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• A Guided Tour of Complexity

  - by JoshReuben

  I just re-read Complexity – A Guided Tour by Melanie Mitchell , protégé of Douglas Hofstadter ( author of “Gödel, Escher, Bach”) http://www.amazon.com/Complexity-Guided-Tour-Melanie-Mitchell/dp/0199798109/ref=sr_1_1?ie=UTF8&qid=1339744329&sr=8-1 here are some notes and links:   Evolved from Cybernetics, General Systems Theory, Synergetics some interesting transdisciplinary fields to investigate: Chaos Theory - http://en.wikipedia.org/wiki/Chaos_theory – small differences in initial conditions (such as those due to rounding errors in numerical computation) yield widely diverging outcomes for chaotic systems, rendering long-term prediction impossible. System Dynamics / Cybernetics - http://en.wikipedia.org/wiki/System_Dynamics – study of how feedback changes system behavior Network Theory - http://en.wikipedia.org/wiki/Network_theory – leverage Graph Theory to analyze symmetric  / asymmetric relations between discrete objects Algebraic Topology - http://en.wikipedia.org/wiki/Algebraic_topology – leverage abstract algebra to analyze topological spaces There are limits to deterministic systems & to computation. Chaos Theory definitely applies to training an ANN (artificial neural network) – different weights will emerge depending upon the random selection of the training set. In recursive Non-Linear systems http://en.wikipedia.org/wiki/Nonlinear_system – output is not directly inferable from input. E.g. a Logistic map: Xt+1 = R Xt(1-Xt) Different types of bifurcations, attractor states and oscillations may occur – e.g. a Lorenz Attractor http://en.wikipedia.org/wiki/Lorenz_system Feigenbaum Constants http://en.wikipedia.org/wiki/Feigenbaum_constants express ratios in a bifurcation diagram for a non-linear map – the convergent limit of R (the rate of period-doubling bifurcations) is 4.6692016 Maxwell’s Demon - http://en.wikipedia.org/wiki/Maxwell%27s_demon - the Second Law of Thermodynamics has only a statistical certainty – the universe (and thus information) tends towards entropy. While any computation can theoretically be done without expending energy, with finite memory, the act of erasing memory is permanent and increases entropy. Life & thought is a counter-example to the universe’s tendency towards entropy. Leo Szilard and later Claude Shannon came up with the Information Theory of Entropy - http://en.wikipedia.org/wiki/Entropy_(information_theory) whereby Shannon entropy quantifies the expected value of a message’s information in bits in order to determine channel capacity and leverage Coding Theory (compression analysis). Ludwig Boltzmann came up with Statistical Mechanics - http://en.wikipedia.org/wiki/Statistical_mechanics – whereby our Newtonian perception of continuous reality is a probabilistic and statistical aggregate of many discrete quantum microstates. This is relevant for Quantum Information Theory http://en.wikipedia.org/wiki/Quantum_information and the Physics of Information - http://en.wikipedia.org/wiki/Physical_information. Hilbert’s Problems http://en.wikipedia.org/wiki/Hilbert's_problems pondered whether mathematics is complete, consistent, and decidable (the Decision Problem – http://en.wikipedia.org/wiki/Entscheidungsproblem – is there always an algorithm that can determine whether a statement is true).  Godel’s Incompleteness Theorems http://en.wikipedia.org/wiki/G%C3%B6del's_incompleteness_theorems  proved that mathematics cannot be both complete and consistent (e.g. “This statement is not provable”). Turing through the use of Turing Machines (http://en.wikipedia.org/wiki/Turing_machine symbol processors that can prove mathematical statements) and Universal Turing Machines (http://en.wikipedia.org/wiki/Universal_Turing_machine Turing Machines that can emulate other any Turing Machine via accepting programs as well as data as input symbols) that computation is limited by demonstrating the Halting Problem http://en.wikipedia.org/wiki/Halting_problem (is is not possible to know when a program will complete – you cannot build an infinite loop detector). You may be used to thinking of 1 / 2 / 3 dimensional systems, but Fractal http://en.wikipedia.org/wiki/Fractal systems are defined by self-similarity & have non-integer Hausdorff Dimensions !!!  http://en.wikipedia.org/wiki/List_of_fractals_by_Hausdorff_dimension – the fractal dimension quantifies the number of copies of a self similar object at each level of detail – eg Koch Snowflake - http://en.wikipedia.org/wiki/Koch_snowflake Definitions of complexity: size, Shannon entropy, Algorithmic Information Content (http://en.wikipedia.org/wiki/Algorithmic_information_theory - size of shortest program that can generate a description of an object) Logical depth (amount of info processed), thermodynamic depth (resources required). Complexity is statistical and fractal. John Von Neumann’s other machine was the Self-Reproducing Automaton http://en.wikipedia.org/wiki/Self-replicating_machine  . Cellular Automata http://en.wikipedia.org/wiki/Cellular_automaton are alternative form of Universal Turing machine to traditional Von Neumann machines where grid cells are locally synchronized with their neighbors according to a rule. Conway’s Game of Life http://en.wikipedia.org/wiki/Conway's_Game_of_Life demonstrates various emergent constructs such as “Glider Guns” and “Spaceships”. Cellular Automatons are not practical because logical ops require a large number of cells – wasteful & inefficient. There are no compilers or general program languages available for Cellular Automatons (as far as I am aware). Random Boolean Networks http://en.wikipedia.org/wiki/Boolean_network are extensions of cellular automata where nodes are connected at random (not to spatial neighbors) and each node has its own rule –> they demonstrate the emergence of complex  & self organized behavior. Stephen Wolfram’s (creator of Mathematica, so give him the benefit of the doubt) New Kind of Science http://en.wikipedia.org/wiki/A_New_Kind_of_Science proposes the universe may be a discrete Finite State Automata http://en.wikipedia.org/wiki/Finite-state_machine whereby reality emerges from simple rules. I am 2/3 through this book. It is feasible that the universe is quantum discrete at the plank scale and that it computes itself – Digital Physics: http://en.wikipedia.org/wiki/Digital_physics – a simulated reality? Anyway, all behavior is supposedly derived from simple algorithmic rules & falls into 4 patterns: uniform , nested / cyclical, random (Rule 30 http://en.wikipedia.org/wiki/Rule_30) & mixed (Rule 110 - http://en.wikipedia.org/wiki/Rule_110 localized structures – it is this that is interesting). interaction between colliding propagating signal inputs is then information processing. Wolfram proposes the Principle of Computational Equivalence - http://mathworld.wolfram.com/PrincipleofComputationalEquivalence.html - all processes that are not obviously simple can be viewed as computations of equivalent sophistication. Meaning in information may emerge from analogy & conceptual slippages – see the CopyCat program: http://cognitrn.psych.indiana.edu/rgoldsto/courses/concepts/copycat.pdf Scale Free Networks http://en.wikipedia.org/wiki/Scale-free_network have a distribution governed by a Power Law (http://en.wikipedia.org/wiki/Power_law - much more common than Normal Distribution). They are characterized by hubs (resilience to random deletion of nodes), heterogeneity of degree values, self similarity, & small world structure. They grow via preferential attachment http://en.wikipedia.org/wiki/Preferential_attachment – tipping points triggered by positive feedback loops. 2 theories of cascading system failures in complex systems are Self-Organized Criticality http://en.wikipedia.org/wiki/Self-organized_criticality and Highly Optimized Tolerance http://en.wikipedia.org/wiki/Highly_optimized_tolerance. Computational Mechanics http://en.wikipedia.org/wiki/Computational_mechanics – use of computational methods to study phenomena governed by the principles of mechanics. This book is a great intuition pump, but does not cover the more mathematical subject of Computational Complexity Theory – http://en.wikipedia.org/wiki/Computational_complexity_theory I am currently reading this book on this subject: http://www.amazon.com/Computational-Complexity-Christos-H-Papadimitriou/dp/0201530821/ref=pd_sim_b_1   stay tuned for that review!

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• Improving the Performance of the Secure Hash Algorithm (SHA-1)

  Parallelization can make a difference Algorithm - Math - Cryptography - Communication Theory - Parallel computing

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• Examples of different architecture methodologies

  - by Lane

  Is there a resource or site which illustrates building the same application (desktop or web) using several different contrasting architectures? Such as MVP versus MVVM versus MVC, etc. It would be very helpful to see how they look side-by-side using real-world code instead of comparing written theory to written theory. I've often found that something can be described well in a book, but when you go to implement it, the subtleties and weaknesses of the theory become readily apparent.

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• Select All CheckBoxes in GridView ASP.NET using JQuery

  - by dexter

  I have checkBoxes in my Gridview templete columns called "Category A" and "Category B". I want Select-All functionality, i.e. when the user checks the Select-All check Box in category A column, all the checkboxes must get checked under that column. Same for Category B. I am trying with the code below. The problem with my code is, it selects all the check boxes in the entire gridview, "Category A" as well as "Category B"s checkboxes. But, I want only checkboxes selected under the same column. function SelectAllCheckboxesA(chk) { $('#<%=gvSurveys.ClientID %>').find("input:checkbox").each(function() { if (this != chk) { if ($(this).hasClass('CatA') != false) { this.checked = chk.checked; } } else { alert($(this)); } }); } <asp:GridView ID="gvSurveys" runat="server" AutoGenerateColumns="false" AllowSorting="True" Width="1500px"> <Columns> <asp:TemplateField> <HeaderTemplate>Category A <asp:CheckBox ID="chkSelectAllCatA" runat="server" Visible="false" onclick="javascript:SelectAllCheckboxesA(this);" CssClass="SACatA" /> </HeaderTemplate> <ItemTemplate> <asp:CheckBox ID="chkCatA" runat="server" Enabled="false" CssClass="CatA" /> </ItemTemplate> </asp:TemplateField> <asp:TemplateField> <HeaderTemplate> Category B <asp:CheckBox ID="chkSelectAllCatB" runat="server" Visible="false" CssClass="CatB" onclick="javascript:SelectAllCheckboxesB(this);" /> </HeaderTemplate> <ItemTemplate> <asp:CheckBox ID="chkCatB" runat="server" Enabled="false" /> </ItemTemplate> </asp:TemplateField> </Columns> </asp:GridView>

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• rails search nested set (categories and sub categories)

  - by bob

  Hello, I am using the http://github.com/collectiveidea/awesome_nested_set awesome nested set plugin and currently, if I choose a sub category as my category_id for an item, I can not search by its parent. Category.parent Category.Child I choose Category.child as the category that my item is in. So now my item has category_id of 4 stored in it. If I go to a page in my rails application, lets say teh Category page and I am on the Category.parent's page, I want to show products that have category_id's of all the descendants as well. So ideally i want to have a find method that can take into account the descendants. You can get the descendants of a root by calling root.descendants (a built in plugin method). How would I go about making it so I can query a find that gets the descendants of a root instead of what its doing now which is binging up nothing unless the product had a specific category_id of the Category.parent. I hope I am being clear here. I either need to figure out a way to create a find method or named_scope that can query and return an array of objects that have id's corresponding tot he descendants of a root OR if I have any other options, what are they? I thought about creating a field in my products table like parent_id which can keep track of the parent so i can then create two named scopes one finding the parent stuff and one finding the child stuff and chaining them. I know I can create a named scope for each child and chain them together for multiple children but this seems a very tedious process and also, if you add more children, you would need to specify more named scopes.

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• Remaking this loop by user?

  - by Elliot

  I'm wondering if theres a best practice for what I'm trying to accomplish... First we have the model categories, categories, has_many posts. Now lets say, users add posts. Now, I have a page, that I want to display only the current user's posts by category. Lets say we have the following categories: A, B, and C User 1, has posted in Categories A and B. In my view I have something like: <% @categories.select {|cat| cat.posts.count > 0}.each do |category| %> <%= category.name %><br/> <% category.posts.select {|post| post.user == current_user}.each do |post| %> <%= post.content %><br/> <% end %> <% end %> For the most part its almost there. The issue is, it will still show an empty category if any posts have been entered in it at all (even if the current user has not input posts into that category. So the question boils down to: How do I make the following loop only count posts in the category from the current user? <% @categories.select {|cat| cat.posts.count 0}.each do |category| % Best, Elliot

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• Core Data Relationship problem

  - by awattar

  I have a very simple model with two objects: Name and Category. One Name can be in many Categories (it's one way relationship). I'm trying to create 8 Categories every with 8 Names. Example code: NSMutableArray *localArray = [NSMutableArray arrayWithObjects: [NSMutableDictionary dictionaryWithObjectsAndKeys: @"g1", @"Name", @"g1", @"Icon", [NSNumber numberWithBool:YES] , @"Male", nil], [NSMutableDictionary dictionaryWithObjectsAndKeys: @"g2", @"Name", @"g2", @"Icon", [NSNumber numberWithBool:YES] , @"Male", nil], [NSMutableDictionary dictionaryWithObjectsAndKeys: @"g3", @"Name", @"g3", @"Icon", [NSNumber numberWithBool:YES] , @"Male", nil], [NSMutableDictionary dictionaryWithObjectsAndKeys: @"g4", @"Name", @"g4", @"Icon", [NSNumber numberWithBool:YES] , @"Male", nil], [NSMutableDictionary dictionaryWithObjectsAndKeys: @"g5", @"Name", @"g5", @"Icon", [NSNumber numberWithBool:YES] , @"Male", nil], [NSMutableDictionary dictionaryWithObjectsAndKeys: @"g6", @"Name", @"g6", @"Icon", [NSNumber numberWithBool:YES] , @"Male", nil], [NSMutableDictionary dictionaryWithObjectsAndKeys: @"g7", @"Name", @"g7", @"Icon", [NSNumber numberWithBool:YES] , @"Male", nil], [NSMutableDictionary dictionaryWithObjectsAndKeys: @"g8", @"Name", @"g8", @"Icon", [NSNumber numberWithBool:YES] , @"Male", nil], nil]; NSMutableArray *localArray2 = [NSMutableArray arrayWithObjects: [NSMutableDictionary dictionaryWithObjectsAndKeys: @"Test1", @"Name", nil], [NSMutableDictionary dictionaryWithObjectsAndKeys: @"Test2", @"Name", nil], [NSMutableDictionary dictionaryWithObjectsAndKeys: @"Test3", @"Name", nil], [NSMutableDictionary dictionaryWithObjectsAndKeys: @"Test4", @"Name", nil], [NSMutableDictionary dictionaryWithObjectsAndKeys: @"Test5", @"Name", nil], [NSMutableDictionary dictionaryWithObjectsAndKeys: @"Test6", @"Name", nil], [NSMutableDictionary dictionaryWithObjectsAndKeys: @"Test7", @"Name", nil], [NSMutableDictionary dictionaryWithObjectsAndKeys: @"Test8", @"Name", nil], nil]; NSError *error; NSManagedObjectContext *moc = [(AppDelegate *)[[UIApplication sharedApplication] delegate] managedObjectContext]; for(NSMutableDictionary *item in localArray) { NSManagedObject *category = [NSEntityDescription insertNewObjectForEntityForName:@"Category" inManagedObjectContext:managedObjectContext]; [category setValue:[item objectForKey:@"Name"] forKey:@"Name"]; [category setValue:[item objectForKey:@"Icon"] forKey:@"Icon"]; [category setValue:[item objectForKey:@"Male"] forKey:@"Male"]; for(NSMutableDictionary *item2 in localArray2) { NSManagedObject *name = [NSEntityDescription insertNewObjectForEntityForName:@"Name" inManagedObjectContext:managedObjectContext]; [name setValue:[item2 objectForKey:@"Name"] forKey:@"Name"]; [[name mutableSetValueForKey:@"CategoryRelationship"] addObject:category]; } } [moc save:&error]; And here's a problem - i've checked that 8 Categories are saved, 64 Names are saved but only 8 from all Names are connected with any category. So when i query for Names in Categories [NSPredicate predicateWithFormat:@"CategoryRelationship.@count != 0"] there are 8 elements and when [NSPredicate predicateWithFormat:@"CategoryRelationship.@count = 0"] there are 56 elements. What is going one here?

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• iphone mkmapview

  - by karthik

  Hi, This is karthik. I am developing an app using mapview in iphone. I have to use two different pins to show user locations. That two users are different type . One user is belong to some category and another one is some other category. I have to check that category and want to plot pin depend upon that category. When I try to do that, that pin is not showing properly. For a certain category it shows another pin, not what i set there. Can anyone help me? What i need is i want to load two different pins in map depend upon some category. For example , if that category is shopping mall then i have to show building image then if there is any garden i have to show some other image at a same time not one by one . I want to plot two pins with different category at the same time. For that,what could i do? I tried lot of solution , but its not showing properly. Help me?

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• sqlite3 - stringWithUTF8String is leaking!

  - by Darko Hebrang

  I would appreciate if someone could help me solve my leaking problem. The leaks occur at: aImage, aCategory, aDescription, category and categories. I release them in dealloc, but obviously that is not sufficient: -(void) readListFromDatabase:(char *) sqlStatement { // Setup some globals databaseName = @"mydatabase.sql"; // Get the path to the documents directory and append the databaseName NSArray *documentPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); NSString *documentsDir = [documentPaths objectAtIndex:0]; databasePath = [documentsDir stringByAppendingPathComponent:databaseName]; // Setup the database object sqlite3 *database; // Init the categories Array categories = [[NSMutableArray alloc] init]; // Open the database from the users filessytem if(sqlite3_open([databasePath UTF8String], &database) == SQLITE_OK) { // Setup the SQL Statement and compile it for faster access sqlite3_stmt *compiledStatement; if(sqlite3_prepare_v2(database, sqlStatement, -1, &compiledStatement, NULL) == SQLITE_OK) { // Loop through the results and add them to the feeds array while(sqlite3_step(compiledStatement) == SQLITE_ROW) { // Read the data from the result row aImage = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 0)]; aCategory = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 1)]; aDescription = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 2)]; // Create a new category object with the data from the database category=[[Category alloc] initWithName:aImage category_name:aCategory description_text:aDescription]; // Add the category object to the categories Array [categories addObject:category]; [category release]; } } // Release the compiled statement from memory sqlite3_finalize(compiledStatement); } sqlite3_close(database); } - (void)dealloc { [databaseName release]; [databasePath release]; [categories release]; [aImage release]; [aCategory release]; [aDescription release]; [category release]; [super dealloc]; }

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• Android ExpandableListView From Database

  - by SterAllures

  I want to create a two level ExpandableListView from a local database. The group level I want to get the names from the database Category table category_id | name ------------------- 1 | NameOfCategory the children level I want to get the names from the List table list_id | name | foreign_category_id -------------------------------- 1 | Listname | 1 I've got a method in DatabaseDAO to get all the values from the table public List<Category> getAllCategories() { database = dbHelper.getReadableDatabase(); List<Category> categories = new ArrayList<Category>(); Cursor cursor = database.query(SQLiteHelper.TABLE_CATEGORY, null, null, null, null, null, null); cursor.moveToFirst(); while(!cursor.isAfterLast()) { Category category = cursorToCategory(cursor); categories.add(category); cursor.moveToNext(); } cursor.close(); return categories; } Now adding the names to the group level is easy I do it the following way: ArrayList<String> groups; for(Category c : databaseDao.getAllCategories()) { groups.add(c.getName()); } Now I want to add the children to the ExpandableListView in the following array ArrayList<ArrayList<ArrayList<String>>> children;. How do I get the children under the correct group name? I think it has to do somenthing with groups.indexOf() but in the list table I only have a foreign category_id and not the actual name.

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• jquery closest dl element

  - by Sebastiaan

  HTML: <dl id="feature-list"> <dt id="basic" class="category-name"> <dd id="basic-toggle" class="category-recepient"> <div class="feature"> <div class="feature-content"> <input id="checkbox1" type="checkbox"> </div> </div> </dd> <dt id="options" class="category-name"> <dd id="options-toggle" class="category-recepient"> <div class="feature"> <div class="feature-content"> <input id="checkbox2" type="checkbox"> </div> </div> </dd> </dl> JQUERY $('input').change(function () { var value = $(this).closest("dt"); //do something with value.id }); $(this).closest("dt") returns the checkbox instead of <dt id="(category)" class="category-name"> I tried $(this).closest(.category-name), $(this).closest("dt").find(.category-name)

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• EFv1 mapping 1 to many Relationship to POCOs

  - by Scott

  I'm trying to work through a problem where I'm mapping EF Entities to POCO which serve as DTO. I have two tables within my database, say Products and Categories. A Product belongs to one category and one category may contain many Products. My EF entities are named efProduct and efCategory. Within each entity there is the proper Navigation Property between efProduct and efCategory. My Poco objects are simple public class Product { public string Name { get; set; } public int ID { get; set; } public double Price { get; set; } public Category ProductType { get; set; } } public class Category { public int ID { get; set; } public string Name { get; set; } public List<Product> products { get; set; } } To get a list of products I am able to do something like public IQueryable<Product> GetProducts() { return from p in ctx.Products select new Product { ID = p.ID, Name = p.Name, Price = p.Price ProductType = p.Category }; } However there is a type mismatch error because p.Category is of type efCategory. How can I resolve this? That is, how can I convert p.Category to type Category? I know in .NET EF has added support for POCO, but I'm forced to use .NET 3.5 SP1.

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• how to call subactivity of another application android?

  - by Are

  Hi. To call main activity I saw componentName class in android. intent = new Intent(new ComponentName(packageNam,classname); if same is used in case of child activity, I got error , "is activity delcared in andorid manifest?" like error. how to call app1 child activity in app2 by using intent ? In app1 the activity is declared like this in manifest <activity android:name=".activity.MessageCompose" android:label="@string/app_name" android:enabled="false"> - <intent-filter> <action android:name="android.intent.action.VIEW" /> <action android:name="android.intent.action.SENDTO" /> <data android:scheme="mailto" /> <category android:name="android.intent.category.DEFAULT" /> <category android:name="android.intent.category.BROWSABLE" /> </intent-filter> - <intent-filter android:label="@string/app_name"> <action android:name="android.intent.action.SEND" /> <data android:mimeType="*/*" /> <category android:name="android.intent.category.DEFAULT" /> </intent-filter> - <intent-filter android:label="@string/app_name"> <action android:name="android.intent.action.SEND_MULTIPLE" /> <data android:mimeType="*/*" /> <category android:name="android.intent.category.DEFAULT" /> </intent-filter> </activity>

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• Need a set based solution to group rows

  - by KM

  I need to group a set of rows based on the Category column, and also limit the combined rows based on the SUM(Number) column to be less than or equal to the @Limit value. For each distinct Category column I need to identify "buckets" that are <=@limit. If the SUM(Number) of all the rows for a Category column are <=@Limit then there will be only 1 bucket for that Category value (like 'CCCC' in the sample data). However if the SUM(Number)@limit, then there will be multiple bucket rows for that Category value (like 'AAAA' in the sample data), and each bucket must be <=@Limit. There can be as many buckets as necessary. Also, look at Category value 'DDDD', its one row is greater than @Limit all by itself, and gets split into two rows in the result set. Given this simplified data: DECLARE @Detail table (DetailID int primary key, Category char(4), Number int) SET NOCOUNT ON INSERT @Detail VALUES ( 1, 'AAAA',100) INSERT @Detail VALUES ( 2, 'AAAA', 50) INSERT @Detail VALUES ( 3, 'AAAA',300) INSERT @Detail VALUES ( 4, 'AAAA',200) INSERT @Detail VALUES ( 5, 'BBBB',500) INSERT @Detail VALUES ( 6, 'CCCC',200) INSERT @Detail VALUES ( 7, 'CCCC',100) INSERT @Detail VALUES ( 8, 'CCCC', 50) INSERT @Detail VALUES ( 9, 'DDDD',800) INSERT @Detail VALUES (10, 'EEEE',100) SET NOCOUNT OFF DECLARE @Limit int SET @Limit=500 I need one of these result set: DetailID Bucket | DetailID Category Bucket -------- ------ | -------- -------- ------ 1 1 | 1 'AAAA' 1 2 1 | 2 'AAAA' 1 3 1 | 3 'AAAA' 1 4 2 | 4 'AAAA' 2 5 3 OR 5 'BBBB' 1 6 4 | 6 'CCCC' 1 7 4 | 7 'CCCC' 1 8 4 | 8 'CCCC' 1 9 5 | 9 'DDDD' 1 9 6 | 9 'DDDD' 2 10 7 | 10 'EEEE' 1

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• RESTful API: How to model JSON representation?

  - by Jan P.

  I am designing a RESTful API for a booking application. You can request a list of accommodations. And that's where I don't really know how to design the JSON represenation. This is my XML representation: <?xml version="1.0" encoding="utf-8"?> <accommodations> <accommodation> <name>...</name> <category>couch</category> </accommodation> <accommodation> <name>...</name> <category>room</category> </accommodation> <accommodations> My first try to convert this to JSON resulted in this output (1): { "0": { "name": "...", "category": "couch" }, "1": { "name": "...", "category": "room" } } But as I looked how others APIs did it, I found something looking more like this (2): [ { "name": "...", "category": "couch" }, { "name": "...", "category": "room" } ] I know version 1 is an object, and version 2 an array. But which one is better in this case?

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• Jboss logging issue

  - by balaji

  Our application is deployed on JBoss As 4.0x and we face some issues with JBoss logging. Whenever the server is restarted, JBoss stops logging, and there is no update in server.log. After that it is not updating the log file. Then we do touch cmd on log4j.xml, so that it creates the log files again. Please help me in fixing the issue we cant do touch everytime. We face this issue in both the nodes. I could not figure where the problem is? If any other issues, we can check the log files. If log itself is not getting updated/logged, how can we move further in analyzing the issues without the recent/updated logs? Contents of log4j.xml, copied from the comments below: <appender name="FILE" class="org.jboss.logging.appender.DailyRollingFileAppender"> <errorHandler class="org.jboss.logging.util.OnlyOnceErrorHandler"/> <param name="File" value="${jboss.server.log.dir}/server.log"/> <param name="Append" value="false"/> <param name="DatePattern" value="'.'yyyy-MM-dd"/> <layout class="org.apache.log4j.PatternLayout"> <param name="ConversionPattern" value="%d %-5p [%c] %m%n"/> </layout> </appender> <appender name="CONSOLE" class="org.apache.log4j.ConsoleAppender"> <errorHandler class="org.jboss.logging.util.OnlyOnceErrorHandler"/> <param name="Target" value="System.out"/> <param name="Threshold" value="INFO"/> <layout class="org.apache.log4j.PatternLayout"> <!-- The default pattern: Date Priority [Category] Message\n --> <param name="ConversionPattern" value="%d{ABSOLUTE} %-5p [%c{1}] %m%n"/> </layout> </appender> <root> <appender-ref ref="CONSOLE"/> <appender-ref ref="FILE"/> </root> <category name="org.apache"> <priority value="INFO"/> </category> <category name="org.apache.axis"> <priority value="INFO"/> </category> <category name="org.jgroups"> <priority value="WARN"/> </category> <category name="jacorb"> <priority value="WARN"/> </category> <category name="org.jboss.management"> <priority value="INFO"/> </category>

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• Looking for a better design: A readonly in-memory cache mechanism

  - by Dylan Lin

  Hi all, I have a Category entity (class), which has zero or one parent Category and many child Categories -- it's a tree structure. The Category data is stored in a RDBMS, so for better performance, I want to load all categories and cache them in memory while launching the applicaiton. Our system can have plugins, and we allow the plugin authors to access the Category Tree, but they should not modify the cached items and the tree(I think a non-readonly design might cause some subtle bugs in this senario), only the system knows when and how to refresh the tree. Here are some demo codes: public interface ITreeNode<T> where T : ITreeNode<T> { // No setter T Parent { get; } IEnumerable<T> ChildNodes { get; } } // This class is generated by O/R Mapping tool (e.g. Entity Framework) public class Category : EntityObject { public string Name { get; set; } } // Because Category is not stateless, so I create a cleaner view class for Category. // And this class is the Node Type of the Category Tree public class CategoryView : ITreeNode<CategoryView> { public string Name { get; private set; } #region ITreeNode Memebers public CategoryView Parent { get; private set; } private List<CategoryView> _childNodes; public IEnumerable<CategoryView> ChildNodes { return _childNodes; } #endregion public static CategoryView CreateFrom(Category category) { // here I can set the CategoryView.Name property } } So far so good. However, I want to make ITreeNode interface reuseable, and for some other types, the tree should not be readonly. We are not able to do this with the above readonly ITreeNode, so I want the ITreeNode to be like this: public interface ITreeNode<T> { // has setter T Parent { get; set; } // use ICollection<T> instead of IEnumerable<T> ICollection<T> ChildNodes { get; } } But if we make the ITreeNode writable, then we cannot make the Category Tree readonly, it's not good. So I think if we can do like this: public interface ITreeNode<T> { T Parent { get; } IEnumerable<T> ChildNodes { get; } } public interface IWritableTreeNode<T> : ITreeNode<T> { new T Parent { get; set; } new ICollection<T> ChildNodes { get; } } Is this good or bad? Are there some better designs? Thanks a lot! :)

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• ASP.NET MVC validation problem

  - by ile

  ArticleRepostitory.cs: using System; using System.Collections.Generic; using System.Linq; using System.Web; using CMS.Model; using System.Web.Mvc; namespace CMS.Models { public class ArticleDisplay { public ArticleDisplay() { } public int CategoryID { set; get; } public string CategoryTitle { set; get; } public int ArticleID { set; get; } public string ArticleTitle { set; get; } public DateTime ArticleDate; public string ArticleContent { set; get; } } public class ArticleRepository { private DB db = new DB(); // // Query Methods public IQueryable<ArticleDisplay> FindAllArticles() { var result = from category in db.ArticleCategories join article in db.Articles on category.CategoryID equals article.CategoryID select new ArticleDisplay { CategoryID = category.CategoryID, CategoryTitle = category.Title, ArticleID = article.ArticleID, ArticleTitle = article.Title, ArticleDate = article.Date, ArticleContent = article.Content }; return result; } public IQueryable<ArticleDisplay> FindTodayArticles() { var result = from category in db.ArticleCategories join article in db.Articles on category.CategoryID equals article.CategoryID where article.Date == DateTime.Today select new ArticleDisplay { CategoryID = category.CategoryID, CategoryTitle = category.Title, ArticleID = article.ArticleID, ArticleTitle = article.Title, ArticleDate = article.Date, ArticleContent = article.Content }; return result; } public Article GetArticle(int id) { return db.Articles.SingleOrDefault(d => d.ArticleID == id); } public IQueryable<ArticleDisplay> DetailsArticle(int id) { var result = from category in db.ArticleCategories join article in db.Articles on category.CategoryID equals article.CategoryID where id == article.ArticleID select new ArticleDisplay { CategoryID = category.CategoryID, CategoryTitle = category.Title, ArticleID = article.ArticleID, ArticleTitle = article.Title, ArticleDate = article.Date, ArticleContent = article.Content }; return result; } // // Insert/Delete Methods public void Add(Article article) { db.Articles.InsertOnSubmit(article); } public void Delete(Article article) { db.Articles.DeleteOnSubmit(article); } // // Persistence public void Save() { db.SubmitChanges(); } } } ArticleController.cs: using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.Mvc; using System.Web.Mvc.Ajax; using CMS.Models; using CMS.Model; namespace CMS.Controllers { public class ArticleController : Controller { ArticleRepository articleRepository = new ArticleRepository(); ArticleCategoryRepository articleCategoryRepository = new ArticleCategoryRepository(); // // GET: /Article/ public ActionResult Index() { var allArticles = articleRepository.FindAllArticles().ToList(); return View(allArticles); } // // GET: /Article/Details/5 public ActionResult Details(int id) { var article = articleRepository.DetailsArticle(id).Single(); if (article == null) return View("NotFound"); return View(article); } // // GET: /Article/Create public ActionResult Create() { ViewData["categories"] = new SelectList ( articleCategoryRepository.FindAllCategories().ToList(), "CategoryId", "Title" ); Article article = new Article() { Date = DateTime.Now, CategoryID = 1 }; return View(article); } // // POST: /Article/Create [AcceptVerbs(HttpVerbs.Post)] public ActionResult Create(Article article) { if (ModelState.IsValid) { try { // TODO: Add insert logic here articleRepository.Add(article); articleRepository.Save(); return RedirectToAction("Index"); } catch { return View(article); } } else { return View(article); } } // // GET: /Article/Edit/5 public ActionResult Edit(int id) { ViewData["categories"] = new SelectList ( articleCategoryRepository.FindAllCategories().ToList(), "CategoryId", "Title" ); var article = articleRepository.GetArticle(id); return View(article); } // // POST: /Article/Edit/5 [AcceptVerbs(HttpVerbs.Post)] public ActionResult Edit(int id, FormCollection collection) { Article article = articleRepository.GetArticle(id); try { // TODO: Add update logic here UpdateModel(article, collection.ToValueProvider()); articleRepository.Save(); return RedirectToAction("Details", new { id = article.ArticleID }); } catch { return View(article); } } // // HTTP GET: /Article/Delete/1 public ActionResult Delete(int id) { Article article = articleRepository.GetArticle(id); if (article == null) return View("NotFound"); else return View(article); } // // HTTP POST: /Article/Delete/1 [AcceptVerbs(HttpVerbs.Post)] public ActionResult Delete(int id, string confirmButton) { Article article = articleRepository.GetArticle(id); if (article == null) return View("NotFound"); articleRepository.Delete(article); articleRepository.Save(); return View("Deleted"); } } } View/Article/Create.aspx: <%@ Page Title="" Language="C#" MasterPageFile="~/Views/Shared/Site.Master" Inherits="System.Web.Mvc.ViewPage<CMS.Model.Article>" %> <asp:Content ID="Content1" ContentPlaceHolderID="TitleContent" runat="server"> Create </asp:Content> <asp:Content ID="Content2" ContentPlaceHolderID="MainContent" runat="server"> <h2>Create</h2> <%= Html.ValidationSummary("Create was unsuccessful. Please correct the errors and try again.") %> <% using (Html.BeginForm()) {%> <fieldset> <legend>Fields</legend> <p> <label for="Title">Title:</label> <%= Html.TextBox("Title") %> <%= Html.ValidationMessage("Title", "*") %> </p> <p> <label for="Content">Content:</label> <%= Html.TextArea("Content", new { id = "Content" })%> <%= Html.ValidationMessage("Content", "*")%> </p> <p> <label for="Date">Date:</label> <%= Html.TextBox("Date") %> <%= Html.ValidationMessage("Date", "*") %> </p> <p> <label for="CategoryID">Category:</label> <%= Html.DropDownList("CategoryId", (IEnumerable<SelectListItem>)ViewData["categories"])%> </p> <p> <input type="submit" value="Create" /> </p> </fieldset> <% } %> <div> <%=Html.ActionLink("Back to List", "Index") %> </div> </asp:Content> If I remove DropDownList from .aspx file then validation (on date only because no other validation exists) works, but of course I can't create new article because one value is missing. If I leave dropdownlist and try to insert wrong date I get following error: System.InvalidOperationException: The ViewData item with the key 'CategoryId' is of type 'System.Int32' but needs to be of type 'IEnumerable'. If I enter correct date than the article is properly inserted. There's one other thing that's confusing me... For example, if I try manually add the categoyID: [AcceptVerbs(HttpVerbs.Post)] public ActionResult Create(Article article) { if (ModelState.IsValid) { try { // TODO: Add insert logic here // Manually add category value article.CategoryID = 1; articleRepository.Add(article); articleRepository.Save(); return RedirectToAction("Index"); } catch { return View(article); } } else { return View(article); } } ..I also get the above error. There's one other thing I noticed. If I add partial class Article, when returning to articleRepository.cs I get error that 'Article' is an ambiguous reference between 'CMS.Models.Article' and 'CMS.Model.Article' Any thoughts on this one?

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• overriding the Home Key Long press in a category.HOME activity.

  - by Profete162

  Hello all, I just created my own "Home" to replace the stock android one or Sense. All is working fine and I get all I want. My only problem is to replace to long press on home key ( that usually show the last 6 activities you launched) by my own launcher. I successfully replace the long press on MENU button with this code: @Override public boolean onKeyDown(int keyCode, KeyEvent event) { //Log.i(TAG,"Keycode: "+keyCode); if (keyCode == KeyEvent.KEYCODE_MENU) { // this tells the framework to start tracking for // a long press and eventual key up. it will only // do so if this is the first down (not a repeat). event.startTracking(); return true; } (...) and this part part for the long press: @Override public boolean onKeyLongPress(int keyCode, KeyEvent event) { //Log.i(TAG,"LONG"+keyCode); Toast.makeText(Launcher.this,"LONG "+keyCode, Toast.LENGTH_SHORT).show(); if (keyCode == KeyEvent.KEYCODE_MENU) { (...) But the problem is that I wasn't able to replace the KeyEvent.KEYCODE_MENU with KeyEvent.KEYCODE_HOME is that something locked in the code that avoid user to use a Home long press? Thank a lot for all the information you woulg give me.

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• NHibernate: No persister error

  - by Mike

  Hello, In my quest to further my knowledge, I'm trying to get get NHibernate running. I have the following structure to my solution Core Class Library Project Infrastructure Class Library Project MVC Application Project Test Project In my Core project I have created the following entity: using System; namespace Core.Domain.Model { public class Category { public virtual Guid Id { get; set; } public virtual string Name { get; set; } } } In my Infrastructure Project I have the following mapping: <?xml version="1.0" encoding="utf-8" ?> <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" namespace="Core.Domain.Model" assembly="Core"> <class name="Category" table="Categories" dynamic-update="true"> <cache usage="read-write"/> <id name="Id" column="Id" type="Guid"> <generator class="guid"/> </id> <property name="Name" length="100"/> </class> </hibernate-mapping> With the following config file: <hibernate-configuration xmlns="urn:nhibernate-configuration-2.2"> <session-factory> <property name="connection.driver_class">NHibernate.Driver.SqlClientDriver</property> <property name="connection.connection_string">server=xxxx;database=xxxx;Integrated Security=true;</property> <property name="show_sql">true</property> <property name="dialect">NHibernate.Dialect.MsSql2008Dialect</property> <property name="cache.use_query_cache">false</property> <property name="adonet.batch_size">100</property> <property name="proxyfactory.factory_class">NHibernate.ByteCode.Castle.ProxyFactoryFactory, NHibernate.ByteCode.Castle</property> <mapping assembly="Infrastructure" /> </session-factory> </hibernate-configuration> In my test project, I have the following Test [TestMethod] [DeploymentItem("hibernate.cfg.xml")] public void CanCreateCategory() { IRepository<Category> repo = new CategoryRepository(); Category category = new Category(); category.Name = "ASP.NET"; repo.Save(category); } I get the following error when I try to run the test: Test method Volunteer.Tests.CategoryTests.CanCreateCategory threw exception: NHibernate.MappingException: No persister for: Core.Domain.Model.Category. Any help would be greatly appreciated. I do have the cfg build action set to embedded resource. Thanks!

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• Odd Drag and drag bug in nested attributes Rails

  - by Senthil

  I've got this weird bug when trying to use drag and drag for two models (one nested within another). I've a category model which has many apps. In my category index page, I tried use "content_tag_for" to sort categories and apps within each category. But for some odd reason only the first element has drag, drop enabled. I can drag and drop categories all I want, but I can't drag the app in the second category, just the first category. Copy and paste gets ridiculously hopeless with HAML, so here's a Pastie instead. I made a sample app on heroku for you to check out here. Drag and drag work for both category and app, so I'm guessing it has to do something with the ul or li. Any help is appreciated. Thanks.

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• Odd Drag and drop sorting error Rails for nested attributes

  - by Senthil

  I've got this weird bug when trying to use drag and drag for two models (one nested within another). I've a category model which has many apps. In my category index page, I tried use "content_tag_for" to sort categories and apps within each category. But for some odd reason only the first element has drag, drop enabled. I can drag and drop categories all I want, but I can't drag the app in the second category, just the first category. Copy and paste gets ridiculously hopeless with HAML, so here's a Pastie instead. I made a sample app on heroku for you to check out here. Drag and drag work for both category and app, so I'm guessing it has to do something with the ul or li. Any help is appreciated. Thanks.

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• how to get obj2.name via obj1.categories(), thanks (gae python)

  - by zjm1126

  i using google-app-engine webapp ,code is : class Post(db.Model): title = db.StringProperty(required=True) def categories(self): return (x.category for x in self.postcategory_set) class Category(db.Model): name = db.StringProperty() class PostCategory(db.Model): post = db.ReferenceProperty(Post) category = db.ReferenceProperty(Category) class sss(webapp.RequestHandler): def get(self): obj1 = Post(title='hhaa') #obj1.title = 'haha' obj1.put() obj2 = Category() obj2.name='haha-kao' obj2.put() obj3=PostCategory() obj3.post=obj1 obj3.category=obj2 obj3.put() self.response.out.write(obj1.categories().get().name) the error is : Traceback (most recent call last): File "D:\Program Files\Google\google_appengine\google\appengine\ext\webapp\__init__.py", line 511, in __call__ handler.get(*groups) File "D:\zjm_code\helloworld\a.py", line 131, in get self.response.out.write(obj1.categories().get().name) AttributeError: 'generator' object has no attribute 'get' so how to get the obj2.name via obj1's method thanks

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• Binding Dropdownlist using jquery

  - by Geetha

  Hi All, I am try to bind the dropdowmlist using jquery. But is showing some error. Code: $.ajax({ type: "POST", contentType: "application/json; charset=utf-8", data: "{product: '" + product + "'}", url: "Search.aspx/FetchCategory", dataType: "json", success: function(data) { $.each(data.d, function() { $("#ddlCategory").append($("<option></option>").val(this['ID']).html(this['Category'])); }); } }); values in the data: [{"Category":"All","ID":"%"},"Category":"Action,"ID":"4"},"Category":"Race,"ID":"5"},"Category":"Sports,"ID":"6"}] Error: $("#ddlCategory").append($("").val(this['ID']).html(this['Category'])); Microsoft JScript runtime error: Object doesn't support this property or method Geetha

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• How do you assign a variable with the result of a if..else block?

  - by Pierre Olivier Martel

  I had an argument with a colleague about the best way to assign a variable in an if..else block. His orignal code was : @products = if params[:category] Category.find(params[:category]).products else Product.all end I rewrote it this way : if params[:category] @products = Category.find(params[:category]).products else @products = Product.all end This could also be rewritten with a one-liner using a ternery operator (? :) but let's pretend that product assignment was longer than a 100 character and couldn't fit in one line. Which of the two is clearer to you? The first solution takes a little less space but I thought that declaring a variable and assigning it three lines after can be more error prone. I also like to see my if and else aligned, makes it easier for my brain to parse it!

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