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• <= vs < when proving big-o notation

  - by user600197

  We just started learning big-o in class. I understand the general concept that f(x) is big-o of g(x) if there exists two constants c,k such that for all xk |f(x)|<=c|g(x)|. I had a question whether or not it is required that we include the <= to sign or whether it is just sufficient to put the < sign? For example: suppose f(x)=17x+11 and we are to prove that this is O(x^2). Then if we take c=28 and xk=1 we know that 17x+11<=28x^2. So since we know that x will always be greater than 1 this implies that 28x^2 will always be greater than 17x+11. So, do we really need to include the equal sign (<=) or is it okay if we just write (<)? Thanks in advance.

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• Delphi developer switching to C#

  - by Dorin Duminica

  Hello, I'm a Delphiholic for quite some time now and lately I was thinking of learning some C# as well, however I'm kinda' "afraid of the unknown", I've done some simple apps as a test drive for C# and I have to admit that I've liked it, HOWEVER I do not really like the IDE... that being said here's the question that I would appreciate if others who went down this path would answer: As a Delphi developer what are the "main basic" changes from the Delphi language(by basic I mean basic -- utility functions, streams, etc.), I'm used to add "System, Classes, Windows" to uses not "use System.XXX.YYY.ZZZ", I'm trying to make a partial equality in my mind from Delphi to C# until I can see where does Delphi go hand-in-hand with C# and so on... I hope the question is pretty clear, if not, do not hesitate to swear me and I'll try to clarify as well as I can :-)

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• Can layouts be chosen by Grails controllers?

  - by maerics

  I'm building a CMS as a learning exercise in Grails and would like to give content managers the ability to choose between different HTML page structures (e.g. 2 column, 3 column, etc). Grails Layouts seem like a logical choice but is it possible for a Grails controller to explicitly name which layout will be used for rendering? Ideally there would be a layout option to the render method, per Ruby on Rails but I don't see anything like it. It seems like it might be possible using the applyLayout method by passing the name of the layout but this requires each GSP page to explicitly request layout (annoying overhead per-page) rather than using Layout by Convention. Any ideas?

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• Can't remove first node in linked list

  - by carlmonday

  I'm trying to make a linked list class in python (pointless I know, but it's a learning exercise), and the method I have written to remove a node doesn't work if I try to remove the first element of the linked list. If the node to be removed is anywhere else in the linked list the method works fine. Can someone give me some insight as to where I've gone wrong? Here's my code thus far: class Node: def __init__(self, data=None, next=None): self.data = data self.next = next def __repr__(self): return repr(self.data) def printNodes(self): while self: print self.data self = self.next def removeNode(self, datum): """removes node from linked list""" if self.data == datum: return self.next while self.next: if self.next.data == datum: self.next = self.next.next return self self = self.next

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• passing get parameters through named route and then to controller model; stringify_keys!

  - by user368937

  Hey, I'm just learning ruby on rails and I've been stumped on this for awhile now. Here's my url request: http://192.168.2.20:8080/Location/new/123.123,-123.123/ Here's my routes.rb: map.connect '/Location/new/:coords/', :controller => 'Location', :action => 'new', :coords => /\d+.\d+,-\d+.\d+/ map.connect '/Location/list/', :controller => 'Location', :action => 'list' map.connect '/Location/create/', :controller => 'Location', :action => 'create' Here's my location_controller.rb def new @coords = Location.new(params[:coords]) end Here's the error message it gives me: NoMethodError in LocationController#new undefined method `stringify_keys!' for "123.123,-123.123":String

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• Mapping tables from an existing database to an object -- is Hibernate suited?

  - by Bernhard V

  Hello! I've got some tables in an existing database and I want to map them to a Java object. Actually it's one table that contains the main information an some other tables that reference to such a table entry with a foreign key. I don't want to store objects in the database, I only want to read from it. The program should not be allowed to apply any changes to the underlying database. Currently I read from the database with 5 JDBC sql queries and set the results then on an object. I'm now looking for a less code intensive way. Another goal is the learning aspect. Is Hibernate suitable for this task, or is there another ORM framework that better fits my requirement?

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• Is there a better way to do SELECT queries in MySQL and sort them in PHP than this way?

  - by Kent

  I am just learning PHP/MySQL, one this I am having to do a lot is displaying data that was previously inserted into the database out to the user's browser. So I am doing this: $select = mysql_query('SELECT * FROM pages'); while ($return = mysql_fetch_assoc($select)) { $title = $return['title']; $author = $return['author']; $content = $return['content']; } then I can use these variables through out the page. Now, doing it the above way isn't an issue when I only have 3 columns in a database but what if I am dealing with a huge database with many more columns. I have a nagging feeling that the pros do it in some more efficient way where they maybe loop through the table they are selecting from to find all columns it has and associate them with variables automatically. Is that the case? or is the above how you guys do it too?

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• what is a TOPIC in Struts2

  - by nacho4d

  HI, I am learning struts 2 with Tiles 2 and the word "topic" shows up very frequently... What is a topic? for example: The sx:a tag (specifically the ajax a template) and the div tag support an ajax event system, providing the ability to broadcast events to topics. You can specify the topics to listen to using a comma separated list in the listenTopics attribute. What this means is that when a topic is published, usually through the ajax a template, the URL specified in the href attribute will be re-requested. Placeholder... Refresh

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• Is there a semantic difference <span>'s and <div>'s?

  - by DavidR

  I know when coding HTML, I'm supposed to keep semantics in mind, e.g., h1 needs to be a main header, h2 needs to be a subheader, tables need to be tables, use <em> for emphasis instead of <i>, etc. Is there a proper difference between divs and spans except one is a block and the other is in-line? When I was learning I was told that <span>'s were for styling text mid-line. If I had a small blurb of text that I needed positioned at a certain point in my webpage, one that doesn't warrent a <p> tag, would I use a span should I stick with div's? What if that text needs to cover two lines (i.e., it needs a width) if it contains nothing but text, what should I use?

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• MVC, how view should be accessed from controller?

  - by Kirzilla

  Hello, I'm just learning MVC so you could find my question rather strange... My Controller have access to different shared objects through Container object passed to Controller's constructor. To access shared objects I should do $this-container-db to access Database adapter or $this-container-memcache to access Memcached adapter. I want to know should I put View object into Container with shared objects or no? From one side it is really comfortable to take view from this container, but this way I couldn't create multiple Views instances (for example, every time I'm calling Controller's method from View I should have one more View instance). What is the solution? How should I pass View object into Controller and/or how should I create new View instances from Controller? Thank you!

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• C# How to place a comma after each word but the last in the list

  - by user576712

  I totally new to C# and learning as I go. I am stuck on issue which I'm hoping an experienced programmer can help. I have added a CheckedListBox to my form and added a collection of 6 items to it. I need all but the last item selected to have a comma placed beside it, so my question is: how can I tell C# NOT to place a comma beside the last item selected? foreach (object itemChecked in RolesCheckedListBox.CheckedItems) { sw.Write(itemChecked.ToString() + ","); } Thanks for any help received! Dan

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• Quick CPU ring mode protection question

  - by b-gen-jack-o-neill

  Hi, me again :) I am very curious in messing up with HW. But my top level "messing" so far was linked or inline assembler in C program. If my understanding of CPU and ring mode is right, I cannot directly from user mode app access some low level CPU features, like disabling interrupts, or changing protected mode segments, so I must use system calls to do everything I want. But, if I am right, drivers can run in ring mode 0. I actually don´t know much about drivers, but this is what I ask for. I just want to know, is learning how to write your own drivers and than call them the way I should go, to do what I wrote? I know I could write whole new OS (at least to some point), but what I exactly want to do is acessing some low level features of HW from standart windows application. So, is driver the way to go?

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• Errors when using a Ruby On Rails scaffold with a data type of interger

  - by bublebboy

  I am learning Ruby On Rails. I am on a shared hosting with Ruby version 1.8.1 and Rails version 2.3.10. I am working my way through a tutorial at http://railstutorial.org/chapters/a-demo-app?version=2.3#top and at one point in the tutorial it has me run: script/generate scaffold Micropost content:string user_id:interger The tutorial is using the default database, SQLite3. The command works and I use rake db:migrate to create the database. I can view the page listing the microposts (which is empty), but when I try to add a micropost (microposts/new) I get an error undefined method `user_id' for #<Micropost:0x7f710e4988e8> After doing some testing on my own it seems I experience the problem by using the data type of interger. While I understand that using a scaffold is not the best way of building a ruby on rails, I'm just beginning and would still like to know why I am experiencing this problem to help me better understand how rails works.

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• How do I ensure GUI responsiveness when using OpenCL on the display GPU?

  - by pauldoo

  In my relatively short time learning OpenCL I frequently see my application cause the operating system UI to become significantly less responsive (several seconds for a window to respond to a drag for example). I have encountered this problem on Windows Vista and Mac OS X both with NVidia GPUs. What can I do when using OpenCL on the same GPU as the display to ensure that my application does not significantly degrade the UI responsiveness like this? Also, can this be done without taking needless performance losses within my application? (Ie, if the user is not doing some UI intensive task then I would not expect my application to run any slower than it does now.) I understand that any answers will be very platform specific (where platform includes OS/GPU/driver combo).

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• No recent books on MPI: is it dying?

  - by Jono

  I've never used Message Passing Interface (MPI), but I've heard its name thrown about, most recently with Windows HPC Server. I had a quick look on amazon to see if there were any books on it, but they're all dated around 7 or more years ago. Is MPI still a valid technology choice for new applications, or has it been largely superceded by other distributed programming alternatives (e.g. DataSynapse GridServer)? As it's not really an implementation, but rather a standard, what is the likelihood (assuming it's not dead) that learning it will result in better design of distributed programming systems? Is there something else I should be looking at instead?

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• PHP to C# and Vice versa

  - by Daniel Sh.

  I'm in this project: A web page that's gonna be used by the front-end company people to query and update data from a SQL DB. I'm working with visual studio and the code behind (C#) is almost done, so the interactions between SQL and C# and ok. My original idea was to work with ASP.NET which is familiar to me, but that's not gonna be possible. I have to switch to PHP. So, today is my first day learning PHP, checking http://php.net/manual/en/index.php and a lot of things seem quite similar to ASP.NET so I guess it won't be that hard. Anyways, some questions popped up quite fast as I wanted to script something else than a "hello world" . Is there an easy way to get/send C# variables from my class using a php page? I've read soemthing about using XML in order to do so, but still I'm scratching my head, is there another, easier, way to do this?

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• Difference between var and Class class in object creation

  - by Divine

  Its a silly question, however shocked to see different behaviors. Learning a lot. Lets say I have two classes below Class A { public void Display() { } } Class B : A { public void Display() { } } Class C : B { public void Display() { } } Class Final { static void Main() { var c = new C(); // B c = new C(); //My doubt is, both of the above gives different results. May I know B c = new C() creates object of B or C? What I understood is, it creates object of B. Then why we say "new C()"? I agree with C c = new C(); But I thought, B b = new C(); creates object of B. Where we use this style? Only when utilizing runtime polymorphism? (Overriding methods)? } }

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• Change function into dependencyproperty

  - by Jaya Willianto

  Hi everyone.. I am new to XAML and WPF and I am learning about DependencyProperty and Path. For example, I have a function like this public byte[] DownloadPicture() { WebClient webClient = new WebClient(); byte[] data; data = webClient.DownloadData("https://graph.facebook.com/4/picture&type=large"); return data; } and I have dependencyproperty like this public static DependencyProperty DownloadPicProperty = DependencyProperty.Register("DownloadPic", typeof(byte), typeof(ImageControl), new PropertyMetadata(false)); How can I connect the DependencyProperty with the DownloadPicture function I wrote? Any suggestions? What should I write in the CLR wrapper?

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• How to Print the contents of a textbox in C++/CLI?

  - by Smoka

  I'm still learning C++ coding. I'm having troubles getting say ResultsBox-Text to printer successfully. What is the proper way to print in C++/CLI? I think im missing something simple. Ive tried multiple different routes/syntax's that ive read online/ in books. All of which got me to a dead end. Please even a rundown on the method of printing in any C based language might point me the right way. Thank you.

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• How to keep up the interest in job?

  - by stranger

  Hi, I have been working as Software Developer for 6+ yrs. And I have worked from start ups to big companies. I always feel some elements missing in me and those are interest, passion etc. In short, I don't feel motivated while coming to work. This makes me think how my work-life balance will look like once I reach at more responsible positions. I don't want to change my field and I feel blessed as well but I think I am not working passionately for my learning, future growth, improvement, skills etc. Any pointers will be highly appreciated. Thx

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• Get list of running processes, get active process (and it's application) Flex/AIR

  - by Adam Kiss

  Hello, just a quickie (or maybe not:] ): Is it possible to get somehow list of running applications/processes and, while running in background, check which process is active? Additionally - if somehow, the answer was yes, is it possible to react for change of active window / application react just as if it was Event, or bind to it custom event (e.g. Event.SystemActiveAppChange)? Thank you for answers as well as pointers. EDIT: Due to probable missunderstanding, I mean local applications - on your win/mac/linux machine - I would like to (in process of learning of language) track what apps I use the most, make a little graph maybe? So, the point is: in AIR app, developed in FLEX, I would like to get/list all running applications/processes, as well as which one is active (on user's PC/Mac/Linux)

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• Function return type style

  - by JB

  I'm learning c++0x, at least the parts supported by the Visual C++ Express 2010 Beta. This is a question about style rather than how it works. Perhaps it's too early for style and good practice to have evolved yet for a standard that isn't even released yet... In c++0x you can define the return type of a method using - type at the end of the function instead of putting the type at the start. I believe this change in syntax is required due to lambdas and some use cases of the new decltype keyword, but you can use it anywhere as far as I know. // Old style int add1(int a, int b) { return a + b; } // New style return type auto add2(int a, int b) -> int { return a + b; } My question really then, is given that some functions will need to be defined in the new way is it considered good style to define all functions in this way for consistency? Or should I stick to only using it when necessary?

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• pyschool is wrong ?

  - by geekkid

  I'm currently learning python and trying to do exercises at pyschools (if anyone knows what it is). Anyway, i have an exercise that asks me to do the following : Write a function percent(value, total) that takes in two numbers as arguments, and returns the percentage value as an integer. Here's my code: def percent(value, total): percent = value / total * 100 return int(percent) It works great in my Python Idle and it gives all the correct answers. however, when i run it in the pyschools website, it says that , for example , when the function is called with parameters 46 and 90 , the function returns 0. However, in my python idle , it correctly returns 51. What might be the problem ? Thank you very much for your help!

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• Are frameworks really necessary for beginners/intermediates? (PHP)

  - by ggfan

  I have been programming for around 6months and currently learning PHP/Mysql. I can create basic functionally sites starting from a plain sheet of paper. Is it necessary I use frameworks to create sites? Currently, everything I do is from scratch. I'll borrow codes from old codes, ask people for help, etc. Are frameworks going to help me much more? Is it alright if I put a site public without using a framework? (I have not looked a lot into frameworks, so my knowledge is limited, but I'm just curious)

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• Calculation of derived field in sql

  - by Matt

  Taking Sql this quarter and not having any luck with the following question: The height of players in feet (inches/12). Include their name. Hint: Calculation or derived field. Be sure to give the calculated field a column header. We're learning the basic Select statment and didn't find any reference on how to make custom data at w3schools. I'm using Microsoft SQL server Management Express Here's my statment so far: select nameLast, nameFirst, height from Master where height (I assume its something like 'Player_Height' = height/12) order by nameLast, nameFirst, height Thanks for the help

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