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  • design patterns for hierarchical structures

    - by JLBarros
    Anyone knows some design patterns for hierarchical structures? For example, to manage inventory categories, accounting chart of accounts, divisions of human resources, etc.. Thank you very much in advance EDIT: Thanks for your interest. I am looking for a better way of dealing with hierarchical items to which they should apply operations depending on the level of hierarchy. I have been studying the patterns by Martin Fowler, for example Accounting, but I wonder if there are other more generic. The problem is that operations apply to the items must be possible to change even at run time and may depend on other external variables. I thought of a kind of strategy pattern but would like to combine it with the fact that it is a hierarchical scheme. I would appreciate any reference to hierarchical patterns and you'll take care of them in depth.

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  • MySQL - How do I insert an additional where clause into this full-text search query

    - by Steven
    I want to add a WHERE clause to a full text search query (to limit to past 24 hours), but wherever I insert it I get Low Level Error. Is it possible to add the clause and if so, how? $query = "SELECT * WHERE story_time > time()-86400 AND MATCH (story_title) AGAINST ('".validate_input($_GET['q'])."' IN BOOLEAN MODE) AS Relevance FROM ".$config['db']['pre']."stories WHERE MATCH (story_title) AGAINST ('+".validate_input($_GET['q'])."' IN BOOLEAN MODE) HAVING Relevance > 0.2 ORDER BY Relevance DESC, story_time DESC LIMIT ".validate_input(($_GET['page']-1)*10).",10";

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  • Adapting methods which return true/false

    - by James P.
    What's the best practise when adapting C-style functions which return a true/false to Java? Here's a simple method to illustrate where the problem lies. public static boolean fileNameEndsWithExtension( String filename, String fileExtension) { return filename.endsWith( fileExtension ); } Note that there's probably a more elegant way of filtering files (feel free to comment on this). Anyway, if filename is a null value, does one: Return a false if filename is null? If so, how does one go about distinguishing between the case where filename is null and the case where the String or file name doesn't end with a given file extension? Change the return type to the wrapper class Boolean which allows a null value. Throw an Exception and force the programmer to make sure that a null value is never passed to the method? Use another solution?

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  • In Scala 2.8 collections, why was the Traversable type added above Iterable?

    - by Seth Tisue
    I know that to be Traversable, you need only have a foreach method. Iterable requires an iterator method. Both the Scala 2.8 collections SID and the "Fighting Bitrot with Types" paper are basically silent on the subject of why Traversable was added. The SID only says "David McIver... proposed Traversable as a generalization of Iterable." I have vaguely gathered from discussions on IRC that it has to do with reclaiming resources when traversal of a collection terminates? The following is probably related to my question. There are some odd-looking function definitions in TraversableLike.scala, for example: def isEmpty: Boolean = { var result = true breakable { for (x <- this) { result = false break } } result } I assume there's a good reason that wasn't just written as: def isEmpty: Boolean = { for (x <- this) return false true }

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  • arrayListOutOfBoundsException... Please Help?

    - by Jacob
    This is my class Debugger. Can anyone try and run it and see whens wrong? Ive spent hours on it already. :( public class Debugger { private String codeToDebug = ""; public Debugger(String code) { codeToDebug = code; } /** * This method itterates over a css file and adds all the properties to an arraylist */ public void searchDuplicates() { boolean isInside = false; ArrayList<String> methodStorage = new ArrayList(); int stored = 0; String[] codeArray = codeToDebug.split(""); try { int i = 0; while(i<codeArray.length) { if(codeArray[i].equals("}")) { isInside = false; } if(isInside && !codeArray[i].equals(" ")) { boolean methodFound = false; String method = ""; int c = i; while(!methodFound) { method += codeArray[c]; if(codeArray[c+1].equals(":")) { methodFound = true; } else { c++; } } methodStorage.add(stored, method); System.out.println(methodStorage.get(stored)); stored++; boolean stillInside = true; int skip = i; while(stillInside) { if(codeArray[skip].equals(";")) { stillInside = false; } else { skip++; } } i = skip; } if(codeArray[i].equals("{")) { isInside = true; } i++; } } catch(ArrayIndexOutOfBoundsException ar) { System.out.println("------- array out of bounds exception -------"); } } /** * Takes in String and outputs the number of characters it contains * @param input * @return Number of characters */ public static int countString(String input) { String[] words = input.split(""); int counter = -1; for(int i = 0; i<words.length; i++){ counter++; } return counter; } public static void main(String[] args) { Debugger h = new Debugger("body {margin:;\n}"); h.searchDuplicates(); } }

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  • Config file format

    - by Felics
    Hello, does anyone knows a file format for configuration files easy to read by humans? I want to have something like tag = value where value may be: String Number(int or float) Boolean(true/false) Array(of String values, Number values, Boolean values) Another structure(it will be more clear what I mean in the fallowing example) Now I use something like this: IntTag=1 FloatTag=1.1 StringTag="a string" BoolTag=true ArrayTag1=[1 2 3] ArrayTag2=[1.1 2.1 3.1] ArrayTag3=["str1" "str2" "str3"] StructTag= { NestedTag1=1 NestedTag2="str1" } and so on. Parsing is easy but for large files I find it hard to read/edit in text editors. I don't like xml for the same reason, it's hard to read. INI does not support nesting and I want to be able to nest tags. I also don't want a complicated format because I will use limited kind of values as I mentioned above. Thanks for any help.

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  • Interface name as a Type

    - by user1889148
    I am trying to understand interfaces in Java and have this task to do which I am a stack with. It must be something easy, but I don't seem to see the solution. Interface contains a few methods, one of them should return true if all elements of this set are also in the set. I.e. public interface ISet{ //some methods boolean isSubsetOf(ISet x); } Then the class: public class myClass implements ISet{ ArrayList<Integer> mySet; public myClass{ mySet = new ArrayList<Integer>(); } //some methods public boolean isSubsetOf(ISet x){ //method body } } What do I need to write in method body? How do I check that the instance of myClass is a subset of ISet collection? I was trying to cast, but it gives an error: ArrayList<Integer> param = (ArrayList<Integer>)x; return param.containsAll(mySet);

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  • Big-O for Eight Year Olds?

    - by Jason Baker
    I'm asking more about what this means to my code. I understand the concepts mathematically, I just have a hard time wrapping my head around what they mean conceptually. For example, if one were to perform an O(1) operation on a data structure, I understand that the amount of operations it has to perform won't grow because there are more items. And an O(n) operation would mean that you would perform a set of operations on each element. Could somebody fill in the blanks here? Like what exactly would an O(n^2) operation do? And what the heck does it mean if an operation is O(n log(n))? And does somebody have to smoke crack to write an O(x!)?

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  • Parameter is not valid when getting image from stream

    - by duka1
    Hi guys, I have this code: MemoryStream ms = new MemoryStream(newbytes, 0, newbytes.Length); ms.Position = 0; ms.Write(newbytes, 0, newbytes.Length); Image img = Image.FromStream(ms); img.Save(@"C:\Users\gsira\Pictures\Blue hills5.jpg"); I get this error at the Image.FromStream(ms) call: System.ArgumentException: Parameter is not valid. at System.Drawing.Image.FromStream(Stream stream, Boolean useEmbeddedColorManagement, Boolean validateIma How can I resolve this? A couple of links which solve this problem (one on an MSDN thread) are broken so I am lost.

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  • API verbs for an interruptible operation

    - by 280Z28
    I have a long running task as part of my application. The task can be started, paused, resumed, and cancelled. I'm trying to find the best interface for these operations. Two seem clear: Pause and Cancel. This leaves the start and resume operations. I could include both Start and Resume. This has the downside of either requiring the API consumer to check the state before starting/resuming the operation to call the right method, or making the methods aliases of each other. I'm thinking I should include either Start or Resume, but I don't know which one is the most appropriate. Does anyone have any examples in the .NET Framework of such behavior? I prefer to follow established patterns whenever they are available.

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  • Can I compose a WCF callback contract out of multiple interfaces?

    - by mafutrct
    Followup question to http://stackoverflow.com/questions/2502930/how-can-i-compose-a-wcf-contract-out-of-multiple-interfaces. I tried to merge multiple callback interfaces in a single interface. This yields an InvalidOperationException claiming that the final interface contains no operations. Technically, this is true, however, the inherited interfaces do contain operations. How can I fix this? Or is this a limitation of WCF? Edit: interface A { [OperationContract]void X(); } interface B { [OperationContract]void Y(); } interface C: A, B {} // this is the public callback contract

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  • Good overview tool / board for visualizing Subversion branch acitivity?

    - by Sam
    Our team is sometimes finding it a bit confusing and time-consuming to figure out which subversion operations have been perrformed on our different branches in Subversion. Example, when has the Development branch last been merged into the Trunk? When was this particular Tag created, based on what branch etc etc. All of this information can of course be extracted from the Subversion Log, but thats always a manual, time-consuming and error-prone process. Simplest solution seems to be a simple whiteboard with a visualization of all the different branches/tags/trunk in Subversion and people drawing on it, whenever something significant happens. But we're not averse to finding some kind of a digital solution as well, stored centrally. Obviously both systems depend on people actually maintaining the model, but you'll always more or less have that. What do you use as best practice for keeping a clear view on all Subversion operations in the current Sprint (or beyond)?

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  • Questions about "casting operation" in OOP

    - by rhapsodyn
    When programming, we usually use some type-casting operations. When the casting happens on the objects "on the same level", it feels ok. But when it happens on the ojects "on the different levels"(mainly between father and son), it feels weird. Considering this: Class Son extends Father WhenSon s = (Son)father;, it's absolutely unreasonable. Because a "Son" is not a "Father" anymore, "Son" may grow up with some new properties "Father" doesn't have, the casting operation makes these properties unknown. On the other hand, Father f = (Father)son seems reasonable, but according to LSP "An instance of a derived should be able to replace any instance of its superclass" A "Son" can do anything his "Father" can, so the casting operation seems useless. So can i say that these casting operations are agaisnt OO design principle but necessary?

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  • How can CopyOnWriteArrayList be thread-safe?

    - by Shooshpanchick
    I've taken a look into OpenJDK's sources of CopyOnWriteArrayList and it seems that all write operations are protected by the same lock and read operations are not protected at all. As I understand, under JMM all accesses to a variable (both read and write) should be protected by lock or reordering effects may occur. For example, set(int, E) method contains these lines (under lock): /* 1 */ int len = elements.length; /* 2 */ Object[] newElements = Arrays.copyOf(elements, len); /* 3 */ newElements[index] = element; /* 4 */ setArray(newElements); The get(int) method, on the other hand, only does return get(getArray(), index);. In my understanding of JMM, this means that get may observe the array in an inconsistent state if statements 1-4 are reordered like 1-2(new)-4-2(copyOf)-3. Do I understand JMM incorrectly or is there any other explanations on why CopyOnWriteArrayList is thread-safe?

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  • Processing large recordsets in Rails

    - by japancheese
    Hello, I'm trying to perform a daily operation on a larger than normal dataset (2m+ records). However, Rails seems to take a very long time performing operations on such a dataset. Operations like Dataset.all.each do |data| ... end take a very long time to complete (I assume this is because it can't fit all the items into memory at once, right?). Does anyone have any strategies on how I could handle this situation? I know SQL would probably speed up the process, but I'm looking to use the Rails environment as I can do many more complicated things to the data than I can with just SQL statements.

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  • Android: How to set the contents of a Edit text from a Button click?

    - by primal
    Hi, I am a rookie to android. I am thinking of implementing a simple calculator in android to get a hold of the basics in android. I want to display a keypad with numbers and mathematical operations and when the user presses the keys the corresponding number is displayed in edit text. I tried using gettext() and updating the contents of edit text but it shows just the contents of pressed button. Also how do I read the contents of button so as to do mathematical operations in code? Any help would be much appreciated. regards, Primal

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  • DispatcherOperations.Wait()

    - by Mark
    What happens if you call dispatcherOperation.Wait() on an operation that has already completed? Also, the docs say that it returns a DispatcherOperationStatus, but wouldn't that always be Completed since it (supposedly) doesn't return until it's done? I was trying to use it like this: private void Update() { while (ops.Count > 0) ops.Dequeue().Wait(); } public void Add(T item) { lock (sync) { if (dispatcher.CheckAccess()) { list.Add(item); OnCollectionChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, item)); } else { ops.Enqueue(dispatcher.BeginInvoke(new Action<T>(Add), item)); } } } I'm using this in WPF, so all the Add operations have to occur on the UI thread, but I figured I could basically just queue them up without having to wait for it to switch threads, and then just call Update() before any read operations to ensure that the list is up to date, but my program started hanging.

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  • How do I do import hooks in IronPython/Silverlight?

    - by ahlatimer
    I'm extending TryPython to (along with various other things) allow users to save a file and subsequently import that file. TryPython overloads the built in file operations, so I need to know what parts of import need to hooked into in order for import to use the overloaded file operations. Really, a basic overview of IronPython's import when used in Silverlight would be extremely helpful. I don't need a complete working solution (although I won't stop you from writing one! :). I'm a Python newbie, and I really have no idea where to even begin. Thanks!

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  • Returnimng collection of interfaces

    - by apoorv020
    I have created the following interface public interface ISolutionSpace { public boolean isFeasible(); public boolean isSolution(); public Set<ISolutionSpace> generateChildren(); } However, in the implementation of ISolutionSpace in a class called EightQueenSolutionSpace, I am going to return a set of EightQueenSolutionSpace instances, like the following stub: @Override public Set<ISolutionSpace> generateChildren() { return new HashSet<EightQueenSolutionSpace>(); } However this stub wont compile. What changes do I need to make? EDIT: I tried 'HashSet' as well and had tried using the extends keyword. However since 'ISolutionSpace' is an interface and EightQueenSolutionSpace is an implementation(and not a subclass) of 'ISolutionSpace', it is still not working.

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  • Strategy for Storing Multiple Nullable Booleans in SQL

    - by Eric J.
    I have an object (happens to be C#) with about 20 properties that are nullable booleans. There will be perhaps a few million such objects persisted to a SQL database (currently SQL Server 2008 R2, but MySQL may need to be supported in the future). The instances themselves are relatively large because they contain about a paragraph of text as well as some other unrelated properties. For a given object instance, most of the properties will be null most of the time. When users search for instances of such objects, they will select perhaps 1-3 of the nullable boolean properties and search for instances where at least one of those 1-3 properties is non-null (OR search). My first thought is to persist the object to a single table with nullable BIT columns representing the nullable boolean properties. However, this strategy will require one index per BIT column to avoid performing a table scan when searching. Further, each index would not be particularly selective since there are only three possible values per index. Is there a better way to approach this problem?

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  • How to get the if the Page is Liked in my Facebook Application page

    - by Axe
    I'm using the Facebook sdk from codeplex I've tried the suggestion at How to get the Page Id in my Facebook Application page which is this: if (FacebookWebContext.Current.SignedRequest != null) { dynamic data = FacebookWebContext.Current.SignedRequest.Data; if (data.page != null) { var pageId = (String)data.page.id; var isUserAdmin = (Boolean)data.page.admin; var userLikesPage = (Boolean)data.page.liked; } else { // not on a page } } But my data.page is null. Do I need to ask for some extra permissions on the authorization or something? Also tried this the FQL suggested at http://blog.woodylabs.com/2010/09/facebook-graph-api-is-user-a-fan-of-page-id-using-fql-and-opengraph-to-mimic-pages-isfan/ But I only have an appId not a page ID. Any ideas?

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  • Overfocus in GridView

    - by chuck258
    I'm trying to implement a GridView that Focuses the next Item and "Overscrolls at the End of a List. E.g. 1 2 3 4 5 6 7 8 9 I want to scroll 1 2 3 4 5 6 ... just by pressing the right Key. Right now I can only Scroll 1 2 3 and then it stops and I have to scroll with the down Key. I already tried to set the focusViews in code (In the getView() method of my ArrayList Adapter, that fills the GridView) view.setId(position); view.setNextFocusLeftId(position-1); view.setNextFocusRightId(position+1); But that doesn't work. I found the boolean *Scroll(int direction) Methods on grepcode But theese are Package Local and I can't overwrite them. Any suggestions on how to solve this. Can I use another View and get the same Layout as a Gridview? I also set a OnFocusChangeListener to see what happens with no reaction. Edit: I just added this to my MainActivity, but now it seems to onKeyDown only get called when the GridView doesn't handle the KeyEvent (If the Last Item in a row is selected). @Override public boolean onKeyDown(int keyCode, KeyEvent event) { switch (keyCode) { case KeyEvent.KEYCODE_DPAD_LEFT: if (focusedView > 0) { mContainer.setSelection(--focusedView); Log.v("TEST", focusedView+""); } return true; case KeyEvent.KEYCODE_DPAD_RIGHT: if (focusedView < mAdapter.getCount() - 1) { mContainer.setSelection(++focusedView); Log.v("TEST", focusedView+""); } return true; } return super.onKeyDown(keyCode, event); } Edit 2: This is so f***ing stupid but works so damn fine :D @Override public boolean onKeyDown(int keyCode, KeyEvent event) { switch (keyCode) { case KeyEvent.KEYCODE_DPAD_LEFT: mContainer.onKeyDown(KeyEvent.KEYCODE_DPAD_UP, new KeyEvent(KeyEvent.ACTION_DOWN, KeyEvent.KEYCODE_DPAD_UP)); mContainer.onKeyDown(KeyEvent.KEYCODE_DPAD_RIGHT, new KeyEvent(KeyEvent.ACTION_DOWN, KeyEvent.KEYCODE_DPAD_RIGHT)); mContainer.onKeyDown(KeyEvent.KEYCODE_DPAD_RIGHT, new KeyEvent(KeyEvent.ACTION_DOWN, KeyEvent.KEYCODE_DPAD_RIGHT)); return true; case KeyEvent.KEYCODE_DPAD_RIGHT: mContainer.onKeyDown(KeyEvent.KEYCODE_DPAD_DOWN, new KeyEvent(KeyEvent.ACTION_DOWN, KeyEvent.KEYCODE_DPAD_DOWN)); mContainer.onKeyDown(KeyEvent.KEYCODE_DPAD_LEFT, new KeyEvent(KeyEvent.ACTION_DOWN, KeyEvent.KEYCODE_DPAD_LEFT)); mContainer.onKeyDown(KeyEvent.KEYCODE_DPAD_LEFT, new KeyEvent(KeyEvent.ACTION_DOWN, KeyEvent.KEYCODE_DPAD_LEFT)); return true; } return super.onKeyDown(keyCode, event); } I really don't want to post this as Answer, and I really don't want to have to use this Code because it is such a stupid workaround ;TLDR: Help still needed

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  • Create Class objects based on type signature

    - by Andreas_D
    Class.forName(boolean.class.getName()); This doesn't work in Java - the virtual machine slaps you with a ClassNotFoundException. I was in need for something like that because I wanted to reflect methods based on Strings that included the method signatures, like public void doSomething(boolean yesWeCan, java.lang.String[] presidents); At the end I came up with a custom 'ClassFactory' which translates the type Strings to class objects. This factory includes a lot of handlers for primitive and array type values. The handler for array type objects is something like: if (isArrayOfObjects) { return Class.forName("L["+typeName.replace("[]", "")+";"); } My question is - have I missed something in the Java 1.5+ API that might do the trick?

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