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  • Would you see any use of a Trilean (True, False, ??)

    - by Sybiam
    I don't know if I'm alone but sometimes I have a function that should return true or false. But in some case there would be a third result that would make more sense. In some language theses cases would be handled with integers or with exception. For exemple you want to handle the age of a user if he is over 18 years old. And you have a function like this. if(user.isAdult(country_code)){ //Go On }else{ // Block access or do nothing } But in some case depending how your app is built I could see case where the birthday field is incomplete. Then this function should return something undetermined. switch(user.isAdult()){ case true: // go on break; case undetermined: //Inform user birthday is incomplete case false: //Block access } As i said we can handle that with Exceptions and Int, but I would find it quite sexy to have a true, false, undetermined embeded in the language instead of using some home defined constants.

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  • How can i return abstract class from any factory?

    - by programmerist
    using System; using System.Collections.Generic; using System.Linq; using System.Web; namespace EfTestFactory { public abstract class _Company { public abstract List<Personel> GetPersonel(); public abstract List<Prim> GetPrim(); public abstract List<Finans> GetFinans(); } public abstract class _Radyoloji { public abstract List<string> GetRadyoloji(); } public abstract class _Satis { public abstract List<string> GetSatis(); } public abstract class _Muayene { public abstract List<string> GetMuayene(); } public class Company : _Company { public override List<Personel> GetPersonel() { throw new NotImplementedException(); } public override List<Prim> GetPrim() { throw new NotImplementedException(); } public override List<Finans> GetFinans() { throw new NotImplementedException(); } } public class Radyoloji : _Radyoloji { public override List<string> GetRadyoloji() { throw new NotImplementedException(); } } public class Satis : _Satis { public override List<string> GetSatis() { throw new NotImplementedException(); } } public class Muayene : _Muayene { public override List<string> GetMuayene() { throw new NotImplementedException(); } } public class GenoTipController { public object CreateByEnum(DataModelType modeltype) { string enumText = modeltype.ToString(); // will return for example "Company" Type classType = Type.GetType(enumText); // the Type for Company class object t = Activator.CreateInstance(classType); // create an instance of Company class return t; } } public class AntsController { static Dictionary<DataModelType, Func<object>> s_creators = new Dictionary<DataModelType, Func<object>>() { { DataModelType.Radyoloji, () => new _Radyoloji() }, { DataModelType.Company, () => new _Company() }, { DataModelType.Muayene, () => new _Muayene() }, { DataModelType.Satis, () => new _Satis() }, }; public object CreateByEnum(DataModelType modeltype) { return s_creators[modeltype](); } } public class CompanyView { public static List<Personel> GetPersonel() { GenoTipController controller = new GenoTipController(); _Company company = controller.CreateByEnum(DataModelType.Company) as _Company; return company.GetPersonel(); } } public enum DataModelType { Radyoloji, Satis, Muayene, Company } } if i write above codes i see some error: Cannot create an instance of abstract class or interface 'EfTestFactory_Company'How can i solve it? Look please below pic.

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  • WPF tree data binding

    - by Am
    Hi, I have a well defined tree repository. Where I can rename items, move them up, down, etc. Add new and delete. The data is stored in a table as follows: Index Parent Label Left Right 1 0 root 1 14 2 1 food 2 7 3 2 cake 3 4 4 2 pie 5 6 5 1 flowers 8 13 6 5 roses 9 10 7 5 violets 11 12 Representing the following tree: (1) root (14) (2) food (7) (8) flowers (13) (3) cake (4) (5) pie (6) (9) roeses (10) (11) violets (12) or root food cake pie flowers roses violets Now, my problem is how to represent this in a bindable way, so that a TreeView can handle all the possible data changes? Renaming is easy, all I need is to make the label an updatble field. But what if a user moves flowers above food? I can make the relevant data changes, but they cause a complete data change to all other items in the tree. And all the examples I found of bindable hierarchies are good for non static trees.. So my current (and bad) solution is to reload the displayed tree after relocation change. Any direction will be good. Thanks

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  • Binary Search Tree for specific intent

    - by Luís Guilherme
    We all know there are plenty of self-balancing binary search trees (BST), being the most famous the Red-Black and the AVL. It might be useful to take a look at AA-trees and scapegoat trees too. I want to do deletions insertions and searches, like any other BST. However, it will be common to delete all values in a given range, or deleting whole subtrees. So: I want to insert, search, remove values in O(log n) (balanced tree). I would like to delete a subtree, keeping the whole tree balanced, in O(log n) (worst-case or amortized) It might be useful to delete several values in a row, before balancing the tree I will most often insert 2 values at once, however this is not a rule (just a tip in case there is a tree data structure that takes this into account) Is there a variant of AVL or RB that helps me on this? Scapegoat-trees look more like this, but would also need some changes, anyone who has got experience on them can share some thougts? More precisely, which balancing procedure and/or removal procedure would help me keep this actions time-efficient?

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  • "Subforms" associated with tree view in VB

    - by knomdeguerre
    I am using VB Express 2008 to demonstrate my ideas for an improved UI for an existing product for my colleagues at work. The current UI has a certain page with ten tabs, allowing the user to define up to ten "things". The available choices for each of the ten "things" are all the same. On each of the ten tabs, there is a checkbox to enable that definition. Generally, a user will never use more than 5 or 6 unique definitions, the rest will remain disabled. So far, my prototype has a tree view control with one branch to contain this list of definitions, Add and Delete buttons. My idea is: there is one sub-branch to start with (corresponding to the first tab in the current UI); if the user wants addtional definitions, they click Add and other branches are added to the tree view, up to maximum of ten. I think I should be able to create a "class" that has a sub-UI (like a sub-form in Access) along with behavior code, that can be instantiated with each press of the Add button; each instantiation's settings can be set independently and is displayed in the main UI form )in a panel or frame) when selected in the tree view. For example, suppose the user Adds to make a total of three definitions: the tree view now has three sub-branches, each of which presents the same sub-UI with settings that can be set specific to the selected sub-branch. I'm sure it's possible but not sure how to do it. I know a comprehensive "answer" might be complicated and long, but I may just need some quick hints to get underway - don't be shy! Thanks in advance!

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  • WPF tree data binding model & repository

    - by Am
    Hi, I have a well defined tree repository. Where I can rename items, move them up, down, etc. Add new and delete. The data is stored in a table as follows: Index Parent Label Left Right 1 0 root 1 14 2 1 food 2 7 3 2 cake 3 4 4 2 pie 5 6 5 1 flowers 8 13 6 5 roses 9 10 7 5 violets 11 12 Representing the following tree: (1) root (14) (2) food (7) (8) flowers (13) (3) cake (4) (5) pie (6) (9) roeses (10) (11) violets (12) or root food cake pie flowers roses violets Now, my problem is how to represent this in a bindable way, so that a TreeView can handle all the possible data changes? Renaming is easy, all I need is to make the label an updatble field. But what if a user moves flowers above food? I can make the relevant data changes, but they cause a complete data change to all other items in the tree. And all the examples I found of bindable hierarchies are good for non static trees.. So my current (and bad) solution is to reload the displayed tree after relocation change. Any direction will be good. Thanks

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  • C# expression tree for ordinary code

    - by rwallace
    It's possible to create an expression tree, if you declare it as such. But is it possible to get an expression tree for an ordinary chunk of code such as a method or property getter? What I'm trying to do is, let's say for an order processing system, I have a class for order items: class Item : Entity { [Cascade] public Document document { get; set; } public int line { get; set; } public Product product { get; set; } public string description { get; set; } public decimal qty { get; set; } public decimal price { get; set; } public decimal net { get { return qty * price; } } public VatCode vat_code { get; set; } } where the net value equals qty * price, so I'd like to declare it as such, either with a property or method, and then also have the framework introspect that expression so it can generate appropriate SQL for defining a corresponding calculated column in a corresponding database view. The most obvious way to do this would be to get the expression tree for a property getter or a method, but I can't find any indication how to do this, or that it is possible. (I have found a way to get a method body as a byte stream, but that's not what's desired here.) If that isn't possible, I suppose the recommended solution would be to declare something like a static field that is an expression tree, and compile/run it at run time for internal use, and also introspect as normal for SQL generation?

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  • How to render all records from a nested set into a real html tree

    - by Christoph Schiessl
    I'm using the awesome_nested_set plugin in my Rails project. I have two models that look like this (simplified): class Customer < ActiveRecord::Base has_many :categories end class Category < ActiveRecord::Base belongs_to :customer # Columns in the categories table: lft, rgt and parent_id acts_as_nested_set :scope => :customer_id validates_presence_of :name # Further validations... end The tree in the database is constructed as expected. All the values of parent_id, lft and rgt are correct. The tree has multiple root nodes (which is of course allowed in awesome_nested_set). Now, I want to render all categories of a given customer in a correctly sorted tree like structure: for example nested <ul> tags. This wouldn't be too difficult but I need it to be efficient (the less sql queries the better). Update: Figured out that it is possible to calculate the number of children for any given Node in the tree without further SQL queries: number_of_children = (node.rgt - node.lft - 1)/2. This doesn't solve the problem but it may prove to be helpful.

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  • How to improve Minecraft-esque voxel world performance?

    - by SomeXnaChump
    After playing Minecraft I marveled a bit at its large worlds but at the same time I found them extremely slow to navigate, even with a quad core and meaty graphics card. Now I assume Minecraft is fairly slow because: A) It's written in Java, and as most of the spatial partitioning and memory management activities happen in there, it would naturally be slower than a native C++ version. B) It doesn't partition its world very well. I could be wrong on both assumptions; however it got me thinking about the best way to manage large voxel worlds. As it is a true 3D world, where a block can exist in any part of the world, it is basically a big 3D array [x][y][z], where each block in the world has a type (i.e BlockType.Empty = 0, BlockType.Dirt = 1 etc.) Now, I am assuming to make this sort of world perform well you would need to: A) Use a tree of some variety (oct/kd/bsp) to split all the cubes out; it seems like an oct/kd would be the better option as you can just partition on a per cube level not a per triangle level. B) Use some algorithm to work out which blocks can currently be seen, as blocks closer to the user could obfuscate the blocks behind, making it pointless to render them. C) Keep the block object themselves lightweight, so it is quick to add and remove them from the trees. I guess there is no right answer to this, but I would be interested to see peoples' opinions on the subject. How would you improve performance in a large voxel-based world?

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  • What is the best way to manage large 3d worlds (i.e minecraft style)?

    - by SomeXnaChump
    After playing minecraft I was marvelling a bit at their large worlds but at the same time finding it extremely slow to navigate, even with a quad core and meaty graphics card. Now I assume its fairly slow because: A) Its written in Java, and as most of the actual spatial partitioning and other memory management activities happen in there it would be slower than a native C++ version. B) They are not partitioning their world very well I could be wrong on both assumptions, however it got me thinking about the best way to manage large worlds. As it is more of a true 3d world, where a block can exist in any part of the world, it is basically a big 3d array [x][y][z], where each block in the world has a type (i.e BlockType.Empty = 0, BlockType.Dirt = 1 etc). Now I am assuming to make this sort of world performant you would need to: a) Use a tree of some variety (oct/kd/bsp) to split all the cubes out, it seems like an oct/kd would be the better option as you can just partition on a per cube level not a per triangle level. b) Use some algorithm to work out if the blocks within the scene can currently be seen, as blocks closer to the user could obfuscate the blocks behind, making it pointless to render them. c) Keep the block object themselves lightweight, so it is quick to add and remove them from the trees I guess there is no right answer to this, but I would be interested to see peoples opinions on the subject.

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  • Inheritance Problem in Perl OOP

    - by Sam
    Hello, I have a sub class that calls a method from a super class. and the method in the super class use a method that is defined in the super class as asbstract(not really abstract) but implemented in the sub class. for example: package BaseClass; sub new { } sub method1 { return someAbstractMethod(); } sub someAbtsractMethod { die "oops, this is an abstract method that should be implemented in a subclass" ; } 1; package SubClass; sub new { } sub someAbtsractMethod { print "now we implement the asbtract method"; } 1; now when I do: $sub = new SubClass(); $sub-method1(); It calls the abstract message and i get the specified error message. if I took off the abstractmethod from the super class and just leave the implementation in the subclass, It does not recognize the method and I get subroutine abstractmethod not found error.

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  • Tree structured troubleshooting survey which gives solution based on answers

    - by japie1001
    Is there some online tool which let me design a tree structured questionaire/survey which suggests a solution to a problem. Example troubleshooting survey for the problem of black monitor screen: Q1: Is the powercable connected to the monitor? 0 Yes 0 NO If answer is no: "The solution to your problem is to connect the power cable" If answer is yes: Contiue with Q2 Q2: Is the computer turned on: 0 yes 0 no etc Is there something like Google Forms where I can achieve this with online?

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  • How Spanning Tree Protocol detects Loops

    - by AMIT
    For last few days I've been reading about Spanning Tree Protocol ,L2 protocol and understood how it prevents loop in network ,various steps in STP but one thing i wanted to know how STP actually detects the loops in network so that it can prevent it.Somewhere I read STP uses BPDU as probe and detects loops I mean how it happen is when switch send a BPDU with Destination Address as multicast and receive same BPDU again mean there is loop in network . But is it how STP detects loops in network?

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  • Difference between Class Abstraction and Object Interfaces in PHP?

    - by Mark Tomlin
    What is the difference between a Class Abstraction and an Object Interfaces in PHP? I ask because, I don't really see the point to both of them, they both do the same thing! So, what are the advantages of disadvantages using both against one or the other? Class Abstraction: abstract class aClass { // Force extending class to define these methods abstract public function setVariable($name, $var); abstract public function getHtml($template); } Object Interface: interface iClass { // Force impementing class to define these methods public function setVariable($name, $var); public function getHtml($template); }

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  • Question about decorator pattern and the abstract decorator class?

    - by es11
    This question was asked already here, but rather than answering the specific question, descriptions of how the decorator pattern works were given instead. I'd like to ask it again because the answer is not immediately evident to me just by reading how the decorator pattern works (I've read the wikipedia article and the section in the book Head First Design Patterns). Basically, I want to know why an abstract decorator class must be created which implements (or extends) some interface (or abstract class). Why can't all the new "decorated classes" simply implement (or extend) the base abstract object themselves (instead of extending the abstract decorator class)? To make this more concrete I'll use the example from the design patterns book dealing with coffee beverages: There is an abstract component class called Beverage Simple beverage types such as HouseBlend simply extend Beverage To decorate beverage, an abstract CondimentDecorator class is created which extends Beverage and has an instance of Beverage Say we want to add a "milk" condiment, a class Milk is created which extends CondimentDecorator I'd like to understand why we needed the CondimentDecorator class and why the class Milk couldn't have simply extended the Beverage class itself and been passed an instance of Beverage in its constructor. Hopefully this is clear...if not I'd simply like to know why is the abstract decorator class necessary for this pattern? Thanks. Edit: I tried to implement this, omitting the abstract decorator class, and it seems to still work. Is this abstract class present in all descriptions of this pattern simply because it provides a standard interface for all of the new decorated classes?

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  • Building a directory tree from a list of file paths

    - by Abignale
    I am looking for a time efficient method to parse a list of files into a tree. There can be hundreds of millions of file paths. The brute force solution would be to split each path on occurrence of a directory separator, and traverse the tree adding in directory and file entries by doing string comparisons but this would be exceptionally slow. The input data is usually sorted alphabetically, so the list would be something like: C:\Users\Aaron\AppData\Amarok\Afile C:\Users\Aaron\AppData\Amarok\Afile2 C:\Users\Aaron\AppData\Amarok\Afile3 C:\Users\Aaron\AppData\Blender\alibrary.dll C:\Users\Aaron\AppData\Blender\and_so_on.txt From this ordering my natural reaction is to partition the directory listings into groups... somehow... before doing the slow string comparisons. I'm really not sure. I would appreciate any ideas. Edit: It would be better if this tree were lazy loaded from the top down if possible.

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  • Google Closure Library - Adding non-TreeNode children to a TreeNode

    - by Andreas Jansson
    Hi, I'm using the Google Closure Library and goog.ui.tree in particular to build a tree structure GUI component. It works pretty well out of the box, but I'd like to add a few extra controls to each of the leaves (goog.ui.Checkboxes in particular). The problem is that Component.addChild has been overridden in BaseNode so that each added child is treated as a child tree node as opposed to a child component. In effect plenty of errors are thrown if you try to add anything else than an actual tree node as a child, as these children are traversed and BaseNode-specific functions are called on them. I must admit I'm quite a Closure newb, but I reckon there must be some workaround for this, right? Essentially all I want to do is have a bunch of checkboxes appear next to each leaf in my tree. Thanks, Andreas

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  • JQuery treeview - add node(s) in middle of tree

    - by Chris
    Hi all, I'm just getting started with JQuery and the treeview plugin so this should be a relatively easy question: The example code for adding branches to the tree: var newnodes = $("<li><span class='folder'>New Sublist</span><ul>" + "<li><span class='file'>Item1</span></li>" + "<li><span class='file'>Item2</span></li></ul></li>").appendTo("#browser"); $("#browser").treeview({ add: branches }); Works fine for me, but adds the new branch at the end of the tree - instead what I want is to be able to select a specific node and add to that branch. I've managed to get the node being added by using the id of the particular node instead of the whole treeview in - appendTo("nodeID") However I can't get the tree to render correctly, either with: $("nodeID").treeview({ add: branches }); or $("browser").treeview({ add: branches }); or calling it on both without arguments. Cheers in advance

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  • Setting TreeView.DataContext doesn't refresh the tree

    - by dan gibson
    I have a List that I've bound to a TreeView. Setting TreeView.DataContext works - everything displays correctly. I then change the list (add an item to it) and set TreeView.DataContext again (to the same value) but the tree does not refresh with the new items. How do I get the treeview to refresh? This is basically my code: public class xItemCollection : ObservableCollection<xItem> { } public class xItem : INotifyPropertyChanged { xItemCollection _Items; public xItem() { _Items = new xItemCollection(); } public xItemCollection Items {get{return _Items;}} } ... this.RootItem = new xItem(); treeView.DataContext = this; Adding items to the list works until the tree is rendered for the first time. After it is rendered, adding/removing items does not refresh the tree.

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  • Expression Tree

    - by nettguy
    My understanding of expression tree is : Expression trees are in-memory representation of expression like arithmetic or boolean expression.The expressions are stored into the parsed tree.so we can easily transalate into any other language. Linq to SQL uses expression tree.Normally in LINQ to SQL query the compiler translates it into parsed expression trees.These are passed to Sql Server as T-SQL Statements.The Sql server executes the T-SQL query and sends down the result back.That is why when you execute LINQ to SQL you gets IQueryable<T> not IEnumetrable<T>.Because IQuerybale contains public IQueryable:IEnumerable { Type Element {get;} Expression Expression {get;} IQueryaleProvider Provider {get;} } Questions : Microsoft uses Expression trees to play with LINQ-to-Sql.What are the different ways can i use expression trees to boost my code. Apart from LINQ to SQL,Linq to amazon ,who used expression trees in their applications? Linq to Object return IEnumerable,Linq to SQL return IQueryable ,What does LINQ to XML return?

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  • Design a GUI browser to view a tree

    - by iamrohitbanga
    I have a large tree. I want to be able to visualize it using a GUI tool. I want the ability to pan and zoom the tree image so that i can focus on part of the tree. Is there an existing tool to achieve this? If not i would like to write a small tool for myself to be able to do this. what is the simplest way of doing this? what computer language should i use? the image should look something like http://upload.wikimedia.org/wikipedia/commons/d/df/Binary_tree.png I should be able to zoom and pan the image.

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  • How to get a reference to node in DOM tree in Google Chrome debugger console

    - by .yahoo.co.jpaqwsykcj3aulh3h1k0cy6nzs3isj
    In the Google Chrome debugger, I often want to get a reference to a node in the DOM tree. I can click the "magnifying glass" button and then click the desired element in the browser window to select the corresponding node in the DOM tree displayed in the debugger. But how can I get a reference to that node in the console? If the element has an id, document.getElementById works, but if there is no id, is there a better alternative to XPath or manual traversal of the DOM tree using children? In case XPath is the best way, is there a better way than doing something like this: var evaluator = new XPathEvaluator(); var result = evaluator.evaluate("//div", document.documentElement, null, XPathResult.FIRST_ORDERED_NODE_TYPE, null); which is a pain to type out each time.

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