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  • Reduce function calls

    - by Curious2learn
    Hello, I profiled my python program and found that the following function was taking too long to run. Perhaps, I can use a different algorithm and make it run faster. However, I have read that I can also possibly increase the speed by reducing function calls, especially when it gets called repeatedly within a loop. I am a python newbie and would like to learn how to do this and see how much faster it can get. Currently, the function is: def potentialActualBuyers(setOfPeople,theCar,price): count=0 for person in setOfPeople: if person.getUtility(theCar) >= price and person.periodCarPurchased==None: count += 1 return count where setOfPeople is a list of person objects. I tried the following: def potentialActualBuyers(setOfPeople,theCar,price): count=0 Utility=person.getUtility for person in setOfPeople: if Utility(theCar) >= price and person.periodCarPurchased==None: count += 1 return count This, however, gives me an error saying local variable 'person' referenced before assignment Any suggestions, how I can reduce function calls or any other changes that can make the code faster. Again, I am a python newbie and even though I may possibly be able to use a better algorithm, it is still worthwhile learning the answer to the above question. Thanks very much.

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  • Rails: creating a custom data type, to use with generator classes and a bunch of questions related t

    - by Shyam
    Hi, After being productive with Rails for some weeks, I learned some tricks and got some experience with the framework. About 10 days ago, I figured out it is possible to build a custom data type for migrations by adding some code in the Table definition. Also, after learning a bit about floating points (and how evil they are) vs integers, the money gem and other possible solutions, I decided I didn't WANT to use the money gem, but instead try to learn more about programming and finding a solution myself. Some suggestions said that I should be using integers, one for the whole numbers and one for the cents. When playing in script/console, I discovered how easy it is to work with calculations and arrays. But, I am talking to much (and the reason I am, is to give some sufficient background). Right now, while playing with the scaffold generator (yes, I use it, because I like they way I can quickly set up a prototype while I am still researching my objectives), I like to use a DRY method. In my opinion, I should build a custom "object", that can hold two variables (Fixnum), one for the whole, one for the cents. In my big dream, I would be able to do the following: script/generate scaffold Cake name:string description:text cost:mycustom Where mycustom should create two integer columns (one for wholes, one for cents). Right now I could do this by doing: script/generate scaffold Cake name:string description:text cost_w:integer cost_c:integer I had also had an idea that would be creating a "cost model", which would hold two columns of integers and create a cost_id column to my scaffold. But wouldn't that be an extra table that would cause some kind of performance penalty? And wouldn't that be defy the purpose of the Cake model in the first place, because the costs are an attribute of individual Cake entries? The reason why I would want to have such a functionality because I am thinking of having multiple "costs" inside my rails application. Thank you for your feedback, comments and answers! I hope my message got through as understandable, my apologies for incorrect grammar or weird sentences as English is not my native language.

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  • How can I make NSUndoManager's undo/redo action names work properly?

    - by Gabe
    I'm learning Cocoa, and I've gotten undo to work without much trouble. But the setActionName: method is puzzling me. Here's a simple example: a toy app whose windows contain a single text label and two buttons. Press the On button and the label reads 'On'. Press the Off button and the label changes to read 'Off'. Here are the two relevant methods (the only code I wrote for the app): -(IBAction) turnOnLabel:(id)sender { [[self undoManager] registerUndoWithTarget:self selector:@selector(turnOffLabel:) object:self]; [[self undoManager] setActionName:@"Turn On Label"]; [theLabel setStringValue:@"On"]; } -(IBAction) turnOffLabel:(id)sender { [[self undoManager] registerUndoWithTarget:self selector:@selector(turnOnLabel:) object:self]; [[self undoManager] setActionName:@"Turn Off Label"]; [theLabel setStringValue:@"Off"]; } Here's what I expect: I click the On button The label changes to say 'On' In the Edit menu is the item 'Undo Turn On Label' I click that menu item The label changes to say 'Off' In the Edit menu is the item 'Redo Turn On Label' In fact, all these things work as I expect apart from the last one. The item in the Edit menu reads 'Redo Turn Off Label', not 'Redo Turn On Label'. (When I click that menu item, the label does turn to On, as I'd expect, but this makes the menu item's name even more of a mystery. What am i misunderstanding, and how can I get these menu items to display the way I want them to?

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  • smlnj rephrased question for listdir(filename, directoryname)

    - by czy1985
    i am a newbie learning sml and the question i am thrown with involves IO functions that i have no idea how it works even after reading it. Here is the 2 questions that i really need help with to get me started, please provide me with codings and some explaination, i will be able to trial and error with the code given for the other questions. Q1) listdir(filename,directoryname), which given the name of a directory, list its contents in a text file. The listing is in a form that makes it easy to seperate filenames, dates and sizes from each other. (similar to what msdos does with "dir" but instead of just listing it out, it places all the files and details into a text file. Q2) readlist(filename) which reads a list of filenames (each of which were produced by listdir in (Q1) and combines them into one large list. (reads from the text file in Q1 and then assigning the contents into 1 big list containing all the information) Thing is, i only learned from the lecturer in school on the introduction section, there isnt even a system input or output example shown, not even the "use file" function is taught. if anyone that knows sml sees this, please help. Thanks to anyone who took the effort helping me. Thanks for the reply, current I am using SMLNJ to try and do this. Basically, Q1 requires me to list the directory's files of the "directoryname" provided into a text file in "filename". The Q2 requires me to read from the "filename" text file and then place the contents into one large list. Duplicate of: smlnj listdir

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  • C++ return a "NULL" object if search result not found

    - by aduric
    I'm pretty new to C++ so I tend to design with a lot of Java-isms while I'm learning. Anyway, in Java, if I had class with a 'search' method that would return an object T from a Collection< T that matched a specific parameter, I would return that object and if the object was not found in the collection, I would return a NULL. Then in my calling function I would just check if(T != NULL) { ... } In C++, I'm finding out that I can't return a NULL if the object doesn't exist. I just want to return an 'indicator' of type T that notifies the calling function that no object has been found. I don't want to throw an exception because it's not really an exceptional circumstance. class Node { .... Attr& getAttribute(const string& attribute_name) const { //search collection //if found at i return attributes[i]; //if not found return NULL; } private: vector<Attr> attributes; }

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  • Protecting Content with AuthLogic

    - by Rob Wilkerson
    I know this sounds like a really, really simple use case and I'm hoping that it is, but I swear I've looked all over the place and haven't found any mention of any way - not even the best way - of doing this. I'm brand-spanking new to Ruby, Rails and everything surrounding either (which may explain a lot). The dummy app that I'm using as my learning tool requires authentication in order to do almost anything meaningful, so I chose to start by solving that problem. I've installed the AuthLogic gem and have it working nicely to the extent that is covered by the intro documentation and Railscast, but now that I can register, login and logout...I need to do something with it. As an example, I need to create a page where users can upload images. I'm planning to have an ImagesController with an upload action method, but I want that only accessible to logged in users. I suppose that in every restricted action I could add code to redirect if there's no current_user, but that seems really verbose. Is there a better way of doing this that allows me to define or identify restricted areas and handle the authentication check in one place?

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  • c++ use of winmain()

    - by Jack
    Hi, I just started learning programming for windows in c++. I had this crazy image, that win32 programming is based on calling windows functions and sending parameters to and from them. Like, when you want to create window, you call some win32 function that handles windows GUI and say "Hi, please, create me new window, 100 x 100 px, with two buttons", and that GUI function says "Hi, no problem, when something happends, like user clicks one button, I will change this variable xy located in this location". So, I thought that it will be very similiar to console programming. But the very first instruction surprised me. I always thought that every program executes main() function first. So, when I launch app, windows stores some parameters on top of stack and run that application. So I assumed that initializing main() is just a c++ way to tell the compiler where the first instruction should be. But in win32 programming, there is function called winmain() which starts first. So I am little confused. I thought it´s rule that compiler must have main() to start with, that main just defines where ti start, like some start point identifier. So, please, why is there winmain() function instead of main()? When I thought that C++ programming is as logical as assembler, it confuses me once again.

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  • c++ use of winmain()

    - by Jack
    Hi, I just started learning programming for windows in c++. I had this crazy image, that win32 programming is based on calling windows functions and sending parameters to and from them. Like, when you want to create window, you call some win32 function that handles windows GUI and say "Hi, please, create me new window, 100 x 100 px, with two buttons", and that GUI function says "Hi, no problem, when something happends, like user clicks one button, I will change this variable xy located in this location". So, I thought that it will be very similiar to console programming. But the very first instruction surprised me. I always thought that every program executes main() function first. So, when I launch app, windows stores some parameters on top of stack and run that application. So I assumed that initializing main() is just a c++ way to tell the compiler where the first instruction should be. But in win32 programming, there is function called winmain() which starts first. So I am little confused. I thought it´s rule that compiler must have main() to start with, that main just defines where ti start, like some start point identifier. So, please, why is there winmain() function instead of main()? When I thought that C++ programming is as logical as assembler, it confuses me once again.

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  • Why is debugging better in an IDE?

    - by Bill Karwin
    I've been a software developer for over twenty years, programming in C, Perl, SQL, Java, PHP, JavaScript, and recently Python. I've never had a problem I could not debug using some careful thought, and well-placed debugging print statements. I respect that many people say that my techniques are primitive, and using a real debugger in an IDE is much better. Yet from my observation, IDE users don't appear to debug faster or more successfully than I can, using my stone knives and bear skins. I'm sincerely open to learning the right tools, I've just never been shown a compelling advantage to using visual debuggers. Moreover, I have never read a tutorial or book that showed how to debug effectively using an IDE, beyond the basics of how to set breakpoints and display the contents of variables. What am I missing? What makes IDE debugging tools so much more effective than thoughtful use of diagnostic print statements? Can you suggest resources (tutorials, books, screencasts) that show the finer techniques of IDE debugging? Sweet answers! Thanks much to everyone for taking the time. Very illuminating. I voted up many, and voted none down. Some notable points: Debuggers can help me do ad hoc inspection or alteration of variables, code, or any other aspect of the runtime environment, whereas manual debugging requires me to stop, edit, and re-execute the application (possibly requiring recompilation). Debuggers can attach to a running process or use a crash dump, whereas with manual debugging, "steps to reproduce" a defect are necessary. Debuggers can display complex data structures, multi-threaded environments, or full runtime stacks easily and in a more readable manner. Debuggers offer many ways to reduce the time and repetitive work to do almost any debugging tasks. Visual debuggers and console debuggers are both useful, and have many features in common. A visual debugger integrated into an IDE also gives you convenient access to smart editing and all the other features of the IDE, in a single integrated development environment (hence the name).

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  • how to change ASP.NET Configuration tool connection string

    - by Zviadi
    Hello, how can I change ASP.NET Configuration tool-s connection string name? (Which connection string will ASP.NET Configuration tool will use) I'm learning ASP.NET and everywhere and in book that I'm reading now theres connection string named: LocalSqlServer. I want to use my local sql server database instead of sql express to store Roles, Membership and other data. I have used aspnet_regsql.exe to create needed data structures in my database. after that I changed my web.config to look like: <connectionStrings> <remove name="LocalSqlServer"/> <add name="LocalSqlServer" connectionString="Server=(LOCAL); Database=MyDatabase;Integrated Security=True" providerName="System.Data.SqlClient" /> </connectionStrings> but when I run ASP.NET Configuration tool it says that: "The connection name 'ApplicationServices' was not found in the applications configuration or the connection string is empty." ASP.NET Configuration tool uses connection string named: ApplicationServices not LocalSqlServer. cause of that I have to modify web.config to: <connectionStrings> <add name="ApplicationServices" connectionString="Server=(LOCAL); Database=MyDatabase;Integrated Security=True" providerName="System.Data.SqlClient" /> </connectionStrings> and everything works fine. I wish to know why the hell my web site uses connection string named: ApplicationServices and all books and online documentations uses LocalSqlServer? and how to change it to LocalSqlServer? I have: Windows 7 Sql Server 2008 R2 Visual Studio 2010 Premium Project type is website

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  • Clarification of atomic memory access for different OSs

    - by murrekatt
    I'm currently porting a Windows C++ library to MacOS as a hobby project as a learning experience. I stumbled across some code using the Win Interlocked* functions and thus I've been trying to read up on the subject in general. Reading related questions here in SO, I understand there are different ways to do these operations depending on the OS. Interlocked* in Windows, OSAtomic* in MacOS and I also found that compilers have builtin (intrinsic) operations for this. After reading gcc builtin atomic memory access, I'm left wondering what is the difference between intrinsic and the OSAtomic* or Interlocked* ones? I mean, can I not choose between OSAtomic* or gcc builtin if I'm on MacOS when I use gcc? The same if I'd be on Windows using gcc. I also read that on Windows Interlocked* come as both inline and intrinsic versions. What to consider when choosing between intrinsic or inline? In general, are there multiple options on OSs what to use? Or is this again "it depends"? If so, what does it depend on? Thanks!

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  • Where to master HTML, CSS ans Javascript?

    - by Shahensha
    I got interested in web-development lately. I am still a student. I learnt basics of HTML, CSS and JavaScript! Then I thought I should improve my server side scripting. So I am learning Struts2 and I am doing better there. Now I have decided I should finally put my skill to some use. So I and my friend have decided to come up with a fun website for our class. But now I am realizing that, though I know server-side scripting to a good extent (not great, just good considering I am a beginner), I am nowhere near good in the basic elements viz. HTML, CSS and JavaScript! I mean, I can't do cool stuff with it. I am aware of w3schools, but it would be great if you can point out a more intuitive place where I can learn to do all the cool stuff in a short time. Some of the problems I am facing are: 1) How should I design the basic layout of my website? 2) How can I use 3rd party APIs like that of Facebook graph? regards shahensha

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  • Python function correctly/incorrectly?

    - by Anthony Kernan
    I'm just starting too use python, learning experience. I know the basics logic of programming. I have a function in python that is running everytime, even when it's not supposed to. I use an if statement in the beginning of the function. I don't know why this if statement is not working, confused. I have another function that is similar and works correctly. Am I missing something simple? Here's the function that is not working... def check_artist_art(): if os.path.exists("/tmp/artistinfo") and open("/tmp/artistinfo").read() != title: #if artist == "": if os.path.exists(home + "/.artist"): os.remove(home + "/.artist") if os.path.exists("/tmp/artistinfo"): os.remove("/tmp/artistinfo") print artist return False else: os.path.exists("/tmp/artistinfo") and open("/tmp/artistinfo").read() == artist return False return True And this is the similar function that is working correctly.. def check_album(): if os.path.exists("/tmp/albuminfo") and open("/tmp/albuminfo").read() != album: if os.path.exists(home + "/.album"): os.remove(home + "/.album") if os.path.exists("/tmp/albuminfo"): os.remove("/tmp/albuminfo") return False elif os.path.exists("/tmp/trackinfo") and open("/tmp/trackinfo").read() == artist + album: return False return True Any help is greatly appreciated.

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  • Conditional column values in NSTableView?

    - by velocityb0y
    I have an NSTableView that binds via an NSArrayController to an NSMutableArray. What's in the array are derived classes; the first few columns of the table are bound to properties that exist on the base class. That all works fine. Where I'm running into problem is a column that should only be populated if the row maps to one specific subclass. The property that column is meant to display only exists in that subclass, since it makes no sense in terms of the base class. The user will know, from the first two columns, why the third column's cell is populated/editable or not. The binding on the third column's value is on arrangedObjects, with a model path of something like "foo.name" where foo is the property on the subclass. However, this doesn't work, as the other subclasses in the hierarchy are not key-value compliant for foo. It seems like my only choice is to have foo be a property on the base class so everybody responds to it, but this clutters up the interfaces of the model objects. Has anyone come up with a clean design for this situation? It can't be uncommon (I'm a relative newcomer to Cocoa and I'm just learning the ins and outs of bindings.)

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  • How to get the most out of a 3 month intern?

    - by firoso
    We've got a software engineering intern coming in who's fairly competent and shows promise. There's one catch: we have him for 3 months full time and can't count on anything past that. He still has a year of school left, which is why we can't say for sure that we have him past 3 months. We have a specific project we're putting him on. How can we maximize his productivity while still giving him a positive learning experience? He wants to learn about development cycles and real-world software engineering. Anything that you think would be critical that you wish you had learned earlier? Nearly six months later: He's preformed admirably and even I have learned a lot from him. Thank you all for the input. Now I want to provide feedback to YOU! He has benefited most from sitting down and writing code. However, he has had a nasty history of bad software engineering practices which I'm trying to replace with good habits (properly finishing a method before moving on, not hacking code together, proper error channeling, etc). He has also really gained a lot by feeling involved in design decisions, even if most of the time they're related to my own design plans.

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  • Replacing a word in a text file with a value using python

    - by Jamde Jam
    I have been trying to replace a word in a text file with a value (say 1), but my outfile is blank.I am new to python (its only been a month since I have been learning it). My file is relatively large, but I just want to replace a word with the value 1 for now. Here is a segment of what the file looks like: NAME SECOND_1 ATOM 1 6 0 0 0 # ORB 1 ATOM 2 2 0 12/24 0 # ORB 2 ATOM 3 2 12/24 0 0 # ORB 2 ATOM 4 2 0 0 4/24 # ORB 3 ATOM 5 2 0 0 20/24 # ORB 3 ATOM 6 2 0 0 8/24 # ORB 3 ATOM 7 2 0 0 16/24 # ORB 3 ATOM 8 6 0 0 12/24 # ORB 1 ATOM 9 2 12/24 0 12/24 # ORB 2 ATOM 10 2 0 12/24 12/24 # ORB 2 #1 #2 #3 I want to first replace the word ATOM with the value 1. Next I want to replace #ORB with a space. Here is what I am trying thus far. input = open('SECOND_orbitsJ22.txt','r') output=open('SECOND_orbitsJ22_out.txt','w') for line in input: word=line.split(',') if(word[0]=='ATOM'): word[0]='1' output.write(','.join(word)) Can anyone offer any suggestions or help? Thanks so much.

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  • How would I go about sharing variables in a C++ class with Lua?

    - by Nicholas Flynt
    I'm fairly new to Lua, I've been working on trying to implement Lua scripting for logic in a Game Engine I'm putting together. I've had no trouble so far getting Lua up and running through the engine, and I'm able to call Lua functions from C and C functions from Lua. The way the engine works now, each Object class contains a set of variables that the engine can quickly iterate over to draw or process for physics. While game objects all need to access and manipulate these variables in order for the Game Engine itself to see any changes, they are free to create their own variables, a Lua is exceedingly flexible about this so I don't forsee any issues. Anyway, currently the Game Engine side of things are sitting in C land, and I really want them to stay there for performance reasons. So in an ideal world, when spawning a new game object, I'd need to be able to give Lua read/write access to this standard set of variables as part of the Lua object's base class, which its game logic could then proceed to run wild with. So far, I'm keeping two separate tables of objects in place-- Lua spawns a new game object which adds itself to a numerically indexed global table of objects, and then proceeds to call a C++ function, which creates a new GameObject class and registers the Lua index (an int) with the class. So far so good, C++ functions can now see the Lua object and easily perform operations or call functions in Lua land using dostring. What I need to do now is take the C++ variables, part of the GameObject class, and expose them to Lua, and this is where google is failing me. I've encountered a very nice method here which details the process using tags, but I've read that this method is deprecated in favor of metatables. What is the ideal way to accomplish this? Is it worth the hassle of learning how to pass class definitions around using libBind or some equivalent method, or is there a simple way I can just register each variable (once, at spawn time) with the global lua object? What's the "current" best way to do this, as of Lua 5.1.4?

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  • Getting started with open source

    - by lola
    Hi all, I'm an undergraduate who has decided that he wants to join the open source community and contribute. However, I have come to think that, once you have chosen an open source project, a lot of time is spent in learning the nitty gritties of that project in addition to stuff like subversion,etc which a typical undergraduate isn't exposed to. So, you have to stick with that project for a long time, say a year or two, before moving on to other projects. In this case, choosing the right(for you) initial project is very important since if you choose one,and say, the development in your field of interest(in that project) is a low priority and not exciting enough, you'll lose interest and stop contributing to open source all together. So what I wanted to know was, since there are thousands of open source projects, is all this being documented somewhere with tags,etc so that a beginner can choose his projects. The GSoc 2010 ideas list is a great starting point, but it only covers a handful. Hence, I thought why not ask this at stackoverflow: if you have any pointers as to where to start, when choosing a FOSS project or any other tips related to starting with FOSS. P.S. I'm interested in projects involving mobile ad hoc networks(those using TinyOS, preferably), so pointers related to these will be great. I'm looking through Freifunk and OLPC as of now, needed more ideas.

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  • Javascript JQUERY AJAX: When Are These Implemented

    - by Michael Moreno
    I'm learning javascript. Poked around this excellent site to gather intel. Keep coming across questions / answers about javascript, JQUERY, JQUERY with AJAX, javascript with JQUERY, AJAX alone. My conclusion: these are all individually powerful and useful. My confusion: how does one determine which/which combination to use ? I've concluded that javascript is readily available on most browsers. For example, I can extend a simple HTML page with <html> <body> <script type="text/javascript"> document.write("Hello World!"); </script> </body> </html> However, within the scope of Python/DJANGO, many of these questions are JQUERY and AJAX related. At which point or under what development circumstances would I conclude that javascript alone isn't going to "cut it", and I need to implement JQUERY and/or AJAX and/or some other permutation ?

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  • Cryptic Erlang Errors

    - by Jim
    Okay so I started learning erlang recently but am baffled by the errors it keeps returning. I made a bunch of changes but I keep getting errors. The syntax is correct as far as I can tell but clearly I'm doing something wrong. Have a look... -module(pidprint). -export([start/0]). dostuff([]) - receive begin - io:format("~p~n", [This is a Success]) end. sender([N]) - N ! begin, io:format("~p~n", [N]). start() - StuffPid = spawn(pidprint, dostuff, []), spawn(pidprint, sender, [StuffPid]). Basically I want to compile the script, call start, spawn the "dostuff" process, pass its process identifier to the "sender" process, which then prints it out. Finally I want to send a the atom "begin" to the "dostuff" process using the process identifier initially passed into sender when I spawned it. The errors I keep getting occur when I try to use c() to compile the script. Here they are.. ./pidprint.erl:6: syntax error before: '-' ./pidprint.erl:11: syntax error before: ',' What am I doing wrong?

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  • Wnat is the preferred method of building extremely lightweight business object / DAL now that I have

    - by Seth Spearman
    Hello, I have completed a simple database for a project. Only 6tables. Of the 6, one is a "lookup" table. There is one "master" table that is the driver for the system. It is referenced as a foreign key by the other four tables. Give that this step is completed. What is the FASTEST, EASIEST way to create POCOs/BizObjects that can load load the data and the child data. Here are my CAVEATS. *I don't want to spend more than 30-60 minutes learning how? *There is very little biz logic needed in the POCOs. They will pretty much load data. Don't even really need to write back data. *I already know CSLA (up to version 3) but I feel that is overkill for this little project. *Nevertheless, I would love it if it ROOT objects could have collection classes that contain the CHILD objects as in CSLA...but again, without using CSLA. *Please give the answer for .NET 35 but also if I was restricted to only use .NET 20. *Ideally I could just point a tool at the database and the POCOs would be genn'ed. *FREE Just curious what you guys use for this kind of scenario. I understand that this question is subjective but I want to hear a variety of answers. Seth

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  • iPhone OpenGL ES Texture2D Masking

    - by Robert Neagu
    What's the best choice when trying to mask a texture like ColorSplash or other apps like iSteam, etc? I started learning OPENGL ES like... 4 days ago (I'm a total rookie) and tried the following approach: 1) I created a colored texture2D, a grayscale version of the first texture and a third texture2D called mask 2) I also created a texture2D for the brush... which is grayscale and it's opaque (brush = black = 0,0,0,1 and surroundings = white = 1,1,1,1). My intention was to create an antialiased brush with smooth edges but i'm fine with a normal one right now 3) I searched for masking techniques on the internet and found this tutorial ZeusCMD - Design and Development Tutorials : OpenGL ES Programming Tutorials - Masking about masking. The tutorial tells me to use blending to achieve masking... first draw colored, then mask with glBlendFunc(GL_DST_COLOR, GL_ZERO) and then grayscale with glBlendFunc(GL_ONE, GL_ONE) ... and this gives me something close to what i want... but not exactly what i want. The result is masked but it's somehow overbright-ed 4) For drawing to the mask texture i used an extra frame buffer object (FBO) I'm not really happy with the resulting image (overbright-ed picture) nor with the speed achieved with this method. I think the normal way was to draw directly to the grayscale (overlay) texture2D affecting only it's alpha channel in the places where the brush hits. Is there a fast way to achieve this? I have searched a lot and never got an answer that's clear and understandable. Then, in the main draw loop I could only draw the colored texture and then blend the grayscale ontop with glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA). I just want to learn to use OPENGL ES and it's driving me nuts because i can't get it to work properly. An advice, a link to a tutorial would be much appreciated.

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  • Why does this program take up so much memory?

    - by Adrian
    I am learning Objective-C. I am trying to release all of the memory that I use. So, I wrote a program to test if I am doing it right: #import <Foundation/Foundation.h> #define DEFAULT_NAME @"Unknown" @interface Person : NSObject { NSString *name; } @property (copy) NSString * name; @end @implementation Person @synthesize name; - (void) dealloc { [name release]; [super dealloc]; } - (id) init { if (self = [super init]) { name = DEFAULT_NAME; } return self; } @end int main (int argc, const char * argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; Person *person = [[Person alloc] init]; NSString *str; int i; for (i = 0; i < 1e9; i++) { str = [NSString stringWithCString: "Name" encoding: NSUTF8StringEncoding]; person.name = str; [str release]; } [person release]; [pool drain]; return 0; } I am using a mac with snow leopard. To test how much memory this is using, I open Activity Monitor at the same time that it is running. After a couple of seconds, it is using gigabytes of memory. What can I do to make it not use so much?

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  • Most elegant way to break CSV columns into separate data structures using Python?

    - by Nick L
    I'm trying to pick up Python. As part of the learning process I'm porting a project I wrote in Java to Python. I'm at a section now where I have a list of CSV headers of the form: headers = [a, b, c, d, e, .....] and separate lists of groups that these headers should be broken up into, e.g.: headers_for_list_a = [b, c, e, ...] headers_for_list_b = [a, d, k, ...] . . . I want to take the CSV data and turn it into dict's based on these groups, e.g.: list_a = [ {b:val_1b, c:val_1c, e:val_1e, ... }, {b:val_2b, c:val_2c, e:val_2e, ... }, {b:val_3b, c:val_3c, e:val_3e, ... }, . . . ] where for example, val_1b is the first row of the 'b' column, val_3c is the third row of the 'c' column, etc. My first "Java instinct" is to do something like: for row in data: for col_num, val in enumerate(row): col_name = headers[col_num] if col_name in group_a: dict_a[col_name] = val elif headers[col_cum] in group_b: dict_b[col_name] = val ... list_a.append(dict_a) list_b.append(dict_b) ... However, this method seems inefficient/unwieldy and doesn't posses the elegance that Python programmers are constantly talking about. Is there a more "Zen-like" way I should try- keeping with the philosophy of Python?

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  • What's the next steps for moving from appengine to full django?

    - by tomcritchlow
    Hey guys, I'm super new to programming and I've been using appengine to help me learn python and general coding. I'm getting better quickly and I'm loving it all the way :) Appengine was awesome for allowing me to just dive into writing my app and getting something live that works (see http://www.7bks.com/). But I'm realising that the longer I continue to learn on appengine the more I'm constraining myself and locking myself into a single system. I'd like to move to developing on full django (since django looks super cool!). What are my next steps? To give you a feel for my level of knowledge: I'm not a unix user I'm not familiar with command line controls (I still use appengine/python completely via the appengine SDK) I've never programmed in anything other than python, anywhere other than appengine I know the word SQL, but don't know what MySQL is really or how to use it. So, specifically: What are the skills I need to learn to get up and running with full django/python? If I'm going to host somewhere else I suppose I'll need to learn some sysadmin type skills (maybe even unix?). Is there anywhere that offers easy hosting (like appengine) but that supports django? I hear such great things about heroku I'm considering switching to RoR and going there I appreciate that I'm likely not quite ready to move away from appengine just yet but I'm a fiercely passionate learner (http://www.7bks.com/blog/179001) and would love it if I knew all the steps I needed to learn so I could set about learning them. At the moment, I don't even know what the steps are I need to learn! Thank you very much. Sorry this isn't a specific programming question but I've looked around and haven't found a good how-to for someone of my level of experience and I think others would appreciate a good roadmap for the things we need to learn to get up and running. Thanks, Tom PS - if anyone is in London and fancies showing me the ropes in person that would be super awesome :)

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