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• Subroutine & GoTo design

  - by sub

  I have a strange question concerning subroutines: As I'm creating a minimal language and I don't want to add high-level loops like while or for I was planning on just adding gotos to keep it Turing-Complete. Now I thought, eww - gotos - I wouldn't want to program in that language if I had to use gotos so often. So I thought about adding subroutines instead. I see the difference as the following: gotos Go to (captain obvious) a previously defined point and continue executing the program from there. Leads to hardly understandable and buggy code, I think that's a fact. subroutines Similiar: You define their starting point somewhere, as you call them the program jumps there - but the subroutine can go back to the point it was called from with return. Okay. Why didn't I just add the more function-like, nice looking subroutines? Because: In order to make return work if I call subroutines from within subroutines from within other subroutines, I'd have to use a stack containing the point where the currently running subroutine came from at top. That would then mean that I would, if I create loops using the subroutines, end up with an extremely memory-eating, overflowing stack with return locations. Not good. Don't think of my subroutines as functions. They are just gotos that return to the point they were called from, they don't actually give back values like the return x; statement in nearly all today's languages. Now to my actual questions: How can I solve the above problem with the stack overflow on loops with subroutines? Do I have to add a separate goto language construct without the return option? Assembler doesn't have loops but as I have seen myJumpPoint:, jnz, jz, retn. That means to me that there must also be a stack containing all the return locations. Am I right with that? What about long running loops then? Don't they overflow the stack/eat memory then? Am I getting the retn symbol in assembler totally wrong? If yes, please explain it to me.

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• Can you find a pattern to sync files knowing only dates and filenames?

  - by Robert MacLean

  Imagine if you will a operating system that had the following methods for files Create File: Creates (writes) a new file to disk. Calling this if a file exists causes a fault. Update File: Updates an existing file. Call this if a file doesn't exist causes a fault. Read File: Reads data from a file. Enumerate files: Gets all files in a folder. Files themselves in this operating system only have the following meta data: Created Time: The original date and time the file was created, by the Create File method. Modified Time: The date and time the file was last modified by the Update File method. If the file has never been modified, this will equal the Create Time. You have been given the task of writing an application which will sync the files between two directories (lets call them bill and ted) on a machine. However it is not that simple, the client has required that The application never faults (see methods above). That while the application is running the users can add and update files and those will be sync'd next time the application runs. Files can be added to either the ted or bill directories. File names cannot be altered. The application will perform one sync per time it is run. The application must be almost entirely in memory, in other words you cannot create a log of filenames and write that to disk and then check that the next time. The exception to point 6 is that you can store date and times between runs. Each date/time is associated with a key labeled A through J (so you have 10 to use) so you can compare keys between runs. There is no way to catch exceptions in the application. Answer will be accepted based on the following conditions: First answer to meet all requirements will be accepted. If there is no way to meet all requirements, the answer which ensures the smallest amount of missed changes per sync will be accepted. A bounty will be created (100 points) as soon as possible for the prize. The winner will be selected one day before the bounty ends. Please ask questions in the comments and I will gladly update and refine the question on those.

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• Rails "NoMethodError" with sub-resources

  - by Tchock

  Hi. I'm a newbie Rails developer who is getting the following error when trying to access the 'new' action on my CityController: undefined method `cities_path' for #<#<Class:0x104608c18>:0x104606f08> Extracted source (around line #2): 1: <h1>New City</h1> 2: <%= form_for(@city) do |f| %> 3: <%= f.error_messages %> 4: 5: <div class="field"> As some background, I have a State model with many Cities. I'm getting this error after clicking on the following link coming from a State show page: <p>Add a city: <%= link_to "Add city", new_state_city_path(@state) %></p> When I run 'rake:routes' it says this is a legit route... For more background, here is the CityController 'new' action: def new @city = City.new respond_to do |format| format.html # new.html.erb format.xml { render :xml => @city } end end Here is the (complete) form in the view: <%= form_for(@city) do |f| %> <%= f.error_messages %> <div class="field"> <%= f.label :name %><br /> <%= f.text_field :name %> </div> <div class="actions"> <%= f.submit %> </div> <% end %> This initially made me think that it's a resources/routes issue since it came back with a mention of 'cities_path' (in fact, that's what another person posting to Stack Overflow had wrong (http://stackoverflow.com/questions/845315/rails-error-nomethoderror-my-first-ruby-app). However, that doesn't seem to be the case from what I can see. Here are how my resources look in my routes file: resources :states do resources :cities end I can get it working when they are not sub-resources, but I really need to keep them as sub-resources for my future plans with the app. Any help would be very much appreciated, since I've been racking my brains on this for more hours than I would care to admit... Thanks! (Not sure this matters at all, but I'm running the very latest version of Rails 3 beta2).

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• Swing: Scroll to bottom of JScrollPane, conditionally on current viewport location

  - by I82Much

  Hi all, I am attempting to mimic the functionality of Adium and most other chat clients I've seen, wherein the scrollbars advance to the bottom when new messages come in, but only if you're already there. In other words, if you've scrolled a few lines up and are reading, when a new message comes in it won't jump your position to the bottom of the screen; that would be annoying. But if you're scrolled to the bottom, the program rightly assumes that you want to see the most recent messages at all times, and so auto-scrolls accordingly. I have had a bear of a time trying to mimic this; the platform seems to fight this behavior at all costs. The best I can do is as follows: In constructor: JTextArea chatArea = new JTextArea(); JScrollPane chatAreaScrollPane = new JScrollPane(chatArea); // We will manually handle advancing chat window DefaultCaret caret = (DefaultCaret) chatArea.getCaret(); caret.setUpdatePolicy(DefaultCaret.NEVER_UPDATE); In method that handles new text coming in: boolean atBottom = isViewAtBottom(); // Append the text using styles etc to the chatArea if (atBottom) { scrollViewportToBottom(); } public boolean isAtBottom() { // Is the last line of text the last line of text visible? Adjustable sb = chatAreaScrollPane.getVerticalScrollBar(); int val = sb.getValue(); int lowest = val + sb.getVisibleAmount(); int maxVal = sb.getMaximum(); boolean atBottom = maxVal == lowest; return atBottom; } private void scrollToBottom() { chatArea.setCaretPosition(chatArea.getDocument().getLength()); } Now, this works, but it's janky and not ideal for two reasons. By setting the caret position, whatever selection the user may have in the chat area is erased. I can imagine this would be very irritating if he's attempting to copy/paste. Since the advancement of the scroll pane occurs after the text is inserted, there is a split second where the scrollbar is in the wrong position, and then it visually jumps towards the end. This is not ideal. Before you ask, yes I've read this blog post on Text Area Scrolling, but the default scroll to bottom behavior is not what I want. Other related (but to my mind, not completely helpful in this regard) questions: Setting scroll bar on a jscrollpane Making a JScrollPane automatically scroll all the way down. Any help in this regard would be very much appreciated.

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• Oracle Schema Design: Seperate Schema with I/O Overhead?

  - by Guru

  We are designing database schema for a new system based on Oracle 11gR1. We have identified a main schema which would have close to 100 tables, these will be accessed from the front end Java application. We have a requirement to audit the values which got changed in close to 50 tables, this has to be done every row. Which means, it is possible that, for a single row in MYSYS.T1 there might be 50 (or more) rows in MYSYS_AUDIT.T1_AUD table. We might be having old values of every column entry and new values available from T1. DBA gave an observation, advising against this method, because he said, separate schema meant an extra I/O for every operation. Basically AUDIT schema would be used only to do some analyse and enter values (thus SELECT and INSERT). Is it true that, "a separate schema means an extra I/O" ? I could not find justification. It appears logical to me, as the AUDIT data should not be tampered with, so a separate schema. Also, we designed a separate schema for archiving some tables from MYSYS. From MYSYS_ARC the table might be backed up into tapes or deleted after sufficient time. Few stats: Few tables (close to 20, 30) in MYSYS schema could grow to around 50M rows. We have asked for a total disk space of 4 TB. MYSYS_AUDIT schema might be having 10 times that of MYSYS but we wont keep them more than 3 months. Questions Given all these, can you suggest me any improvements? Separate schema affects disc I/O? (one extra I/O for every schema ?) Any general suggestions? Figure: +-------------------+ +-------------------+ | MYSYS | | MYSYS_AUDIT | | | | | | 1. T1 | | 1. T1_AUD | | 2. T2 | | 2. T2_AUD | | 3. T3 |--------->| 3. T3_AUD | | 4. T4 |(SELECT, | 4. T4_AUD | | . | INSERT) | . | | . | | . | | . | | . | | 100. T100 | | 50. T50_AUD | +-------------------+ +-------------------+ | | | | |(INSERT) | | | * +-------------------+ | MYSYS_ARC | | | | 1. T1_ARC | | 2. T2_ARC | | 3. T3_ARC | | 4. T4_ARC | | . | | . | | . | | 100. T100_ARC | +-------------------+ Apart from this, we have two more schemas with only read only rights, but mainly they are for adhoc purpose and we dont mind the performance on them.

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• Linked List Design

  - by Jim Scott

  The other day in a local .NET group I attend the following question came up: "Is it a valid interview question to ask about Linked Lists when hiring someone for a .NET development position?" Not having a computer sciense degree and being a self taught developer my response was that I did not feel it was appropriate as I in 5 years of developer with .NET had never been exposed to linked lists and did not hear any compeling reason for a use for one. However the person commented that it is a very common interview question so I decided when I left that I would do some reasearch on linked lists and see what I might be missing. I have read a number of posts on stack overflow and various google searches and decided the best way to learn about them was to write my own .NET classes to see how they worked from the inside out. Here is my class structure Single Linked List Constructor public SingleLinkedList(object value) Public Properties public bool IsTail public bool IsHead public object Value public int Index public int Count private fields not exposed to a property private SingleNode firstNode; private SingleNode lastNode; private SingleNode currentNode; Methods public void MoveToFirst() public void MoveToLast() public void Next() public void MoveTo(int index) public void Add(object value) public void InsertAt(int index, object value) public void Remove(object value) public void RemoveAt(int index) Questions I have: What are typical methods you would expect in a linked list? What is typical behaviour when adding new records? For example if I have 4 nodes and I am currently positioned in the second node and perform Add() should it be added after or before the current node? Or should it be added to the end of the list? Some of the designs I have seen explaining things seem to expose outside of the LinkedList class the Node object. In my design you simply add, get, remove values and know nothing about any node object. Should the Head and Tail be placeholder objects that are only used to define the head/tail of the list? I require my Linked List be instantiated with a value which creates the first node of the list which is essentially the head and tail of the list. Would you change that ? What should the rules be when it comes to removing nodes. Should someone be able to remove all nodes? Here is my Double Linked List Constructor public DoubleLinkedList(object value) Properties public bool IsHead public bool IsTail public object Value public int Index public int Count Private fields not exposed via property private DoubleNode currentNode; Methods public void AddFirst(object value) public void AddLast(object value) public void AddBefore(object existingValue, object value) public void AddAfter(object existingValue, object value) public void Add(int index, object value) public void Add(object value) public void Remove(int index) public void Next() public void Previous() public void MoveTo(int index)

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• list of polymorphic objects

  - by LivingThing

  I have a particular scenario below. The code below should print 'say()' function of B and C class and print 'B says..' and 'C says...' but it doesn't .Any ideas.. I am learning polymorphism so also have commented few questions related to it on the lines of code below. class A { public: // A() {} virtual void say() { std::cout << "Said IT ! " << std::endl; } virtual ~A(); //why virtual destructor ? }; void methodCall() // does it matters if the inherited class from A is in this method { class B : public A{ public: // virtual ~B(); //significance of virtual destructor in 'child' class virtual void say () // does the overrided method also has to be have the keyword 'virtual' { cout << "B Sayssss.... " << endl; } }; class C : public A{ public: //virtual ~C(); virtual void say () { cout << "C Says " << endl; } }; list<A> listOfAs; list<A>::iterator it; # 1st scenario B bObj; C cObj; A *aB = &bObj; A *aC = &cObj; # 2nd scenario // A aA; // B *Ba = &aA; // C *Ca = &aA; // I am declaring the objects as in 1st scenario but how about 2nd scenario, is this suppose to work too? listOfAs.insert(it,*aB); listOfAs.insert(it,*aC); for (it=listOfAs.begin(); it!=listOfAs.end(); it++) { cout << *it.say() << endl; } } int main() { methodCall(); retrun 0; }

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• If Then Statement Condition Being Ignored With Optimisations On

  - by Matma

  I think im going mad but can some show me what im missing, it must be some stupidly simple i just cant see the wood for the trees. BOTH side of this if then else statement are being executed? Ive tried commenting out the true side and moving the condition to a seperate variable with the same result. However if i explicitly set the condition to 1=0 or 1=1 then the if then statement is operating as i would expect. i.e. only executing one side of the equation... The only time ive seen this sort of thing is when the compiler has crashed and is no longer compiling (without visible indication that its not) but ive restarted studio with the same results, ive cleaned the solution, built and rebuilt with no change? please show me the stupid mistake im making using vs2005 if it matters. Dim dset As DataSet = New DataSet If (CboCustomers.SelectedValue IsNot Nothing) AndAlso (CboCustomers.SelectedValue <> "") Then Dim Sql As String = "Select sal.SalesOrderNo As SalesOrder,cus.CustomerName,has.SerialNo, convert(varchar,sal.Dateofpurchase,103) as Date from [dbo].[Customer_Table] as cus " & _ " inner join [dbo].[Hasp_table] as has on has.CustomerID=cus.CustomerTag " & _ " inner join [dbo].[salesorder_table] as sal On sal.Hasp_ID =has.Hasp_ID Where cus.CustomerTag = '" & CboCustomers.SelectedValue.ToString & "'" Dim dap As SqlDataAdapter = New SqlDataAdapter(Sql, FormConnection) dap.Fill(dset, "dbo.Customer_Table") DGCustomer.DataSource = dset.Tables("dbo.Customer_Table") Else Dim erm As String = "wtf" End If EDIT: i have found that this is something to do with the release config settings im using, i guesing its the optimisations bit. does anyone know of any utils/addons for vs that show if a line has been optimised out. delphi, my former language showed blue dots in the left margin to show that it was a compiled line, no dot meaning it wasnt compiled in, is there anything like that for vs? alternatively can someone explain how optimisations would affect this simple if statement causeing it to run both sides? EDIT2: using this thread as possible causes/solutions : http://stackoverflow.com/questions/2135509/bug-only-occurring-when-compile-optimization-enabled. It does the same with release = optimisations on, x86, x64 and AnyCPU Goes away with optimisations off. Im using V2005 on a x64 win7 machine, if that matters. Thanks

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• Mercurial for Beginners: The Definitive Practical Guide

  - by Laz

  Inspired by Git for beginners: The definitive practical guide. This is a compilation of information on using Mercurial for beginners for practical use. Beginner - a programmer who has touched source control without understanding it very well. Practical - covering situations that the majority of users often encounter - creating a repository, branching, merging, pulling/pushing from/to a remote repository, etc. Notes: Explain how to get something done rather than how something is implemented. Deal with one question per answer. Answer clearly and as concisely as possible. Edit/extend an existing answer rather than create a new answer on the same topic. Please provide a link to the the Mercurial wiki or the HG Book for people who want to learn more. Questions: Installation/Setup How to install Mercurial? How to set up Mercurial? How do you create a new project/repository? How do you configure it to ignore files? Working with the code How do you get the latest code? How do you check out code? How do you commit changes? How do you see what's uncommitted, or the status of your current codebase? How do you destroy unwanted commits? How do you compare two revisions of a file, or your current file and a previous revision? How do you see the history of revisions to a file? How do you handle binary files (visio docs, for instance, or compiler environments)? How do you merge files changed at the "same time"? Tagging, branching, releases, baselines How do you 'mark' 'tag' or 'release' a particular set of revisions for a particular set of files so you can always pull that one later? How do you pull a particular 'release'? How do you branch? How do you merge branches? How do you merge parts of one branch into another branch? Other Good GUI/IDE plugin for Mercurial? Advantages/disadvantages? Any other common tasks a beginner should know? How do I interface with Subversion? Other Mercurial references Mercurial: The Definitive Guide Mercurial Wiki Meet Mercurial | Peepcode Screencast

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• Debugging site written mainly in JScript with AJAX code injection

  - by blumidoo

  Hello, I have a legacy code to maintain and while trying to understand the logic behind the code, I have run into lots of annoying issues. The application is written mainly in Java Script, with extensive usage of jQuery + different plugins, especially Accordion. It creates a wizard-like flow, where client code for the next step is downloaded in the background by injecting a result of a remote AJAX request. It also uses callbacks a lot and pretty complicated "by convention" programming style (lots of events handlers are created on the fly based on certain object names - e.g. current page name, current step name). Adding to that, the code is very messy and there is no obvious inner structure - the functions are scattered in the code, file names do not reflect the business role of the code, lots of functions and code snippets are most likely not used at all etc. PROBLEM: How to approach this code base, so that the inner flow of the code can be sort-of "reverse engineered" using a suite of smart debugging tools. Ideally, I would like to be able to attach to the running application and step through the code, breaking on each new function call. Also, it would be nice to be able to create a "diagram of calls" in the application (i.e. in order to run a particular page logic, this particular flow of function calls was executed in a particular order). Not to mention to be able to run a coverage analysis, identifying potentially orphaned code fragments. I would like to stress out once more, that it is impossible to understand the inner logic of the application just by looking at the code itself, unless you have LOTS of spare time and beer crates, which I unfortunately do not have :/ (shame...) An IDE of some sort that would aid in extending that code would be also great, but I am currently looking into possibility to use Visual Studio 2010 to do the job, as the site itself is a mix of Classic ASP and ASP.NET (I'd say - 70% Java Script with jQuery, 30% ASP). I have obviously tried FireBug, but I was unable to find a way to define a breakpoint or step into the code, which is "injected" into the client JS using AJAX calls (i.e. the application retrieves the code by invoking an URL and injects it to the client local code). Venkman debugger had similar issues. Any hints would be welcome. Feel free to ask additional questions.

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• Strange iPhone memory leak in xml parser

  - by Chris

  Update: I edited the code, but the problem persists... Hi everyone, this is my first post here - I found this place a great ressource for solving many of my questions. Normally I try my best to fix anything on my own but this time I really have no idea what goes wrong, so I hope someone can help me out. I am building an iPhone app that parses a couple of xml files using TouchXML. I have a class XMLParser, which takes care of downloading and parsing the results. I am getting memory leaks when I parse an xml file more than once with the same instance of XMLParser. Here is one of the parsing snippets (just the relevant part): for(int counter = 0; counter < [item childCount]; counter++) { CXMLNode *child = [item childAtIndex:counter]; if([[child name] isEqualToString:@"PRODUCT"]) { NSMutableDictionary *product = [[NSMutableDictionary alloc] init]; for(int j = 0; j < [child childCount]; j++) { CXMLNode *grandchild = [child childAtIndex:j]; if([[grandchild stringValue] length] > 1) { NSString *trimmedString = [[grandchild stringValue] stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]; [product setObject:trimmedString forKey:[grandchild name]]; } } // Add product to current category array switch (categoryId) { case 0: [self.mobil addObject: product]; break; case 1: [self.allgemein addObject: product]; break; case 2: [self.besitzeIch addObject: product]; break; case 3: [self.willIch addObject: product]; break; default: break; } [product release]; } } The first time, I parse the xml no leak shows up in instruments, the next time I do so, I got a lot of leaks (NSCFString / NSCFDictionary). Instruments points me to this part inside CXMLNode.m, when I dig into a leaked object: theStringValue = [NSString stringWithUTF8String:(const char *)theXMLString]; if ( _node->type != CXMLTextKind ) xmlFree(theXMLString); } return(theStringValue); I really spent a long time and tried multiple approaches to fix this, but to no avail so far, maybe I am missing something essential? Any help is highly appreciated, thank you!

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• Google Bookmarks Accelerator for IE8

  - by MACHiNESMiTH

  To Editors: Sorry, I didnt realise the question thing till you pointed it out. Also I didn't know about the appengine tag, I'm assuming it was selected by mistake from that JS autosuggestion box (it usually happens with me, I run a P3) my apologies for that too. I've edited it now, if it doesnt work let me know. Hi all, I'm making (or at least trying to make) a Google bookmarks accelerator for IE8, but I keep running into "Internet Explorer could not install this accelerator. There was a problem with the Accelerator's information." Does anyone know why this is happening? Here is the code I've made <?xml version="1.0" encoding="UTF-8" ?> <os:openServiceDescription xmlns="http://www.microsoft.com/schemas/openservicedescription/1.0"> <os:homepageUrl>http://www.google.com/bookmarks</os:homepageUrl> <os:display> <os:description>Add this page to GoogleBookmarks</os:description> <os:name>Add to GoogleBookmarks</os:name> <os:icon>http://www.google.com/favicon.ico</os:icon> </os:display> <os:activity category="Bookmarks"> <os:activityAction context="document"> <os:execute method="get" action="http://www.google.com/bookmarks/mark?op=add&output=popup"> <os:parameter name="bkmk" value="{documentUrl}" /> <os:parameter name="title" value="{documentTitle}" /> <os:parameter name="annotation" value="{selection}" /> </os:execute> </os:activityAction> </os:activity> </os:openServiceDescription> These are the references I used: MSDN Developers Guide MSDN Format Specification Unofficial Google API (used as a look up so far) and yes i know that I cannot send document variables between schemes (HTTP - HTTPS, for example) or between servers in different security zones (Intranet - Internet etc) Also, if this is the wrong place, what are the recommended sites and/or forums for xml related posts? (not really questions - but more like full blown detailed rant like posts) Thanks

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• In Rails, how should I implement a Status field for a Tasks app - integer or enum?

  - by Doug

  For a Rails 3.0 Todo app, I have a Tasks model with a Status field. What's the best way to store the Status field data (field type) and still display a human-readable version in a view (HTML table)? Status can be: 0 = Normal 1 = Active 2 = Completed Right now I have this: Rails Schema Here: create_table "tasks", :force = true do |t| t.integer "status", :limit = 1, :default = 0, :null = false Rails Model Here: class Task < ActiveRecord::Base validates_inclusion_of :status, :in => 0..2, :message => "{{value}} must be 0, 1, or 2" Rails View Here: <h1>Listing tasks</h1> <table> <tr> <th>Status</th> <th>Name</th> <th></th> <th></th> <th></th> </tr> <% @tasks.each do |task| %> <tr> <td><%= task.status %></td> <td><%= task.name %></td> <td><%= link_to 'Show', task %></td> <td><%= link_to 'Edit', edit_task_path(task) %></td> <td><%= link_to 'Delete', task, :confirm => 'Are you sure?', :method => :delete %></td> </tr> <% end %> </table> Requirements Store a Task's status in the db such that the values are easily localizable, i.e. I'm not sure I want to store "normal", "active", "completed" as a string field. Solution must work with Rails 3.0. Questions: Should I store the field as an integer (see above)? If so, how do I display the correct human readable status in an HTML table in my Rails view, e.g. show "Active" instead of "1" in the HTML table. Should I use an enum? If so, is this easy to localize later? Should I use straight strings, e.g. "Normal", "Active", "Completed" Can you provide a quick code sample of the view helper, controller or view code to make this work?

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• Creating a column of RadioButtons in Adobe Flex

  - by adnan

  I am having an un-predictable behavior of creating radio buttons in advancedDataGrid column using itemRenderer. Similar kind of problem has been reported at http://stackoverflow.com/questions/112036/creating-a-column-of-radiobuttons-in-adobe-flex. I tried to use the same procedure i.e. bind every radio button selectedValue and value attributes with the property specified in the property of the associated bean but still facing the problem. The button change values! The selected button becomes deselected, and unselected ones become selected. Here is the code of my advancedDataGrid: <mx:AdvancedDataGrid id="adDataGrid_rptdata" width="100%" height="100%" dragEnabled="false" sortableColumns="false" treeColumn="{action}" liveScrolling="false" displayItemsExpanded="true" > <mx:dataProvider> <mx:HierarchicalData source="{this.competenceCollection}" childrenField="competenceCriteria"/> </mx:dataProvider> <mx:columns> <mx:AdvancedDataGridColumn headerText="" id="action" dataField="criteriaName" /> <mx:AdvancedDataGridColumn headerText="Periode 1" dataField="" width="200"> <mx:itemRenderer> <mx:Component> <mx:HBox horizontalAlign="center" width="100%" verticalAlign="middle"> <mx:RadioButton name="period1" value="{data}" selected="{data.period1}" group="{data.radioBtnGrpArray[0]}" visible="{data.showRadioButton}" /> </mx:HBox> </mx:Component> </mx:itemRenderer> </mx:AdvancedDataGridColumn> <mx:AdvancedDataGridColumn headerText="Periode 2" dataField="" width="200"> <mx:itemRenderer> <mx:Component> <mx:HBox horizontalAlign="center" width="100%" verticalAlign="middle"> <mx:RadioButton name="period2" value="{data}" selected="{data.period2}" group="{data.radioBtnGrpArray[1]}" visible="{data.showRadioButton}" /> </mx:HBox> </mx:Component> </mx:itemRenderer> </mx:AdvancedDataGridColumn> <mx:AdvancedDataGridColumn headerText="Periode 3" dataField="" width="200"> <mx:itemRenderer> <mx:Component> <mx:HBox horizontalAlign="center" width="100%" verticalAlign="middle"> <mx:RadioButton name="period3" value="{data}" selected="{data.period3}" group="{data.radioBtnGrpArray[2]}" visible="{data.showRadioButton}" /> </mx:HBox> </mx:Component> </mx:itemRenderer> </mx:AdvancedDataGridColumn> </mx:columns> </mx:AdvancedDataGrid> Any work around is highly appreciated in this regard!

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• paypal IPN sends two different twice

  - by Patrick

  I've come across something a bit strange I was hoping someone with more experience with Paypal can explain, Specifically the IPN feature. It seems I'm getting two very different hits to my IPN listener. The first one always fails, The second one passes. Now I know Paypal tends to send duplicates, But what I've noticed is two very different $_POST arrays being recieved. Here's the respones : [2014-06-08 23:51:19] RAW POST DATA : Array ( [transaction] => Array ( [0] => ILS 20.00 ) [payment_request_date] => Sun Jun 08 13:52:12 PDT 2014 [return_url] => MY_URL [fees_payer] => EACHRECEIVER [ipn_notification_url] => MY_URL [sender_email] => [email protected] //fake email [verify_sign] => ANp5TpLat3.2ylx.cECtVZ..5HejAsVcs05tdVC7RldmeYNJ91SKaqFJ [test_ipn] => 1 [cancel_url] => MY_URL [pay_key] => AP-04B74091M7083584A [action_type] => PAY [transaction_type] => Adaptive Payment PAY [tracking_id] => 13 // This is a number I passed, But it doesn't exist in the 2nd POST [status] => COMPLETED [log_default_shipping_address_in_transaction] => false [charset] => windows-1252 [notify_version] => UNVERSIONED [reverse_all_parallel_payments_on_error] => false ) [2014-06-08 23:51:19] RAW POST DATA : Array ( [transaction_subject] => [payment_date] => 13:52:28 Jun 08, 2014 PDT [txn_type] => web_accept [last_name] => test [residence_country] => US [item_name] => .... (this continues for quite a bit more) .... [payment_fee] => [mc_fee] => 1.78 [mc_gross] => 20.00 [custom] => [charset] => windows-1252 [notify_version] => 3.8 [ipn_track_id] => f93ce8bdd4382 ) My problem The first IPN with the juicy tracking_id fails, the 2nd IPN is verified, But once the IPN is verified I no longer have access to the tracking_id. My questions Why does paypal send two different IPN's Why are they different? Why isn't any of this documented on Paypal? :(

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• Swing: Scroll to bottom of JScrollPane, conditional on current viewport location

  - by I82Much

  Hi all, I am attempting to mimic the functionality of Adium and most other chat clients I've seen, wherein the scrollbars advance to the bottom when new messages come in, but only if you're already there. In other words, if you've scrolled a few lines up and are reading, when a new message comes in it won't jump your position to the bottom of the screen; that would be annoying. But if you're scrolled to the bottom, the program rightly assumes that you want to see the most recent messages at all times, and so auto-scrolls accordingly. I have had a bear of a time trying to mimic this; the platform seems to fight this behavior at all costs. The best I can do is as follows: In constructor: JTextArea chatArea = new JTextArea(); JScrollPane chatAreaScrollPane = new JScrollPane(chatArea); // We will manually handle advancing chat window DefaultCaret caret = (DefaultCaret) chatArea.getCaret(); caret.setUpdatePolicy(DefaultCaret.NEVER_UPDATE); In method that handles new text coming in: boolean atBottom = isViewAtBottom(); // Append the text using styles etc to the chatArea if (atBottom) { scrollViewportToBottom(); } public boolean isAtBottom() { // Is the last line of text the last line of text visible? Adjustable sb = chatAreaScrollPane.getVerticalScrollBar(); int val = sb.getValue(); int lowest = val + sb.getVisibleAmount(); int maxVal = sb.getMaximum(); boolean atBottom = maxVal == lowest; return atBottom; } private void scrollToBottom() { chatArea.setCaretPosition(chatArea.getDocument().getLength()); } Now, this works, but it's janky and not ideal for two reasons. By setting the caret position, whatever selection the user may have in the chat area is erased. I can imagine this would be very irritating if he's attempting to copy/paste. Since the advancement of the scroll pane occurs after the text is inserted, there is a split second where the scrollbar is in the wrong position, and then it visually jumps towards the end. This is not ideal. Before you ask, yes I've read this blog post on Text Area Scrolling, but the default scroll to bottom behavior is not what I want. Other related (but to my mind, not completely helpful in this regard) questions: Setting scroll bar on a jscrollpane Making a JScrollPane automatically scroll all the way down. Any help in this regard would be very much appreciated.

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• Advice for Architecture Design Logic for software application

  - by Prasad

  Hi, I have a framework of basic to complex set of objects/classes (C++) running into around 500. With some rules and regulations - all these objects can communicate with each other and hence can cover most of the common queries in the domain. My Dream: I want to provide these objects as icons/glyphs (as I learnt recently) on a workspace. All these objects can be dragged/dropped into the workspace. They have to communicate only through their methods(interface) and in addition to few iterative and conditional statements. All these objects are arranged finally to execute a protocol/workflow/dataflow/process. After drawing the flow, the user clicks the Execute/run button. All the user interaction should be multi-touch enabled. The best way to show my dream is : Jeff Han's Multitouch Video. consider Jeff is playing with my objects instead of the google maps. :-) it should be like playing a jigsaw puzzle. Objective: how can I achieve the following while working on this final product: a) the development should be flexible to enable provision for web services b) the development should enable easy web application development c) The development should enable client-server architecture - d) further it should also enable mouse based drag/drop desktop application like Adobe programs etc. I mean to say: I want to economize on investments. Now I list my efforts till now in design : a) Created an Editor (VB) where the user writes (manually) the object / class code b) On Run/Execute, the code is copied into a main() function and passed to interpreter. c) Catch the output and show it in the console. The interpreter can be separated to become a server and the Editor can become the client. This needs lot of standard client-server architecture work. But some how I am not comfortable in the tightness of this system. Without interpreter is there much faster and better embeddable solution to this? - other than writing a special compiler for these objects. Recently learned about AXIS-C++ can help me - looks like - a friend suggested. Is that the way to go ? Here are my questions: (pl. consider me a self taught programmer and NOT my domain) a) From the stage of C++ objects to multi-touch product, how can I make sure I will develop the parallel product/service models as well.? What should be architecture aspects I should consider ? b) What technologies are best suited for this? c) If I am thinking of moving to Cloud Computing, how difficult/ how redundant / how unnecessary my efforts will be ? d) How much time in months would it take to get the first beta ? I take the liberty to ask if any of the experts here are interested in this project, please email me: [email protected] Thank you for any help. Looking forward.

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• Boggling Direct3D9 dynamic vertex buffer Lock crash/post-lock failure on Intel GMA X3100.

  - by nj

  Hi, For starters I'm a fairly seasoned graphics programmer but as wel all know, everyone makes mistakes. Unfortunately the codebase is a bit too large to start throwing sensible snippets here and re-creating the whole situation in an isolated CPP/codebase is too tall an order -- for which I am sorry, do not have the time. I'll do my best to explain. B.t.w, I will of course supply specific pieces of code if someone wonders how I'm handling this-or-that! As with all resources in the D3DPOOL_DEFAULT pool, when the device context is taken away from you you'll sooner or later will have to reset your resources. I've built a mechanism to handle this for all relevant resources that's been working for years; but that fact nothingwithstanding I've of course checked, asserted and doubted any assumption since this bug came to light. What happens is as follows: I have a rather large dynamic vertex buffer, exact size 18874368 bytes. This buffer is locked (and discarded fully using the D3DLOCK_DISCARD flag) each frame prior to generating dynamic geometry (isosurface-related, f.y.i) to it. This works fine, until, of course, I start to reset. It might take 1 time, it might take 2 or it might take 5 resets to set off a bug that causes an access violation either on the pointer returned by the Lock() operation on the renewed resource or a plain crash -- regarding a somewhat similar address, but without the offset that it has tacked on to it in the first case because in that case we're somewhere halfway writing -- iside the D3D9 dll Lock() call. I've tested this on other hardware, upgraded my GMA X3100 drivers (using a MacBook with BootCamp) to the latest ones, but I can't reproduce it on any other machine and I'm at a loss about what's wrong here. I have tried to reproduce a similar situation with a similar buffer (I've got a large scratch pad of the same type I filled with quads) and beyond a certain amount of bytes it started to behave likewise. I'm not asking for a solution here but I'm very interested if there are other developers here who have battled with the same foe or maybe some who can point me in some insightful direction, maybe ask some questions that might shed a light on what I may or may not be overlooking. Another interesting artifact is that the vertex buffer starts to bug if I supply both D3DLOCK_DISCARD and D3DLOCK_NOOVERWRITE together which, even though not very logical (you're not going to overwrite if you've just discarded all), gives graphics glitches. Thanks and any corrections are more than welcome. Niels p.s - A friend of mine raised the valid point that it is a huge buffer for onboard video RAM and it's being at least double or triple buffered internally due to it's dynamic nature. On the other hand, the debug output (D3D9 debug DLL + max. warning output) remains silent. p.s 2 - Had it tested on more machines and still works -- it's probably a matter of circumstance: the huge dynamic, internally double/trippled buffered buffer, not a lot of memory and drivers that don't complain when they should.. Unless someone has a better suggestion; I'd still love to hear it :)

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• SimpleXML SOAP response Namespace issues

  - by Stu

  Hi. After spending SEVERAL frustrated hours on this I am asking for your help. I am trying to get the content of particular nodes from a SOAP response. The response is $XmlStr = <?xml version="1.0" encoding="UTF-8"?><env:Envelope xmlns:env="http://www.w3.org/2003/05/soap-envelope"<xmlns:ns1="http://soap.xxxxxx.co.uk/"><env:Body><ns1:PlaceOrderResponse><xxxxxOrderNumber></xxxxxOrderNumber><ErrorArray><Error><ErrorCode>24</ErrorCode><ErrorText>The+client+order+number+3002254+is+already+in+use</ErrorText></Error><Error><ErrorCode>1</ErrorCode><ErrorText>Aborting</ErrorText></Error></ErrorArray></ns1:PlaceOrderResponse></env:Body></env:Envelope> I am trying to get at the nodes and children of <ErrorArray. Because of the XML containing namespaces $XmlArray = new SimpleXMLElement($XmlStr); foreach ($XmlArray->env:Envelope->env:Body->ns1:PlaceOrderResponse->ErrorArray->Error as $Error) { echo $Error->ErrorCode."<br />";<br /> } doesn't work. I have read a number of articles such as http://www.sitepoint.com/blogs/2005/10/20/simplexml-and-namespaces/ htp://blog.stuartherbert.com/php/2007/01/07/using-simplexml-to-parse-rss-feeds/ and about 20 questions on this site which unfortunately are not helping. (the second link has htp:// as a newbie here I cannot post more than one link) Even writing, $XmlArray = new SimpleXMLElement($XmlStr); echo "<br /><br /><pre>\n"; print_r($XmlArray); echo "<pre><br /><br />\n"; gives SimpleXMLElement Object ( ) which makes me wonder if the soap response ($XmlStr) is actually a valid input for SimpleXMLElement. It seems that the line $XmlArray = new SimpleXMLElement($XmlStr); is not doing what I expect it to. Any help on how to get the nodes from the XML above would be very welcome. Obviously getting it to work (having a working example) is what I need in the short term, but if someone could help me understand what I am doing wrong would be better in the long term. Cheers. Stu

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• SaaS Architecture Question from Newbie

  - by user226767

  I have developed a number of departmental client-server applications, and am now ready to begin working on moving one of these applications to a SaaS model. I have done some basic web development, but I'm a newbie when it comes to SaaS architectures. One of the first questions that comes to mind as I try to design the architecture is the question of single vs. multi tenancy. The pros and cons of each vary significantly depending on the type of application and scale required, so I'd like to describe my application and scale needs below, and hope others can comment on how I should get started with the architecture. The client-server application currently consists of a Firebird database and a Windows application. The database contains about 20 tables containing a few thousand records in 4 primary tables, and a few hundred records in various lookup and related tables. Although the number of records is small, the size can get large, as the database can contain large BLOBS. Each customer sets up their own database and has a handful of users within the organization connected to it. When I update the db schema, a new windows application is released, and it checks the db schema and then applies the updates as needed. For the SaaS application, I am designing for 100's (not 1000's or millions) of new customers per year. My first thought was to go with a multi tenancy model to make updates easy (shut down apply the updates to one database, and then start up). On the other hand, a single tenancy model would provide a means to roll updates out to a group of customers at a time, and spread the risk of data corruption - i.e. if something goes wrong with a database, it will impact one customer instead of all customers. With this idea, I was thinking of having a single web front-end which would connect to a single customer database upon login. Thus, when a new customer creates an account, a new database would be created (each customer would have their own db with multiple users as needed for the customer). In this model, a db update would require either a process to go through each db to apply schema changes, or a trigger upon logging in to initiate a schema update similar to the client-server model currently in use. Can anyone point me to information for similar applications which have been ported from client-server to SaaS? Or provide any pointers to consider? Basically I'm looking for architecture examples of taking a departmental application and making it available as a self service website for multiple customers. Thanks for any suggestions, resources, etc.

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• Best Practices / Patterns for Enterprise Protection/Remediation of SSNs (Social Security Numbers)

  - by Erik Neu

  I am interested in hearing about enterprise solutions for SSN handling. (I looked pretty hard for any pre-existing post on SO, including reviewing the terriffic SO automated "Related Questions" list, and did not find anything, so hopefully this is not a repeat.) First, I think it is important to enumerate the reasons systems/databases use SSNs: (note—these are reasons for de facto current state—I understand that many of them are not good reasons) Required for Interaction with External Entities. This is the most valid case—where external entities your system interfaces with require an SSN. This would typically be government, tax and financial. SSN is used to ensure system-wide uniqueness. SSN has become the default foreign key used internally within the enterprise, to perform cross-system joins. SSN is used for user authentication (e.g., log-on) The enterprise solution that seems optimum to me is to create a single SSN repository that is accessed by all applications needing to look up SSN info. This repository substitutes a globally unique, random 9-digit number (ASN) for the true SSN. I see many benefits to this approach. First of all, it is obviously highly backwards-compatible—all your systems "just" have to go through a major, synchronized, one-time data-cleansing exercise, where they replace the real SSN with the alternate ASN. Also, it is centralized, so it minimizes the scope for inspection and compliance. (Obviously, as a negative, it also creates a single point of failure.) This approach would solve issues 2 and 3, without ever requiring lookups to get the real SSN. For issue #1, authorized systems could provide an ASN, and be returned the real SSN. This would of course be done over secure connections, and the requesting systems would never persist the full SSN. Also, if the requesting system only needs the last 4 digits of the SSN, then that is all that would ever be passed. Issue #4 could be handled the same way as issue #1, though obviously the best thing would be to move away from having users supply an SSN for log-on. There are a couple of papers on this: UC Berkely: http://bit.ly/bdZPjQ Oracle Vault: bit.ly/cikbi1

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• Variable sized packet structs with vectors

  - by Rev316

  Lately I've been diving into network programming, and I'm having some difficulty constructing a packet with a variable "data" property. Several prior questions have helped tremendously, but I'm still lacking some implementation details. I'm trying to avoid using variable sized arrays, and just use a vector. But I can't get it to be transmitted correctly, and I believe it's somewhere during serialization. Now for some code. Packet Header class Packet { public: void* Serialize(); bool Deserialize(void *message); unsigned int sender_id; unsigned int sequence_number; std::vector<char> data; }; Packet ImpL typedef struct { unsigned int sender_id; unsigned int sequence_number; std::vector<char> data; } Packet; void* Packet::Serialize(int size) { Packet* p = (Packet *) malloc(8 + 30); p->sender_id = htonl(this->sender_id); p->sequence_number = htonl(this->sequence_number); p->data.assign(size,'&'); //just for testing purposes } bool Packet::Deserialize(void *message) { Packet *s = (Packet*)message; this->sender_id = ntohl(s->sender_id); this->sequence_number = ntohl(s->sequence_number); this->data = s->data; } During execution, I simply create a packet, assign it's members, and send/receive accordingly. The above methods are only responsible for serialization. Unfortunately, the data never gets transferred. Couple of things to point out here. I'm guessing the malloc is wrong, but I'm not sure how else to compute it (i.e. what other value it would be). Other than that, I'm unsure of the proper way to use a vector in this fashion, and would love for someone to show me how (code examples please!) :) Edit: I've awarded the question to the most comprehensive answer regarding the implementation with a vector data property. Appreciate all the responses!

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• How to I serialize a large graph of .NET object into a SQL Server BLOB without creating a large bu

  - by Ian Ringrose

  We have code like: ms = New IO.MemoryStream bin = New System.Runtime.Serialization.Formatters.Binary.BinaryFormatter bin.Serialize(ms, largeGraphOfObjects) dataToSaveToDatabase = ms.ToArray() // put dataToSaveToDatabase in a Sql server BLOB But the memory steam allocates a large buffer from the large memory heap that is giving us problems. So how can we stream the data without needing enough free memory to hold the serialized objects. I am looking for a way to get a Stream from SQL server that can then be passed to bin.Serialize() so avoiding keeping all the data in my processes memory. Likewise for reading the data back... Some more background. This is part of a complex numerical processing system that processes data in near real time looking for equipment problems etc, the serialization is done to allow a restart when there is a problem with data quality from a data feed etc. (We store the data feeds and can rerun them after the operator has edited out bad values.) Therefore we serialize the object a lot more often then we de-serialize them. The objects we are serializing include very large arrays mostly of doubles as well as a lot of small “more normal” objects. We are pushing the memory limit on a 32 bit system and make the garage collector work very hard. (Effects are being made elsewhere in the system to improve this, e.g. reusing large arrays rather then create new arrays.) Often the serialization of the state is the last straw that courses an out of memory exception; our peak memory usage is while this serialization is being done. I think we get large memory pool fragmentation when we de-serialize the object, I expect there are also other problem with large memory pool fragmentation given the size of the arrays. (This has not yet been investigated, as the person that first looked at this is a numerical processing expert, not a memory management expert.) Are customers use a mix of Sql Server 2000, 2005 and 2008 and we would rather not have different code paths for each version of Sql Server if possible. We can have many active models at a time (in different process, across many machines), each model can have many saved states. Hence the saved state is stored in a database blob rather then a file. As the spread of saving the state is important, I would rather not serialize the object to a file, and then put the file in a BLOB one block at a time. Other related questions I have asked How to Stream data from/to SQL Server BLOB fields? Is there a SqlFileStream like class that works with Sql Server 2005?

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• Display lable character by character using javascript

  - by Muhammad Sajid

  Hi, I am creating Hang a Man using PHP, MySQL & Javascript. Every thing is going perfect, I get a word randomly from DB show it as a label apply it a class where display = none. Now when I click on a Character that character become disable fine which i actually want but the label-character does not show. My code is: <link href="style.css" rel="stylesheet" type="text/css" media="screen" /> <?php include( 'config.php' ); $question = questions(); // Get question. $alpha = alphabats(); // Get alphabets. ?> <script language="javascript"> function clickMe( name ){ var question = '<?php echo $question; ?>'; var questionLen = <?php echo strlen($question); ?>; for ( var i = 0; i < questionLen; i++ ){ if ( question[i] == name ){ var link = document.getElementById( name ); link.style.display = 'none'; var label = document.getElementById( 'questionLabel' + i ); label.style.display = 'none'; } } } </script> <div> <table align="center" style="border:solid 1px"> <tr> <?php for ( $i = 0; $i < 26; $i++ ) { echo "<td><a href='#' id=$alpha[$i] name=$alpha[$i] onclick=clickMe('$alpha[$i]');>". $alpha[$i] ."</a>&nbsp;</td>"; } ?> </tr> </table> <br/> <table align="center" style="border:solid 1px"> <tr> <?php for ( $i = 0; $i < strlen($question); $i++ ) { echo "<td class='question'><label id=questionLabel$i >". $question[$i] ."</label></td>"; } ?> </tr> </table> </div>

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• Function-Local Static Const variable Initialization semantics.

  - by Hassan Syed

  The questions are in bold, for those that cannot be bothered reading a question in depth. This is a followup to this question. It is to do with the initialization semantics of static variables in functions. Static variables should be initialized once, and their internal state might be altered later - as I (currently) do in the linked question. However, the code in question does not require the feature to change the state of the variable later. Let me clarrify my position, since I don't require the string object's internal state to change. The code is for a trait class for meta programming, and as such would would benifit from a const char * const ptr -- thus Ideally a local cost static const variable is needed. My educated guess is that in this case the string in question will be optimally placed in memory by the link-loader, and that the code is more secure and maps to the intended semantics. This leads to the semantics of such a variable "The C++ Programming language Third Edition -- Stroustrup" does not have anything (that I could find) to say about this matter. All that is said is that the variable is initialized once when the flow of control of the thread first reaches the code. This leads me to ponder if the following code would be sensible, and if not what are the intended semantics ?. #include <iostream> const char * const GetString(const char * x_in) { static const char * const x = x_in; return x; } int main() { const char * const temp = GetString("yahoo"); std::cout << temp << std::endl; const char * const temp2 = GetString("yahoo2"); std::cout << temp2 << std::endl; } The following compiles on GCC and prints "yahoo" twice. Which is what I want -- However it might not be standards compliant (which is why I post this question). It might be more elegant to have two functions, "SetString" and "String" where the latter forwards to the first. If it is standards compliant does someone know of a templates implementation in boost (or elsewhere) ?

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