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  • Scala class to implement two Java Interfaces - how?

    - by puudeli
    Hi, I have just started learning Scala and I'm now wondering how I could implement two different Java interfaces with one Scala class? Let's say I have the following interfaces written in Java public interface EventRecorder { public void abstract record(Event event); } public interface TransactionCapable { public void abstract commit(); } But a Scala class can extend only one class at a time. How can I have a Scala class that could fulfill both contracts? Do I have to map those interfaces into traits? Note, my Scala classes would be used from Java as I am trying to inject new functionality written in Scala into an existing Java application. And the existing framework expects that both interface contracts are fulfilled.

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  • Switching/Linking to another external stylesheet in a .js file using Ruby on Rails

    - by Jake
    Im learning JQuery from a Sitepoint Book but Im trying to apply all the lessons to a Rails App. In one lesson, we are taught how to switch to a different stylesheet if the browser window is resized beyond a certain point. Here's the javascript code: if ($('body').width() > 900) { $('<link rel="stylesheet" href="wide.css" type="text/css" />') .appendTo('head'); } else { $('link[href=wide.css]').remove(); } Rails doesn't seem to want to link to the new stylesheet using 'link rel'. I've tried using the Rails helper: <%= stylesheet_link_tag 'base', :media => 'screen' %> but that doesn't work in a .js file. How do I link to an external stylesheet in a .js file using Ruby? Can I use Ruby on Rails code in a .js file? Thanks.

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  • Why are the contents of my UITableViewCell disappearing?

    - by barfoon
    Hey everyone, I am learning about using the checkmark cell accessory and am wondering why the contents of my cell is disappearing when toggling it. Here is my code: + (void) toggleCheckmarkedCell:(UITableViewCell *)cell { if (cell.accessoryType == UITableViewCellAccessoryNone) cell.accessoryType = UITableViewCellAccessoryCheckmark; else cell.accessoryType = UITableViewCellAccessoryNone; } And here is didSelectRowAtIndexPath: UITableViewCell *cell = [tableView cellForRowAtIndexPath:indexPath]; [cell setSelectionStyle:UITableViewCellSelectionStyleNone]; [RootViewController toggleCheckmarkedCell:cell]; The checkmark is toggling on/off and is visible but the main contents of the cell disappears. Can anyone explain why this is happening? Thank you,

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  • Shall i learn Assembly Language or C, to Understand how "real programming" works?

    - by Daniel Upton
    Hello, World.. I'm a web developer mostly working in Ruby and C#.. I wanna learn a low level language so i dont look like an ass infront of my (computer science expert) boss. Ive heard a lot of purist buzz about how assembly language is the only way to learn how computers actually work, but on the other hand C would probably be more useful as a language rather than just for theory. So my question is.. Would Learning C teach me enough computer science theory / low level programming to not look like a common dandy (complete tool)? Thanks! Daniel

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  • argv[1] loadImage problem xcode 3.2 and snow leopard

    - by ignacionieto
    Hi Im on mac snow leopard and test these code on xcode3.2 of the Learning OpenCV everything works fine but the image doesnt appear and in the windows. I had try to understand searching for two days what does argv[1] means, but Im still no clear. Im a newbie en C++. I had the image in the same directory where the main.cpp is #include <OpenCV/cv.h> #include <OpenCV/highgui.h> int main(int argc, char** argv) { IplImage* interest_img; CvRect interest_rect; if( argc == 7 && ((interest_img= cvLoadImage( argv[1],1) ) != 0 )) { A more easy example is here: http://books.google.cl/books?id=seAgiOfu2EIC&pg=PA17&lpg=PA17&dq=cvLoadImage%28argv[1]&source=bl&ots=hRJ5bhkAOf&sig=gyYAqZBnS6lCCXJz9Fz7vzOsF-U&hl=es&ei=dvdvS-fWG8eWtgePy_WCBg&sa=X&oi=book_result&ct=result&resnum=6&ved=0CBwQ6AEwBTgK#v=onepage&q=cvLoadImage%28argv[1]&f=false both I have test it but they dont work. Please help me

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  • django left join with null

    - by SledgehammerPL
    The model: class Product(models.Model): name = models.CharField(max_length = 128) def __unicode__(self): return self.name class Receipt(models.Model): name = models.CharField(max_length=128) components = models.ManyToManyField(Product, through='ReceiptComponent') class Admin: pass def __unicode__(self): return self.name class ReceiptComponent(models.Model): product = models.ForeignKey(Product) receipt = models.ForeignKey(Receipt) quantity = models.FloatField(max_length=9) unit = models.ForeignKey(Unit) def __unicode__(self): return unicode(self.quantity!=0 and self.quantity or '') + ' ' + unicode(self.unit) + ' ' + self.product.genitive The idea: there are a components on stock. I'd like to find out which recipes I can made with components which I have. It's not easy - but possible - I made a SQL view, which gets the solution. But I'm learning python and Django so I'd like to make it Django-style ;D The concept of solution: get the set of recipes which has at last one component: list_of_available_components = ReceiptComponent.objects.filter(product__in=list_of_available_products).distinct() list_of_related_receipts = Receipt.objects.filter(receiptcomponent__in = list_of_available_components).distinct() get recipes (from list_of_related_receipts) which has not at last one component list_of_incomplete_recipes = (SELECT * FROM drinkbook_receiptcomponent LEFT JOIN drinkstore_stock_products USING(product_id) WHERE drinkstore_stock_products.stock_id IS NULL AND receipt_id IN (SELECT receipt_id FROM drinkbook_receiptcomponent JOIN drinkstore_stock_products USING(product_id))) get recipes (from list_of_related_receipts) which are not in "list_of_incomplete_recipes"

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  • Interested in embedded systems. Where to begin?

    - by Ala ABUDEEB
    Hello, i'm a computer systems engineering student. i'm interested in designing embedded systems but i don't know where to begin learning this, and what topics are essentially needed to proceed in this domain. So can you please tell me what topics do i have to study, and what books are available there in market or online that can help me??? please help me p.s. normally as an engineering student i have basic knowledge of circuit theory and microcontroller realm. thank you in advance.

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  • Jquery: how make div slide in and out

    - by Jeddizero
    Hi, I am currently learning jQuery. I'd like to know how to make an image slide in when you click on its edge, then click again and it slides away. Similar to this: http://www.karenmillen.com/ If you see the right hand side and click, there is the effect that i'm looking for. I assume this will involve making a div and giving it a background image then using some jquery to make the div slide into view. Of course the div could have other content such as html. Any ideas? Would the .slideDown() method work?

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  • How to use NSTableView's selectedRowIndexes?

    - by Jakub Lédl
    Hi guys, I'm just learning some basic programming in Objective C and Cocoa. I'm trying to get some data from NSTableView. Based on what I read in one tutorial, I wrote this: NSArray * items = [[itemsTableView selectedRowEnumerator] allObjects]; But then I learned that selectedRowEnumerator was deprecated already in 10.3 Panther and that I should use selectedRowIndexes. The problem is, I didn't find how to actually use the returned NSIndexSet to achieve the same result as with code written above. So, If anyone could give me a tip, I would be very grateful. Thanks.

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  • Get all folder / directories list in VB.net

    - by Henry
    Hi, this is my first Stackoverflow question, im learning VB and having a few problems with getting a list of all folders/directories on the system, im using the code included here and it seems to work until it hits the recycle bin folder, and some other system folders Sub main() Dim DirList As New ArrayList GetDirectories("c:\", DirList) For Each item In DirList 'add item to listbox or text etc here Next End sub End Sub Sub GetDirectories(ByVal StartPath As String, ByRef DirectoryList As ArrayList) Dim Dirs() As String = Directory.GetDirectories(StartPath) DirectoryList.AddRange(Dirs) For Each Dir As String In Dirs GetDirectories(Dir, DirectoryList) Next End Sub Can anyone help me with this, id like to know what is causing this first, and a good fix, or alternative way to do this. Thanks in advance.

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  • Ruby on Rails - where to write business logic while processing a request? (newbie)

    - by Genadinik
    I am learning Ruby on Rails. I made a simple link like this: <%= link_to "Alex Link", alexes_path(@alex) %> then I routed it in routes.rb like this: resources :alexes get "home/index" then I am a bit unclear, but I think it goes to this part of the controller: def index #@alexes = Alex.all respond_to do |format| format.html # index.html.erb format.json { render json: @alexes } end end Am I correct that it goes to this part of the controller? Then nothing much happens and it goes to the next page which is index.html.rb under views\alexes So what I am wondering is - if I needed to do some business logic, would I write that in the controller snippet? Where inside the snippet? An example would be nice to take a look. Also, I would like to connect to a MongoDb database. Would I also write that in the middle of the controller? Thanks!

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  • Resources to learn about engineering aspects of data analytics (OLAP, warehousing, ETL, etc.)

    - by JT
    I'm a math/stats guy, interested in learning more about the engineering aspects of "data analytics" (this may be an overly broad term, this is a case of "I don't know what I don't know", so I'm not sure how to be more specific). I'm fine with manipulating and analyzing the data once it's already stored somewhere and I can access it, and I'm fine with writing scripts and SQL queries (and have a general knowledge of things like normalization). What I don't know is the whole engineering process of capturing and storing the data. For example, terms I've heard thrown about that I only vaguely understand the meaning of include: - OLAP, OLTP - Data warehousing - ETL - ??? What's a good book (or any other resource) to learn about these kinds of things? What are things I should know about database design (normalization seems kinda "obvious" to me, something I would have done even before I knew the term -- is there anything else?)? In other words, for jobs falling under the umbrella term of "analytics engineer", what kinds of things should I know?

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  • How JQuery data validation plugin works on the submit action

    - by kwokwai
    Hi all, I am learning how to use JQuery validation plugin, and came across some questions about the JQuery magic that works on the sumbit action. I got a simple HTML form which has got an input text field like this: <form class="cmxform" id="commentForm" method="get" action=""> <input id="cname" name="name" size="25" class="required" minlength="2" /> <input class="submit" type="submit" value="Submit"/> </form> The magic happened when I tried not to input any data into the field and pressed the submit button. I saw an error message in red pop up, and no matter how hard and how many times I pressed the submit button, nothing was submitted. It seemed that there was some scripts that disabled the submit action, but I just couldn't find which lines of codes in the JQuery Validatyion Plugin that did it.

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  • I have Person.Surname field implemented as a string if I change the implementation of the field to a

    - by AndyM
    This is me going right back to basics with TDD for learning purposes. I originally implemented Person.Surname as field of type object (the simplest possible way of passing the test. I then added a test setting Person.Surname stating that the return value should be a string and set Person.Surname=20. I 'fixed' the test by changing the implementation to use string rather than object. The test now long compiles due to static type checking, so I commented it out. So I'm left with no way of leaving my intention in the test. Is there a way of having a failing test in this circumstance?

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  • Location of my own directories

    - by Nicsoft
    Hello, I am trying to understand how to create my own directory tree and access it from my application. I am doing some kind of learning program and want to create a directory structure like this: -MyLessonsDirectory --LessonDirectory_1 ---Step_1 ---Step_2 ---Step_3 --LessonDirectory_2 ---Step_1 ---Step_2 ---Step_3 . . and so on In each "Step"-directory I will have specific content for that step of the lesson. The content is added by me while developing. Hence, I don't want to create the structure and content from within the application, just access it and reading the content of the directories. If I can create this kind of structure and use it it will be very easy to create a nice design that makes it easy to create new lessons in my app. What I cannot figure out is where I should create those directories in the file-structure in xCode and what is the path to those directories from my application. Thanks in advance!

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  • microsoft certification in c# 3.5 and its tutorials

    - by user238284
    i am 2010 passed out. i am interested in completing a certification in c#. certifications available are MCTS Exam 70 536 (for framework 3.5 / 2) and MCTS Exam 70 515(for framework 4.0). wer wil i get its proper study material and tutorials. is there any recommendation from u about, from which exam a beginner in c# should start with.. please help me ....... **thanking u** http://www.microsoft.com/learning/en/us/certification/cert-vstudio.aspx#tab2 http://en.csharp-online.net/CSharp_Certification%2C_Development%2C_and_Training

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  • Are there any good videos out there on Java Design Patterns?

    - by Becky Reamy
    My team would like to spend some time at lunch learning design patterns. Previously, we watched some videos on Javascript which we found very useful as a way to start discussions. We would like to do the same thing with design patterns so that we don't have to spend a lot of time (outside of work) researching individual patterns in order to give a presentation. I did a little searching and came up fairly empty handed. Any help would be appreciated. It doesn't even have to be a video, even something that we can listen to (maybe a book on tape even).

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  • The next step & technology towards web services.

    - by webzide
    Hi, My name is Dennis and I am pretty ambitious of creating the next big thing for the web. I have ideas but now I gotta get to work to learn the tools. I am learning Javascript. I don't know if next step for me to take is PHP or some suggests RUBY on Rails. What are the pros and cons. With your experience, I wish you could hint me to the right direction. Thanks. I don't mind working hard. My goal is to create a comprehensive and secure web service platform as well as a fast and user friendly UI.

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  • What unix text editor should I learn? [closed]

    - by sixtyfootersdude
    Maybe this should be a community wiki page... What unix text editor should I learn? My co-workers mostly use vi. I am thinking about vim because the syntax highlighting seems appealing. Is there any advantage to vi over vim? I know that there are a lot of emacs fans out there too? Is there any reason to learn a specific editor? Can you point me to some good learning references (for your suggested editor)? Thanks!

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  • abstract method signature, inheritance, and "Do" naming convention

    - by T. Webster
    I'm learning about design patterns and in examples of code I've seen a convention where the abstract class declares a method, for example: public abstract class ServiceBase { ... public virtual object GetSomething(); and then protected abstract object DoGetSomething(); My question is on why these two methods exist, since they appear to serve the same purpose. Is this so that the base class GetSomething() method logic cannot be overridden by inherited classes? But then again, the method is marked virtual, so it can be overridden anyway. What is the usefulness here in requiring derived class implementers to implement the abstract method when the virtual method can be called anyway?

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  • How can I detect whether an image is a PNG or APNG format?

    - by perlit
    APNG is backwards compatible with PNG. I opened up an apng and png file in a hex editor and the first few bytes look identical. So if a user uploads either of these formats, how do I detect what the format really is? I've seen this done on some sites that block apng. I'm guessing the ImageMagick library makes this easy, but what if I were to do the detect without the use of an image processing library (for learning purposes)? Can I look for specific bytes that tell me if the file is apng? Solutions in any language is welcome.

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  • Copy constructor with more than one parameter

    - by Ravi Gupta
    I am learning C++ and was reading copy constructor from the C++: The Complete Reference. The books says that It is permissible for a copy constructor to have additional parameters as long as they have default arguments defined for them. However, in all cases the first parameter must be a reference to the object doing the initializing. But I am confused that how we are going to pass those additional parameters? I am sure there should be some way which is not given in the book and which I am unable to figure out. Can anyone help me out? EDIT: Also is it possible to pass these extra parameters in all three cases i.e. ¦ When one object explicitly initializes another, such as in a declaration ¦ When a copy of an object is made to be passed to a function ¦ When a temporary object is generated (most commonly, as a return value)

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  • How to select the nth row in a SQL database table?

    - by Charles Roper
    I'm interested in learning some (ideally) database agnostic ways of selecting the nth row from a database table. It would also be interesting to see how this can be achieved using the native functionality of the following databases: SQL Server MySQL PostgreSQL SQLite Oracle I am currently doing something like the following in SQL Server 2005, but I'd be interested in seeing other's more agnostic approaches: WITH Ordered AS ( SELECT ROW_NUMBER() OVER (ORDER BY OrderID) AS RowNumber, OrderID, OrderDate FROM Orders) SELECT * FROM Ordered WHERE RowNumber = 1000000 Credit for the above SQL: Firoz Ansari's Weblog Update: See Troels Arvin's answer regarding the SQL standard. Troels, have you got any links we can cite?

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  • Are Scala "continuations" just a funky syntax for defining and using Callback Functions?

    - by Alex R
    And I mean that in the same sense that a C/Java for is just a funky syntax for a while loop. I still remember when first learning about the for loop in C, the mental effort that had to go into understanding the execution sequence of the three control expressions relative to the loop statement. Seems to me the same sort of effort has to be applied to understand Continuations (in Scala and I guess probably other languages). And then there's the obvious follow-up question... if so, then what's the point? It seems like a lot of pain (language complexity, programmer errors, unreadable programs, etc) for no gain.

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  • iPhone Accelerometer > csv > email

    - by Bradley Powers
    Hi all, I'm trying to collect data for a machine learning project I'm working on. What I'd like to do is collect accelerometer data from an iPhone, save it to a csv and email it to myself. My app currently is able to acquire data from the accelerometer, but I'm at a bit of a loss as to how to proceed. First of all, I'd like to acquire data for a preset amount of time (after playing a sound to the user) which I don't really know how to do, and I can't find good documentation for. Also, I'd like to save that to a csv, which there is some documentation on (specifically using the NSString writeToFile method). Any recommendations/ ideas? Thanks!

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