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  • Entity Framework query builder methods: why "it" and not lambdas?

    - by nlawalker
    I'm just getting started with EF and a query like the following strikes me as odd: var departmentQuery = schoolContext.Departments.Include("Courses"). OrderBy("it.Name"); Specifically, what sticks out to me is "it.Name." When I was tooling around with LINQ to SQL, pretty much every filter in a query-builder query could be specified with a lambda, like, in this case, d = d.Name. I see that there are overrides of OrderBy that take lambdas that return an IOrderedQueryable or an IOrderedEnumable, but those obviously don't have the Execute method needed to get the ObjectResult that can then be databound. It seems strange to me after all I've read about how lambdas make so much sense for this kind of stuff, and how they are translated into expression trees and then to a target language - why do I need to use "it.Name"?

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  • Top tips for designing GUIs?

    - by oxbow_lakes
    A while back I read (before I lost it) a great book called GUI Bloopers which was full of examples of bad GUI design but also full of useful tidbits like Don't call something a Dialog one minute and a Popup the next. What top tips would you give for designing/documenting a GUI? It would be particularly useful to hear about widgets you designed to cram readable information into as little screen real-estate as possible. I'm going to roll this off with one of my own: avoid trees (e.g. Swing's JTree) unless you really can't avoid it, or have a unbounded hierarchy of stuff. I have found that users don't find them intuitive and they are hard to navigate and filter. PS. I think this question differs from this one as I'm asking for generalist tips

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  • Data Structure for a particular problem??

    - by AGeek
    Hi, Which data structure can perform insertion, deletion and searching operation in O(1) time in the worst case. We may assume the set of elements are integers drawn from a finite set 1,2,...,n, and initialization can take O(n) time. I can only think of implementing a hash table. Implementing it with Trees will not give O(1) time complexity for any of the operation. Or is it possible?? Kindly share your views on this, or any other data structure apart from these.. Thanks..

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  • Extracting Information from Images

    - by Khorkrak
    What are some fast and somewhat reliable ways to extract information about images? I've been tinkering with openCV and this seems so far to be the best route plus it has Python bindings. So to be more specific I'd like to determine what I can about what's in an image. So for example the haar face detection and full body detection classifiers are great - now I can tell that most likely there are faces and / or people in the image as well as about how many. okay - what else - how about whether there are any buildings and if so what do they seem to be - huts, office buildings etc? Is there sky visible, grass, trees and so forth. From what I've read about training classifiers to detect objects, it seems like a rather laborious process 10,000 or so wrong images and 5,000 or so correct samples to train a classifier. I'm hoping that there are some decent ones around already instead of having to do this all myself for a bunch of different objects - or is there some other way to go about this sort of thing?

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  • emacs delete directory recursively?

    - by Stephen
    I was searching through for a way to copy/delete directory trees... dired seems to have dired-copy-file-recursive (though sans documentation) and a search on 'recursive' also returns: tramp-handle-dired-recursive-delete-directory is a compiled Lisp function in `tramp.el'. (tramp-handle-dired-recursive-delete-directory FILENAME) Recursively delete the directory given. This is like `dired-recursive-delete-directory' for Tramp files. But I can't find dired-recursive-delete-directory anywhere! Anyone know what's going on? Thanks ~

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  • Are there .NET Framework methods to parse an email (MIME)?

    - by Neil C. Obremski
    Is there a class or set of functions built into the .NET Framework (3.5+) to parse raw emails (MIME documents)? I am not looking for anything fancy or a separate library, it needs to be built-in. I'm going to be using this in some unit tests and need only grab the main headers of interest (To, From, Subject) along with the body (which in this case will always be text and therefore no MIME trees or boundaries). I've written several MIME parsers in the past and if there isn't anything readily available, I'll just put together something from regular expressions. It would be great to be able to do something like: MailMessage msg = MailMessage.Parse(text); Thoughts?

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  • LINQ to Entities and Business / Validation Rules

    - by Chris
    We have a requirement where we need to allow users to dynamically create custom reports that will run against our database and return sets of data. It would be something similar to this: http://www.marcuswhitworth.com/2009/12/dynamic-linq-with-expression-trees/ but would ultimately contain the ability to create more complicated logic. I believe LINQ to Entities might possibly allow us to do something like we're attempting to achieve. I should note that these reports are going to need to run against multiple tables. Can anyone point me in the right direction for something like this? Has anyone done anything similar with LINQ to Entities?

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  • Android source referencing missing classes

    - by jqpubliq
    I cloned some of the trees from the Android Open Source Project to take a look at the code, but I can't build them because they reference classes which don't seem to exist. For instance, the music application here references android.media.MediaFile which according to the package summary does not exist, as well as things like ArrayListCursor which has an old javadoc around but is absent in current documentation. So is the open source project disjoint from the released SDK? Also, is there a way to build these open source packages with the current SDK? Thanks, -JQP

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  • A B+tree simple implementation in C

    - by initpy
    Hi guys, I'm working on a fun project where I need a simple key/value store that uses B+Trees. I studied them some years ago, and to be honest, I don't want to reinvent the wheel, so I'm looking for a simple implementation in C of b+tree that I can just include in my project. I know of sqlite's, dbm's and tokyocabinet's ones but they're a little too "complicated" for my needs. Is there any (even pedagogical) work on this you can refer me to? Do you have some code to share? Thanks a lot!

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  • How do I learn Flash Game Development?

    - by grokker
    I'm currently a PHP programmer and one of my childhood dreams is to create a game. The problem is I don't know Flash. I'm not great at drawing stuff or even artistic. I could program a little with JavaScript and I could consider myself intermediate with JQuery. Question How do I get started with Flash Game development? What books do I read first? The type of game is a side scroller about an Indiana Jones type of character and the setting is on the jungle with trees and snakes and a lot of animals.

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  • How to implement arrays in an interpreter?

    - by Ray
    I have managed to write several interpreters including Tokenizing Parsing, including more complicated expressions such as ((x+y)*z)/2 Building bytecode from syntax trees Actual bytecode execution What I didn't manage: Implementation of dictionaries/lists/arrays. I always got stuck with getting multiple values into one variable. My value structure (used for all values passed around, including variables) looks like this, for example: class Value { public: ValueType type; int integerValue; string stringValue; } Works fine with integers and strings, but how could I implement arrays? (From now on with array I mean arrays in my experimental language, not in C++) How can I fit the array concept into the Value class above? Is it possible? How should I make arrays able to be passed around just as you could pass around integers and strings in my language, using the class above? Accessing array elements or memory allocation wouldn't be the problem, I just don't know how to store them.

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  • A datastructure for Robotic Sort

    - by amit.codename13
    I am trying to solve this problem : https://www.spoj.pl/problems/CERC07S/ I have identified that i need a datastructure in which reversing operations have lesser time complexity. I tried to create one using a doubly linked list, in which (i thought) reversing can be done in O(1) by just changing a value associated with the starting and ending node which indicates the direction of traversing the list. I tried to implement it but got stuck. Maybe the approach is wrong! Are trees applicable here? If yes, how? Any ideas or links are appreciated? Thanks in advance.

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  • Easiest way to convert json data into objects with methods attached?

    - by John Mee
    What's the quickest and easiest way to convert my json, containing the data of the objects, into actual objects with methods attached? By way of example, I get data for a fruitbowl with an array of fruit objects which in turn contain an array of seeds thus: {"fruitbowl": [{ "name": "apple", "color": "red", "seeds": [] },{ "name": "orange", "color": "orange", "seeds": [ {"size":"small","density":"hard"}, {"size":"small","density":"soft"} ]} } That's all nice and good but down on the client we do stuff with this fruit, like eat it and plant trees... var fruitbowl = [] function Fruit(name, color, seeds){ this.name = name this.color = color this.seeds = seeds this.eat = function(){ // munch munch } } function Seed(size, density){ this.size = size this.density = density this.plant = function(){ // grow grow } } My ajax's success routine currently is currently looping over the thing and constructing each object in turn and it doesn't handle the seeds yet, because before I go looping over seed constructors I'm thinking Is there not a better way? success: function(data){ fruitbowl.length = 0 $.each(data.fruitbowl, function(i, f){ fruitbowl.push(new Fruit(f.name, f.color, f.seeds)) }) I haven't explored looping over the objects as they are and attaching all the methods. Would that work?

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  • What data is actually stored in a B-tree database in CouchDB?

    - by Andrey Vlasovskikh
    I'm wondering what is actually stored in a CouchDB database B-tree? The CouchDB: The Definitive Guide tells that a database B-tree is used for append-only operations and that a database is stored in a single B-tree (besides per-view B-trees). So I guess the data items that are appended to the database file are revisions of documents, not the whole documents: +---------|### ... | | +------|###|------+ ... ---+ | | | | +------+ +------+ +------+ +------+ | doc1 | | doc2 | | doc1 | ... | doc1 | | rev1 | | rev1 | | rev2 | | rev7 | +------+ +------+ +------+ +------+ Is it true? If it is true, then how the current revision of a document is determined based on such a B-tree? Doesn't it mean, that CouchDB needs a separate "view" database for indexing current revisions of documents to preserve O(log n) access? Wouldn't it lead to race conditions while building such an index? (as far as I know, CouchDB uses no write locks).

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  • From my code, I can't trace the out of bounds exception.

    - by Matt
    public override Models.CalculationNode Parse(string expression) { var calNode = new Models.CalculationNode(); int i = expression.Length; char[] x = expression.ToCharArray(); string temp = ""; //Backwards assembly of the tree //Right Node while (!IsOperator(x[i]) && i > 0) { if (!x[i].Equals(' ')) temp = x[i] + temp; i--; } } It has been a while since I've used trees and I'm getting an out of bounds exception in the while loop.

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  • Select in a many-to-many relationship in MySQL

    - by Joff Williams
    I have two tables in a MySQL database, Locations and Tags, and a third table LocationsTagsAssoc which associates the two tables and treats them as a many-to-many relationship. Table structure is as follows: Locations --------- ID int (Primary Key) Name varchar(128) LocationsTagsAssoc ------------------ ID int (Primary Key) LocationID int (Foreign Key) TagID int (Foreign Key) Tags ---- ID int (Primary Key) Name varchar(128) So each location can be tagged with multiple tagwords, and each tagword can be tagged to multiple locations. What I want to do is select only Locations which are tagged with all of the tag names supplied. For example: I want all locations which are tagged with both "trees" and "swings". Location "Park" should be selected, but location "Forest" should not. Any insight would be appreciated. Thanks!

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  • "lock request time out period exceeded" Error When Trying to See DB Hierarchies

    - by Lloyd Banks
    I have a DB that I can run basic queries (albeit much slower than normal) off of. When I try to see the hierarchy trees for tables, views, or procedures in SSMS Object Explorer, I get the "lock request time out period exceeded". My Report Server reports that run off of objects in this DB are no longer completing. Jobs associated with procedures stored on this DB also do not run. I tried using sp_who2 to find and kill all connections on the DB. This has not solved the problem. What is going on here? How can I resolve this?

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  • Are protected constructors considered good practice?

    - by Álvaro G. Vicario
    I'm writing some little helper classes to handle trees. Basically, I have a node and a special root node that represents the tree. I want to keep it generic and simple. This is part of the code: <?php class Tree extends TreeNode{ public function addById($node_id, $parent_id, $generic_content){ if( $parent = $this->findNodeById($parent_id) ){ $parent->addChildById($node_id, $generic_content); } } } class TreeNode{ public function __construct($node_id, $parent_id, $generic_content){ // ... } protected function addChildById($node_id, $generic_content){ $this->children[] = new TreeNode($this->node_id, $node_id, $generic_content); } } $Categories = new Tree; $Categories->addById(1, NULL, $foo); $Categories->addById(2, NULL, $bar); $Categories->addById(3, 1, $gee); ?> My questions: Is it sensible to force TreeNode instances to be created through TreeNode::addById()? If it's so, would it be good practise to declare TreeNode::__construct() as private/protected?

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  • How to make a table view which is not the full width of the screen?

    - by mystify
    For some strange reason, UITableView resizes my cells to 320 width no matter how I set the frame for the UITableView object. Even if I go in later and resize the cell back to 250, UITableView seems to resize it again to 320 some time. Is there some property or method that must be set / called additionally to get that right? However, I can add my contents in a way that it looks like 250 width, but my whole layouting code is a big mess since I can't rely on the cell frame width which is "wrong". Also it seems like a big waste of memory since the bitmaps in the layer trees are nonsenseless 320 width instead of 250, even though the frame of the UITableView is not 320 width.

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  • Turn database result into array

    - by Industrial
    Hi everyone, I have just made the update/add/delete part for the "Closure table" way of organizing query hierarchical data that are shown on page 70 in this slideshare: http://www.slideshare.net/billkarwin/sql-antipatterns-strike-back My database looks like this: Table Categories: ID Name 1 Top value 2 Sub value1 Table CategoryTree: child parent 1 1 2 2 2 1 However, I have a bit of an issue getting the full tree back as an multidimensional array from a single query. Here's what I would like to get back: array ( 'topvalue' = array ( 'Subvalue', 'Subvalue2', 'Subvalue3' = array ('Subvalue 1', 'Subvalue 2', 'Subvalue 3' ) ); ); Update: Found this link, but I still have a hard time to convert it into an array: http://karwin.blogspot.com/2010/03/rendering-trees-with-closure-tables.html

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  • UUIDs in CouchDB

    - by PartlyCloudy
    I am wondering about the format UUIDs are by default represented in CouchDB. While the RFC 4122 describes UUIDs like 550e8400-e29b-11d4-a716-446655440000, CouchDB uses continuously chars like 3069197232055d39bc5bc39348a36417. I've searched some time in both their wiki and their documentation what this actually is, however without any result. Do you know whether this is either a non RFC-conform format omitting all - or is this a completely different representation of the 128 bits. The background is that I'm using Java UUIDs which are formatted as noted in the RFC. I see the advantage that the CouchDB-style is probably more handy for building internal trees, but I want to be sure to use a consistent implementation.

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  • How do I prevent a pair of XMLEvent[Reader|Writer] from splitting empty tags into start+end tags?

    - by java.is.for.desktop
    Hello, everyone! I have an understanding problem of how the following code works: XMLInputFactory xif = XMLInputFactory.newFactory(); XMLOutputFactory xof = XMLOutputFactory.newFactory(); XMLEventReader reader = xif.createXMLEventReader(/* ... */); XMLEventWriter writer = xof.createXMLEventWriter(/* ... */); writer.add(reader); The method writer.add([some reader]) reads all events from reader and writes them consequently. Sadly, following happens: The input <root><c/></root> gets transformed to <root><c><c/></root> I know, from XML point of view, these are equal trees, but not for a human ;) What can I do to get the same output? FYI: I need a XMLEvent[Reader|Writer] pair later to filter "XML events".

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  • Python: Pickling highly-recursive objects without using `setrecursionlimit`

    - by cool-RR
    I've been getting RuntimeError: maximum recursion depth exceeded when trying to pickle a highly-recursive tree object. Much like this asker here. He solved his problem by setting the recursion limit higher with sys.setrecursionlimit. But I don't want to do that: I think that's more of a workaround than a solution. Because I want to be able to pickle my trees even if they have 10,000 nodes in them. (It currently fails at around 200.) (Also, every platform's true recursion limit is different, and I would really like to avoid opening this can of worms.) Is there any way to solve this at the fundamental level? If only the pickle module would pickle using a loop instead of recursion, I wouldn't have had this problem. Maybe someone has an idea how I can cause something like this to happen, without rewriting the pickle module? Any other idea how I can solve this problem will be appreciated.

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  • Get PropertyInfo from property instead of name

    - by Sam
    Say, for example, I've got this simple class: public class MyClass { public String MyProperty { get; set; } } The way to get the PropertyInfo for MyProperty would be: typeof(MyClass).GetProperty("MyProperty"); This sucks! Why? Easy: it will break as soon as I change the Name of the Property, it needs a lot of dedicated tests to find every location where a property is used like this, refactoring and usage trees are unable to find these kinds of access. Ain't there any way to properly access a property? Something, that is validated on compile time? I'd love a command like this: propertyof(MyClass.MyProperty);

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  • Efficient determination of which strings in an array are substrings of the others?

    - by byte
    In C#, Say you have an array of strings, which contain only characters '0' and '1': string[] input = { "0101", "101", "11", "010101011" }; And you'd like to build a function: public void IdentifySubstrings(string[] input) { ... } That will produce the following: "0101 is a substring of 010101011" "101 is a substring of 0101" "101 is a substring of 010101011" "11 is a substring of 010101011" And you are NOT able to use built-in string functionality (such as String.Substring). How would one efficiently solve this problem? Of course you could plow through it via brute force, but it just feels like there ought to be a way to accomplish it with a tree (since the only values are 0's and 1's, it feels like a binary tree ought to fit somehow). I've read a little bit about things like suffix trees, but I'm uncertain if that's the right path to be going down. Any efficient solutions you can think of?

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