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• haskell: a data structure for storing ascending integers with a very fast lookup

  - by valya

  Hello! (This question is related to my previous question, or rather to my answer to it.) I want to store all qubes of natural numbers in a structure and look up specific integers to see if they are perfect cubes. For example, cubes = map (\x -> x*x*x) [1..] is_cube n = n == (head $ dropWhile (<n) cubes) It is much faster than calculating the cube root, but It has complexity of O(n^(1/3)) (am I right?). I think, using a more complex data structure would be better. For example, in C I could store a length of an already generated array (not list - for faster indexing) and do a binary search. It would be O(log n) with lower ?oefficient than in another answer to that question. The problem is, I can't express it in Haskell (and I don't think I should). Or I can use a hash function (like mod). But I think it would be much more memory consuming to have several lists (or a list of lists), and it won't lower the complexity of lookup (still O(n^(1/3))), only a coefficient. I thought about a kind of a tree, but without any clever ideas (sadly I've never studied CS). I think, the fact that all integers are ascending will make my tree ill-balanced for lookups. And I'm pretty sure this fact about ascending integers can be a great advantage for lookups, but I don't know how to use it properly (see my first solution which I can't express in Haskell).

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• Where to put external archives to configure running in Eclipse?

  - by Buggieboy

  As a Java/Eclipse noob coming from a Visual Studio .NET background, I'm trying to understand how to set up my run/debug environment in the Eclipse IDE so I can start stepping through code. I have built my application with separate src and bin hierarchies for each library project, and each project has its own jar. For example, in a Windows environment, I have something like: c:\myapp\myapp_main\src\com\mycorp\myapp\main ...and a parallel "bin" tree like this: c:\myapp\myapp_main\bin\com\mycorp\myapp\main Other supporting projects are, similarly: **c:\myapp\myapp_util\src\com\mycorp\myapp\uti**l (and a parallel "bin" tree.) ... etc. So, I end up with, e.g., myapp_util.jar in the ...\myapp_util\bin... path and then add that as an external archive to my myapp_main project. I also use utilities like gluegen-rt.jar, which I add ad external dependencies to the projects requiring them. I have been able to run outside of the Eclipse environment, by copying all my project jars, gluegen-rt DLL, etc., into a "lib" subfolder of some directory and executing something like: java -Djava.library.path=lib -DfullScreen=false -cp lib/gluegen-rt.jar;lib/myapp_main.jar;lib/myapp_util.jar; com.mycorp.myapp.Main When I first pressed F11 to debug, however, I got a message about something like /com/sun/../glugen... not being found by the class loader. So, to debug, or even just run, in Ecplipse, I tried setting up my VM arguments in the Galileo Debug - (Run/Debug) Configurations to be the command line above, beginning at "-Djava.libary.path...". I've put a lib subdirectory - just like the above with all jars and the native gluegen DLL - in various places, such as beneath the folder that my main jar is built in and as a subfolder of my Ecplipse starting workspace folder, but now Eclipse can't find the main class: java.lang.NoClassDefFoundError: com.mycorp.myapp.Main Although the Classpath says that it is using the "default classpath", whatever that is. Bottom line, how do I assemble the constituent files of a multi-project application so that I can run or debug in Ecplipse?

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• perl dynamic path given to 'use lib'

  - by Ed Hyer

  So, my code (Perl scripts and Perl modules) sits in a tree like this: trunk/ util/ process/ scripts/ The 'util' directory has, well, utilities, that things in the 'process/' dir need. They get access like this: use FindBin; use lib "$FindBin::Bin/../util"; use UtilityModule qw(all); That construct doesn't care where you start, as long as you're at the same level in the tree as "util/". But I decided that 'scripts/' was getting too crowded, so I created scripts/scripts1 scripts/scripts2 Now I see that this doesn't work. If I run a script 'trunk/scripts/scripts1/call_script.pl', and it calls '/trunk/process/process_script.pl', then 'process_script.pl' will fail trying to get the routines from UtilityModule(), because the path that FindBin returns is the path of the top-level calling script. The first ten ways I thought of to solve this all involved something like: use lib $path_that_came_from_elsewhere; but that seems to be something Perl doesn't like to do, except via that FindBin trick. I tried some things involving BEGIN{} blocks, but i don't really know what I'm doing there, and will likely just end up refactoring. But if someone has some clever insight into this type of problem, this would be a good chance to earn some points!

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• Silverlight 4 seems like starving of memory

  - by Marco

  I have been playing a bit with Silverlight and try to port my Silverlight 3.0 application to Silverlight 4.0. My application loads different XAP files and upon a user request create an instance of a Xaml user control and adds it to the main container, in a sort of MEF approach in order I can have an extensible and pluggable application. The application is pretty huge and to keep acceptable the performances and the initial loading I have built up some helper classes to load in the background all pages and user controls that might be used later on. On Silverlight 3.0 everything was running smoothly without any problem so far. Switching to SL 4.0 I have noticed that when the process approaches to create the instances of the user controls the layout freezes unexpectedly for a minute and sometimes for more. Looking at the task manager the memory usage of IE jumps from 50MB to 400MB and sometimes up to 1.5 GB. If the process won't take that much the layout is rendered properly even though the memory usage is still extremely high. Otherwise everything crashes due to out of memory exception. Running the same application compiled in SL3, the memory used is about 200MB when all the usercontrols are loaded. Time spent to load the application in SL3 is about 10 seconds, while it takes up to 3 mins in SL4 There are no transparencies, no opacities set, no effects and animations in the layout. User controls are instantied on the fly and added or removed in the visual tree on purpose when the user switches from one screen to another. The resources are all cleaned properly when a usercontrol is removed from the visual tree to allow the GC to operate in the background. I may do something wrong but I could not figure out where exactly nail out the source of this problem. As far as I know there is no memory profiler in SL4 that can help me out to find where to look at. But again I could not be updated on new debugging tools available.

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• Lightweight spinlocks built from GCC atomic operations?

  - by Thomas

  I'd like to minimize synchronization and write lock-free code when possible in a project of mine. When absolutely necessary I'd love to substitute light-weight spinlocks built from atomic operations for pthread and win32 mutex locks. My understanding is that these are system calls underneath and could cause a context switch (which may be unnecessary for very quick critical sections where simply spinning a few times would be preferable). The atomic operations I'm referring to are well documented here: http://gcc.gnu.org/onlinedocs/gcc-4.4.1/gcc/Atomic-Builtins.html Here is an example to illustrate what I'm talking about. Imagine a RB-tree with multiple readers and writers possible. RBTree::exists() is read-only and thread safe, RBTree::insert() would require exclusive access by a single writer (and no readers) to be safe. Some code: class IntSetTest { private: unsigned short lock; RBTree<int>* myset; public: // ... void add_number(int n) { // Aquire once locked==false (atomic) while (__sync_bool_compare_and_swap(&lock, 0, 0xffff) == false); // Perform a thread-unsafe operation on the set myset->insert(n); // Unlock (atomic) __sync_bool_compare_and_swap(&lock, 0xffff, 0); } bool check_number(int n) { // Increment once the lock is below 0xffff u16 savedlock = lock; while (savedlock == 0xffff || __sync_bool_compare_and_swap(&lock, savedlock, savedlock+1) == false) savedlock = lock; // Perform read-only operation bool exists = tree->exists(n); // Decrement savedlock = lock; while (__sync_bool_compare_and_swap(&lock, savedlock, savedlock-1) == false) savedlock = lock; return exists; } }; (lets assume it need not be exception-safe) Is this code indeed thread-safe? Are there any pros/cons to this idea? Any advice? Is the use of spinlocks like this a bad idea if the threads are not truly concurrent? Thanks in advance. ;)

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• How to force an HTML JLabel in a JTree to resize when the font changes

  - by Mike

  I'm updating a Java Swing application to support the user switching the app's font from normal size to a larger size (so the user can switch between the two sizes at runtime). One problem I'm having is with a JTree that uses HTML for the tree nodes to underline the text in some nodes (the HTML is just embedded in the JLabel of each tree node). One extra thing to know about the nodes is that they're a custom component, adding a JCheckBox in front of each JLabel. The problem is that once the JTree is visible, increasing the font size causes the nodes (containing underlined text) to not resize. The HTML for those nodes seems to prevent the node from becoming wider, so when the font changes, the text becomes truncated. I think my options are to either: 1) use another approach to make the text underlined, since removing the HTML from the JLabel causes it to resize properly when the font size changes, or 2) keep the HTML formatting and somehow force the JTree/JLabels to resize when the font size is updated (possibly by firing a property change event?). The code already calls SwingUtilities.updateComponentTreeUI() on the parent JFrame when the font size gets updated. Any help would be greatly appreciated. Thanks in advance! -Mike

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• Dynamic Linq Property Converting to Sql

  - by Matthew Hood

  I am trying to understand dynamic linq and expression trees. Very basically trying to do an equals supplying the column and value as strings. Here is what I have so far private IQueryable<tblTest> filterTest(string column, string value) { TestDataContext db = new TestDataContext(); // The IQueryable data to query. IQueryable<tblTest> queryableData = db.tblTests.AsQueryable(); // Compose the expression tree that represents the parameter to the predicate. ParameterExpression pe = Expression.Parameter(typeof(tblTest), "item"); Expression left = Expression.Property(pe, column); Expression right = Expression.Constant(value); Expression e1 = Expression.Equal(left, right); MethodCallExpression whereCallExpression = Expression.Call( typeof(Queryable), "Where", new Type[] { queryableData.ElementType }, queryableData.Expression, Expression.Lambda<Func<tblTest, bool>>(e1, new ParameterExpression[] { pe })); // Create an executable query from the expression tree. IQueryable<tblTest> results = queryableData.Provider.CreateQuery<tblTest>(whereCallExpression); return results; } That works fine for columns in the DB. But fails for properties in my code eg public partial class tblTest { public string name_test { get { return name; } } } Giving an error cannot be that it cannot be converted into SQL. I have tried rewriting the property as a Expression<Func but with no luck, how can I convert simple properties so they can be used with linq in this dynamic way? Many Thanks

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• How best to use XPath with very large XML files in .NET?

  - by glenatron

  I need to do some processing on fairly large XML files ( large here being potentially upwards of a gigabyte ) in C# including performing some complex xpath queries. The problem I have is that the standard way I would normally do this through the System.XML libraries likes to load the whole file into memory before it does anything with it, which can cause memory problems with files of this size. I don't need to be updating the files at all just reading them and querying the data contained in them. Some of the XPath queries are quite involved and go across several levels of parent-child type relationship - I'm not sure whether this will affect the ability to use a stream reader rather than loading the data into memory as a block. One way I can see of making it work is to perform the simple analysis using a stream-based approach and perhaps wrapping the XPath statements into XSLT transformations that I could run across the files afterward, although it seems a little convoluted. Alternately I know that there are some elements that the XPath queries will not run across, so I guess I could break the document up into a series of smaller fragments based on it's original tree structure, which could perhaps be small enough to process in memory without causing too much havoc. I've tried to explain my objective here so if I'm barking up totally the wrong tree in terms of general approach I'm sure you folks can set me right...

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• svn import, dont modify revision OR modify the list of files in a transaction

  - by Vaughan Durno

  Hi Ive gained so much knowledge/insight from this site in the past few years, now im actually hoping to get some enlightenment. The scenario is as follows: You have the general structure of the repo (trunk,branches,tags) but added to the layout you have another directory called 'db_revs'. Now in the pre-commit, you take a dump of a specific database (the specifics are irrelevant) into a temporary file, say /tmp/REV.sql (REV being the HEAD revision number of the repo, or the transaction). K all is well and you can just import that temp file into the repo at /db_revs/REV.sql Now obviously that import, even tho its happening during a commit, increments the revision of the repo. So when u do a commit at some point to say 'test.php' in the trunk and it completes at say revision 159, then the pre-commit runs as it should and the DB dump gets imported but then u r sitting with a tree in the repo-browser where 'trunk' is at revision 159, and 'db_revs', which has the imported dump, is at 158 (Ive made it so that the filename matches the revision ie: 159.sql but that file is then at revision 158). NB If you're doing an import in a pre-commit, you need to add some logic to not perform the import, say by checking first for the existence of the temp file, otherwise it will cause, um, a stack overflow and your PC will quickly crawl to a stand still So I wanted to know if it was possible to make an import to not commit its changes. I realise I might be barking up the wrong tree to begin with so I have another idea of doing this so that brings me to the 2nd part of my question, would it be possible to modify the list of files that the transaction is about to commit to the repo. I know this can be done to a WC but that wont help as a WC is a checked out copy of say the trunk so im not sure how u would add a file to the 'db_revs' folder which is above trunk? Any help is greatly appreciated Cheers Vaughan

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• Dojo Widgets not rendering when returned in response to XhrPost

  - by lazynerd

  I am trying to capture the selected item in a Dijit Tree widget to render remaining part of the web page. Here is the code that captures the selected item and sends it to Django backend: <div dojoType="dijit.Tree" id="leftTree" store="leftTreeStore" childrenAttr="folders" query="{type:'folder'}" label="Explorer"> <script type="dojo/method" event="onClick" args="item"> alert("Execute of node " + termStore.getLabel(item)); var xhrArgs = { url: "/load-the-center-part-of-page", handleAs: "text", postData: dojo.toJson(leftTreeStore.getLabel(item), true), load: function(data) { dojo.byId("centerPane").innerHTML = data; //window.location = data; }, error: function(error) { dojo.byId("centerPane").innerHTML = "<p>Error in loading...</p>"; } } dojo.byId("centerPane").innerHTML = "<p>Loading...</p>"; var deferred = dojo.xhrPost(xhrArgs); </script> </div> The remaining part of the page contains HTML code with dojo widgets. This is the code sent back as 'response' to the select item event. Here is a snippet: <div dojoType="dijit.layout.TabContainer" id="tabs" jsId="tabs"> <div dojoType="dijit.layout.BorderContainer" title="Dashboard"> <div dojoType="dijit.layout.ContentPane" region="bottom"> first tab </div> </div> <div dojoType="dijit.layout.BorderContainer" title="Compare"> <div dojoType="dijit.layout.ContentPane" region="bottom"> Second Tab </div> </div> </div> It renders this html 'response' but without the dojo widgets. Is handleAs: "text" in XhrPost the culprit here?

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• JQuery selector for first hierarchy element?

  - by Sebastian P.R. Gingter

  I have this HTML structure: <div class="start"> <div class="someclass"> <div class="catchme"> <div="nested"> <div class="catchme"> <!-- STOP! no, no catchme's within other catchme's --> </div> </div> </div> <div class="someclass"> <div class="catchme"> </div> </div> </div> <div class="otherclass"> <div class="catchme"> </div> </div> </div> I am looking for a JQuery structure that returns all catchme's within my 'start' container, except all catchme's that are contained in a found catchme. In fact I only want all 'first-level' catchme's regardless how deep they are in the DOM tree. This is something near, but not really fine: var start = $('.start'); // do smething $('.catchme:first, .catchme:first:parent + .catchme', start) I sort of want to break further traversing down the tree behind all found elements. Any ideas?

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• Using a version control system as a data backend

  - by JacobM

  I'm involved in a project that, among other things, involves storing edits and changes to a large hierarchical document (HTML-formatted text). We want to include versioning of textual changes and of structural changes. Currently we're maintaining the tree of document sections in a relational database, but as we start working on how to manage versioning of structural changes, it's clear that we're in danger of having to write a lot of the functionality that a version control system provides. We don't want to reinvent the wheel. Is it possible that we could use an existing version control system as the data store, at least for the document itself? Presumably we could do so by writing out new versions to the filesystem, and keeping that directory under version control (and programmatically doing commits and so forth) but it would be better if we could directly interact with the repository via code. The VCS that we are most familiar with is Subversion, but I'm not thrilled with how Subversion represents changes to the directory structure -- it would be nice if we could see that a particular revision included moving a section from Chapter 2 to Chapter 6, rather than just seeing a new version of the tree. This sounds more like the way a system like Mercurial handles changes to the structure. Any advice? Do VCS's have public APIs and so forth? The project is in Java (with Spring) if it matters.

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• Poor LLVM JIT performance

  - by Paul J. Lucas

  I have a legacy C++ application that constructs a tree of C++ objects. I want to use LLVM to call class constructors to create said tree. The generated LLVM code is fairly straight-forward and looks repeated sequences of: ; ... %11 = getelementptr [11 x i8*]* %Value_array1, i64 0, i64 1 %12 = call i8* @T_string_M_new_A_2Pv(i8* %heap, i8* getelementptr inbounds ([10 x i8]* @0, i64 0, i64 0)) %13 = call i8* @T_QueryLoc_M_new_A_2Pv4i(i8* %heap, i8* %12, i32 1, i32 1, i32 4, i32 5) %14 = call i8* @T_GlobalEnvironment_M_getItemFactory_A_Pv(i8* %heap) %15 = call i8* @T_xs_integer_M_new_A_Pvl(i8* %heap, i64 2) %16 = call i8* @T_ItemFactory_M_createInteger_A_3Pv(i8* %heap, i8* %14, i8* %15) %17 = call i8* @T_SingletonIterator_M_new_A_4Pv(i8* %heap, i8* %2, i8* %13, i8* %16) store i8* %17, i8** %11, align 8 ; ... Where each T_ function is a C "thunk" that calls some C++ constructor, e.g.: void* T_string_M_new_A_2Pv( void *v_value ) { string *const value = static_cast<string*>( v_value ); return new string( value ); } The thunks are necessary, of course, because LLVM knows nothing about C++. The T_ functions are added to the ExecutionEngine in use via ExecutionEngine::addGlobalMapping(). When this code is JIT'd, the performance of the JIT'ing itself is very poor. I've generated a call-graph using kcachegrind. I don't understand all the numbers (and this PDF seems not to include commas where it should), but if you look at the left fork, the bottom two ovals, Schedule... is called 16K times and setHeightToAtLeas... is called 37K times. On the right fork, RAGreed... is called 35K times. Those are far too many calls to anything for what's mostly a simple sequence of call LLVM instructions. Something seems horribly wrong. Any ideas on how to improve the performance of the JIT'ing?

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• org.hibernate.hql.ast.QuerySyntaxException: TABLE NAME is not mapped

  - by Coronatus

  I have two models, Item and ShopSection. They have a many-to-many relationship. @Entity(name = "item") public class Item extends Model { @ManyToMany(cascade = CascadeType.PERSIST) public Set<ShopSection> sections; } @Entity(name = "shop_section") public class ShopSection extends Model { public List<Item> findActiveItems(int page, int length) { return Item.find("select distinct i from Item i join i.sections as s where s.id = ?", id).fetch(page, length); } } findActiveItems is meant to find items in a section, but I get this error: org.hibernate.hql.ast.QuerySyntaxException: Item is not mapped [select distinct i from Item i join i.sections as s where s.id = ?] at org.hibernate.hql.ast.util.SessionFactoryHelper.requireClassPersister(SessionFactoryHelper.java:180) at org.hibernate.hql.ast.tree.FromElementFactory.addFromElement(FromElementFactory.java:111) at org.hibernate.hql.ast.tree.FromClause.addFromElement(FromClause.java:93) at org.hibernate.hql.ast.HqlSqlWalker.createFromElement(HqlSqlWalker.java:322) at org.hibernate.hql.antlr.HqlSqlBaseWalker.fromElement(HqlSqlBaseWalker.java:3441) at org.hibernate.hql.antlr.HqlSqlBaseWalker.fromElementList(HqlSqlBaseWalker.java:3325) at org.hibernate.hql.antlr.HqlSqlBaseWalker.fromClause(HqlSqlBaseWalker.java:733) at org.hibernate.hql.antlr.HqlSqlBaseWalker.query(HqlSqlBaseWalker.java:584) at org.hibernate.hql.antlr.HqlSqlBaseWalker.selectStatement(HqlSqlBaseWalker.java:301) at org.hibernate.hql.antlr.HqlSqlBaseWalker.statement(HqlSqlBaseWalker.java:244) at org.hibernate.hql.ast.QueryTranslatorImpl.analyze(QueryTranslatorImpl.java:254) at org.hibernate.hql.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:185) at org.hibernate.hql.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:136) at org.hibernate.engine.query.HQLQueryPlan.<init>(HQLQueryPlan.java:101) at org.hibernate.engine.query.HQLQueryPlan.<init>(HQLQueryPlan.java:80) at org.hibernate.engine.query.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:124) at org.hibernate.impl.AbstractSessionImpl.getHQLQueryPlan(AbstractSessionImpl.java:156) at org.hibernate.impl.AbstractSessionImpl.createQuery(AbstractSessionImpl.java:135) at org.hibernate.impl.SessionImpl.createQuery(SessionImpl.java:1770) at org.hibernate.ejb.AbstractEntityManagerImpl.createQuery(AbstractEntityManagerImpl.java:272) ... 8 more What am I doing wrong?

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• MS Query Analyzer / Management Studio replacement?

  - by kprobst

  I've been using SQL Server since version 6.5 and I've always been a bit amazed at the fact that the tools seem to be targeted to DBAs rather than developers. I liked the simplicity and speed of the Query Analyzer for example, but hated the built-in editor, which was really no better than a syntax coloring-capable Notepad. Now that we have Management Studio the management part seems a bit better but from a developer standpoint the tools is even worse. Visual Studio's excellent text editor... without a way to customize keyboard bindings!? Don't get me started on how unusable is the tree-based management hierarchy. Why can't I re-root the tree on a list of stored procs for example the way the Enterprise Manager used to allow? Now I have a treeview that needs to be scrolled horizontally, which makes it eminently useless. The SQL server support in Visual Studio is fantastic for working with stored procedures and functions, but it's terrible as a general ad hoc data query tool. I've tried various tools over the years but invariably they seem to focus on the management side and shortchange the developer in me. I just want something with basic admin capabilities, good keyboard support and requisite DDL functionality (ideally something like the Query Analyzer). At this point I'm seriously thinking of using vim+sqlcmd and a console... I'm that desperate :) Those of you who work day in and day out with SQL Server and Visual Studio... do you find the tools to be adequate? Have you ever wished they were better and if you have found something better, could you share please? Thanks!

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• stack overflow problem in program

  - by Jay

  So I am currently getting a strange stack overflow exception when i try to run this program, which reads numbers from a list in a data/text file and inserts it into a binary search tree. The weird thing is that when the program works when I have a list of 4095 numbers in random order. However when i have a list of 4095 numbers in increasing order (so it makes a linear search tree), it throws a stack overflow message. The problem is not the static count variable because even when i removed it, and put t=new BinaryNode(x,1) it still gave a stack overflow exception. I tried debugging it, and it broke at if (t == NULL){ t = new BinaryNode(x,count); Here is the insert function. BinaryNode *BinarySearchTree::insert(int x, BinaryNode *t) { static long count=0; count++; if (t == NULL){ t = new BinaryNode(x,count); count=0; } else if (x < t->key){ t->left = insert(x, t->left); } else if (x > t->key){ t->right = insert(x, t->right); } else throw DuplicateItem(); return t; }

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• Help regarding composite pattern with hibernate

  - by molleman

  Hello, So i am stuck, i am creating a gwt web application, i will be using a tree(gwt Tree and TreeItems) structure to show a list of folders(class Folder) and files(class FileLocation), the folder and filelocation class will all implement a Hierarchy interface basing the classes on the composite pattern. but i am using hibernate to store my data , and i am using annotations for the mapping of the data to the database. my trouble is i do not know how to annotate my interface. have any of you guys used the composite pattern while persisting the data with hibernate public interface Hierarchy(){ // a few abstract methods that will be implemented by the sub classes } @Entity @Table() public class Folder extends Hierarchy implements Serializable { @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name = "folder_id", updatable = false, nullable = false) private int id; @OneToMany(cascade = CascadeType.ALL,fetch = FetchType.EAGER) @JoinTable(name = "FOLDER_FILELOCATION", joinColumns = { @JoinColumn(name = "folder_id") }, inverseJoinColumns = { @JoinColumn(name = "file_information_id") }) private List<Hierarchy> children = new ArrayList<Hierarchy>() ; @Column(name = "folder_name") private String folderName; @Column(name = "tree_item") private TreeItem item; @Column (name = "parent") private Hierarchy parent; @Entity @Table(name = "FILE_INFORMATION_TABLE") public class FileInformation extends Hierarchy implements Serializable { @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name = "file_information_id", updatable = false, nullable = false) private int fiId; @Column (name = "location") private String location; @Column(name = "tree_item") private TreeItem item; @Column (name = "parent") private Hierarchy parent;

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• Java Generic Casting Type Mismatch

  - by Kay

  public class MaxHeap<T extends Comparable<T>> implements Heap<T>{ private T[] heap; private int lastIndex; public void main(String[] args){ int i; T[] arr = {1,3,4,5,2}; //ERROR HERE ******* foo } public T[] Heapsort(T[]anArray, int n){ // build initial heap T[]sortedArray = anArray; for (int i = n-1; i< 0; i--){ //assert: the tree rooted at index is a semiheap heapRebuild(anArray, i, n); //assert: the tree rooted at index is a heap } //sort the heap array int last = n-1; //invariant: Array[0..last] is a heap, //Array[last+1..n-1] is sorted for (int j=1; j<n-1;j++) { sortedArray[0]=sortedArray[last]; last--; heapRebuild(anArray, 0, last); } return sortedArray; } protected void heapRebuild(T[ ] items, int root, int size){ foo } } The error is on the line with "T[arr] = {1,3,4,5,2}" Eclispe complains that there is a: "Type mismatch: cannot convert from int to T" I've tried to casting nearly everywhere but to no avail.A simple way out would be to not use generics but instead just ints but that's sadly not an option. I've got to find a way to resolve the array of ints "{1,3,4,5,2}" into an array of T so that the rest of my code will work smoothly.

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• Flex 3: should I provide prepared data to my component or make it to process data before display?

  - by grapkulec

  I'm starting to learn a little Flex just for fun and maybe to prove that I still can learn something new :) I have some idea for a project and one of its parts is a tree component which could display data in different ways depending on configuration. The idea There is list of objects having properties like id, date, time, name, description. And sometimes list should be displayed like this: first level: date second level: time third level: name and sometimes like this: first level: year second level: month third level: day fourth level: time and name By level I mean level of nesting of course. So, we can have years, that have months, that have days, that have hours and so forth. The problem What could be the best way to do it? I mean, should I prepare data for different ways of nesting outside of component or even outside of flex? I can do it at web service level in C# where I plan to have database access layer and send to flex nice and ready to display XML or array of objects. But I wonder if that won't cause additional and maybe unneccessary network traffic. I tried to hack some code in my component to convert my data objects into XML or ArrayCollection but I don't know enough of Flex and got stuck on elimination of duplicates or getting specific data by some key value. Usually to do such things I have STL with maps, sets and vectors and I find Flex arrays and even Dictionary a little bit confusing (I've read language reference and googled without any significant luck). The question So, to sum things up: should I give my tree component data prepared just for chosen type of display or should I try to do it internally inside component (or some helper class written in ActionScript)?

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• WPF - DataTemplate to show only one hierarchical level in recursive data

  - by Paull

  Hi all, I am using a tree to display my data: persons grouped by their teams. In my model a team can contain another team, so the recursion. I want do display details about the selected node of the tree using a contentpresenter. If the selection is a person, everything is fine: I can show the person name or datails without problem using a simple datatemplate. If the selection is a team I would like to display the team name followed by a list of member names. If one of these members is another team I would like to display just the team name, without recursion... My code here is wrong because it displays data in a recursive way, what is the right way of doing it? Thanks in advance for any help! best regards, Paolo <ContentPresenter Content="{Binding Path=SelectedItem, ElementName=PeopleTree}" > <ContentPresenter.Resources> <DataTemplate DataType="{x:Type my:PersonViewModel}"> <TextBlock Text="{Binding PersonName}"/> </DataTemplate> <DataTemplate DataType="{x:Type my:TeamViewModel}"> <StackPanel> <TextBlock Text="{Binding TeamName}" /> <ListBox ItemsSource="{Binding Members}" /> </StackPanel> </DataTemplate> </ContentPresenter.Resources> </ContentPresenter>

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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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• How to implement menuitems that depend on current selection in WPF MVVM explorer-like application

  - by Doug

  I am new to WPF and MVVM, and I am working on an application utilizing both. The application is similar to windows explorer, so consider an app with a main window with menu (ShellViewModel), a tree control (TreeViewModel), and a list control (ListViewModel). I want to implement menu items such as Edit - Delete, which deletes the currently selected item (which may be in the tree or in the list). I am using Josh Smith's RelayCommand, and binding the menuitem to a DeleteItemCommand in the ShellViewModel is easy. It seems like implementing the DeleteItemCommand, however, requires some fairly tight coupling between the ShellViewModel and the two child view models (TreeViewModel and ListViewModel) to keep track of the focus/selection and direct the action to the proper child for implementation. That seems wrong to me, and makes me think I'm missing something. Writing a focus manager and/or selection manager to do the bookkeeping does not seem too hard, and could be done without coupling the classes together. The windowing system is already keeping track of which view has the focus, and it seems like I'd be duplicating code. What I'm not sure about is how I would route the command from the ShellViewModel down to either the ListViewModel or the TreeViewModel to do the actual work without making a mess of the code. Some day, the application will be extended to include more than two children, and I want the shell to be as ignorant of the children as possible to make that extension as painless as possible. Looking at some sample WPF/MVVM applications (Karl Shifflett's CipherText, Josh Smith's MVVM Demo, etc.), I haven't seen any code that does this (or I didn't understand it). Regardless of whether you think my approach is way off base or I'm just missing a small nuance, please share your thoughts and help me get back on track. Thanks!

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• Why can't I access elements inside an XML file with XPath in XML::LibXML?

  - by John

  I have an XML file, part of which looks like this: <wave waveID="1"> <well wellID="1" wellName="A1"> <oneDataSet> <rawData>0.1123975676</rawData> </oneDataSet> </well> ... more wellID's and rawData continues here... I am trying to parse the file with Perl's libXML and output the wellName and the rawData using the following: use XML::LibXML; my $parser = XML::LibXML->new(); my $doc = $parser->parse_file('/Users/johncumbers/Temp/1_12-18-09-111823.orig.xml'); my $xc = XML::LibXML::XPathContext->new( $doc->documentElement() ); $xc->registerNs('ns', 'http://moleculardevices.com/microplateML'); my @n = $xc->findnodes('//ns:wave[@waveID="1"]'); #xc is xpathContent # should find a tree from the node representing everything beneath the waveID 1 foreach $nod (@n) { my @c = $nod->findnodes('//rawData'); #element inside the tree. print @c; } It is not printing out anything right now and I think I have a problem with my Xpath statements. Please can you help me fix it, or can you show me how to trouble shoot the xpath statements? Thanks.

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• Dynamically populated NSPopUpButtonCell menu in an NSOutlineView

  - by Mo

  I’m working with an NSOutlineView which has two columns. My dataSource supplies the outline view with a tree of items of a custom class which represents file types (that is, you initialise it with a UTI). The first column is the display name of the file type (e.g., “Source code”, “Interface Builder NIB document”, etc.). The second column is an NSPopUpButtonCell which is supposed to allow the user to pick a handler for the given document type (think of Xcode’s “File Types” preference pane, and you’re pretty much there). I can generate an NSMenu for a given item in the tree, populated with options based upon the Launch Services database entries for the UTI, complete with the relevant application icon and and so on. In fact, the menu itself works wonderfully, populated by way of NSPopUpButtonCellWillPopUpNotification. The problem is, try as I might, the cell when the menu isn’t popped up always contains precisely one of two things: either an empty string, or the default text for the cell, the former if the result of -handlerName on the item (the attribute assigned to the column) is non-nil, the latter otherwise. Moreover, I’m manually calling -selectItem: on the NSPopUpButtonCell instance, which just seems Wrong. In contrast, the left-hand column, which is just an NSTextFieldCell, everything just works (although granted, all it’s got to do is read the value from the item and present it). (Disclaimer: I’m fairly new at Cocoa UI stuff; I know Objective-C, and lots of other programming languages, but I’ve not a huge amount of experience of building Mac OS X UIs, so be gentle).

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• Orphan IBM JVM process

  - by Nicholas Key

  Hi people, I have this issue about orphan IBM JVM process being created in the process tree: For example: C:\Program Files\IBM\WebSphere\AppServer\bin>wsadmin -lang jython -f "C:\Hello.py" Hello.py has the simple implementation: import time i = 0 while (1): i = i + 1 print "Hello World " + str(i) time.sleep(3.0) My machine has such JVM information: C:\Program Files\WebSphere\java\bin>java -verbose:sizes -version -Xmca32K RAM class segment increment -Xmco128K ROM class segment increment -Xmns0K initial new space size -Xmnx0K maximum new space size -Xms4M initial memory size -Xmos4M initial old space size -Xmox1624995K maximum old space size -Xmx1624995K memory maximum -Xmr16K remembered set size -Xlp4K large page size available large page sizes: 4K 4M -Xmso256K operating system thread stack size -Xiss2K java thread stack initial size -Xssi16K java thread stack increment -Xss256K java thread stack maximum size java version "1.6.0" Java(TM) SE Runtime Environment (build pwi3260sr6ifix-20091015_01(SR6+152211+155930+156106)) IBM J9 VM (build 2.4, JRE 1.6.0 IBM J9 2.4 Windows Server 2003 x86-32 jvmwi3260sr6-20091001_43491 (JIT enabled, AOT enabled) J9VM - 20091001_043491 JIT - r9_20090902_1330ifx1 GC - 20090817_AA) JCL - 20091006_01 While the program is running, I tried to kill it and subsequently I found an orphan IBM JVM process in the process tree. Is there a way to fix this issue? Why is there an orphan process in the first place? Is there something wrong with my code? I really don't believe that my simplistic code is wrongly implemented. Any suggestions?

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