operation = new Operation(null, "sendCommand"); operation.resultType = Object; operations["sendCommand"] = operation; ... } } One of the functions that I'm calling fetches users from a MySQL database. There are about 30,000 users right now. The service seems to timeout when fetching more than around 22,000 rows, I get the "Channel Disconnected before an acknowledgement was received" error. If I call the PHP script from a browser, it fetches them all with no problems at all, however. I have tried increasing the timeout in the PHP script (which didn't work), but obviously this isn't the problem since the browser is able to pull them up with no problems. Is there a way to increase the timeout of the PHP service in Flash Builder? I'm a bit of a noob when it comes to Flash, so please be descriptive. Thanks in advance!

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