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• Is Java assert broken?

  - by BlairHippo

  While poking around the questions, I recently discovered the assert keyword in Java. At first, I was excited. Something useful I didn't already know! A more efficient way for me to check the validity of input parameters! Yay learning! But then I took a closer look, and my enthusiasm was not so much "tempered" as "snuffed-out completely" by one simple fact: you can turn assertions off.* This sounds like a nightmare. If I'm asserting that I don't want the code to keep going if the input listOfStuff is null, why on earth would I want that assertion ignored? It sounds like if I'm debugging a piece of production code and suspect that listOfStuff may have been erroneously passed a null but don't see any logfile evidence of that assertion being triggered, I can't trust that listOfStuff actually got sent a valid value; I also have to account for the possibility that assertions may have been turned off entirely. And this assumes that I'm the one debugging the code. Somebody unfamiliar with assertions might see that and assume (quite reasonably) that if the assertion message doesn't appear in the log, listOfStuff couldn't be the problem. If your first encounter with assert was in the wild, would it even occur to you that it could be turned-off entirely? It's not like there's a command-line option that lets you disable try/catch blocks, after all. All of which brings me to my question (and this is a question, not an excuse for a rant! I promise!): What am I missing? Is there some nuance that renders Java's implementation of assert far more useful than I'm giving it credit for? Is the ability to enable/disable it from the command line actually incredibly valuable in some contexts? Am I misconceptualizing it somehow when I envision using it in production code in lieu of statements like if (listOfStuff == null) barf();? I just feel like there's something important here that I'm not getting. *Okay, technically speaking, they're actually off by default; you have to go out of your way to turn them on. But still, you can knock them out entirely.

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• Any tool(s) for knowing the layout (segments) of running process in Windows?

  - by claws

  I've always been curious about How exactly the process looks in memory? What are the different segments(parts) in it? How exactly will be the program (on the disk) & process (in the memory) are related? My previous question: http://stackoverflow.com/questions/1966920/more-info-on-memory-layout-of-an-executable-program-process In my quest, I finally found a answer. I found this excellent article that cleared most of my queries: http://www.linuxforums.org/articles/understanding-elf-using-readelf-and-objdump_125.html In the above article, author shows how to get different segments of the process (LINUX) & he compares it with its corresponding ELF file. I'm quoting this section here: Courious to see the real layout of process segment? We can use /proc//maps file to reveal it. is the PID of the process we want to observe. Before we move on, we have a small problem here. Our test program runs so fast that it ends before we can even dump the related /proc entry. I use gdb to solve this. You can use another trick such as inserting sleep() before it calls return(). In a console (or a terminal emulator such as xterm) do: $ gdb test (gdb) b main Breakpoint 1 at 0x8048376 (gdb) r Breakpoint 1, 0x08048376 in main () Hold right here, open another console and find out the PID of program "test". If you want the quick way, type: $ cat /proc/`pgrep test`/maps You will see an output like below (you might get different output): [1] 0039d000-003b2000 r-xp 00000000 16:41 1080084 /lib/ld-2.3.3.so [2] 003b2000-003b3000 r--p 00014000 16:41 1080084 /lib/ld-2.3.3.so [3] 003b3000-003b4000 rw-p 00015000 16:41 1080084 /lib/ld-2.3.3.so [4] 003b6000-004cb000 r-xp 00000000 16:41 1080085 /lib/tls/libc-2.3.3.so [5] 004cb000-004cd000 r--p 00115000 16:41 1080085 /lib/tls/libc-2.3.3.so [6] 004cd000-004cf000 rw-p 00117000 16:41 1080085 /lib/tls/libc-2.3.3.so [7] 004cf000-004d1000 rw-p 004cf000 00:00 0 [8] 08048000-08049000 r-xp 00000000 16:06 66970 /tmp/test [9] 08049000-0804a000 rw-p 00000000 16:06 66970 /tmp/test [10] b7fec000-b7fed000 rw-p b7fec000 00:00 0 [11] bffeb000-c0000000 rw-p bffeb000 00:00 0 [12] ffffe000-fffff000 ---p 00000000 00:00 0 Note: I add number on each line as reference. Back to gdb, type: (gdb) q So, in total, we see 12 segment (also known as Virtual Memory Area--VMA). But I want to know about Windows Process & PE file format. Any tool(s) for getting the layout (segments) of running process in Windows? Any other good resources for learning more on this subject? EDIT: Are there any good articles which shows the mapping between PE file sections & VA segments?

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• Do you feel underappreciated or resent the geek/nerd stigma?

  - by dotnetdev

  At work we have a piece of A4 paper with the number of everyone in the office. The structure of this document is laid out in rectangles, by department. I work for the department that does all the technical stuff. That includes support—bear in mind that the support staff isn't educated in IT but just has experience in PC maintenance and providing support to a system we resell but don't have source code access to, project manager, team leader, a network administrator, a product manager, and me, a programmer. Anyway, on this paper, we are labelled as nerds and geeks. I did take a little offence to this, as much as it is light hearted (but annoying and old) humour. I have a vivid image that a geek is someone who doesn't go out but codes all day. I code all day at home and at work (when I have something to code...), but I keep balance by going out. I don't know why it is only people who work with computers that get such a stigma. No other profession really gets the same stigma—skilled, technical, or whatever. An account manager (and this is hardly a skilled job) says, "Perhaps [MY NAME HERE] could write some geeky code tomorrow to add this functionality to the website." It is funny how I get such an unfair stigma but I am so pivotal. In fact, if it wasn't for me, the company would have nothing to sell so the account managers would be redundant! I make systems, they get sold, and this is what pays the wages. It's funny how the account managers get a commission for how many systems they sell, or manage to make clients resubscribe to. Yet I built the thing in the first place! On top of that, my brother says all I do is type stuff on a keyboard all day. Surely if I did, I'd be typing at my normal typing speed of 100wpm+ as if I am writing a blog entry. Instead, I plan as I code along on the fly if commercial pressures and time prohibit proper planning. I never type as if I'm writing normal English. There is more to our jobs than just typing code. And my brother is a pipe fitter with no formal qualifications in his name. I could easily, and perhaps more justifiably, say he just manipulates a spanner or something. Does you feel underappreciated or that a geek/nerd stigma is undeserved or unfair?

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• Double Buffering for Game objects, what's a nice clean generic C++ way?

  - by Gary

  This is in C++. So, I'm starting from scratch writing a game engine for fun and learning from the ground up. One of the ideas I want to implement is to have game object state (a struct) be double-buffered. For instance, I can have subsystems updating the new game object data while a render thread is rendering from the old data by guaranteeing there is a consistent state stored within the game object (the data from last time). After rendering of old and updating of new is finished, I can swap buffers and do it again. Question is, what's a good forward-looking and generic OOP way to expose this to my classes while trying to hide implementation details as much as possible? Would like to know your thoughts and considerations. I was thinking operator overloading could be used, but how do I overload assign for a templated class's member within my buffer class? for instance, I think this is an example of what I want: doublebuffer<Vector3> data; data.x=5; //would write to the member x within the new buffer int a=data.x; //would read from the old buffer's x member data.x+=1; //I guess this shouldn't be allowed If this is possible, I could choose to enable or disable double-buffering structs without changing much code. This is what I was considering: template <class T> class doublebuffer{ T T1; T T2; T * current=T1; T * old=T2; public: doublebuffer(); ~doublebuffer(); void swap(); operator=()?... }; and a game object would be like this: struct MyObjectData{ int x; float afloat; } class MyObject: public Node { doublebuffer<MyObjectData> data; functions... } What I have right now is functions that return pointers to the old and new buffer, and I guess any classes that use them have to be aware of this. Is there a better way?

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• Getting a screenshot of a page using .NET - Need help with code

  - by Ender

  I'm writing a specialized crawler and parser for internal use and I require the ability to take a screenshot of a web page in order to check what colours are being used throughout. The program will take in around ten web addresses and will save them as a bitmap image, from there I plan to use LockBits in order to create a list of the five most used colours within the image. To my knowledge it's the easiest way to get the colours used within a web page but if there is an easier way to do it please chime in with your suggestions. Anyway, I was going to use this program until I saw the price tag. I'm also fairly new to C#, having only used it for a few months. Can anyone provide me with a solution to my problem of taking a screenshot of a web page in order to extract the colour scheme? EDIT: Sorry for not getting back to this sooner, but I've been busy with some other things. Anyway, the code seems to work well, but the problem I am having right now is that I am running it within a form, and naturally with Application.Run() being called I cannot run two instances of the same form at once. It recommended Form.showDialog() but that broke everything. Can anyone give me a hand with this code? public static void buildScreenshotFromURL(string url) { int width = 800; int height = 600; using (WebBrowser browser = new WebBrowser()) { browser.Width = width; browser.Height = height; browser.ScrollBarsEnabled = true; // This will be called when the page finishes loading browser.DocumentCompleted += new System.Windows.Forms.WebBrowserDocumentCompletedEventHandler(OnDocumentCompleted); //browser.DocumentCompleted += OnDocumentCompleted; browser.Navigate(url); // This prevents the application from exiting until // Application.Exit is called // Application.Run() does not work as it cannot be called twice, recommended form.showDialog() // but still issues Application.Run(); } } public static void OnDocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e) { // Define size of thumbnail neded int thumbSize = 50; // Now that the page is loaded, save it to a bitmap WebBrowser browser = (WebBrowser)sender; // Code edited from example below to make smaller bitmap and save as PNG using (Graphics graphics = browser.CreateGraphics()) { using (Bitmap bitmap = new Bitmap(browser.Width, browser.Height, graphics)) { Rectangle bounds = new Rectangle(0, 0, bitmap.Width, bitmap.Height); browser.DrawToBitmap(bitmap, bounds); Bitmap thumbBitmap = new Bitmap(bitmap.GetThumbnailImage(thumbSize, thumbSize, thumbCall, IntPtr.Zero)); thumbBitmap.Save("screenshot.png", ImageFormat.Png); handleImage(thumbBitmap); } }

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• How to set a key binding to make Emacs as transparent/opaque as I want?

  - by Vivi

  I want to have a command in Emacs to make it as opaque/transparent as I want (refer to the fabulous question that pointed out that transparency is possible in Emacs, and the EmacsWiki page linked there which has the code I am using below). The EmacsWiki code sets "C-c t" to toggle the previously set transparency on and off: ;;(set-frame-parameter (selected-frame) 'alpha '(<active> [<inactive>])) (set-frame-parameter (selected-frame) 'alpha '(85 50)) (add-to-list 'default-frame-alist '(alpha 85 50)) enter code here(eval-when-compile (require 'cl)) (defun toggle-transparency () (interactive) (if (/= (cadr (find 'alpha (frame-parameters nil) :key #'car)) 100) (set-frame-parameter nil 'alpha '(100 100)) (set-frame-parameter nil 'alpha '(85 60)))) (global-set-key (kbd "C-c t") 'toggle-transparency) What I would like to do is to be able to choose the % transparency when I am in Emacs. If possible, I would like a command where I type for example "C-c t N" (where N is the % opaqueness) for the active frame, and then "M-c t N" for the inactive window. If that can't be done like that, then maybe a command where if I type "C-c t" it asks me for the number which gives the opaqueness of the active window (and the same for the inactive window using "M-c t"). Thanks in advance for your time :) Below are just some comments that are not important to answer the question if you are not interested: I really want this because when I told my supervisor I was learning Emacs he said TexShop is much better and that I am using software from the 80's. I told him about the wonders of Emacs and he said TexShop has all of it and more. I matched everything he showed me except for the transparency (though he couldn't match the preview inside Emacs from preview-latex). I found the transparency thing by chance, and now I want to show him Emacs rules! I imagine this will be a piece of cake for some of you, and even though I could get it done if I spent enough time trying to learn lisp or reading around, I am not a programmer and I have only been using Emacs and a mac for a week. I am lost already as it is! So thanks in advance for your time and help - I will learn lisp eventually!

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• Delaying emails in PHP to avoid exceeding server limit

  - by Andrew P.

  Okay, so here's my problem: I have a list of members on a website, and periodically one of the admins my site (who are not very web or tech savvy) will send a newsletter to the memberlist. My current memberlist is well over 800 individuals long. So, I wrote an email script that sends the email to the full memberlist, with the members listed in the Bcc header. However, I've discovered that my host server has a limit of 300 emails per hour, which I apparently exceed even though the members are listed in the Bcc field. (I wasn't previously aware that the behaviour of Bcc was to send separate emails for each name on the list...) After some thought, I've come to the conclusion that my only solution is to have my script send only the email to only the first 300 emails, wait an hour, and send a second email to the next three hundred, wait another hour, and so on until I've sent the email to the whole member list. Looking around on the internet, I've seen some other solutions people have come up with for delaying emails in PHP. Sleep() is obviously not an option, because I can't just leave the script open and running for 3 or four hours. I've seen some people suggest cron jobs, but I'm not sure how feasible it would be to create three new cron jobs every time I send an email, use them once, and then delete them afterward. The final (and what I think is the smartest) solution I've seen, is to have a table in my database to temporarily store the emails to be delayed and sent later, and then create a cron job that checks this sql table every hour or so, compares the timestamp of the row to the current timestamp, and then sends the email if an hour has passed. So I'm asking you all which method you would recommend. Is there an easier solution that I've completely looked over (aside from getting a different hosting plan. ha!), or is there a cleaner way to do it than the database / cron job approach? tl;dr: I have 800 emails to send in an hour on a server that limits me to 300/hr. Using PHP, find a way to get around this problem in a way that the person sending the email needs only to click "send."

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• Middleware with generic communication media layer

  - by Tom

  Greetings all, I'm trying to implement middleware (driver) for an embedded device with generic communication media layer. Not sure what is the best way to do it so I'm seeking an advice from more experienced stackoverflow users:). Basically we've got devices around the country communicating with our servers (or a pda/laptop in used in field). Usual form of communication is over TCP/IP, but could be also using usb, RF dongle, IR, etc. The plan is to have object corresponding with each of these devices, handling the proprietary protocol on one side and requests/responses from other internal systems on the other. The thing is how create something generic in between the media and the handling objects. I had a play around with the TCP dispatcher using boost.asio but trying to create something generic seems like a nightmare :). Anybody tried to do something like that? What is the best way how to do it? Example: Device connects to our Linux server. New middleware instance is created (on the server) which announces itself to one of the running services (details are not important). The service is responsible for making sure that device's time is synchronized. So it asks the middleware what is the device's time, driver translates it to device language (protocol) and sends the message, device responses and driver again translates it for the service. This might seem as a bit overkill for such a simple request but imagine there are more complex requests which the driver must translate, also there are several versions of the device which use different protocol, etc. but would use the same time sync service. The goal is to abstract the devices through the drivers to be able to use the same service to communicate with them. Another example: we find out that the remote communications with the device are down. So we send somebody out with PDA, he connects to the device using USB cable. Starts up the application which has the same functionality as the timesync service. Again middleware instance is created (on the PDA) to translate communication between application and the device this time only using USB/serial media not TCP/IP as in previous example. I hope it makes more sense now :) Cheers, Tom

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• B-trees, databases, sequential inputs, and speed.

  - by IanC

  I know from experience that b-trees have awful performance when data is added to them sequentially (regardless of the direction). However, when data is added randomly, best performance is obtained. This is easy to demonstrate with the likes of an RB-Tree. Sequential writes cause a maximum number of tree balances to be performed. I know very few databases use binary trees, but rather used n-order balanced trees. I logically assume they suffer a similar fate to binary trees when it comes to sequential inputs. This sparked my curiosity. If this is so, then one could deduce that writing sequential IDs (such as in IDENTITY(1,1)) would cause multiple re-balances of the tree to occur. I have seen many posts argue against GUIDs as "these will cause random writes". I never use GUIDs, but it struck me that this "bad" point was in fact a good point. So I decided to test it. Here is my code: SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO CREATE TABLE [dbo].[T1]( [ID] [int] NOT NULL CONSTRAINT [T1_1] PRIMARY KEY CLUSTERED ([ID] ASC) ) GO CREATE TABLE [dbo].[T2]( [ID] [uniqueidentifier] NOT NULL CONSTRAINT [T2_1] PRIMARY KEY CLUSTERED ([ID] ASC) ) GO declare @i int, @t1 datetime, @t2 datetime, @t3 datetime, @c char(300) set @t1 = GETDATE() set @i = 1 while @i < 2000 begin insert into T2 values (NEWID(), @c) set @i = @i + 1 end set @t2 = GETDATE() WAITFOR delay '0:0:10' set @t3 = GETDATE() set @i = 1 while @i < 2000 begin insert into T1 values (@i, @c) set @i = @i + 1 end select DATEDIFF(ms, @t1, @t2) AS [Int], DATEDIFF(ms, @t3, getdate()) AS [GUID] drop table T1 drop table T2 Note that I am not subtracting any time for the creation of the GUID nor for the considerably extra size of the row. The results on my machine were as follows: Int: 17,340 ms GUID: 6,746 ms This means that in this test, random inserts of 16 bytes was almost 3 times faster than sequential inserts of 4 bytes. Would anyone like to comment on this? Ps. I get that this isn't a question. It's an invite to discussion, and that is relevant to learning optimum programming.

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• How can I remove rows with unique values? As in only keeping rows with duplicate values?

  - by user1456405

  Here's the conundrum, I'm a complete and utter noob when it comes to programming. I understand the basics, but am still learning javascript. I have a spreadsheet of surveys, in which I need to see how particular users have varied over time. As such, I need to disregard all rows with unique values in a particular column. The data looks like this: Response Date Response_ID Account_ID Q.1 10/20/2011 12:03:43 PM 23655956 1168161 8 10/20/2011 03:52:57 PM 23660161 1168152 0 10/21/2011 10:55:54 AM 23672903 1166121 7 10/23/2011 04:28:16 PM 23694471 1144756 9 10/25/2011 06:30:52 AM 23732674 1167449 7 10/25/2011 07:52:28 AM 23734597 1087618 5 I've found a way to do so in VBA, which sucks as I have to use excel, per below: Sub Del_Unique() Application.ScreenUpdating = False Columns("B:B").Insert Shift:=xlToRight Columns("A:A").Copy Destination:=Columns("B:B") i = Application.CountIf(Range("A:A"), "<>") + 50 If i > 65536 Then i = 65536 Do If Application.CountIf(Range("B:B"), Range("A" & i)) = 1 Then Rows(i).Delete End If i = i - 1 Loop Until i = 0 Columns("B:B").Delete Application.ScreenUpdating = True End Sub But that requires mucking about. I'd really like to do it in Google Spreadsheets with a script that won't have to be changed. Closest I can get is retrieving all duplicate user ids from the range, but can't associate that with the row. That code follows: function findDuplicatesInSelection() { var activeRange = SpreadsheetApp.getActiveRange(); var values = activeRange.getValues(); // values that appear at least once var once = {}; // values that appear at least twice var twice = {}; // values that appear at least twice, stored in a pretty fashion! var final = []; for (var i = 0; i < values.length; i++) { var inner = values[i]; for (var j = 0; j < inner.length; j++) { var cell = inner[j]; if (cell == "") continue; if (once.hasOwnProperty(cell)) { if (!twice.hasOwnProperty(cell)) { final.push(cell); } twice[cell] = 1; } else { once[cell] = 1; } } } if (final.length == 0) { Browser.msgBox("No duplicates found"); } else { Browser.msgBox("Duplicates are: " + final); } } Anyhow, sorry if this is the wrong place or format, but half of what I've found so far has been from stack, I thought it was a good place to start. Thanks!

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• How to catch 'exceptions' for out of order execution in Workflow Foundation 4?

  - by Alex Key

  Hi, I am attempting to model a worklfow using a "WCF Workflow Service" in .net / vs 2010 that needs to handle out of order execution gracefully (but not allow it - if thath makes sense!?) For example I have 2 receive activities one called Initialize and the other called GetValue inside a FlowChart. In most cases Initialize should be called first and GetValue after (as modled in the flow chart). However if GetValue is executed before Initialize I do not want to return an "out of order" exception (although when I look at the WCF test client, I can't actually see an exception). But instead a custom exception saying something like "you must initialize first". In theory I could model this with lots of parallel activities and conditions to check if Initialized / Running / Terminated etc. But the business process I am modelling if very very similar to a state machine... except it must handle people executing things in the wrong order. Ideally I would like to catch the "out of order" exception (thought I don't think it's really an exception as such), check the 'exception' to see which function was attempted to run and then handle it. I have done some research around enabling AllowBufferedReceive. However I don't want to be able to execute out of order (I don't think), but instead give a detailed response if it does happen. I've looked at the new beta state machine template for WF 4 - but i'm not sure if it does what i'm after? I'm not sure if I have the wrong end of the stick, so any help would be greatly appreciated. [EDIT] To help clarify... Sorry it's a tricky one to explain. The standard I am trying to implement (the e-learning standard SCORM RTE) is structured like a state machine i.e. certain functions can only be executed in certain states. However the standard specifies that if the calling clients tries to execute a function that it is not meant to, then a warning should be issued... for example "you cannot use GetValue(), because you have not yet Initialized". Ideally I'd like to structure the workflow as the theoretical state machine and not need to have to use multiple if/else's to handle all the scenarios where something could be executed out-of-order. I'd like to catch a out-of-order exception (but I don't think there is such an exception - as it's not in the debugger) and rethrow it.

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• Noob LINQ - reading, filtering XML with XDocument

  - by user316117

  I'm just learning XDocument and LINQ queries. Here's some simple XML (which doesn't look formatted exactly right in this forum in my browser, but you get the idea . . .) <?xml version="1.0" encoding="utf-8"?> <quiz xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.example.com/name XMLFile2.xsd" title="MyQuiz1"> <q_a> <q_a_num>1</q_a_num> <q_>Here is question 1</q_> <_a>Here is the answer to 1</_a> </q_a> <q_a> <q_a_num>2</q_a_num> <q_>Here is question 2</q_> <_a>Here is the answer to 2</_a> </q_a> </quiz> I can iterate across all elements in my XML file and display their Name, Value, and NodeType in a ListBox like this, no problem: XDocument doc = XDocument.Load(sPath); IEnumerable<XElement> elems = doc.Descendants(); IEnumerable<XElement> elem_list = from elem in elems select elem; foreach (XElement element in elem_list) { String str0 = "Name = " + element.Name.ToString() + ", Value = " + element.Value.ToString() + ", Nodetype = " + element.NodeType.ToString(); System.Windows.Controls.Label strLabel = new System.Windows.Controls.Label(); strLabel.Content = str0; listBox1.Items.Add(strLabel); } ...but now I want to add a "where" clause to my query so that I only select elements with a certain name (e.g., "qa") but my element list comes up empty. I tried . . . IEnumerable<XElement> elem_list = from elem in elems where elem.Name.ToString() == "qa" select elem; Could someone please explain what I'm doing wrong? (and in general are there some good tips for debugging Queries?) Thanks in advance!

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• How hard programming is? Really. [closed]

  - by Bubba88

  Hi! The question is about your perception of programming activity. How hard/exacting this task is? There is much buzz about programming nowadays, people say that programmers are smart, very technical and abstract at a time, know much about world, psychology etc.. They say, that programmers got really powerful brain thing, cause there is much to keep in consideration simultaneously again with much information folded into each other associatively (up 10 levels of folding they say))) Still, there are some terms to specify at our own.. So that is the question: What do you think about programming in general? Is it hard? Is it 'for everyone' or for the particular kind of people only? How much non-CS background do you need to program (just to program, really; enterprise applications for example)? How long is the learning curve? (again, for programming in general) And another bunch of random questions: - If you were not to like/love programming, would that be a serious trouble bothering your current employment? - If you were to start from the beginning, would you chose that direction this time? - What other areas (jobs or maybe hobbies) are comparable to programming in the way they can explode someone's lovely brain? - Is 'non turing-complete programming' (SQL, XML, etc.) comparable to what we do or is it really way easier, less requiring, cheap and akin to cooking :)? Well, the essence is: How would you describe programming activity WRT to its difficulty? Or, on the other hand: Did you ever catch yourself thinking at some point: OMG, it's sooo hard! I don't know how would I ever program, even carried away this way and doing programming just for fun? It's very interesting to know your opinion, your'e the programmers after all. I mean much people must be exaggerating/speculating about the thing they do not really know about. But that musn't be the case here on SO :) P.S.: I'll try my best to update this post later, and you please edit it too. At least I'll get decent English in my question text :)

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• xml dom node children

  - by matt

  Need some help I've got lots of code and i want to make it shorter i know there's a way but I can't remember it this is code example: <?xml version="1.0" encoding="ISO-8859-1"?> <bookstore> <book category="cooking"> <title lang="en">Everyday Italian</title> <author>Giada De Laurentiis</author> <year>2005</year> <price>30.00</price> </book> <book category="children"> <title lang="en">Harry Potter</title> <author>J K. Rowling</author> <year>2005</year> <price>29.99</price> </book> <book category="web"> <title lang="en">XQuery Kick Start</title> <author>James McGovern</author> <author>Per Bothner</author> <author>Kurt Cagle</author> <author>James Linn</author> <author>Vaidyanathan Nagarajan</author> <year>2003</year> <price>49.99</price> </book> <book category="web" cover="paperback"> <title lang="en">Learning XML</title> <author>Erik T. Ray</author> <year>2003</year> <price>39.95</price> </book> </bookstore As you can see the different nodes, children now is there a way to make this code smaller so I don't have to keep writing the nodes and children

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• Web-Frameworks for Education Management Systems?

  - by Indebi

  So, I'm working on an idea and I'll go into a brief overview of that but my question is, What are some good web frameworks for this situation? I have some experience in the following languages: C# Python I have considerably more experience in C# than Python, however I am expecting to learn new things. My idea is this, a completely web-based community-oriented Education Management System that focuses on making students and teachers day-to-day lives easier. For students it will provide a centralized place for them to do homework, study for tests, and reinforce concepts learned previously in class. For teachers it will give them a centralized place to handle assignments, attendance, homework, tests, and all other major parts of classroom management. All of that, but in a community-oriented fashion. Everything a teacher does is shared and open to constructive criticism, allowing other teachers to use their assignments/tests and for students or other teachers to comment, rate and criticize their assignments. This encourages an environment of openness that will allow teacher's to focus on teaching and student's to focus on learning. And that community wouldn't be limited to one school or school-district, this system would be completely school-independent. Please note that I have no problem with hearing constructive criticism on this idea, however I would prefer if this post was more focused on my question. I have somewhat explored about the following options: Django ASP.NET Ruby on Rails Silverlight (1) I have Django installed and I played with it for a little bit, I really like how easy setting up databases are and how it handles the database completely for you. I don't really know how to use it very well and I don't quite understand the Model-View-Controller paradigm(?) for it yet but I haven't thought about it much. I also like the fact that it uses Python. (2) I don't really like Visual Studio for developing in ASP.NET, I hate the way the web-designer works and it just feels clunky and old. I like the server-side development part though. I don't like how expensive ASP.NET and overall Visual Studio is, even if I do get it for free for now using DreamSpark (3) I haven't been able to explore much with this, I could not get Rails (or maybe Ruby) properly installed. I first installed it within RadRails and that didn't work so I uninstalled RadRails and then installed the latest version of Ruby off the official Windows Installer and then installed Ruby on Rails through gem and even after all that it still didn't work, so I installed Netbeans and attempted to use it there but it still did not work (4) I like Silverlight in some extents, I've played with this one the most, it's very similar to WPF (which I've used the most) in a lot of ways but I don't like how database connectivity works, at least in comparison to Django. I also dislike how expensive everything with Microsoft is, even if I get it for free for now with DreamSpark. I would like to hear some suggestions from experienced web-developers as to what I should use and why, or at least what some good options are for my scenario Your help would be very appreciated

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• AD-DirectoryServices: .NET2.0 - Speaking architecture, approach and best practices... Suggestions?

  - by Will Marcouiller

  I've been mandated to write an application to migrate the Active Directory access models to another environment. Here's the context: I'm stuck with VB.NET 2005 and .NET Framework 2.0; The application must use the Windows authenticated user to manage AD; The objects I have to handle are Groups, Users and OrganizationalUnits; I intend to use the Façade design pattern to provider ease of use and a fully reusable code; I plan to write a factory for each of the objects managed (group, ou, user); The use of Attributes should be useful here, I guess; As everything is about the DirectoryEntry class when accessing the AD, it seems a good candidate for generic types. Obligatory features: User creates new OUs manually; User creates new group manually; User creates new user (these users are services accounts) manually; Application reads an XML file which contains the OUs, groups and users to create; Application informs the user about the OUs, groups and users that shall be created; User specifies the domain environment where to migrate the XML input file designated objects; User makes changes if needed, and launches the task operations; Application performs required by the XML input file operations against the underlying AD as specified by the user; Application informs the user upon completion. Linear features: User fetches OUs, groups, users; User changes OUs, groups, users; User deletes OUs, groups, users; The application logs AD entries and operations performed, plus errors and exceptions; Nice-to-have features: Application rollbacks operations on error or exception. I've been working for weeks now to get acquainted with the AD and the System.DirectoryServices assembly. But I don't seem to find a way to be fully satisfied with what I'm doing and always looking for better. I have studied Bret de Smet's Linq to AD on CodePlex, but then again, I can't use it as I'm stuck with .NET 2.0, so no Linq! But I've learned about Attributes, and seen that he's working with generic types as he codes a DirectorySource class to perform the operations for OUs, groups and users. I have been able to add groups to the AD; I have been able to add users to the AD; The created user is automatically disabled? I seem to get confused with the use of a LDAP path to add objects. For instance, one needs two instances of a System.DirectoryServices.DirectoryEntry class to add a group, for instance. Why this? Any suggestions? Thanks for any help, code sample, ideas, architural solution, everything!

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• Optimize date query for large child tables: GiST or GIN?

  - by Dave Jarvis

  Problem 72 child tables, each having a year index and a station index, are defined as follows: CREATE TABLE climate.measurement_12_013 ( -- Inherited from table climate.measurement_12_013: id bigint NOT NULL DEFAULT nextval('climate.measurement_id_seq'::regclass), -- Inherited from table climate.measurement_12_013: station_id integer NOT NULL, -- Inherited from table climate.measurement_12_013: taken date NOT NULL, -- Inherited from table climate.measurement_12_013: amount numeric(8,2) NOT NULL, -- Inherited from table climate.measurement_12_013: category_id smallint NOT NULL, -- Inherited from table climate.measurement_12_013: flag character varying(1) NOT NULL DEFAULT ' '::character varying, CONSTRAINT measurement_12_013_category_id_check CHECK (category_id = 7), CONSTRAINT measurement_12_013_taken_check CHECK (date_part('month'::text, taken)::integer = 12) ) INHERITS (climate.measurement) CREATE INDEX measurement_12_013_s_idx ON climate.measurement_12_013 USING btree (station_id); CREATE INDEX measurement_12_013_y_idx ON climate.measurement_12_013 USING btree (date_part('year'::text, taken)); (Foreign key constraints to be added later.) The following query runs abysmally slow due to a full table scan: SELECT count(1) AS measurements, avg(m.amount) AS amount FROM climate.measurement m WHERE m.station_id IN ( SELECT s.id FROM climate.station s, climate.city c WHERE -- For one city ... -- c.id = 5182 AND -- Where stations are within an elevation range ... -- s.elevation BETWEEN 0 AND 3000 AND 6371.009 * SQRT( POW(RADIANS(c.latitude_decimal - s.latitude_decimal), 2) + (COS(RADIANS(c.latitude_decimal + s.latitude_decimal) / 2) * POW(RADIANS(c.longitude_decimal - s.longitude_decimal), 2)) ) <= 50 ) AND -- -- Begin extracting the data from the database. -- -- The data before 1900 is shaky; insufficient after 2009. -- extract( YEAR FROM m.taken ) BETWEEN 1900 AND 2009 AND -- Whittled down by category ... -- m.category_id = 1 AND m.taken BETWEEN -- Start date. (extract( YEAR FROM m.taken )||'-01-01')::date AND -- End date. Calculated by checking to see if the end date wraps -- into the next year. If it does, then add 1 to the current year. -- (cast(extract( YEAR FROM m.taken ) + greatest( -1 * sign( (extract( YEAR FROM m.taken )||'-12-31')::date - (extract( YEAR FROM m.taken )||'-01-01')::date ), 0 ) AS text)||'-12-31')::date GROUP BY extract( YEAR FROM m.taken ) The sluggishness comes from this part of the query: m.taken BETWEEN /* Start date. */ (extract( YEAR FROM m.taken )||'-01-01')::date AND /* End date. Calculated by checking to see if the end date wraps into the next year. If it does, then add 1 to the current year. */ (cast(extract( YEAR FROM m.taken ) + greatest( -1 * sign( (extract( YEAR FROM m.taken )||'-12-31')::date - (extract( YEAR FROM m.taken )||'-01-01')::date ), 0 ) AS text)||'-12-31')::date The HashAggregate from the plan shows a cost of 10006220141.11, which is, I suspect, on the astronomically huge side. There is a full table scan on the measurement table (itself having neither data nor indexes) being performed. The table aggregates 237 million rows from its child tables. Question What is the proper way to index the dates to avoid full table scans? Options I have considered: GIN GiST Rewrite the WHERE clause Separate year_taken, month_taken, and day_taken columns to the tables What are your thoughts? Thank you!

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• Why is this OpenGL ES code slow on iPhone?

  - by f3r3nc

  I've slightly modified the iPhone SDK's GLSprite example while learning OpenGL ES and it turns out to be quite slow. Even in the simulator (on the hw worst) so I must be doing something wrong since it's only 400 textured triangles. const GLfloat spriteVertices[] = { 0.0f, 0.0f, 100.0f, 0.0f, 0.0f, 100.0f, 100.0f, 100.0f }; const GLshort spriteTexcoords[] = { 0,0, 1,0, 0,1, 1,1 }; - (void)setupView { glViewport(0, 0, backingWidth, backingHeight); glMatrixMode(GL_PROJECTION); glLoadIdentity(); glOrthof(0.0f, backingWidth, backingHeight,0.0f, -10.0f, 10.0f); glMatrixMode(GL_MODELVIEW); glClearColor(0.3f, 0.0f, 0.0f, 1.0f); glVertexPointer(2, GL_FLOAT, 0, spriteVertices); glEnableClientState(GL_VERTEX_ARRAY); glTexCoordPointer(2, GL_SHORT, 0, spriteTexcoords); glEnableClientState(GL_TEXTURE_COORD_ARRAY); // sprite data is preloaded. 512x512 rgba8888 glGenTextures(1, &spriteTexture); glBindTexture(GL_TEXTURE_2D, spriteTexture); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, spriteData); free(spriteData); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glEnable(GL_TEXTURE_2D); glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA); glEnable(GL_BLEND); } - (void)drawView { .. glClear(GL_COLOR_BUFFER_BIT); glLoadIdentity(); glTranslatef(tx-100, ty-100,10); for (int i=0; i<200; i++) { glTranslatef(1, 1, 0); glDrawArrays(GL_TRIANGLE_STRIP, 0, 4); } .. } drawView is called every time the screen is touched or the finger on the screen is moved and tx,ty are set to the x,y coordinates where that touch happened. I've also tried using GLBuffer, when translation was pre-generated and there was only one DrawArray but gave the same performance (~4 FPS). ===EDIT=== Meanwhile I've modified this so that much smaller quads are used (sized: 34x20) and much less overlapping is done. There are ~400 quads-800 triangles spread on the whole screen. Texture size is 512x512 atlas and RGBA_8888 while the texture coordinates are in float. The code is very ugly in terms of API efficiency: there are two MatrixMode change along with two loads and two translation then a drawarrays for a triangle strip (quad). Now this produces ~45 FPS.

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• What Can I Do To One Of My Team Number (Good Friend As Well) Who Lost His Passion.

  - by skyflyer

  It seems this question is not program related, but there are lot of similar questions. So please bear with me! By the way, I am programmer and my team is also charging a software project. And SO is the only place which solved me lot of thorny troubles!THANK YOU GUYS! I joined my company with him years ago. At that time he was quite passionate on his job which is a front-end development. He gave us lot of useful suggestions concerning his work like design. And I believed he was a smart guy. I believe he still is smart too by the way. One years later, however, he seemed lost his passion and fooling around every day, did not care about his work any more and produced poorwork. Even worse he literally stopped learning new skills and honing his work related skills. For me it is horrible, we got to keep abreast with new technology development, otherwise we will be throw out. Since we were just coworkers, I did not care about it too much except mentioned my thoughts several times. But last month, we resembled a new group and assigned very important project. And I am the team leader, sadly! My boss gave me lot of support and expectation as well. I did a pretty good job before and I am very optimism to our future. But as a team, if my team does not work hard, we will be doomed to failure no matter how hard I work and push. In order to revitalize his passion, I tried couple of ways like talking to him about my concern and my boss's angry. I offered his new task which is quite new to him. I even persuaded my boss to give him new incentive package. But all of them knocked wall. His reaction was just he did not care. Even worse he did not want to talk about his situation. I want to be hard on him, but since we are friends and coworkers, I really can not see it will work. Even it works, I can not so quickly change my self from friend and coworker into manager. As a novice in management, I am really overwhelmed! I do not want get him fired, we are friends and I do not see him fired as my team number. What can I do? Thank you guys!

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• Wix Bootstrapper - difficulty detecting if software is already installed c++ redistributable, sql server ce 3.5 sp2

  - by gdeck

  I apologize if this is answered elsewhere. So far (thanks to a post from Rob Mensching), my code will detect .NET 4.0 if it's installed and it'll pass right over it. I'm not able to correctly detect Microsoft Visual C++ 2010 x86 Redistributable OR Microsoft SQL Server Compact 3.5 Service Pack 2. My code is below. I'm learning, so I would appreciate as much constructive criticism as possible. <!--Search for .NET 4.0--> <util:RegistrySearch Id="NETFRAMEWORK40" Root="HKLM" Key="SOFTWARE\Microsoft\Net Framework Setup\NDP\v4\Full" Value="Install" Variable="NETFRAMEWORK40" Result="value"/> <!--Search for Microsoft Visual C++ 2010 x86 Redistributable--> <util:RegistrySearch Id="SearchForCPP2010X86" Root="HKLM" Key="SOFTWARE\Microsoft\VisualStudio\10.0\VC\VCRedist\x86" Value="Install" Variable="CPP2010Redist" Result="exists"/> <!--Search for Microsoft SQL Server Compact 3.5 Service Pack 2--> <util:RegistrySearch Id="SearchForSQLSvrCE35SP2" Root="HKLM" Key="SOFTWARE\Microsoft\Microsoft SQL Server Compact Edition\v3.5\ENU" Value="Install" Variable="SQLSvrCE35SP2" Result="exists"/> <Chain> <!-- Install .Net 4 Full --> <PackageGroupRef Id="Net4Full"/> <!-- Install Microsoft Visual C++ 2010 x86 Redistributable --> <PackageGroupRef Id="MSVisCPP2010x86Redist"/> <!-- Install Microsoft SQL Server Compact 3.5 Service Pack 2 --> <PackageGroupRef Id="SQLExpressCE"/> </Chain> <!--Install .NET 4.0--> <PackageGroup Id="Net4Full"> <ExePackage Id="Net4Full" Name="Microsoft .NET Framework 4.0 Setup" Cache="no" Compressed="yes" PerMachine="yes" Permanent="yes" Vital="yes" SourceFile="BootstrapperLibrary\dotNetFx40_Full_setup.exe" DetectCondition="NETFRAMEWORK40"/> </PackageGroup> <!--Install Microsoft Visual C++ 2010 x86 Redistributable--> <PackageGroup Id="MSVisCPP2010x86Redist"> <ExePackage Id="MSVisCPP2010x86Redis" Name="Microsoft Visual C++ 2010 x86 Redistributable " Cache="no" Compressed="yes" PerMachine="yes" Permanent="yes" Vital="yes" SourceFile="BootstrapperLibrary\vcredist_x86.exe" DetectCondition="CPP2010Redist"/> </PackageGroup> <!--Install Microsoft SQL Server Compact 3.5 Service Pack 2--> <PackageGroup Id="SQLExpressCE"> <ExePackage Id="SQLExpressCE" Name="Microsoft SQL Server Compact 3.5 Service Pack 2 Setup" Cache="no" Compressed="yes" PerMachine="yes" Permanent="yes" Vital="yes" SourceFile="BootstrapperLibrary\SSCERuntime-ENU.exe"/> </PackageGroup>

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• DCVS + hosting for a startup commercial multiplatform phone app

  - by AG

  I'm in lean startup mode, working on a simple phone app that will be published initially as a iThingy app and an Android app with, possibly, Blackberry and Symbian versions to follow. I'm about to go from no repository to needing a central repository that up to 4 very part-time resources will be sharing. Two of us have no version control background, one has used Subversion, and I've used most of the major centralized VCS systems. I'm not going to be pushing the technical limitations of any VCS for a long time; I'm sure that any of the major systems would work fine. And the hosting accounts I've looked at seem reasonable. So I'm really focussed on minimizing the downside risks. That is, I'd like to find a stable setup that is easy to learn in general, easy to use from Windows/Eclipse, and won't paint me into any obvious corners for the next 12 months or so. A quick search of the web had led me to consider the following pairs of DVCS and hosting service, with what I think I'm hearing as their strengths and weaknesses (for my purposes): Bazaar/Launchpad -- My initial choice since I need to get more familiar with this pair for the Google Summer of Code mentoring I'm doing. But, whatever the technical merits, a non-starter for me because they are purely open source, no private repositories plans to purchase that I can see. Git/GitHub -- Git: Fast, light, ultimately flexible, but relatively less Windows friendly, Eclipse plugin (eGit) available but relatively young, GitHub: widely used, pricing is fine Mercurial/BitBucket -- Mercurial: a little less flexible, a little more Windows friendly, Eclipse plugin seems a bit more mature, BitBucket: widely used, pricing is fine, includes a wiki and an issue tracker that we might be able to use instead of something like BaseCamp, at least for a while. Mercurial/BitBucket seem like the winning pair so far for my particular situation; at least two of us are definitely going to be working mostly from Eclipse on Windows and reducing my own learning curve is a priority. ;-) But I have two specific questions: 1) Am I wrong about Bazaar/Launchpad and is there a viable, secure way to use them for proprietary code? 2) Any reason to think that the Mecurial/Bitbucket pair will end up being a headache for my Mac developer, soon, or for Blackberry or Symbian developers a little later? ag

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• dojo layout tutorial dor version 1.7 doesn't work for 1.7.2

  - by Sheena

  This is sortof a continuation to dojo1.7 layout acting screwy. So I made some working widgets and tested them out, i then tried altering my work using the tutorial at http://dojotoolkit.org/documentation/tutorials/1.7/dijit_layout/ to make the layout nice. After failing at that in many interesting ways (thus my last question) I started on a new path. My plan is now to implement the layout tutorial example and then stick in my widgets. For some reason even following the tutorial wont work... everything loads then disappears and I'm left with a blank browser window. Any ideas? It just struck me that it could be browser compatibility issues, I'm working on Firefox 13.0.1. As far as I know Dojo is supposed to be compatible with this... anyway, have some code: HTML: <body class="claro"> <div id="appLayout" class="demoLayout" data-dojo-type="dijit.layout.BorderContainer" data-dojo-props="design: 'headline'"> <div class="centerPanel" data-dojo-type="dijit.layout.ContentPane" data-dojo-props="region: 'center'"> <div> <h4>Group 1 Content</h4> <p>stuff</p> </div> <div> <h4>Group 2 Content</h4> </div> <div> <h4>Group 3 Content</h4> </div> </div> <div class="edgePanel" data-dojo-type="dijit.layout.ContentPane" data-dojo-props="region: 'top'"> Header content (top) </div> <div id="leftCol" class="edgePanel" data-dojo-type="dijit.layout.ContentPane" data-dojo-props="region: 'left', splitter: true"> Sidebar content (left) </div> </div> </body> Dojo Configuration: var dojoConfig = { baseUrl: "${request.static_url('mega:static/js')}", //this is in a mako template tlmSiblingOfDojo: false, packages: [ { name: "dojo", location: "libs/dojo" }, { name: "dijit", location: "libs/dijit" }, { name: "dojox", location: "libs/dojox" }, ], parseOnLoad: true, has: { "dojo-firebug": true, "dojo-debug-messages": true }, async: true }; other js stuff: require(["dijit/layout/BorderContainer", "dijit/layout/TabContainer", "dijit/layout/ContentPane", "dojo/parser"]); css: html, body { height: 100%; margin: 0; overflow: hidden; padding: 0; } #appLayout { height: 100%; } #leftCol { width: 14em; }

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• help merging perl code routines together for file processing

  - by jdamae

  I need some perl help in putting these (2) processes/code to work together. I was able to get them working individually to test, but I need help bringing them together especially with using the loop constructs. I'm not sure if I should go with foreach..anyways the code is below. Also, any best practices would be great too as I'm learning this language. Thanks for your help. Here's the process flow I am looking for: -read a directory -look for a particular file -use the file name to strip out some key information to create a newly processed file -process the input file -create the newly processed file for each input file read (if i read in 10, I create 10 new files) Sample Recs: col1,col2,col3,col4,col5 [email protected],[email protected],8,2009-09-24 21:00:46,1 [email protected],[email protected],16,2007-08-18 22:53:12,33 [email protected],[email protected],16,2007-08-18 23:41:23,33 Here's my test code: Target Filetype: `/backups/test/foo101.name.aue-foo_p002.20110124.csv` Part 1: my $target_dir = "/backups/test/"; opendir my $dh, $target_dir or die "can't opendir $target_dir: $!"; while (defined(my $file = readdir($dh))) { next if ($file =~ /^\.+$/); #Get filename attributes if ($file =~ /^foo(\d{3})\.name\.(\w{3})-foo_p(\d{1,4})\.\d+.csv$/) { print "$1\n"; print "$2\n"; print "$3\n"; } print "$file\n"; } Part 2: use strict; use Digest::MD5 qw(md5_hex); #Create new file open (NEWFILE, ">/backups/processed/foo$1.name.$2-foo_p$3.out") || die "cannot create file"; my $data = ''; my $line1 = <>; chomp $line1; my @heading = split /,/, $line1; my ($sep1, $sep2, $eorec) = ( "^A", "^E", "^D"); while (<>) { my $digest = md5_hex($data); chomp; my (@values) = split /,/; my $extra = "__mykey__$sep1$digest$sep2" ; $extra .= "$heading[$_]$sep1$values[$_]$sep2" for (0..scalar(@values)); $data .= "$extra$eorec"; print NEWFILE "$data"; } #print $data; close (NEWFILE);

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• Speeding up templates in GAE-Py by aggregating RPC calls

  - by Sudhir Jonathan

  Here's my problem: class City(Model): name = StringProperty() class Author(Model): name = StringProperty() city = ReferenceProperty(City) class Post(Model): author = ReferenceProperty(Author) content = StringProperty() The code isn't important... its this django template: {% for post in posts %} <div>{{post.content}}</div> <div>by {{post.author.name}} from {{post.author.city.name}}</div> {% endfor %} Now lets say I get the first 100 posts using Post.all().fetch(limit=100), and pass this list to the template - what happens? It makes 200 more datastore gets - 100 to get each author, 100 to get each author's city. This is perfectly understandable, actually, since the post only has a reference to the author, and the author only has a reference to the city. The __get__ accessor on the post.author and author.city objects transparently do a get and pull the data back (See this question). Some ways around this are Use Post.author.get_value_for_datastore(post) to collect the author keys (see the link above), and then do a batch get to get them all - the trouble here is that we need to re-construct a template data object... something which needs extra code and maintenance for each model and handler. Write an accessor, say cached_author, that checks memcache for the author first and returns that - the problem here is that post.cached_author is going to be called 100 times, which could probably mean 100 memcache calls. Hold a static key to object map (and refresh it maybe once in five minutes) if the data doesn't have to be very up to date. The cached_author accessor can then just refer to this map. All these ideas need extra code and maintenance, and they're not very transparent. What if we could do @prefetch def render_template(path, data) template.render(path, data) Turns out we can... hooks and Guido's instrumentation module both prove it. If the @prefetch method wraps a template render by capturing which keys are requested we can (atleast to one level of depth) capture which keys are being requested, return mock objects, and do a batch get on them. This could be repeated for all depth levels, till no new keys are being requested. The final render could intercept the gets and return the objects from a map. This would change a total of 200 gets into 3, transparently and without any extra code. Not to mention greatly cut down the need for memcache and help in situations where memcache can't be used. Trouble is I don't know how to do it (yet). Before I start trying, has anyone else done this? Or does anyone want to help? Or do you see a massive flaw in the plan?

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• Design Technique: How to design a complex system for processing orders, products and units.

  - by Shyam

  Hi, Programming is fun: I learned that by trying out simple challenges, reading up some books and following some tutorials. I am able to grasp the concepts of writing with OO (I do so in Ruby), and write a bit of code myself. What bugs me though is that I feel re-inventing the wheel: I haven't followed an education or found a book (a free one that is) that explains me the why's instead of the how's, and I've learned from the A-team that it is the plan that makes it come together. So, armed with my nuby Ruby skills, I decided I wanted to program a virtual store. I figured out the following: My virtual Store will have: Products and Services Inventories Orders and Shipping Customers Now this isn't complex at all. With the help of some cool tools (CMapTools), I drew out some concepts, but quickly enough (thanks to my inferior experience in designing), my design started to bite me. My very first product-line were virtual "laptops". So, I created a class (Ruby): class Product attr_accessor :name, :price def initialize(name, price) @name = name @price = price end end which can be instantiated by doing (IRb) x = Product.new("Banana Pro", 250) Since I want my virtual customers to be able to purchase more than one product, or various types, I figured out I needed some kind of "Order" mechanism. class Order def initialize(order_no) @order_no = order_no @line_items = [] end def add_product(myproduct) @line_items << myproduct end def show_order() puts @order_no @line_items.each do |x| puts x.name.to_s + "\t" + x.price.to_s end end end that can be instantiated by doing (IRb) z = Order.new(1234) z.add_product(x) z.show_order Splendid, I have now a very simple ordering system that allows me to add products to an order. But, here comes my real question. What if I have three models of my product (economy, business, showoff)? Or have my products be composed out of separate units (bigger screen, nicer keyboard, different OS)? Surely I could make them three separate products, or add complexity to my product class, but I am looking for are best practices to design a flexible product object that can be used in the real world, to facilitate a complex system. My apologies if my grammar and my spelling are with error, as english is not my first language and I took the time to check as far I could understand and translate properly! Thank you for your answers, comments and feedback!

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