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• MySQL table organization and optimization (Rails)

  - by aguynamedloren

  I've been learning Ruby on Rails over the past few months with no prior programming experience. Lately, I've been thinking about database optimization and table organization. I know there are great books on the subject, but I typically learn by example / as I go. Here's a hypothetical situation: Let's say I am building a social network for a niche community with 250,000 members (users). The users have the ability to attend events. Let's say there are 50,000 past/present/future events. Much like Facebook events, a user can attend any number of events and an event can have any number of attendees. In the database, there would be a table for users and a table for events. Somehow I would have to create an association between the users and events. I could create an "events" column in the users table such that each user row would contain a hash of event IDs, or I could create an "attendees" column in the events table such that each event row would contain a hash of user IDs. Neither of these solutions seem ideal, however. On a users profile page, I want to display the list of events they are associated with, which would require scanning the 50,000 event rows for the user ID of said user if I include an "attendees" column in the events table. Likewise, on an event page, I want to display a list of attendees for the event, which would require scanning the 250,000 user rows for the event ID of said event if I include an "events" column in the users table. Option 3 would be to create a third table that contains the attendee information for each and every event - but I don't see how this would solve any problems. Are these non-issues? Rails makes accessing all of this information easy, but I guess I'm worried about scale. It is entirely possible that I am under-estimating the speed and processing power of modern databases / servers / etc. How long would it take to scan 250,000 user rows for specific event IDs - 10ms? 100ms? 1,000ms? I guess that's not that bad. Am I just over-thinking this?

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• CustomValidatation control that fire on multiple control events

  - by George

  I am trying to create a UserControl that is a composite control for entering Dates. It involves 2 drop down controls (one for month and one for day) and a text box for year. It also has a CustomValidation control that I would like the user of the UserControl to be able to set the ClientValidationFunction property and have it triggered whenever the value in any of the 3 date part controls changes. To hook up each of the 3 controls to the validation control, I use teh AJAX ValidatorHookupControlID method. If I hard code the following code directly in my aspx page that houses the usercontrol, my Client Validation Function is successfulluy called when any of the 3 date part control values are changed: <script type="text/javascript"> //<![CDATA[ debugger; alert('hooking up'); ValidatorHookupControlID("ctl00_phPageContent_dtmPassportExpirationDate_txtYear", document.all("ctl00_phPageContent_dtmPassportExpirationDate_CustomValidator1")); ValidatorHookupControlID("ctl00_phPageContent_dtmPassportExpirationDate_ddlDate", document.all("ctl00_phPageContent_dtmPassportExpirationDate_CustomValidator1")); ValidatorHookupControlID("ctl00_phPageContent_dtmPassportExpirationDate_ddlMonth", document.all("ctl00_phPageContent_dtmPassportExpirationDate_CustomValidator1")); //]]> However, I would like my usercontrol to emit this Javascript, so I added the following Code. Public Property ClientValidationFunction() As String Get Return CustomValidator1.ClientValidationFunction End Get Set(ByVal value As String) CustomValidator1.ClientValidationFunction = value End Set End Property Public Property EnableClientScript() As Boolean Get Return CustomValidator1.EnableClientScript End Get Set(ByVal value As Boolean) CustomValidator1.EnableClientScript = value End Set End Property Protected Sub Page_PreRender(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.PreRender If Me.ClientValidationFunction.Trim <> "" AndAlso Me.EnableClientScript Then RegisterValidationScript() End If End Sub Private Sub RegisterValidationScript() Dim Key As String = Me.ClientID & "_ClientValidate" If Not Page.ClientScript.IsClientScriptBlockRegistered(Key) Then Page.ClientScript.RegisterClientScriptBlock(GetType(String), Key, GetJavascript, True) End If End Sub Private Function GetJavascript() As String Dim Out As String = "" Const Quote As String = Chr(34) Out &= "debugger;" & vbCrLf Out &= "ValidatorHookupControlID(" & Quote & txtYear.ClientID & Quote & ", document.all(" & Quote & CustomValidator1.ClientID & Quote & "));" & vbCrLf Out &= "ValidatorHookupControlID(" & Quote & ddlDate.ClientID & Quote & ", document.all(" & Quote & CustomValidator1.ClientID & Quote & "));" & vbCrLf Out &= "ValidatorHookupControlID(" & Quote & ddlMonth.ClientID & Quote & ", document.all(" & Quote & CustomValidator1.ClientID & Quote & "));" & vbCrLf Return Out End Function Unfortunately, when the ValidatorHookupControlID method is called, the second parameter (the one that locates the validation control) always evaluates to null and the method fails. ValidatorHookupControlID("ctl00_phPageContent_DateSelector21_txtYear", document.all("ctl00_phPageContent_DateSelector21_CustomValidator1")); Can you tell me how to correct this error?

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• How does MySQL's ORDER BY RAND() work?

  - by Eugene

  Hi, I've been doing some research and testing on how to do fast random selection in MySQL. In the process I've faced some unexpected results and now I am not fully sure I know how ORDER BY RAND() really works. I always thought that when you do ORDER BY RAND() on the table, MySQL adds a new column to the table which is filled with random values, then it sorts data by that column and then e.g. you take the above value which got there randomly. I've done lots of googling and testing and finally found that the query Jay offers in his blog is indeed the fastest solution: SELECT * FROM Table T JOIN (SELECT CEIL(MAX(ID)*RAND()) AS ID FROM Table) AS x ON T.ID >= x.ID LIMIT 1; While common ORDER BY RAND() takes 30-40 seconds on my test table, his query does the work in 0.1 seconds. He explains how this functions in the blog so I'll just skip this and finally move to the odd thing. My table is a common table with a PRIMARY KEY id and other non-indexed stuff like username, age, etc. Here's the thing I am struggling to explain SELECT * FROM table ORDER BY RAND() LIMIT 1; /*30-40 seconds*/ SELECT id FROM table ORDER BY RAND() LIMIT 1; /*0.25 seconds*/ SELECT id, username FROM table ORDER BY RAND() LIMIT 1; /*90 seconds*/ I was sort of expecting to see approximately the same time for all three queries since I am always sorting on a single column. But for some reason this didn't happen. Please let me know if you any ideas about this. I have a project where I need to do fast ORDER BY RAND() and personally I would prefer to use SELECT id FROM table ORDER BY RAND() LIMIT 1; SELECT * FROM table WHERE id=ID_FROM_PREVIOUS_QUERY LIMIT 1; which, yes, is slower than Jay's method, however it is smaller and easier to understand. My queries are rather big ones with several JOINs and with WHERE clause and while Jay's method still works, the query grows really big and complex because I need to use all the JOINs and WHERE in the JOINed (called x in his query) sub request. Thanks for your time!

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• Purpose of Explicit Default Constructors

  - by Dennis Zickefoose

  I recently noticed a class in C++0x that calls for an explicit default constructor. However, I'm failing to come up with a scenario in which a default constructor can be called implicitly. It seems like a rather pointless specifier. I thought maybe it would disallow Class c; in favor of Class c = Class(); but that does not appear to be the case. Some relevant quotes from the C++0x FCD, since it is easier for me to navigate [similar text exists in C++03, if not in the same places] 12.3.1.3 [class.conv.ctor] A default constructor may be an explicit constructor; such a constructor will be used to perform default-initialization or value initialization (8.5). It goes on to provide an example of an explicit default constructor, but it simply mimics the example I provided above. 8.5.6 [decl.init] To default-initialize an object of type T means: — if T is a (possibly cv-qualified) class type (Clause 9), the default constructor for T is called (and the initialization is ill-formed if T has no accessible default constructor); 8.5.7 [decl.init] To value-initialize an object of type T means: — if T is a (possibly cv-qualified) class type (Clause 9) with a user-provided constructor (12.1), then the default constructor for T is called (and the initialization is ill-formed if T has no accessible default constructor); In both cases, the standard calls for the default constructor to be called. But that is what would happen if the default constructor were non-explicit. For completeness sake: 8.5.11 [decl.init] If no initializer is specified for an object, the object is default-initialized; From what I can tell, this just leaves conversion from no data. Which doesn't make sense. The best I can come up with would be the following: void function(Class c); int main() { function(); //implicitly convert from no parameter to a single parameter } But obviously that isn't the way C++ handles default arguments. What else is there that would make explicit Class(); behave differently from Class();? The specific example that generated this question was std::function [20.8.14.2 func.wrap.func]. It requires several converting constructors, none of which are marked explicit, but the default constructor is.

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• List of Django model instance foreign keys losing consistency during state changes.

  - by Joshua

  I have model, Match, with two foreign keys: class Match(model.Model): winner = models.ForeignKey(Player) loser = models.ForeignKey(Player) When I loop over Match I find that each model instance uses a unique object for the foreign key. This ends up biting me because it introduces inconsistency, here is an example: >>> def print_elo(match_list): ... for match in match_list: ... print match.winner.id, match.winner.elo ... print match.loser.id, match.loser.elo ... >>> print_elo(teacher_match_list) 4 1192.0000000000 2 1192.0000000000 5 1208.0000000000 2 1192.0000000000 5 1208.0000000000 4 1192.0000000000 >>> teacher_match_list[0].winner.elo = 3000 >>> print_elo(teacher_match_list) 4 3000 # Object 4 2 1192.0000000000 5 1208.0000000000 2 1192.0000000000 5 1208.0000000000 4 1192.0000000000 # Object 4 >>> I solved this problem like so: def unify_refrences(match_list): """Makes each unique refrence to a model instance non-unique. In cases where multiple model instances are being used django creates a new object for each model instance, even if it that means creating the same instance twice. If one of these objects has its state changed any other object refrencing the same model instance will not be updated. This method ensure that state changes are seen. It makes sure that variables which hold objects pointing to the same model all hold the same object. Visually this means that a list of [var1, var2] whose internals look like so: var1 --> object1 --> model1 var2 --> object2 --> model1 Will result in the internals being changed so that: var1 --> object1 --> model1 var2 ------^ """ match_dict = {} for match in match_list: try: match.winner = match_dict[match.winner.id] except KeyError: match_dict[match.winner.id] = match.winner try: match.loser = match_dict[match.loser.id] except KeyError: match_dict[match.loser.id] = match.loser My question: Is there a way to solve the problem more elegantly through the use of QuerySets without needing to call save at any point? If not, I'd like to make the solution more generic: how can you get a list of the foreign keys on a model instance or do you have a better generic solution to my problem? Please correct me if you think I don't understand why this is happening.

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• Fairness: Where can it be better handled?

  - by Srinivas Nayak

  Hi, I would like to share one of my practical experience with multiprogramming here. Yesterday I had written a multiprogram. Modifications to sharable resources were put under critical sections protected by P(mutex) and V(mutex) and those critical section code were put in a common library. The library will be used by concurrent applications (of my own). I had three applications that will use the common code from library and do their stuff independently. my library --------- work_on_shared_resource { P(mutex) get_shared_resource work_with_it V(mutex) } --------- my application ----------- application1 { *[ work_on_shared_resource do_something_else_non_ctitical ] } application2 { *[ work_on_shared_resource do_something_else_non_ctitical ] } application3 { *[ work_on_shared_resource ] } *[...] denote a loop. ------------ I had to run the applications on Linux OS. I had a thought in my mind, hanging over years, that, OS shall schedule all the processes running under him with all fairness. In other words, it will give all the processes, their pie of resource-usage equally well. When first two applications were put to work, they run perfectly well without deadlock. But when the third application started running, always the third one got the resources, but since it is not doing anything in its non-critical region, it gets the shared resource more often when other tasks are doing something else. So the other two applications were found almost totally halted. When the third application got terminated forcefully, the previous two applications resumed their work as before. I think, this is a case of starvation, first two applications had to starve. Now how can we ensure fairness? Now I started believing that OS scheduler is innocent and blind. It depends upon who won the race; he got the largest pie of CPU and resource. Shall we attempt to ensure fairness of resource users in the critical-section code in library? Or shall we leave it up to the applications to ensure fairness by being liberal, not greedy? To my knowledge, adding code to ensure fairness to the common library shall be an overwhelming task. On the other hand, believing on the applications will also never ensure 100% fairness. The application which does a very little task after working with shared resources shall win the race where as the application which does heavy processing after their work with shared resources shall always starve. What is the best practice in this case? Where we ensure fairness and how? Sincerely, Srinivas Nayak

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• Android: dynamically setting links to text in strings.xml

  - by Martyn

  I'm trying to make an app with localisation built in, but I want a way that I can create a web link within the text, the URL being defined elsewhere (for ease of maintenance). So, I have my links in res/values/strings.xml: <?xml version="1.0" encoding="utf-8"?> <resources> ... <string name="link1">http://some.link.com</string> <string name="link2">http://some.link2.com</string> </resources> and my localised text in res/values-en-rGB/strings.xml <?xml version="1.0" encoding="utf-8"?> <resources> ... <string name="sampleText">Sample text\nMore text and link1\nMore text and link2.</string> </resources> I've not tested this bit, but from the localization section of developer.android.com it says that this approach to reducing content duplication should work, although I'm not sure what folder I should put Italian, for example. Would it be in 'res/values-it-rIT/strings.xml'? Lets assume that I have various other languages too. I'm looking for a way of taking the base localised 'sampleText' and inserting my html links in, and getting them to work when clicked on. I've tried two approaches so far: 1, Putting some formatting in the 'sampleText' (%s): <string name="sampleText">Sample text\nMore text and <a href="%s">link1</a>\nMore text and <a href="%s">link2</a>.</string> and then processing the text like this: TextView tv = (TextView) findViewById(R.id.textHolder); tv.setText(getResources().getString(R.string.sampleText, getResources().getString(R.string.link1), getResources().getString(R.string.link2))); But this didn't work when I click on the link, even though the link text is being put in to the correct places. 2, I tried to use Linkify but the regular expression route may be difficult as I'm looking at supporting non-Latin based languages. I tried to put a custom xml tag around the link text and then do something like this: Pattern wordMatcher = Pattern.compile("<span1>.*</span1>"); String viewURL = "content://" + getResources().getString(R.string.someLink); Linkify.addLinks(tv, wordMatcher , viewURL ); But this didn't work either. So, I'd like to know if there's a way of dynamically adding multiple URLs to different sections of the same text which will link to web content? Thank you, Martyn

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• Are free operator->* overloads evil?

  - by Potatoswatter

  I was perusing section 13.5 after refuting the notion that built-in operators do not participate in overload resolution, and noticed that there is no section on operator->*. It is just a generic binary operator. Its brethren, operator->, operator*, and operator[], are all required to be non-static member functions. This precludes definition of a free function overload to an operator commonly used to obtain a reference from an object. But the uncommon operator->* is left out. In particular, operator[] has many similarities. It is binary (they missed a golden opportunity to make it n-ary), and it accepts some kind of container on the left and some kind of locator on the right. Its special-rules section, 13.5.5, doesn't seem to have any actual effect except to outlaw free functions. (And that restriction even precludes support for commutativity!) So, for example, this is perfectly legal (in C++0x, remove obvious stuff to translate to C++03): #include <utility> #include <iostream> #include <type_traits> using namespace std; template< class F, class S > typename common_type< F,S >::type operator->*( pair<F,S> const &l, bool r ) { return r? l.second : l.first; } template< class T > T & operator->*( pair<T,T> &l, bool r ) { return r? l.second : l.first; } template< class T > T & operator->*( bool l, pair<T,T> &r ) { return l? r.second : r.first; } int main() { auto x = make_pair( 1, 2.3 ); cerr << x->*false << " " << x->*4 << endl; auto y = make_pair( 5, 6 ); y->*(0) = 7; y->*0->*y = 8; // evaluates to 7->*y = y.second cerr << y.first << " " << y.second << endl; } I can certainly imagine myself giving into temp[la]tation. For example, scaled indexes for vector: v->*matrix_width[2][5] = x; Did the standards committee forget to prevent this, was it considered too ugly to bother, or are there real-world use cases?

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• What is the best way to archive data in a relational database?

  - by GenericTypeTea

  I have a bit of an issue with a particular aspect of a program I'm working on. I need the ability to archive (fix) a table so that a change anywhere in the system will not affect the results it returns. This is the basic structure of what I need to fix: Recipe --> Recipe (as sub recipe) Recipe --> Ingredients So, if I fix a Recipe, I need to ensure all the sub recipes (including all the sub recipes sub recipes and so forth) are fixed and all its ingredients are fixed. The problem is that the sub recipe and ingredients still need to be modifiable as they are used by other recipes that are not fixed. I came up with a solution whereby I serialize (with protobuf-net) a master object that deals with the recipe and all the sub recipes and ingredients and save the archive data to a table like follows: Archive{ ReferenceId, (i.e. RecipeId) ReferenceTypeId, (i.e. Recipe) ArchiveData varbinary(max) } Now, this works great and is almost perfect... however I totally forgot (I'd love to blame the agile development mentally, however this was just short sighted) that this information needs to be reported on. As far as I'm aware I can't think how I could inflate the serialized data back into my Recipe Object and use it in a Report. I'm using the standard SQL 2005 report services at the moment. Alternatively, I guess I could do the following: Duplicate every table and tag the word "Archive" on the end of the table name. This would then give me an area of specific archive data... but ignoring my simplified example, there'd actually be about 15 tables duplicated. Add a nullable, non-foreign key property called "CopiedFromId" to every table that contains fixed data and duplicate every record that the recipe (and all it's sub recipes and all their sub recipes) touches. Create some sort of denormalised structure that could be restored from at a later date to the original, unfixed recipe. Although I think this would be like option 1 and involve a lot of extra tables. Anyway, I'm at a total loss and do not like any of the ideas particularly. Can anyone please advise the best course of action? EDIT: Or 4) Create tables specific to what the report requires and populate them with the data when the user clicks the report button? This would cause about 4 extra tables for the report in question.

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• A RenderTargetView cannot be created from a NULL Resource

  - by numerical25

  I am trying to create my render target view but I get this error from direct X A RenderTargetView cannot be created from a NULL Resource To my knowledge it seems that I must fill the rendertarget pointer with data before passing it. But I am having trouble figure out how. Below is my declaration and implementation declaration #pragma once #include "stdafx.h" #include "resource.h" #include "d3d10.h" #include "d3dx10.h" #include "dinput.h" #define MAX_LOADSTRING 100 class RenderEngine { protected: RECT m_screenRect; //direct3d Members ID3D10Device *m_pDevice; // The IDirect3DDevice10 // interface ID3D10Texture2D *m_pBackBuffer; // Pointer to the back buffer ID3D10RenderTargetView *m_pRenderTargetView; // Pointer to render target view IDXGISwapChain *m_pSwapChain; // Pointer to the swap chain RECT m_rcScreenRect; // The dimensions of the screen ID3DX10Font *m_pFont; // The font used for rendering text // Sprites used to hold font characters ID3DX10Sprite *m_pFontSprite; ATOM RegisterEngineClass(); void Present(); public: static HINSTANCE m_hInst; HWND m_hWnd; int m_nCmdShow; TCHAR m_szTitle[MAX_LOADSTRING]; // The title bar text TCHAR m_szWindowClass[MAX_LOADSTRING]; // the main window class name void DrawTextString(int x, int y, D3DXCOLOR color, const TCHAR *strOutput); //static functions static LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam); static INT_PTR CALLBACK About(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam); bool InitWindow(); bool InitDirectX(); bool InitInstance(); int Run(); RenderEngine() { m_screenRect.right = 800; m_screenRect.bottom = 600; } }; my implementation bool RenderEngine::InitDirectX() { //potential error. You did not set to zero memory and you did not set the scaling property DXGI_MODE_DESC bd; bd.Width = m_screenRect.right; bd.Height = m_screenRect.bottom; bd.Format = DXGI_FORMAT_R8G8B8A8_UNORM; bd.RefreshRate.Numerator = 60; bd.RefreshRate.Denominator = 1; DXGI_SAMPLE_DESC sd; sd.Count = 1; sd.Quality = 0; DXGI_SWAP_CHAIN_DESC swapDesc; ZeroMemory(&swapDesc, sizeof(swapDesc)); swapDesc.BufferDesc = bd; swapDesc.SampleDesc = sd; swapDesc.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT; swapDesc.OutputWindow = m_hWnd; swapDesc.BufferCount = 1; swapDesc.SwapEffect = DXGI_SWAP_EFFECT_DISCARD, swapDesc.Windowed = true; swapDesc.Flags = 0; HRESULT hr; hr = D3D10CreateDeviceAndSwapChain(NULL, D3D10_DRIVER_TYPE_HARDWARE, NULL, D3D10_CREATE_DEVICE_DEBUG, D3D10_SDK_VERSION , &swapDesc, &m_pSwapChain, &m_pDevice); if(FAILED(hr)) return false; // Create a render target view hr = m_pDevice->CreateRenderTargetView( m_pBackBuffer, NULL, &m_pRenderTargetView); // FAILS RIGHT HERE // if(FAILED(hr)) return false; return true; }

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• MovieClip, counter almost working AS3

  - by VideoDnd

  How do I get my counter to work? This was over my director's head. Please include explanation, and feel free to comment. CONFUSION: I'm confused about the MovieClip container in as3. public class NumbersView extends MovieClip, so that seems to be a container. That may not be the problem, but that's where I got lost. CODE http://videodnd.weebly.com/ The working version of this code is fantastic. My code bellow is an attempt at revising it. The source has been adapted from various smart people. It's a work in progress LIBRARY OBJECT 'vertical number column' Name: mc-NumberImage Class: NumberImage OUTPUT ERRORS 'When I uncomment the code" 1023: Incompatible override. NumbersView... 1021: Duplicate function definition. NumbersView... //NUMBER DOCUMENT CLASS //IMPORT import flash.display.Sprite; import flash.events.Event; import flash.utils.Timer; import flash.events.TimerEvent; import flash.display.DisplayObject; import flash.display.MovieClip; import flash.utils.Dictionary; import caurina.transitions.Tweener; //COUNTER var timer:Timer = new Timer(1000); var count:int = 0; var fcount:int = 0; timer.addEventListener(TimerEvent.TIMER, incrementCounter); timer.start(); function incrementCounter(event:TimerEvent) { count++; fcount=int(count*count/1000); } function formatCount(i:int):String { var fraction:int = i % 100; var whole:int = i / 100; return ("000000000" + i).substr(-9, 9); } //------------------------------------------------------------------------ //PROBLEM AREA function enterFrameHandler(e:Event):void { // numbers.setTime(formatCount(fcount)); } var _listItems:Array = new Array(); var previousNums:Array; const numHeight:int = 120; var NumbersView:Sprite = new Sprite(); //var numbers:NumbersView = new NumbersView; //NUMBERSVIEW // function NumbersView($n:int):void { _listItems = new Array(); previousNums = new Array(); var item:NumberImage; var offset:int = _listItems.length; for (var i:Number = 0; i < 9; i++) { item = new NumberImage(); // }//<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<< //------------------------------------------------------------------------ //PUSH ARRAY addChild(item); item.x = i * item.width; _listItems.push(item); } //TWEENER 'Y SCROLLING' function setTime($number:String):void { var nums:Array = $number.split(""); for (var i:Number = 0; i < nums.length; i++) { if (nums[i] == previousNums[i]) continue; Tweener.removeTweens(_listItems[i]); var newY:int = int(nums[i]) * -numHeight; if (_listItems[i].y < 0) _listItems[i].y = numHeight; Tweener.addTween(_listItems[i], { y:newY, time:3 } ); } previousNums = nums; } D E S C R I P T I O N COUNTER: formatCount needs to get passed to Tweener STAGE: for loop, sets up children to be added to the stage NumbersView becomes item, item array adds children to stage TWEENER: advances the vertical number column every time the count fires adds and removes WHY - Learning - Benifit in simplifying the classes and putting it in one FLA

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• Annoying Captcha >> How to programm a form that can SMELL difference between human and robot?

  - by Sam

  Hi folks. On the comment of my old form needing a CAPTHA, I felt I share my problem, perhaps you recognize it and find its time we had better solutions: FACTUAL PROBLEM I know most of my clients (typical age= 40~60) hate CAPTCHA things. Now, I myself always feel like a robot, when I have to sueeze my eyes and fill in the strange letters from the Capcha... Sometimes I fail! Go back etc. Turnoff. I mean comon its 2011, shouldnt the forms have better A.I. by now? MY NEW IDEA (please dont laugh) Ive thought about it and this is my idea's to tell difference between human and robot: My idea is to give credibility points. 100 points = human 0% = robot. require real human mouse movements require mousemovements that dont follow any mathematical pattern require non-instantaneous reading delays, between load and first input in form when typing in form, delays are measured between letters and words approve as human when typical human behaviour measured (deleting, rephrasing etc) dont allow instant pasting or all fields give points for real keyboard pressures retract points for credibility when hyperlinks in form Test wether fake email field (invisible by human) is populated (suggested by Tomalak) when more than 75% human cretibility, allow to be sent without captcha when less than 25% human crecibility, force captcha puzzle to be sure Could we write a A.I. PHP that replaces the human-annoying capthas, meanwhile stopping most spamservers filing in the data? Not only for the fun of it, but also actually to provide a 99% better alternative than CAPTHCA's. Imagine the userfriendlyness of your forms! Your site distinguishing itself from others, showing your audience your sites KNOWS the difference between a robot and a human. Imagine the advangage. I am trying to capture the essense of that distinguishing edge. PROGRAMMING QUESTION: 1) Are such things possible to programm? 2) If so how would you start such programm? 3) Are there already very good working solutions available elsewhere? 4) If it isn't so hard, your are welcome to share your answer/solutions below. 5) upon completion of hints and new ideas, could this page be the start of a new AI captcha, OR should I forget about it and just go with the flow, forget about the whole AI dream, and use captcha like everyone else.

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• XmlDataProvider and XPath bindings don't allow default namespace of XML data?

  - by Andy Dent

  I am struggling to work out how to use default namespaces with XmlDataProvider and XPath bindings. There's an ugly answer using local-name <Binding XPath="*[local-name()='Name']" /> but that is not acceptable to the client who wants this XAML to be highly maintainable. The fallback is to force them to use non-default namespaces in the report XML but that is an undesirable solution. The XML report file looks like the following. It will only work if I remove xmlns="http://www.acme.com/xml/schemas/report so there is no default namespace. <?xml version="1.0" encoding="utf-8"?> <?xml-stylesheet type='text/xsl' href='PreviewReportImages.xsl'?> <Report xsl:schemaLocation="http://www.acme.com/xml/schemas/report BlahReport.xsd" xmlns:xsl="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.acme.com/xml/schemas/report"> <Service>Muncher</Service> <Analysis> <Date>27 Apr 2010</Date> <Time>0:09</Time> <Authoriser>Service Centre Manager</Authoriser> Which I am presenting in a window with XAML: <Window x:Class="AcmeTest.ReportPreview" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="ReportPreview" Height="300" Width="300" > <Window.Resources> <XmlDataProvider x:Key="Data"/> </Window.Resources> <StackPanel Orientation="Vertical" DataContext="{Binding Source={StaticResource Data}, XPath=Report}"> <TextBlock Text="{Binding XPath=Service}"/> </StackPanel> </Window> with code-behind used to load an XmlDocument into the XmlDataProvider (seems the only way to have loading from a file or object varying at runtime). public partial class ReportPreview : Window { private void InitXmlProvider(XmlDocument doc) { XmlDataProvider xd = (XmlDataProvider)Resources["Data"]; xd.Document = doc; } public ReportPreview(XmlDocument doc) { InitializeComponent(); InitXmlProvider(doc); } public ReportPreview(String reportPath) { InitializeComponent(); var doc = new XmlDocument(); doc.Load(reportPath); InitXmlProvider(doc); } }

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• Is it too early to start designing for Task Parallel Library?

  - by Joe Erickson

  I have been following the development of the .NET Task Parallel Library (TPL) with great interest since Microsoft first announced it. There is no doubt in my mind that we will eventually take advantage of TPL. What I am questioning is whether it makes sense to start taking advantage of TPL when Visual Studio 2010 and .NET 4.0 are released, or whether it makes sense to wait a while longer. Why Start Now? The .NET 4.0 Task Parallel Library appears to be well designed and some relatively simple tests demonstrate that it works well on today's multi-core CPUs. I have been very interested in the potential advantages of using multiple lightweight threads to speed up our software since buying my first quad processor Dell Poweredge 6400 about seven years ago. Experiments at that time indicated that it was not worth the effort, which I attributed largely to the overhead of moving data between each CPU's cache (there was no shared cache back then) and RAM. Competitive advantage - some of our customers can never get enough performance and there is no doubt that we can build a faster product using TPL today. It sounds fun. Yes, I realize that some developers would rather poke themselves in the eye with a sharp stick, but we really enjoy maximizing performance. Why Wait? Are today's Intel Nehalem CPUs representative of where we are going as multi-core support matures? You can purchase a Nehalem CPU with 4 cores which share a single level 3 cache today, and most likely a 6 core CPU sharing a single level 3 cache by the time Visual Studio 2010 / .NET 4.0 are released. Obviously, the number of cores will go up over time, but what about the architecture? As the number of cores goes up, will they still share a cache? One issue with Nehalem is the fact that, even though there is a very fast interconnect between the cores, they have non-uniform memory access (NUMA) which can lead to lower performance and less predictable results. Will future multi-core architectures be able to do away with NUMA? Similarly, will the .NET Task Parallel Library change as it matures, requiring modifications to code to fully take advantage of it? Limitations Our core engine is 100% C# and has to run without full trust, so we are limited to using .NET APIs.

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• Round-twice error in .NET's Double.ToString method

  - by Jeppe Stig Nielsen

  Mathematically, consider for this question the rational number 8725724278030350 / 2**48 where ** in the denominator denotes exponentiation, i.e. the denominator is 2 to the 48th power. (The fraction is not in lowest terms, reducible by 2.) This number is exactly representable as a System.Double. Its decimal expansion is 31.0000000000000'49'73799150320701301097869873046875 (exact) where the apostrophes do not represent missing digits but merely mark the boudaries where rounding to 15 resp. 17 digits is to be performed. Note the following: If this number is rounded to 15 digits, the result will be 31 (followed by thirteen 0s) because the next digits (49...) begin with a 4 (meaning round down). But if the number is first rounded to 17 digits and then rounded to 15 digits, the result could be 31.0000000000001. This is because the first rounding rounds up by increasing the 49... digits to 50 (terminates) (next digits were 73...), and the second rounding might then round up again (when the midpoint-rounding rule says "round away from zero"). (There are many more numbers with the above characteristics, of course.) Now, it turns out that .NET's standard string representation of this number is "31.0000000000001". The question: Isn't this a bug? By standard string representation we mean the String produced by the parameterles Double.ToString() instance method which is of course identical to what is produced by ToString("G"). An interesting thing to note is that if you cast the above number to System.Decimal then you get a decimal that is 31 exactly! See this Stack Overflow question for a discussion of the surprising fact that casting a Double to Decimal involves first rounding to 15 digits. This means that casting to Decimal makes a correct round to 15 digits, whereas calling ToSting() makes an incorrect one. To sum up, we have a floating-point number that, when output to the user, is 31.0000000000001, but when converted to Decimal (where 29 digits are available), becomes 31 exactly. This is unfortunate. Here's some C# code for you to verify the problem: static void Main() { const double evil = 31.0000000000000497; string exactString = DoubleConverter.ToExactString(evil); // Jon Skeet, http://csharpindepth.com/Articles/General/FloatingPoint.aspx Console.WriteLine("Exact value (Jon Skeet): {0}", exactString); // writes 31.00000000000004973799150320701301097869873046875 Console.WriteLine("General format (G): {0}", evil); // writes 31.0000000000001 Console.WriteLine("Round-trip format (R): {0:R}", evil); // writes 31.00000000000005 Console.WriteLine(); Console.WriteLine("Binary repr.: {0}", String.Join(", ", BitConverter.GetBytes(evil).Select(b => "0x" + b.ToString("X2")))); Console.WriteLine(); decimal converted = (decimal)evil; Console.WriteLine("Decimal version: {0}", converted); // writes 31 decimal preciseDecimal = decimal.Parse(exactString, CultureInfo.InvariantCulture); Console.WriteLine("Better decimal: {0}", preciseDecimal); // writes 31.000000000000049737991503207 } The above code uses Skeet's ToExactString method. If you don't want to use his stuff (can be found through the URL), just delete the code lines above dependent on exactString. You can still see how the Double in question (evil) is rounded and cast.

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• Odd performance with C# Asynchronous server socket

  - by The.Anti.9

  I'm working on a web server in C# and I have it running on Asynchronous socket calls. The weird thing is that for some reason, when you start loading pages, the 3rd request is where the browser won't connect. It just keeps saying "Connecting..." and doesn't ever stop. If I hit stop. and then refresh, it will load again, but if I try another time after that it does the thing where it doesn't load again. And it continues in that cycle. I'm not really sure what is making it do that. The code is kind of hacked together from a couple of examples and some old code I had. Any miscellaneous tips would be helpful as well. Heres my little Listener class that handles everything (pastied here. thought it might be easier to read this way) using System; using System.Collections.Generic; using System.Net; using System.Net.Sockets; using System.Text; using System.Threading; namespace irek.Server { public class Listener { private int port; private Socket server; private Byte[] data = new Byte[2048]; static ManualResetEvent allDone = new ManualResetEvent(false); public Listener(int _port) { port = _port; } public void Run() { server = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp); IPEndPoint iep = new IPEndPoint(IPAddress.Any, port); server.Bind(iep); Console.WriteLine("Server Initialized."); server.Listen(5); Console.WriteLine("Listening..."); while (true) { allDone.Reset(); server.BeginAccept(new AsyncCallback(AcceptCon), server); allDone.WaitOne(); } } private void AcceptCon(IAsyncResult iar) { allDone.Set(); Socket s = (Socket)iar.AsyncState; Socket s2 = s.EndAccept(iar); SocketStateObject state = new SocketStateObject(); state.workSocket = s2; s2.BeginReceive(state.buffer, 0, SocketStateObject.BUFFER_SIZE, 0, new AsyncCallback(Read), state); } private void Read(IAsyncResult iar) { try { SocketStateObject state = (SocketStateObject)iar.AsyncState; Socket s = state.workSocket; int read = s.EndReceive(iar); if (read > 0) { state.sb.Append(Encoding.ASCII.GetString(state.buffer, 0, read)); if (s.Available > 0) { s.BeginReceive(state.buffer, 0, SocketStateObject.BUFFER_SIZE, 0, new AsyncCallback(Read), state); return; } } if (state.sb.Length > 1) { string requestString = state.sb.ToString(); // HANDLE REQUEST HERE // Temporary response string resp = "<h1>It Works!</h1>"; string head = "HTTP/1.1 200 OK\r\nContent-Type: text/html;\r\nServer: irek\r\nContent-Length:"+resp.Length+"\r\n\r\n"; byte[] answer = Encoding.ASCII.GetBytes(head+resp); // end temp. state.workSocket.BeginSend(answer, 0, answer.Length, SocketFlags.None, new AsyncCallback(Send), state.workSocket); } } catch (Exception) { return; } } private void Send(IAsyncResult iar) { try { SocketStateObject state = (SocketStateObject)iar.AsyncState; int sent = state.workSocket.EndSend(iar); state.workSocket.Shutdown(SocketShutdown.Both); state.workSocket.Close(); } catch (Exception) { } return; } } } And my SocketStateObject: public class SocketStateObject { public Socket workSocket = null; public const int BUFFER_SIZE = 1024; public byte[] buffer = new byte[BUFFER_SIZE]; public StringBuilder sb = new StringBuilder(); }

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• GCC: Simple inheritance test fails

  - by knight666

  I'm building an open source 2D game engine called YoghurtGum. Right now I'm working on the Android port, using the NDK provided by Google. I was going mad because of the errors I was getting in my application, so I made a simple test program: class Base { public: Base() { } virtual ~Base() { } }; // class Base class Vehicle : virtual public Base { public: Vehicle() : Base() { } ~Vehicle() { } }; // class Vehicle class Car : public Vehicle { public: Car() : Base(), Vehicle() { } ~Car() { } }; // class Car int main(int a_Data, char** argv) { Car* stupid = new Car(); return 0; } Seems easy enough, right? Here's how I compile it, which is the same way I compile the rest of my code: /home/oem/android-ndk-r3/build/prebuilt/linux-x86/arm-eabi-4.4.0/bin/arm-eabi-g++ -g -std=c99 -Wall -Werror -O2 -w -shared -fshort-enums -I ../../YoghurtGum/src/GLES -I ../../YoghurtGum/src -I /home/oem/android-ndk-r3/build/platforms/android-5/arch-arm/usr/include -c src/Inheritance.cpp -o intermediate/Inheritance.o (Line breaks are added for clarity). This compiles fine. But then we get to the linker: /home/oem/android-ndk-r3/build/prebuilt/linux-x86/arm-eabi-4.4.0/bin/arm-eabi-gcc -lstdc++ -Wl, --entry=main, -rpath-link=/system/lib, -rpath-link=/home/oem/android-ndk-r3/build/platforms/android-5/arch-arm/usr/lib, -dynamic-linker=/system/bin/linker, -L/home/oem/android-ndk-r3/build/prebuilt/linux-x86/arm-eabi-4.4.0/lib/gcc/arm-eabi/4.4.0, -L/home/oem/android-ndk-r3/build/platforms/android-5/arch-arm/usr/lib, -rpath=../../YoghurtGum/lib/GLES -nostdlib -lm -lc -lGLESv1_CM -z /home/oem/android-ndk-r3/build/platforms/android-5/arch-arm/usr/lib/crtbegin_dynamic.o /home/oem/android-ndk-r3/build/platforms/android-5/arch-arm/usr/lib/crtend_android.o intermediate/Inheritance.o ../../YoghurtGum/bin/YoghurtGum.a -o bin/Galaxians.android As you can probably tell, there's a lot of cruft in there that isn't really needed. That's because it doesn't work. It fails with the following errors: intermediate/Inheritance.o:(.rodata._ZTI3Car[typeinfo for Car]+0x0): undefined reference to `vtable for __cxxabiv1::__si_class_type_info' intermediate/Inheritance.o:(.rodata._ZTI7Vehicle[typeinfo for Vehicle]+0x0): undefined reference to `vtable for __cxxabiv1::__vmi_class_type_info' intermediate/Inheritance.o:(.rodata._ZTI4Base[typeinfo for Base]+0x0): undefined reference to `vtable for __cxxabiv1::__class_type_info' collect2: ld returned 1 exit status make: *** [bin/Galaxians.android] Fout 1 These are the same errors I get from my actual application. If someone could explain to me where I went wrong in my test or what option or I forgot in my linker, I would be very, extremely grateful. Thanks in advance. UPDATE: When I make my destructors non-inlined, I get new and more exciting link errors: intermediate/Inheritance.o:(.rodata+0x78): undefined reference to `vtable for __cxxabiv1::__si_class_type_info' intermediate/Inheritance.o:(.rodata+0x90): undefined reference to `vtable for __cxxabiv1::__vmi_class_type_info' intermediate/Inheritance.o:(.rodata+0xb0): undefined reference to `vtable for __cxxabiv1::__class_type_info' collect2: ld returned 1 exit status make: *** [bin/Galaxians.android] Fout 1

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• Avoiding circular project/assembly references in Visual Studio with statically typed dependency conf

  - by svnpttrssn

  First, I want to say that I am not interested in debating about any non-helpful "answers" to my question, with suggestions to putting everything in one assembly, i.e. there is no need for anyone to provide webpages such as the page titled with "Separate Assemblies != Loose Coupling". Now, my question is if it somehow (maybe with some Visual Studio configuration to allow for circular project dependencies?) is possible to use one project/assembly (I am here calling it the "ServiceLocator" assembly) for retrieving concrete implementation classes, (e.g. with StructureMap) which can be referred to from other projects, while it of course is also necessary for the the ServiceLocator itself to refer to other projects with the interfaces and the implementations ? Visual Studio project example, illustrating the kind of dependency structure I am talking about: http://img10.imageshack.us/img10/8838/testingdependencyinject.png Please note in the above picture, the problem is how to let the classes in "ApplicationLayerServiceImplementations" retrieve and instantiate classes that implement the interfaces in "DomainLayerServiceInterfaces". The goal is here to not refer directly to the classes in "DomainLayerServiceImplementations", but rather to try using the project "ServiceLocator" to retrieve such classes, but then the circular dependency problem occurrs... For example, a "UserInterfaceLayer" project/assembly might contain this kind of code: ContainerBootstrapper.BootstrapStructureMap(); // located in "ServiceLocator" project/assembly MyDomainLayerInterface myDomainLayerInterface = ObjectFactory.GetInstance<MyDomainLayerInterface>(); // refering to project/assembly "DomainLayerServiceInterfaces" myDomainLayerInterface.MyDomainLayerMethod(); MyApplicationLayerInterface myApplicationLayerInterface = ObjectFactory.GetInstance<MyApplicationLayerInterface>(); // refering to project/assembly "ApplicationLayerServiceInterfaces" myApplicationLayerInterface.MyApplicationLayerMethod(); The above code do not refer to the implementation projects/assemblies ApplicationLayerServiceImplementations and DomainLayerServiceImplementations, which contain this kind of code: public class MyApplicationLayerImplementation : MyApplicationLayerInterface and public class MyDomainLayerImplementation : MyDomainLayerInterface The "ServiceLocator" project/assembly might contain this code: using ApplicationLayerServiceImplementations; using ApplicationLayerServiceInterfaces; using DomainLayerServiceImplementations; using DomainLayerServiceInterfaces; using StructureMap; namespace ServiceLocator { public static class ContainerBootstrapper { public static void BootstrapStructureMap() { ObjectFactory.Initialize(x => { // The two interfaces and the two implementations below are located in four different Visual Studio projects x.ForRequestedType<MyDomainLayerInterface>().TheDefaultIsConcreteType<MyDomainLayerImplementation>(); x.ForRequestedType<MyApplicationLayerInterface>().TheDefaultIsConcreteType<MyApplicationLayerImplementation>(); }); } } } So far, no problem, but the problem occurs when I want to let the class "MyApplicationLayerImplementation" in the project/assembly "ApplicationLayerServiceImplementations" use the "ServiceLocator" project/assembly for retrieving an implementation of "MyDomainLayerInterface". When I try to do that, i.e. add a reference from "MyApplicationLayerImplementation" to "ServiceLocator", then Visual Studio complains about circular dependencies between projects. Is there any nice solution to this problem, which does not imply using refactoring-unfriendly string based xml-configuration which breaks whenever an interface or class or its namespace is renamed ? / Sven

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• [NSIS] Custom radio-buttom INI page via Eclipse

  - by Omegazero

  I'm using Eclipse's create InstallOptions menu to create a custom INI page with radio-buttons for repackaging the Blackberry Desktop installer. There are 2 sections for each type: "Internet" and "Enterprise". I need a user to select 1 of the 2 options and depending on their selection, the page will carry over the selection chosen in the custom page, jump to the INSTFILES page, and continue onto the end. I couldn't find any concrete documentation on getting INI pages to load in the script (I'm probably searching incorrectly), and then pass data from one page to the next (according to fields I guess?) Any help is appreciated. Even if it's to tell me I'm blind and can't read a doc (though a link would help :) ) Here's the INI code: ; Auto-generated by EclipseNSIS InstallOptions Script Wizard ; Jul 29, 2009 5:42:56 PM [Settings] NumFields=7 Title=RIM BlackBerry Desktop 5.0 installation CancelEnabled=1 [Field 1] Type=RadioButton Left=15 Top=28 Right=100 Bottom=38 Text=Internet State= Flags=NOTIFY [Field 4] Type=RadioButton Left=15 Top=95 Right=100 Bottom=105 Text=Enterprise Flags=NOTIFY [Field 2] Type=GroupBox Left=0 Top=10 Right=300 Bottom=75 Text= [Field 5] Type=Label Left=30 Top=42 Right=235 Bottom=52 Text=For users who are NOT on the Enterprise (Exchange) server [Field 6] Type=Label Left=30 Top=111 Right=235 Bottom=121 Text=Choose this only if you are on the Exchange server [Field 3] Type=GroupBox Left=0 Top=75 Right=300 Bottom=140 [Field 7] Type=Label Left=0 Top=0 Right=130 Bottom=10 Text=Please choose your installation method ...And here's the NSI code: Auto-generated by EclipseNSIS Script Wizard Jul 29, 2009 5:42:16 PM Name "BlackBerry Desktop" RequestExecutionLevel admin General Symbol Definitions !define VERSION 5.0.0.11 !define COMPANY RIM !define URL http://www.blackberry.com MUI Symbol Definitions !define MUI_ICON BBD.ico !define MUI_LICENSEPAGE_RADIOBUTTONS Included files !include Sections.nsh !include MUI2.nsh Reserved Files ReserveFile "${NSISDIR}\Plugins\AdvSplash.dll" Installer pages !insertmacro MUI_PAGE_WELCOME !insertmacro MUI_PAGE_LICENSE license.txt !insertmacro MUI_PAGE_COMPONENTS !insertmacro MUI_PAGE_INSTFILES !insertmacro MUI_PAGE_FINISH Installer languages !insertmacro MUI_LANGUAGE English Installer attributes OutFile RIM_BlackBerry_Desktop_5.0.exe InstallDir "$TEMP\RIM BlackBerry Desktop 5.0 Setup Files" CRCCheck on XPStyle on ShowInstDetails hide VIProductVersion 5.0.0.11 VIAddVersionKey /LANG=${LANG_ENGLISH} ProductName "BlackBerry Desktop" VIAddVersionKey /LANG=${LANG_ENGLISH} ProductVersion "${VERSION}" VIAddVersionKey /LANG=${LANG_ENGLISH} CompanyName "${COMPANY}" VIAddVersionKey /LANG=${LANG_ENGLISH} CompanyWebsite "${URL}" VIAddVersionKey /LANG=${LANG_ENGLISH} FileVersion "${VERSION}" VIAddVersionKey /LANG=${LANG_ENGLISH} FileDescription "" VIAddVersionKey /LANG=${LANG_ENGLISH} LegalCopyright "" Installer sections Section /o Main SEC0000 SetOutPath $INSTDIR SetOverwrite ifdiff ; TESTING PHASE SectionEnd SectionGroup /e "BlackBerry Desktop Section" Section /o Internet SEC0001 SetOutPath $INSTDIR\DRIVERS SetOverwrite ifdiff ; Execwait 'msiexec /i "$INSTDIR\BlackBerry USB and Modem Drivers_ENG (DM5.0b28).msi" /passive' SetOutPath $INSTDIR SetOverwrite ifdiff ; File /r * ; ExecWait '"$INSTDIR\Setup.exe" /S/v/qb!' SectionEnd Section /o Enterprise SEC0002 SetOutPath $INSTDIR\DRIVERS SetOverwrite ifdiff ; Execwait 'msiexec /i "$INSTDIR\BlackBerry USB and Modem Drivers_ENG (DM5.0b28).msi" /passive' SetOutPath $INSTDIR SetOverwrite ifdiff ; File /r * ; Delete /REBOOTOK "$INSTDIR\Setup.ini" ; Rename /REBOOTOK "$INSTDIR\Setup_Enterprise.ini" "$INSTDIR\Setup.ini" ; ExecWait '"$INSTDIR\Setup.exe" /S/v/qb!' SectionEnd SectionGroupEnd Section Descriptions !insertmacro MUI_FUNCTION_DESCRIPTION_BEGIN !insertmacro MUI_DESCRIPTION_TEXT ${SEC0000} $(SEC0000_DESC) !insertmacro MUI_DESCRIPTION_TEXT ${SEC0001} $(SEC0001_DESC) !insertmacro MUI_FUNCTION_DESCRIPTION_END Installer Language Strings TODO Update the Language Strings with the appropriate translations. LangString SEC0000_DESC ${LANG_ENGLISH} "Installation for non-Exchange/Enterprise BlackBerry Users" LangString SEC0001_DESC ${LANG_ENGLISH} "Installation for Exchange/Enterprise BlackBerry Users"

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• Bewildering SegFault involving STL sort algorithm.

  - by just_wes

  Hello everybody, I am completely perplexed at a seg fault that I seem to be creating. I have: vector<unsigned int> words; and global variable string input; I define my custom compare function: bool wordncompare(unsigned int f, unsigned int s) { int n = k; while (((f < input.size()) && (s < input.size())) && (input[f] == input[s])) { if ((input[f] == ' ') && (--n == 0)) { return false; } f++; s++; } return true; } When I run the code: sort(words.begin(), words.end()); The program exits smoothly. However, when I run the code: sort(words.begin(), words.end(), wordncompare); I generate a SegFault deep within the STL. The GDB back-trace code looks like this: #0 0x00007ffff7b79893 in std::string::size() const () from /usr/lib/gcc/x86_64-pc-linux-gnu/4.3.4/libstdc++.so.6 #1 0x0000000000400f3f in wordncompare (f=90, s=0) at text_gen2.cpp:40 #2 0x000000000040188d in std::__unguarded_linear_insert<__gnu_cxx::__normal_iterator<unsigned int*, std::vector<unsigned int, std::allocator<unsigned int> > >, unsigned int, bool (*)(unsigned int, unsigned int)> (__last=..., __val=90, __comp=0x400edc <wordncompare(unsigned int, unsigned int)>) at /usr/lib/gcc/x86_64-pc-linux-gnu/4.3.4/include/g++-v4/bits/stl_algo.h:1735 #3 0x00000000004018df in std::__unguarded_insertion_sort<__gnu_cxx::__normal_iterator<unsigned int*, std::vector<unsigned int, std::allocator<unsigned int> > >, bool (*)(unsigned int, unsigned int)> (__first=..., __last=..., __comp=0x400edc <wordncompare(unsigned int, unsigned int)>) at /usr/lib/gcc/x86_64-pc-linux-gnu/4.3.4/include/g++-v4/bits/stl_algo.h:1812 #4 0x0000000000402562 in std::__final_insertion_sort<__gnu_cxx::__normal_iterator<unsigned int*, std::vector<unsigned int, std::allocator<unsigned int> > >, bool (*)(unsigned int, unsigned int)> (__first=..., __last=..., __comp=0x400edc <wordncompare(unsigned int, unsigned int)>) at /usr/lib/gcc/x86_64-pc-linux-gnu/4.3.4/include/g++-v4/bits/stl_algo.h:1845 #5 0x0000000000402c20 in std::sort<__gnu_cxx::__normal_iterator<unsigned int*, std::vector<unsigned int, std::allocator<unsigned int> > >, bool (*)(unsigned int, unsigned int)> (__first=..., __last=..., __comp=0x400edc <wordncompare(unsigned int, unsigned int)>) at /usr/lib/gcc/x86_64-pc-linux-gnu/4.3.4/include/g++-v4/bits/stl_algo.h:4822 #6 0x00000000004012d2 in main (argc=1, args=0x7fffffffe0b8) at text_gen2.cpp:70 I have similar code in another program, but in that program I am using a vector instead of vector. For the life of me I can't figure out what I'm doing wrong. Thanks!

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• jquery ajax post callback - manipulation stops after the "third" call

  - by shanyu

  EDIT: The problem is not related to Boxy, I've run into the same issue when I've used JQuery 's load method. EDIT 2: When I take out link.remove() from inside the ajax callback and place it before ajax load, the problem is no more. Are there restrictions for manipulating elements inside an ajax callback function. I am using JQuery with Boxy plugin. When the 'Flag' link on the page is clicked, a Boxy modal pops-up and loads a form via ajax. When the user submits the form, the link (<a> tag) is removed and a new one is created from the ajax response. This mechanism works for, well, 3 times! After the 3rd, the callback function just does not remove/replace/append (tested several variations of manipulation) the element. The only hint I have is that after the 3rd call, the parent of the link becomes non-selectable. However I can't make anything of this. Sorry if this is a very trivial issue, I have no experience in client-side programming. The relevant html is below: <div class="flag-link"> <img class="flag-img" style="width: 16px; visibility: hidden;" src="/static/images/flag.png" alt=""/> <a class="unflagged" href="/i/flag/showform/9/1/?next=/users/1/ozgurisil">Flag</a> </div> Here is the relevant js code: $(document).ready(function() { $('div.flag-link a.unflagged').live('click', function(e){ doFlag(e); return false; }); ... }); function doFlag(e) { var link = $(e.target); var url = link.attr('href'); Boxy.load(url, {title:'Inappropriate Content', unloadOnHide:true, cache:false, behaviours: function(r) { $("#flag-form").live("submit", function(){ var post_url = $("#flag-form").attr('action'); boxy = Boxy.get(this); boxy.hideAndUnload(); $.post(post_url, $("#flag-form").serialize(), function(data){ par = link.parent(); par.append(data); alert (par.attr('class')); //BECOMES UNDEFINED AT THE 3RD CALL!! par.children('img.flag-img').css('visibility', 'visible'); link.remove(); }); return false; }); }}); }

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• How to call Ajax to run a PHP file while maintaining PHP & Javascript variables.

  - by Umar

  Hi Stackoverflowers. I'm using the Facebook php-sdk to get the users name and friends, right now the loading friends part takes about +3 seconds so I wanted to do it via Ajax, e.g. so the document can load and jQuery then calls an external PHP script which loads the friends (their names and their profile pictures). So to do this I did: $(document).ready(function() { var loadUrl = "http://localhost/fb/getFriends.php" ; $("#friends") .html("Hold on, your friends are loading!") .load(loadUrl); }); But I get a PHP error: Fatal error: Call to a member function api() on a non-object If I do this in the same PHP file (so I don't use Ajax at all to call it) it works fine. Now I think I understand the reason this is happening, but I don't know how to fix it. In my main index.php file I have a bunch of init and session code e.g. FB.init({ appId : '<?php echo $facebook->getAppId(); ?>', session : <?php echo json_encode($session); ?>, // don't refetch the session when PHP already has it status : true, // check login status cookie : true, // enable cookies to allow the server to access the session xfbml : true // parse XFBML }); So I'm just wondering what is the best way to treat my new separate PHP file getFriends.php in a way where it has access to all PHP/JavaScript session data/variables? If you haven't used the Facebook php-sdk I'll quickly explain what I mean: Lets say I have index.php and getUsername.php, from index.php I want to retrieve the getUsername.php file via Ajax using .load. Now the problem is getUsername.php needs to access PHP session data/Javascript Init functions which were created in index.php, so I'm thinking of ways to solve this (I'm new to PHP so sorry if this sounds silly) but I'm thinking maybe I could do a POST in jQuery Ajax and post the session data? Or maybe I could create a PHP class, so something like: class getUsername extends index{} /*Yes I'm a newbie*/ If you have a look at the php-sdk example.php link posted at the top maybe you'd better understand what variables exactly need to be accessed from a new file. Also on a different note, I'm using PHP to work out page rendering times and it seems that fetching the users name alone : // Session based API call. if ($session) { try { $uid = $facebook->getUser(); $me = $facebook->api('/me'); } catch (FacebookApiException $e) { error_log($e); } } Can take a good 4 seconds, is this normal? Once I get the users details is it good to cache it or something? -Speed isn't as important right now, for now I'm just trying to figure out this Ajax-separating php files thing. Woah this is a long post. Thanks very much for your time.

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• .NET: Avoidance of custom exceptions by utilising existing types, but which?

  - by Mr. Disappointment

  Consider the following code (ASP.NET/C#): private void Application_Start(object sender, EventArgs e) { if (!SetupHelper.SetUp()) { throw new ShitHitFanException(); } } I've never been too hesitant to simply roll my own exception type, basically because I have found (bad practice, or not) that mostly a reasonable descriptive type name gives us enough as developers to go by in order to know what happened and why something might have happened. Sometimes the existing .NET exception types even accommodate these needs - regardless of the message. In this particular scenario, for demonstration purposes only, the application should die a horrible, disgraceful death should SetUp not complete properly (as dictated by its return value), but I can't find an already existing exception type in .NET which would seem to suffice; though, I'm sure one will be there and I simply don't know about it. Brad Abrams posted this article that lists some of the available exception types. I say some because the article is from 2005, and, although I try to keep up to date, it's a more than plausible assumption that more have been added to future framework versions that I am still unaware of. Of course, Visual Studio gives you a nicely formatted, scrollable list of exceptions via Intellisense - but even on analysing those, I find none which would seem to suffice for this situation... ApplicationException: ...when a non-fatal application error occurs The name seems reasonable, but the error is very definitely fatal - the app is dead. ExecutionEngineException: ...when there is an internal error in the execution engine of the CLR Again, sounds reasonable, superficially; but this has a very definite purpose and to help me out here certainly isn't it. HttpApplicationException: ...when there is an error processing an HTTP request Well, we're running an ASP.NET application! But we're also just pulling at straws here. InvalidOperationException: ...when a call is invalid for the current state of an instance This isn't right but I'm adding it to the list of 'possible should you put a gun to my head, yes'. OperationCanceledException: ...upon cancellation of an operation the thread was executing Maybe I wouldn't feel so bad using this one, but I'd still be hijacking the damn thing with little right. You might even ask why on earth I would want to raise an exception here but the idea is to find out that if I were to do so then do you know of an appropriate exception for such a scenario? And basically, to what extent can we piggy-back on .NET while keeping in line with rationality?

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• Is this scenario in compliance with GPLv3?

  - by Sean Kinsey

  For arguments sake, say that we create a web application , that depends on a GPLv3 licensed component, lets say Ext JS. Based on Section 0 of the license, the common notion is that the entire web application (the client side javascript) falls under the definition of a covered work: A “covered work” means either the unmodified Program or a work based on the Program. and that it will therefor have to be distributed under the same license Ok, so here comes the fun part: This is a short 'program' that is based on Ext JS var myPanel = new Ext.Panel(); The question that arises is: Have I now violated the GPL by not including the source of Ext JS and its license? Ok, so lets take another example <!doctype html> <html> <head> <title>my title</title> <script type="text/javascript" src="http://extjs.cachefly.net/ext-3.2.1/ext-all.js"> </script> <link rel="stylesheet" type="text/css" href="http://extjs.cachefly.net/ext-3.2.1/resources/css/ext-all.css" /> <script type="text/javascript"> var myPanel = new Ext.Panel(); </script> </head> <body> </body> </html> Have I now violated the terms of the GPL? The code conveyed by me to you is in a non-functional state - it will have to be combined with the actual source of Ext JS, which you(your browser) will have to retrieve, from a source made public by someone else to be usable. Now, if the answer to the above is no, how does me conveying this code in visible form differ from the 'invisible' form conveyed by my web server? As a side note, a very similar thing is done in Linux with many projects that depends on less permissive licenses - the user has to retrieve these on its own and make these available for the primary lib/executable. How is this not the same if the user is informed on beforehand that he (the browser) will have to retrieve the needed resources from a different source? Just to make it clear, I'm pro FLOSS, and I have also published a number of projects licensed under more permissive licenses. The reason I'm asking this is that I still haven't found anyone offering a definitive answer to this.

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• Creating a spam list with a web crawler in python

  - by user313623

  Hey guys, I'm not trying to do anything malicious here, I just need to do some homework. I'm a fairly new programmer, I'm using python 3.0, and I having difficulty using recursion for problem-solving. I've been stuck on this question for quite a while. Here's the assignment: Write a recursive method spam(url, n) that takes a url of a web page as input and a non-negative integer n, collects all the email address contained in the web page and adds them to a global dictionary variable spam_dict, and then recursively calls itself on every http hyperlink contained in the web page. You will use a dictionary so only one copy of every email address is save; your dictionary will store (key,value) pairs (email, email). The recursive call should use the parameter n-1 instead of n. If n = 0, you should collect the email addresses but no recursive calls should be made. The parameter n is used to limit the recursion to at most depth n. You will need to use the solutions of the two above problems; you method spam() will call the methods links2() and emails() and possibly other functions as well. Notes: 1. running spam() directly will produce no output on the screen; to find your spam_dict, you will need to read the value of spam_dict, and you will also need to reset it to the empty dictionary before every run of spam. 2. Recall how global variables are used. Usage: spam_dict = {} spam('http://reed.cs.depaul.edu/lperkovic/csc242/test1.html',0) spam_dict.keys() dict_keys([]) spam_dict = {} spam('http://reed.cs.depaul.edu/lperkovic/csc242/test1.html',1) spam_dict.keys() dict_keys(['[email protected]', '[email protected]']) So far, I've written a function that traverses web pages and puts all the links in a nice little list, and what I wanted to do was call that functions. And why would I use recursion on a dictionary? And how? I don't understand how n ties into all of this. def links2(url): content = str(urlopen(url).read()) myparser = MyHTMLParser() myparser.feed(content) lst = myparser.get() mergelst = [] for link in lst: mergelst.append(urljoin(lst[0],link)) print(mergelst) Any input (except why spam is bad) would be greatly appreciated. Also, I realize that the above function could probably look better, if you have a way to do it, I'm all ears. However, all I need is the point is for the program to produce the proper output.

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