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  • Javascript function as a parameter to another function?

    - by Alex
    Hello there, I'm learning lots of javascript these days, and one of the things I'm not quite understanding is passing functions as parameters to other functions. I get the concept of doing such things, but I myself can't come up with any situations where this would be ideal? My question is: When do you want to have your javascript functions take another function as a parameter? Why not just assign a variable to that functions return value and pass that variable to the function like so: // Why not do this var foo = doStuff(params); callerFunction(foo); //instead of this callerFunction(doStuff); I'm confused as to why I would ever choose to do things as in my second example. Why would you do this? What are the use cases? Thanks!!

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  • IronPython :- Visual Studio 2010 or SharpDevelop?

    - by Cruachan
    I'm considering developing a medium-size project for a client in IronPython. It's a pretty straightforward replacement for an existing system I've been supporting for several years, so the specification is quite well defined and understood. This is my first significant IronPython and .Net project so I'm expecting a bit of a learning curve. I was going to use SharpeDevelop, but I can purchase VisualStudion 2010 for a reasonable price and whilst I understood that IronPython Tools for Visual Studio 2008 were not so good, I haven't seen anything about the update for 2010 yet. Has anyone used either or both of these in a reasonable-sized commercial environment and do you have any recommendations? (and I'm aware of this question, but this is specifically about VS2010)

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  • How do I maintain scroll position in MVC?

    - by Eric Brown
    Im working on a project in MVC and have enjoyed learning about it. There are a few growing pains but once you figure them out it's not bad. One thing that is really simple in the WebForms world is maintaining the scroll position on a page. All you do is set the MaintainScrollPositionOnPostback property to true. However, in MVC, Im not using postbacks so this will not work for me. What is the standard way of handling this? Edit: Ajax is acceptable, but I was also wondering how you would do it without AJAX.

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  • Is using decimal ranges in a switch impossible in C#?

    - by phobia
    I'm justing starting out learning C# and I've become stuck at something very basic. For my first "app" I thought I'd go for something simple, so I decided for a BMI calculator. The BMI is calculated into a decimal type which I'm now trying to use in a switch statement, but aparently decimal can't be used in a switch? What would be the C# solution for this: decimal bmi = calculate_bmi(h, w); switch (bmi) { case < 18.5: bmi_description = "underweight."; break; case > 25: bmi_description = "overweight"; case > 30: bmi_description = "very overweight"; case > 40: bmi_description = "extreme overweight"; break; }

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  • How to unit test internals (organization) of a data structure?

    - by Herms
    I've started working on a little ruby project that will have sample implementations of a number of different data structures and algorithms. Right now it's just for me to refresh on stuff I haven't done for a while, but I'm hoping to have it set up kind of like Ruby Koans, with a bunch of unit tests written for the data structures but the implementations empty (with full implementations in another branch). It could then be used as a nice learning tool or code kata. However, I'm having trouble coming up with a good way to write the tests. I can't just test the public behavior as that won't necessarily tell me about the implementation, and that's kind of important here. For example, the public interfaces of a normal BST and a Red-Black tree would be the same, but the RB Tree has very specific data organization requirements. How would I test that?

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  • Problems with classes (super new)

    - by user260036
    Hi, I've problems to figure it out what's happening in the following exercise, I'm learning Smalltalk, so I'm newbie. Class Anew ^super new initialize. Ainitialize a:=0. Class Bnew: aParameter |instance| instance := super new. instance b: instance a + aParameter. ^instance Binitialize b:=0. The problem says what happen when the following code is executed: B new:10. But I can't not figure it out why instance variable does not belong to A class. Thanks

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  • How can I implement my own version of a MVC framework in ASP.NET?

    - by ace
    Hi - I would like to know how I can go about implementing my own version of a MVC framework in ASP.NET? I know there already is Microsoft provided ASP.NET MVC framework, but I want to learn MVC and thought the best way would be to implement my own flavor of a MVC framework on top of ASP.NET. Any thoughts / guidance ? Also, can anyone point me to a page where I can learn more about how microsoft implemented ASP.NET MVC ? I'm more interested in learning about the under the hood plumbing that goes on to implement the framework on top of asp.net, do they use HttpHandlers / HttpModules ? Thanks.

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  • Php PEAR, Database Abstraction & Factory Methods

    - by pws5068
    I'm interested in learning more about design practices in PHP for Database Abstraction & Factory methods. For background, my site is a special-interest social networking community currently in beta mode. Currently, I've started moving my old code for object retrieval to factory methods. However, I do feel like I'm limiting myself by keeping a lot of SQL table names and structure separated in each function/method. Questions: 1.) Is there a reason to use PEAR (or similar) if I dont anticipate switching databases? 2.) Can PEAR interface with the MySqli prepared statements I currently use? 3.) Will it help me separate table names from each method? (If no, what other design patterns might I want to research?) 4.) Will it slow down my site once I have a significantly large member base?

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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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  • Are there any purely functional Schemes or Lisps?

    - by nickname
    Over the past few months, I've put a lot of effort into learning (or attempting to learn) several functional programming languages. I really like math, so they have been very natural for me to use. Simply to be more specific, I have tried Common Lisp, Scheme, Haskell, OCaml, and (a little bit of) Erlang. I did not like the syntax of OCaml and do not have enough Erlang knowledge to make a judgment on it yet. Because of its consistent and beautiful (non-)syntax, I really like Scheme. However, I really do appreciate the stateless nature of purely functional programming languages such as Haskell. Haskell looks very interesting, but the amount of inconsistent and non-extendable syntax really bothered me. In the interest of preventing a Lisp vs Haskell flame war, just pretend that I can't use Haskell for some other reason. Therefore, my question is: Are there any purely functional Schemes (or Lisps in general)?

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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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  • 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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  • 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 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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  • 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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  • 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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  • 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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  • 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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  • What fields have job security?

    - by computergeek6
    I can program pretty well, and I'm trying to think of a programming area that I can practice so I have a better chance of getting a job when I finish my education. I'm currently learning game development, but there are a ton of other people trying to get into game dev, so I want to find something a little more secure and sustainable to develop skills in. I've thought of things like financial systems and engineering stuff, but nothing I can think of is accessible to someone in high school. I'm trying to find something that involves physics or networking and isn't as popular a field as game dev. Does anyone have any ideas?

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  • How to handle similar items in rails MVC?

    - by mocker
    I'm working on building a pretty simple site mainly as an exercise in learning more about rails. You can see my rough progress at statific.com. It's working pretty much as I wanted it for keeping track of server information, but now I'd like to expand it to other things, next on the list being firewalls. I can pretty easily duplicate all the models, views, etc.. that I have for my servers. The problem I see with that is that it isn't very DRY since most of the code would look the same, the only difference would be the attributes I have setup for firewalls would be different than for servers. I know in plain ruby this is pretty simple, you can have a 'Product' w/ common attributes ('manufacturer', 'model') and then have children with more specific attributes. Does the same type of concept exist for rails, or am I just over thinking this?

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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 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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  • 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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  • BlueJ Chpt 4 - Auction Project - How to make removeLot method work after entering a new lot

    - by Ellaine Ryan
    Hi All I am learning Java through BlueJ I would like to add a removeLot method to the Auction Class in BlueJ Chpt 4. This involves also returning the lot with the given number or null if there is no such lot. If you enter , say 5 lots and then use the remove method, this codes removes whichever lot you specify. However if you enter a new lot after using the removeLot method - an internal error message comes up regarding lotnumbering . Any ideas? Thanks Elaine public Lot removeLot(int number) { if((number >= 1) ) { } Lot lot = getLot (number); if(lot !=null) { lots.remove(lot); } return lot; }

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  • Memory Allocation - Arduino

    - by Joey Arnold Andres
    I'm new to this low level stuff. I'm currently learning arduino. I'm currently using an Arduino Mega 2560 and in our course we are practicing memory management. I'm a pro at memory management in pc but somehow I'm having crazy problems here in arduino. For instance: The arduino have 8192B, I'm trying to overflow it with uint_16 so I made an array of 8192/16 which is 512. so I did uint16_t A[512+1]; Well I expected that to cause an overflow. What is wrong with my concept?

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