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  • Understanding Haskell's filter

    - by dmindreader
    I understand that Haskell's filter is a high order function (meaning a function that takes another function as a parameter) that goes through a list checking which element fulfills certain boolean condition. I don't quite understand its definition: filter:: (a->Bool)->[a]->[a] filter p [] = [] filter p (x:y) | p x = x:filter p y | otherwise = filter p y I understand that if I pass an empty list to the function, it would just return an empty list, but how do I read the last two lines?

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  • how to get path froma variable

    - by yoshco
    following http://stackoverflow.com/questions/659647/how-to-get-folder-path-from-file-path-with-cmd i want to strip the path (without the filename) from a variable. following the logic of the methods discussed above i would like to use batch bellow, which doesnt work. any takers? possible? set cpp="C:\temp\lib.dll" echo %cpp% "C:\temp\lib.dll" echo %~dpcpp "C:\temp\" > doesn't work

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  • How can I inherit an ASP.NET MVC controller and change only the view?

    - by AlexWalker
    I have a controller that's inheriting from a base controller, and I'm wondering how I can utilize all of the logic from the base controller, but return a different view than the base controller uses. The base controller populates a model object and passes that model object to its view, but I'm not sure how I can access that model object in the child controller so that I can pass it to the child controller's view.

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  • java asynchronous task.

    - by Tony
    For some of HTTP requests from clients, there was very complex business logic in server side. Some of these business logics doesn't require to response to the client immediately, like sending a email to somebody. Can I put those tasks in an asynchronous method.

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  • Overload the equals method in java

    - by fastcodejava
    Does anyone overload the equals method in java? The overloaded method will be public boolean equals(final MyClass myClass) This will have the benefit of having the relevant comparison part (guts of the method) in another method. Details are in this blog.

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  • How do I implement a TextBox that displays "Type here"?

    - by mafutrct
    Displaying "Type here to ..." until the user enters text into a TextBox is a well-known usability feature nowadays. How would one implement this feature in C#? My idea is to override OnTextChanged, but the logic to handle the changes of Text from and to "Type here" is a bit tricky... Displaying "Type here" on initialization and removing it on first input is easy, but I want to display the message every time the entered text becomes empty.

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  • How to refactor T-SQL stored procedure encapsulating it's parameters to a class

    - by abatishchev
    On my SQL Server 2008 I have a stored procedure with a large number of parameters. The first part of them is used in every call and parameters from the second part are used rarely. And I can't move the logic to two different stored procedures. Is there a way to encapsulate all this parameters to a class or struct and pass it as a stored procedure parameter? Can I use SQL CLR. Are there other ways?

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  • Overriding or overloading?

    - by atch
    Guys I know this question is silly but just to make sure: Having in my class method: boolean equal(Document d) { //do something } I'm overloading this method nor overriding right? I know that this or similiar question will be on upcoming egzam and would be stupid to not get points for such a simple mistake;

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  • WPF Reusing Xaml Effectively

    - by Steve
    Hi, I've recently been working on a project using WPF to produce a diagram. In this I must show text alongside symbols that illustrate information associated with the text. To draw the symbols I initially used some png images I had produced. Within my diagram these images appeared blurry and only looked worse when zoomed in on. To improve on this I decided I would use a vector rather than a rastor image format. Below is the method I used to get the rastor image from a file path: protected Image GetSymbolImage(string symbolPath, int symbolHeight) { Image symbol = new Image(); symbol.Height = symbolHeight; BitmapImage bitmapImage = new BitmapImage(); bitmapImage.BeginInit(); bitmapImage.UriSource = new Uri(symbolPath); bitmapImage.DecodePixelHeight = symbolHeight; bitmapImage.EndInit(); symbol.Source = bitmapImage; return symbol; } Unfortunately this does not recognise vector image formats. So instead I used a method like the following, where "path" is the file path to a vector image of the format .xaml: public static Canvas LoadXamlCanvas(string path) { //if a file exists at the specified path if (File.Exists(path)) { //store the text in the file string text = File.ReadAllText(path); //produce a canvas from the text StringReader stringReader = new StringReader(text); XmlReader xmlReader = XmlReader.Create(stringReader); Canvas c = (Canvas)XamlReader.Load(xmlReader); //return the canvas return c; } return null; } This worked but drastically killed performance when called repeatedly. I found the logic necessary for text to canvas conversion (see above) was the main cause of the performance problem therefore embedding the .xaml images would not alone resolve the performance issue. I tried using this method only on the initial load of my application and storing the resulting canvases in a dictionary that could later be accessed much quicker but I later realised when using the canvases within the dictionary I would have to make copies of them. All the logic I found online associated with making copies used a XamlWriter and XamlReader which would again just introduce a performance problem. The solution I used was to copy the contents of each .xaml image into its own user control and then make use of these user controls where appropriate. This means I now display vector graphics and performance is much better. However this solution to me seems pretty clumsy. I'm new to WPF and wonder if there is some built in way of storing and reusing xaml throughout an application? Apologies for the length of this question. I thought having a record of my attempts might help someone with any similar problem. Thanks.

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  • translating specifications into query predicates

    - by Jeroen
    I'm trying to find a nice and elegant way to query database content based on DDD "specifications". In domain driven design, a specification is used to check if some object, also known as the candidate, is compliant to a (domain specific) requirement. For example, the specification 'IsTaskDone' goes like: class IsTaskDone extends Specification<Task> { boolean isSatisfiedBy(Task candidate) { return candidate.isDone(); } } The above specification can be used for many purposes, e.g. it can be used to validate if a task has been completed, or to filter all completed tasks from a collection. However, I want to re-use this, nice, domain related specification to query on the database. Of course, the easiest solution would be to retrieve all entities of our desired type from the database, and filter that list in-memory by looping and removing non-matching entities. But clearly that would not be optimal for performance, especially when the entity count in our db increases. Proposal So my idea is to create a 'ConversionManager' that translates my specification into a persistence technique specific criteria, think of the JPA predicate class. The services looks as follows: public interface JpaSpecificationConversionManager { <T> Predicate getPredicateFor(Specification<T> specification, Root<T> root, CriteriaQuery<?> cq, CriteriaBuilder cb); JpaSpecificationConversionManager registerConverter(JpaSpecificationConverter<?, ?> converter); } By using our manager, the users can register their own conversion logic, isolating the domain related specification from persistence specific logic. To minimize the configuration of our manager, I want to use annotations on my converter classes, allowing the manager to automatically register those converters. JPA repository implementations could then use my manager, via dependency injection, to offer a find by specification method. Providing a find by specification should drastically reduce the number of methods on our repository interface. In theory, this all sounds decent, but I feel like I'm missing something critical. What do you guys think of my proposal, does it comply to the DDD way of thinking? Or is there already a framework that does something identical to what I just described?

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  • Simple but good pattern for EJB

    - by Sara
    What would you suggest as a good and practical but simple pattern for a soloution with: HTML + JSP (as a view/presentation) SERVLETS (controller, request, session-handling) EJB (persistence, businesslogic) MySQL DB And is it necessary to use an own layer of DAO for persistence? I use JPA to persist objects to my DB. Should I withdraw business logic from my EJB? Sources online all tell me different things and confuses me...

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  • Can this way of storing typed objects be improved?

    - by Pindatjuh
    This is an "can it be improved"-question. Topic: Storing typed objects in memory. Background information: I'm building a compiler for the x86-32 Windows platform for my language. My goal includes typed objects. Idea: Every primitive is a semi-class (it can be used as if it was a normal class, but it's stored more compact). Every class is represented by primitives and some meta-data (containing class-properties, inheritance stuff, etc.). The meta-data is complex: it doesn't use fields but instead context-switches. For primitives, the meta-data is very small, compared to a "real" class, which is alot bigger. This enables another idea that "primitives are objects", in my language, which I found nessecairy. Example: If I have an array of 32 booleans, then the pure content of this array is exactly 4 byte (32 bits of booleans). The meta-data will contain flags that the type is an array of booleans, which contains 32 entries. The meta-data is very compacted, on bit-level: using a sort of "packing" mechanism, which is read by a FSM at runtime, when doing inspection of the type (like when passing the object to methods for checking, etc.) For instance (read from left to right, top to bottom, remember vertical position when going to the right, and check nearest column header for meaning of switch): Primitive? Array? Type-Meta 1 Byte? || Size (1 byte) 1 1 [...] 1 [...] done 0 2 Bytes? || Size (2 bytes) 1 [...] done || Size (4 bytes) 0 [...] done Integer? 1 Byte? 2 Bytes? 0 1 0 1 done 1 done 0 done Boolean? Byte? 0 1 0 done 1 done More-Primitives 0 .... Class-Stuff (Huge) 0 ... (After reaching done the data is inserted. || = byte alignment. [...] is variable sized. ... is not described here, for simplicity. And let's call them cost-based-data-structures.) For an array of 32 booleans containing all true values, the memory for this type would be (read top-down): 1 Primitive 1 Array 1 ArrayType: Primitive 0 Not-Array 0 Not-Integer 1 Boolean 0 Not-Byte (thus bit) 1 Integer Size: 1 Byte 00100000 Array size 01010101 01010101 01010101 01010101 Data (user defined) Thus, 8 bytes represent 32 booleans in an array: 11100101 00100000 01010101 01010101 01010101 01010101 How can I improve this? (Both performance- and memory-consumption wise)

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  • get Phone numbers from android phone

    - by Luca
    Hi! First of all i'm sorry for my english... I've a problem getting phone numbers from contacts. That's my code import android.app.ListActivity; import android.database.Cursor; import android.os.Bundle; import android.provider.ContactsContract; import android.widget.SimpleAdapter; import android.widget.Toast; import java.util.ArrayList; import java.util.HashMap; public class TestContacts extends ListActivity { private ArrayList<HashMap<String,String>> list = new ArrayList<HashMap<String,String>>(); private SimpleAdapter numbers; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.contacts); numbers = new SimpleAdapter( this, list, R.layout.main_item_two_line_row, new String[] { "line1","line2" }, new int[] { R.id.text1, R.id.text2 } ); setListAdapter( numbers ); Cursor cursor = getContentResolver().query(ContactsContract.Contacts.CONTENT_URI, null, null, null, null); while (cursor.moveToNext()) { String contactId = cursor.getString(cursor.getColumnIndex( ContactsContract.Contacts._ID)); String hasPhone = cursor.getString(cursor.getColumnIndex( ContactsContract.Contacts.HAS_PHONE_NUMBER)); //check if the contact has a phone number if (Boolean.parseBoolean(hasPhone)) { Cursor phones = getContentResolver().query( ContactsContract.CommonDataKinds.Phone.CONTENT_URI, null, ContactsContract.CommonDataKinds.Phone.CONTACT_ID +" = "+ contactId, null, null); while (phones.moveToNext()) { // Get the phone number!? String contactName = phones.getString( phones.getColumnIndex( ContactsContract.CommonDataKinds.Phone.DISPLAY_NAME)); String phoneNumber = phones.getString( phones.getColumnIndex( ContactsContract.CommonDataKinds.Phone.NUMBER)); Toast.makeText(this, phoneNumber, Toast.LENGTH_LONG).show(); drawContact(contactName, phoneNumber); } phones.close(); } }cursor.close(); } private void drawContact(String name, String number){ HashMap<String,String> item = new HashMap<String,String>(); item.put( "line1",name); item.put( "line2",number); list.add( item ); numbers.notifyDataSetChanged(); } } It'seems that no contact have a phone number (i've added 2 contacts on the emulator and i've tried also on my HTC Desire). The problem is that if (Boolean.parseBoolean(hasPhone)) returns always false.. How can i get correctly phone numbers? I've tried to call drawContact(String name, String number) before the if statement without querying for the phone number, and it worked (it draws two times the name). but on the LinearLayout they are not ordered alphabetically... how can i order alphabetically (similar to the original contacts app)? thank you in advice, Luca

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  • how to find copyright code???

    - by micheal
    hi all, we were maintaining an MS Access application. Person who actually developed the application used copyrighted code. Now we want to remove that code and re-write that logic. Problem is we dont know what is the copyrighted code and what is not. Is there any way or tool that can be used to scan through the existing code and flag the code that was directly got from internet and used? Thanks in advance.

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  • Objects With No Behavior

    - by Patrick Donovan
    I've been teaching myself object oriented programming and I'm thinking about a situation where I have an object "Transaction", that has quite a few properties to it like account, amount, date, currency, type, etc. I never plan to mutate these data points, and calculation logic will live in other classes. My question is, is it poor Python design to instantiate thousands of objects just to hold data? I find the data far easier to work with embedded in a class rather than trying to cram it into some combination of data structures.

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  • Django: Is there any way to have "unique for date range"?

    - by tomwolber
    If my model for Items is: class Item(models.Model): name = models.CharField(max_length=500) startDate = models.DateField("Start Date", unique="true") endDate = models.DateField("End Date") Each Item needs to have a unique date range. for example, if i create an Item that has a date range of June 1st to June 8th, how can I keep and Item with a date range of June 3rd to June 5th from being created (or render an error with template logic)?

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  • User Session Management with Spring

    - by Chris
    I am developing a flex java - spring web app and have set up the business logic using hibernate. I want to maintain sessions so that when the user logs in , i can track the logged in user to display information that is related to the username. I want to do this using spring if possible and wondered if anyone could redirect me to a tutorial or even explain the method to which this is achieved , or if it is hard to achieve. Thanks Chris

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  • Store Image in DataTable

    - by Aizaz
    I want to store image into my datatable and while adding colum I want to set its default value, sending you code doing with checkboxes.. public void addCheckBoxesRuntime(){ for (int i = 0; i < InformationOne.Length; i++) { dt = new DataColumn(InformationOne[i][1] + " (" + InformationOne[i][0] + " )"); dt.DataType = typeof(Boolean); viewDataTable.Columns.Add(dt); dt.DefaultValue = false; } }

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  • Rails - Any plugins for building a online quiz/test?

    - by ChrisWesAllen
    Hello guys, I'm trying to add some online tests to my site and before I rolled up my sleeves I was wondering if there is any ruby on rails plugin support for such a task. Essentially I'm looking for something that lets me add multiple choice questions. Performing the scoring logic would be an added bonus. Any one know of anything?

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  • How do you reproduce bugs that occur sporadically?

    - by furtelwart
    We have a bug in our application that does not occur every time and therefore we don't know its "logic". I don't even get it reproduced in 100 times today. Disclaimer: This bug exists and I've seen it. It's not a pebkac or something similar. What are common hints to reproduce this kind of bug?

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  • Enable UIBarButtonItem if multiple UITextFields are all populated

    - by CrystalSkull
    I have 3 UITextFields in a grouped UITableView and am trying to figure out the correct logic to only have my 'Save' UIBarButtonItem enabled when none of the UITextFields are empty. I'm currently using the - (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string UITextField delegate method to detect changes to the field character by character, but it is providing inconsistent results. Any ideas?

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