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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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  • Expression Tree : C#

    - 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 when our LINQ to SQL query compiler translates it to 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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  • Tree position terminology/naming

    - by wst
    This is a naming things question. I am processing trees (XML documents), and there are often special rules applied to nodes based on structure. It's been very difficult coming up with concise naming conventions for some cases, namely for nodes in the first position among their siblings, along with some recursive relationship: Given an arbitrary node, I want to describe its first child, and then that node's first child, and so on recursively. Given another arbitrary node, I want to describe its parent if the parent is first among its siblings, and that parent's parent if it's first, and so on recursively. Is there existing terminology to describe these tree positions? How would you name a variable or function that captures one of these cases so that it's intuitive to an unfamiliar developer trying to understand an algorithm?

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  • Generate sample XML from composite hierarchical structure

    - by Jevgenij Nekrasov
    Let's say I have composite hierarchical structure. Each object in the structure has child collection of the same objects. Each object has XPath property, which stores the exact xpath to the element inside XML file. Right now I am trying to create an extension, which can generate XML string from that hierarchical structure, but first I want to make some sort of research what is the most efficient way to do that? ant what is the easiest way?

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  • converting a treebank of vertical trees to s-expressions

    - by Andreas
    I need to preprocess a treebank corpus of sentences with parse trees. The input format is a vertical representation of trees, like so: S =NP ==(DT +def) the == (N +ani) man =VP ==V walks ...and I need it like: (S (NP (DT the) (N man)) (VP (V walks))) I have code that almost does it, but not quite. There's always a missing paren somewhere. Should I use a proper parser, maybe a CFG? The current code is at http://github.com/andreasvc/eodop/blob/master/arbobanko.py The code also contains real examples from the treebank.

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  • Using Active Directory Security Groups as Hierarchical Tags

    - by Nathan Hartley
    Because active directory security groups can... hold objects regardless of OU. be used for reporting, documentation, inventory, etc. be referenced by automated processes (Get-QADGroupMember). be used to apply policy be used by WSUS I would like to use security groups as hierarchical tags, representing various attributes of a computer or user. I am thinking of (computer centric) tags something like these: /tag/vendor/vendorName /tag/system/overallSystemName /tag/application/vendorsApplicationName /tag/dependantOn/computerName /tag/department/departmentName /tag/updates/Group1 Before fumbling through implementing this, I thought I would seek comments from the community. Specifically in the areas: Does this make sense? Would it work? Has anyone else attempted this? Is there a good reference on the matter I should read? How best to implement the hierarchy? Tag_OU\Type_OU\GroupName (limits quantity in OU, uniqueness not guaranteed) Tag_OU\Type_OU\Tag-Type-GroupName (limits quantity in OU, uniqueness guaranteed, verbose) etc ... Thanks in advance!

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  • [Wordpress] How do you remove a Category-style (hierarchical) taxonomy metabox

    - by Manny Fleurmond
    I was wondering if someone can help me with this. I'm currently following Shibashake's tutorial about creating custom meta-boxes that include taxonomy selection here: http://shibashake.com/wordpress-theme/wordpress-custom-taxonomy-input-panels . They show how to remove the standard metabox Wordpress automatically creates for taxonomies using the remove_meta_box function. Only problem is that the function for some reason doesn't seem to work on taxonomies that work as categories ie ones where the hierarchical option is set to true. I know I have the function working because the ones set up as tags disappear easily enough. I can't if it just isn't possible or if there is something special I need to add in one of the parameters to make it work. Example: $args = array( 'hierarchical' => false, 'label' =>'People', 'query_var' => true, 'rewrite' => true ); register_taxonomy('people', 'post',$args); remove_meta_box('tagsdiv-people','post','side'); That works fine. If I set hierarchical to 'true, however, the meta box stays put. Can anyone shed some light?

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  • KD-Trees and missing values (vector comparison)

    - by labratmatt
    I have a system that stores vectors and allows a user to find the n most similar vectors to the user's query vector. That is, a user submits a vector (I call it a query vector) and my system spits out "here are the n most similar vectors." I generate the similar vectors using a KD-Tree and everything works well, but I want to do more. I want to present a list of the n most similar vectors even if the user doesn't submit a complete vector (a vector with missing values). That is, if a user submits a vector with three dimensions, I still want to find the n nearest vectors (stored vectors are of 11 dimensions) I have stored. I have a couple of obvious solutions, but I'm not sure either one seem very good: Create multiple KD-Trees each built using the most popular subset of dimensions a user will search for. That is, if a user submits a query vector of thee dimensions, x, y, z, I match that query to my already built KD-Tree which only contains vectors of three dimensions, x, y, z. Ignore KD-Trees when a user submits a query vector with missing values and compare the query vector to the vectors (stored in a table in a DB) one by one using something like a dot product. This has to be a common problem, any suggestions? Thanks for the help.

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  • Searching in graphs trees with Depth/Breadth first/A* algorithms

    - by devoured elysium
    I have a couple of questions about searching in graphs/trees: Let's assume I have an empty chess board and I want to move a pawn around from point A to B. A. When using depth first search or breadth first search must we use open and closed lists ? This is, a list that has all the elements to check, and other with all other elements that were already checked? Is it even possible to do it without having those lists? What about A*, does it need it? B. When using lists, after having found a solution, how can you get the sequence of states from A to B? I assume when you have items in the open and closed list, instead of just having the (x, y) states, you have an "extended state" formed with (x, y, parent_of_this_node) ? C. State A has 4 possible moves (right, left, up, down). If I do as first move left, should I let it in the next state come back to the original state? This, is, do the "right" move? If not, must I transverse the search tree every time to check which states I've been to? D. When I see a state in the tree where I've already been, should I just ignore it, as I know it's a dead end? I guess to do this I'd have to always keep the list of visited states, right? E. Is there any difference between search trees and graphs? Are they just different ways to look at the same thing?

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  • Design suggestion for expression tree evaluation with time-series data

    - by Lirik
    I have a (C#) genetic program that uses financial time-series data and it's currently working but I want to re-design the architecture to be more robust. My main goals are: sequentially present the time-series data to the expression trees. allow expression trees to access previous data rows when needed. to optimize performance of the data access while evaluating the expression trees. keep a common interface so various types of data can be used. Here are the possible approaches I've thought about: I can evaluate the expression tree by passing in a data row into the root node and let each child node use the same data row. I can evaluate the expression tree by passing in the data row index and letting each node get the data row from a shared DataSet (currently I'm passing the row index and going to multiple synchronized arrays to get the data). Hybrid: an immutable data set is accessible by all of the expression trees and each expression tree is evaluated by passing in a data row. The benefit of the first approach is that the data row is being passed into the expression tree and there is no further query done on the data set (which should increase performance in a multithreaded environment). The drawback is that the expression tree does not have access to the rest of the data (in case some of the functions need to do calculations using previous data rows). The benefit of the second approach is that the expression trees can access any data up to the latest data row, but unless I specify what that row is, I'll have to iterate through the rows and figure out which one is the last one. The benefit of the hybrid is that it should generally perform better and still provide access to the earlier data. It supports two basic "views" of data: the latest row and the previous rows. Do you guys know of any design patterns or do you have any tips that can help me build this type of system? Should I use a DataSet to hold and present the data, or are there more efficient ways to present rows of data while maintaining a simple interface? FYI: All of my code is written in C#.

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  • Translate a<b to IR Trees

    - by drozzy
    I have to translate the mini-java (java like language) statements into intermediate-representation trees. But for this question I have no idea what it is asking... a>b moves a 1 or 0 into some newly defined temporary, and whose right-hand side is a temporary Does the wording make sense to anyone? (I am using the Java compilers book, and it is question 7.2d) in ch7.)

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  • javascript compare two DOM trees

    - by Paul
    I want to compare the change of a DOM node after a user event is fired on it; but I don't know on which element a user would fire, so my idea is to (1) save the DOM tree before an event and (2) compare the saved tree with the updated DOM tree when an event is fired. My question are (1) is there any better way? and (2) if there is no other way, what would be the fast algorithm to compare two DOM trees?

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  • Linq Expression Trees in Compact Framework.

    - by Michal Drozdowicz
    The lack of expression trees in Compact Framework has bugged me for some time now, but I haven't really looked for a solution. Today, I've found a blog post about an alternative System.Linq.Expressions built on top of Mono System.Core and used e.g. by db4o (you can find it here). My question is - have you used this library and if so, what were your experiences with it (especially regarding performance)?

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  • Languages for implementing decision trees

    - by Shailesh Tainwala
    What would be a good choice of programming language in which to implement a decision tree? The results of the implementation will be for personal use only, so no need to consider ability to publish etc. I have heard that Octave is a good option, can anyone explain why a matrix based language is recommended for implementing decision trees?

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  • Confused about Huffman Trees

    - by ShrimpCrackers
    A quick tutorial on generating a huffman tree Confused about Huffman Trees. Near the end of that link above, it shows the tree with 2 elements left, and then the completed tree. I'm confused about the way that it is branched. Is there a specific way a huffman tree needs to be branched? For example, 57:* with its right child 35:* is branched off to the right. Could it have been 35 branched to the left with 22 branched to the right? Also, why wasn't 22:* paired up with 15:4 - it just paired with 20:5 to create a new tree. From initial obersvations it seems the tree does not need to be balanced or have any specific order other than that the frequencies of a leaf add up to the value of the parent node. Could two people creating a huffman tree with the same data end up with different encoding values?

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  • All minimum spanning trees implementation

    - by russtbarnacle
    I've been looking for an implementation (I'm using networkx library.) that will find all the minimum spanning trees (MST) of an undirected weighted graph. I can only find implementations for Kruskal's Algorithm and Prim's Algorithm both of which will only return a single MST. I've seen papers that address this problem (such as http://fano.ics.uci.edu/cites/Publication/Epp-TR-95-50.html) but my head tends to explode someway through trying to think how to translate it to code. In fact i've not been able to find an implementation in any language!

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  • MS SQL server and Trees

    - by Julian
    Im looking for some way of extrating data form a tree table as defined below. Table Tree Defined as :- TreeID uniqueidentifier TreeParent uniqueidentifier TreeCode varchar(50) TreeDesc varchar(100) Data some (23k rows), Parent Refs back into ID in table The following SQL renders the whole tree (takes arround 2 mins 30) I need to do the following. 1) Render each Tree Node with its LVL 1 parent 2) Render all nodes that have a Description that matches a TreeDesc like 'SomeText%' 3) Render all parent nodes that are for a single tree id. Items 2 and 3 take 2mins30 so this needs to be a lot faster! Item 1, just cant work out how to do it with out killing SQL or taking forever any sugestions would be helpfull Thanks Julian WITH TreeCTE(TreeCode, TreeDesc, depth, TreeParent, TreeID) AS ( -- anchor member SELECT cast('' as varchar(50)) as TreeCode , cast('Trees' as varchar(100)) as TreeDesc, cast('0' as Integer) as depth, cast('00000000-0000-0000-0000-000000000000' as uniqueidentifier) as TreeParent, cast('00000000-0000-0000-0000-000000000000' as uniqueidentifier) as TreeID UNION ALL -- recursive member SELECT s.TreeCode, s.TreeDesc, cte.depth+1, isnull(s.TreeParent, cast('00000000-0000-0000-0000-000000000000' as uniqueidentifier)), isnull(s.TreeID, cast('00000000-0000-0000-0000-000000000000' as uniqueidentifier)) FROM pdTrees AS S JOIN TreeCTE AS cte ON isnull(s.TreeParent, cast('00000000-0000-0000-0000-000000000000' as uniqueidentifier)) = isnull( cte.TreeID , cast('00000000-0000-0000-0000-000000000000' as uniqueidentifier)) ) -- outer query SELECT s.TreeID, s.TreeCode, s.TreeDesc, s.depth, s.TreeParent FROM TreeCTE s

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  • Using Lambda Expressions trees with IEnumerable

    - by Loathian
    I've been trying to learn more about using Lamba expression trees and so I created a simple example. Here is the code, this works in LINQPad if pasted in as a C# program. void Main() { IEnumerable<User> list = GetUsers().Where(NameContains("a")); list.Dump("Users"); } // Methods public IEnumerable<User> GetUsers() { yield return new User{Name = "andrew"}; yield return new User{Name = "rob"}; yield return new User{Name = "chris"}; yield return new User{Name = "ryan"}; } public Expression<Func<User, bool>> NameContains(string namePart) { return u => u.Name.Contains(namePart); } // Classes public class User { public string Name { get; set; } } This results in the following error: The type arguments for method 'System.Linq.Enumerable.Where(System.Collections.Generic.IEnumerable, System.Func)' cannot be inferred from the usage. Try specifying the type arguments explicitly. However if I just substitute the first line in main with this: IEnumerable<User> list = GetUsers().Where(u => u.Name.Contains("a")); It works fine. Can tell me what I'm doing wrong, please?

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  • Reconstructing trees from a "fingerprint"

    - by awshepard
    I've done my SO and Google research, and haven't found anyone who has tackled this before, or at least, anyone who has written about it. My question is, given a "universal" tree of arbitrary height, with each node able to have an arbitrary number of branches, is there a way to uniquely (and efficiently) "fingerprint" arbitrary sub-trees starting from the "universal" tree's root, such that given the universal tree and a tree's fingerprint, I can reconstruct the original tree? For instance, I have a "universal" tree (forgive my poor illustrations), representing my universe of possibilities: Root / / / | \ \ ... \ O O O O O O O (Level 1) /|\/|\...................\ (Level 2) etc. I also have tree A, a rooted subtree of my universe Root / /|\ \ O O O O O / Etc. Is there a way to "fingerprint" the tree, so that given that fingerprint, and the universal tree, I could reconstruct A? I'm thinking something along the lines of a hash, a compression, or perhaps a functional/declarative construction? Big-O analysis (in time or space) is a plus. As a for-instance, a nested expression like: {{(Root)},{(1),(2),(3)},{(2,3),(1),(4,5)}...} representing the actual nodes present at each level in the tree is probably valid, but can it be done more efficiently?

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  • How to define trees with more than one type in ML programing language

    - by user550413
    Well, I am asked to do the next thing: To define a binary tree which can contain 2 different types: ('a,'b) abtree and these are the requirements: Any inner vertex (not a leaf) must be of the type 'a or 'b and the leafs have no value. For every path in the tree all 'a values must appear before the 'b value: examples of paths: 'a->'a->'a-'b (legal) 'a->'b->'b (legal) 'a->'a->'a (legal) 'b->'b->'b (legal) 'a->'b->'a (ILLEGAL) and also I need to define another tree which is like the one described above but now I have got also 'c and in the second requirement it says that for every path I 'a values appear before the 'b values and all the 'b values appear before the 'c values. First, I am not sure how to define binary trees to have more than 1 type in them. I mean the simplest binary tree is: datatype 'a tree = leaf | br of 'a * 'a tree * 'a tree; And also how I can define a tree to have these requirements. Any help will be appreciated. Thanks.

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  • Idea of an algorithm to detect a website's navigation structure?

    - by Uwe Keim
    Currently I am in the process of developing an importer of any existing, arbitrary (static) HTML website into the upcoming release of our CMS. While the downloading the files is solved successfully, I'm pulling my hair off when it comes to detect a site structure (pages and subpages) purely from the HTML files, without the user specifying additional hints. Basically I want to get a tree like: + Root page 1 + Child page 1 + Child page 2 + Child child page1 + Child page 3 + Root page 2 + Child page 4 + Root page 3 + ... I.e. I want to be able to detect the menu structure from the links inside the pages. This has not to be 100% accurate, but at least I want to achieve more than just a flat list. I thought of looking at multiple pages to see similar areas and identify these as menu areas and parse the links there, but after all I'm not that satisfied with this idea. My question: Can you imagine any algorithm when it comes to detecting such a structure? Update 1: What I'm looking for is not a web spider, but an algorithm do create a logical tree of the relationship of the pages to be able to create pages and subpages inside my CMS when importing them. Update 2: As of Robert's suggestion I'll solve this by starting at the root page, and then simply parse links as you go and treat every link inside a page simply as a child page. Probably I'll recurse not in a deep-first manner but rather in a breadth-first manner to get a more balanced navigation structure.

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  • Most efficient way to rebuild a tree structure from data

    - by Ahsan
    Have a question on recursively populating JsTree using the .NET wrapper available via NuGet. Any help would be greatly appreciated. the .NET class JsTree3Node has a property named Children which holds a list of JsTree3Nodes, and the pre-existing table which contains the node structure looks like this NodeId ParentNodeId Data AbsolutePath 1 NULL News /News 2 1 Financial /News/Financial 3 2 StockMarket /News/Financial/StockMarket I have a EF data context from the the database, so my code currently looks like this. var parentNode = new JsTree3Node(Guid.NewGuid().ToString()); foreach(var nodeItem in context.Nodes) { parentNode.Children.Add(nodeItem.Data); // What is the most efficient logic to do this recursively? } as the inline comment says in the above code, what would be the most efficient way to load the JStree data on to the parentNode object. I can change the existing node table to suite the logic so feel free to suggest any changes to improve performance.

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  • How exactly is an Abstract Syntax Tree created?

    - by Howcan
    I think I understand the goal of an AST, and I've build a couple of tree structures before, but never an AST. I'm mostly confused because the nodes are text and not number, so I can't think of a nice way to input a token/string as I'm parsing some code. For example, when I looked at diagrams of AST's, the variable and its value were leaf nodes to an equal sign. This makes perfect sense to me, but how would I go about implementing this? I guess I can do it case by case, so that when I stumble upon an "=" I use that as a node, and add the value parsed before the "=" as the leaf. It just seems wrong, because I'd probably have to make cases for tons and tons of things, depending on the syntax. And then I came upon another problem, how is the tree traversed? Do I go all the way down the height, and go back up a node when I hit the bottom, and do the same for it's neighbor? I've seen tons of diagrams on ASTs, but I couldn't find a fairly simple example of one in code, which would probably help.

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  • Count function on tree structure (non-binary)

    - by Spevy
    I am implementing a tree Data structure in c# based (largely on Dan Vanderboom's Generic implementation). I am now considering approach on handling a Count property which Dan does not implement. The obvious and easy way would be to use a recursive call which Traverses the tree happily adding up nodes (or iteratively traversing the tree with a Queue and counting nodes if you prefer). It just seems expensive. (I also may want to lazy load some of my nodes down the road). I could maintain a count at the root node. All children would traverse up to and/or hold a reference to the root, and update a internally settable count property on changes. This would push the iteration problem to when ever I want to break off a branch or clear all children below a given node. Generally less expensive, and puts the heavy lifting what I think will be less frequently called functions. Seems a little brute force, and that usually means exception cases I haven't thought of yet, or bugs if you prefer. Does anyone have an example of an implementation which keeps a count for an Unbalanced and/or non-binary tree structure rather than counting on the fly? Don't worry about the lazy load, or language. I am sure I can adjust the example to fit my specific needs. EDIT: I am curious about an example, rather than instructions or discussion. I know this is not technically difficult...

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