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• Upload large files via a webpage

  - by Hultner

  What way is the best way to let users upload large files from there webbrowser to a server. I'm talking 200MB+ possible up to a few gigatyes. I have been thinking of a few possible solutions to the problem (not tried them yet) and this is basically the things I came up with. Server download speed will not be a problem but the users connection possibly could. Having some sort of applet on the client side written in Java or Flash which sends the file in parts (is this possible with an applet) to a php/other script on the server and a checksum+ some other info about the file. On the server scripts all the parts and the info file is saved in a temporary directory wich has a unique name based on the checksum of the file and the ip of the user. When the last chunk is sent the applet sends a signal to the server saying it's finished and the server put the file together in the right location. If a chunk doesn't match the checksum for that part the server will send a response to the applet telling it to reupload that chunk. I don't know how important the checksum checking is since it's all tcpackages, someone with more insigth migth be able to answer on that. This is probably the worst way, changing the settings on your server to allow huge fileuploads via an inputfiel. Do it like a normal transfer. User an uploadmanager which does pretty much the same thing as applet i mentioned above. Pros of the first is probably that it would most likely be rather secure, you could show progress as well and possibly resume an upload if ip hasn't changed and do a threaded upload of the chunks. Cons of the first is that the user will need flash/java for it to work. Pros of the 2nd is that it will pretty much work for everyone but cons are big, first there's no way resuming an intruppted download and if something is wrong the whole file would have to be reuploaded is a few of cons. For the third one the pros is pretty muc the same as for the first but the cons is that the user would have to download an application to their computer and run and the application will have to be have to be compatible with their computer and OS. Another way may be a combination of two. Lets say an applet for bigger or more files and a simple input which is rather restricted to maybe max 10-20MB for smaller files and comability. There are probably other much smarter ways to tackle this and that's why I'm asking for advice here on SO.

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• Volunteer for a potential employer?

  - by EoRaptor013

  I've been looking for work since March, and haven't had much luck. Recently, however, I interviewed with a small company near my home for a C#, .NET, SQL development position. I hit it off very well with the hiring manager during the phone screen, and even more so during the face to face. Unfortunately, I failed the practical test: wiring up a web form, creating a couple of SQL stored procedures, saving new data with validation, and creating a minimal search screen. I knew what I was doing, but I was too slow to meet their standards as all the work needed to be done within an hour. Nevertheless, I really liked the place, the environment, the people who I would have been working with, and the boss. (I gave the company an 11 on Joel's 12 point scale.) So, the obvious next step was to scrape the rust off. I've been trying to create little projects for myself, but I don't know that I've been effective in getting any faster. What with all that goes into creating a project, I'm not heads-down coding as much as I think I need. Now, with all that introduction, here's the question. I have been thinking about calling the hiring manager at that place, and asking him to let me volunteer for three or four weeks, with no strings attached. I think it would benefit me, and wouldn't cost him anything (as long as I didn't slow the existing people down!). At the end of that period, he might, or might not, be inclined to hire me, but even if not, I would have had as much as 160 hours of in the trenches development. Maybe not all shiny, but no more rust, I would think. Does this plan make any sense at all? I certainly don't want to sound desperate (although, I'm not far from being there), and I very much need the tuneup, lube, and change the oil. What's the downside, if any, to me doing this? Do any of you see red flags going up—either from the prerspective of the hiring manager, or from the perspective of a developer?

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• realtime diagnostics

  - by Ion Todirel

  I have an application which has a loop, part of a "Scheduler", which runs at all time and is the heart of the application. Pretty much like a game loop, just that my application is a WPF application and it's not a game. Naturally the application does logging at many points, but the Scheduler does some sensitive monitoring, and sometimes it's impossible just from the logs to tell what may have gotten wrong (and by wrong I don't mean exceptions) or the current status. Because Scheduler's inner loop runs at short intervals, you can't do file I/O-based logging (or using the Event Viewer) in there. First, you need to watch it in real-time, and secondly the log file would grow in size very fast. So I was thinking of ways to show this data to the user in the realtime, some things I considered: Display the data in realtime in the UI Use AllocConsole/WriteConsole to display this information in a console Use a different console application which would display this information, communicate between the Scheduler and the console app using pipes or other IPC techniques Use Windows' Performance Monitor and somehow feed it with this information ETW Displaying in the UI would have its issues. First it doesn't integrate with the UI I had in mind for my application, and I don't want to complicate the UI just for this. This diagnostics would only happen rarely. Secondly, there is going to be some non-trivial data protection, as the Scheduler has it's own thread. A separate console window would work probably, but I'm still worried if it's not too much threshold. Allocating my own console, as this is a windows app, would probably be better than a different console application (3), as I don't need to worry about IPC communication, and non-blocking communication. However a user could close the console I allocated, and it would be problematic in that case. With a separate process you don't have to worry about it. Assuming there is an API for Performance Monitor, it wouldn't be integrated too well with my app or apparent to the users. Using ETW also doesn't solve anything, just a random idea, I still need to display this information somehow. What others think, would there be other ways I missed?

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• How to modularize a JSF/Facelets/Spring application with OSGi?

  - by lexicore

  I'm working with very large JSF/Facelets applications which use Spring for DI/bean management. My applications have modular structure and I'm currently looking for approaches to standardize the modularization. My goal is to compose a web application from a number of modules (possibly depending on each other). Each module may contain the following: Classes; Static resources (images, CSS, scripts); Facelet templates; Managed beans - Spring application contexts, with request, session and application-scoped beans (alternative is JSF managed beans); Servlet API stuff - servlets, filters, listeners (this is optional). What I'd like to avoid (almost at all costs) is the need to copy or extract module resources (like Facelets templates) to the WAR or to extend the web.xml for module's servlets, filters, etc. It must be enough to add the module (JAR, bundle, artifact, ...) to the web application (WEB-INF/lib, bundles, plugins, ...) to extend the web application with this module. Currently I solve this task with a custom modularization solution which is heavily based on using classpath resources: Special resources servlet serves static resources from classpath resources (JARs). Special Facelets resource resolver allows loading Facelet templates from classpath resources. Spring loads application contexts via the pattern classpath*:com/acme/foo/module/applicationContext.xml - this loads application contexts defined in module JARs. Finally, a pair of delegating servlets and filters delegate request processing to the servlets and filters configured in Spring application contexts from modules. Last days I read a lot about OSGi and I was considering, how (and if) I could use OSGi as a standardized modularization approach. I was thinking about how individual tasks could be solved with OSGi: Static resources - OSGi bundles which want to export static resources register a ResourceLoader instances with the bundle context. A central ResourceServlet uses these resource loaders to load resources from bundles. Facelet templates - similar to above, a central ResourceResolver uses services registered by bundles. Managed beans - I have no idea how to use an expression like #{myBean.property} if myBean is defined in one of the bundles. Servlet API stuff - use something like WebExtender/Pax Web to register servlets, filters and so on. My questions are: Am I inventing a bicycle here? Are there standard solutions for that? I've found a mentioning of Spring Slices but could not find much documentation about it. Do you think OSGi is the right technology for the described task? Is my sketch of OSGI application more or less correct? How should managed beans (especially request/session scope) be handled? I'd be generally graefult for your comments.

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• Git/Mercurial (hg) opinion

  - by Richard

  First, let me say I'm not a professional programmer, but an engineer who had a need for it and had to learn. I was always working alone, so it was just me and my seven splitted personalities ... and we worked okey as a team :) Most of my stuff is done in C/Fortran/Matlab and so far I've been learning git to manage it all. However, although I've had no unsolvable problems with it, I've never been "that" happy with it ... for everything I cannot do, I hae to look up a book. And, for some time now I've been hearning a lot of good stuff about hg. Now, a coleague of mine will have to work with me on a project (I almost feel sorry for him) and he's started learning hg (says he likes it more), and I'm considering the switch myself. We work almost exclusivly on Windows platform (although I manage relatively ok using unix tools and things that come from that part of the world). So, I was wondering, in a described scenario, what problems could I expect with the switch. I heard that hg is rather more user friendly towards windows users, regarding the user interfaces. How does it handle repositories ? Does it create them the same way as git does (just one subdirectory in a working directory) and can I just copy the whole project directory (including git repo) and just carry them somewhere with no extra thinking ? (I really liked that when I was choosing over git/svn). Are there any good books on it that you can recommend (something like Pro Git, only for Hg). What are good ways to implement hg into Visual Studio/GVim for Windows, or into Windows Explorer so I can work relatively easily (I would like to avoid using the command line for everything regarding it, like in git shell). Is there something else I should be aware of (please, on this don't point me to other questions ... they just give me a ton of info, and I'm not sure what is it that I should take as important, and what to disregard). I'm trying to cut some time, since I cannot spend all that time relearning hg, like I did for git. I've also heard git is c project, while mercurial is python ... is there any noticeable difference in speed. git was pretty speedy ... will I encounter some waiting while working. Notice: All my projects are of let's say, middle size ... mostly numerical simulations ... 10-15000 lines (medium size?)

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• Is this a situation where Qt Model/View architecture is not useful?

  - by csmithmaui

  Hi, I am writing a GUI based application where I read a string of values from serial port every few seconds and I need to display most of the values in some type graphical indicator(I was thinking of QprogressBar maybe) that displays the range and the value. Some of the other data that I am parsing from the string are the date and fault codes. Also, the data is hierarchical. I wanted to use the model/view architecture of Qt because I have been interested in MVC stuff for a while but have never quite wrapped my brain around how to implement it very well. As of now, I have subclassed QAbstractItemModel and in the model I read the serial port and wrap the items parsed from the string in a Tree data structure. I can view all of the data in a QtreeView with no issues. I have also began to subclass QAbstractItemView to build my custom view with all of the Graphical Indicators and such. This is where I am getting stuck. It seems to me that in order for me to design a view that knows how to display my custom model the view needs to know exactly how all of the data in the model is organized. Doesn't that defeat the purpose of Model/View? The QTreeView I tested the model with is basically just displaying the model as it is setup in the Tree structure but I don't want to do that because the data is not all of the same type. Is the type of data or the way you would like to present it to the user a determining factor in whether or not you should use this architecture? I always assumed it was just always better to design in an MVC style. It seems to me like it might have been better to just subclass QWidget and then read in from the serial port and update all of subwidgets(graphical indicators, labels, etc...) from the subclass. Essentially, do everything in one class. Does anybody understand this issue that can explain to me either what I am missing or why I shouldn't be doing it this way. As of now I am a little confused. Thanks so much for any help!

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• Delay keyboard input help

  - by Stradigos

  I'm so close! I'm using the XNA Game State Management example found here and trying to modify how it handles input so I can delay the key/create an input buffer. In GameplayScreen.cs I've declared a double called elapsedTime and set it equal to 0. In the HandleInput method I've changed the Key.Right button press to: if (keyboardState.IsKeyDown(Keys.Left)) movement.X -= 50; if (keyboardState.IsKeyDown(Keys.Right)) { elapsedTime -= gameTime.ElapsedGameTime.TotalMilliseconds; if (elapsedTime <= 0) { movement.X += 50; elapsedTime = 10; } } else { elapsedTime = 0; } The pseudo code: If the right arrow key is not pressed set elapsedTime to 0. If it is pressed, the elapsedTime equals itself minus the milliseconds since the last frame. If the difference then equals 0 or less, move the object 50, and then set the elapsedTime to 10 (the delay). If the key is being held down elapsedTime should never be set to 0 via the else. Instead, after elapsedTime is set to 10 after a successful check, the elapsedTime should get lower and lower because it's being subtracted by the TotalMilliseconds. When that reaches 0, it successfully passes the check again and moves the object once more. The problem is, it moves the object once per press but doesn't work if you hold it down. Can anyone offer any sort of tip/example/bit of knowledge towards this? Thanks in advance, it's been driving me nuts. In theory I thought this would for sure work. CLARIFICATION Think of a grid when your thinking about how I want the block to move. Instead of just fluidly moving across the screen, it's moving by it's width (sorta jumping) to the next position. If I hold down the key, it races across the screen. I want to slow this whole process down so that holding the key creates an X millisecond delay between it 'jumping'/moving by it's width. EDIT: Turns out gameTime.ElapsedGameTime.TotalMilliseconds is returning 0... all of the time. I have no idea why.

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• Computation on db data then list them using either SimpleCursorAdapter or ArrayAdapter

  - by kc2uno

  Hi all, I juststarted programming in android a few weeks ago, so I am not entirely sure how to deal with listing values. Please help me out! I have some questions regarding displaying data sets from db in a list. Currently I have a cursor returned by my db points to a list of rows and I want display 2 columns values in a single row of the list. The row xml looks like this: <TextView android:id="@+id/text1" android:textSize="16sp" android:textStyle="bold" android:layout_width="fill_parent" android:layout_height="wrap_content"/> <TextView android:id="@+id/text2" android:textSize="14sp" android:layout_width="fill_parent" android:layout_height="wrap_content"/> so I was thinking using simplecursoradapter which supposedly makes my life easier by displaying the data in a list. However that is only true if I want to display the raw data. For the purpose of my program I need to do some computations on the raw data sets, then display them. I am not sure how to do that using SimpleCursorAdapter. Here's how I display the raw data: String[] from = new String[]{BtDbAdapter.KEY_EX_TYPE,BtDbAdapter.KEY_EX_TIMESTAMP}; int[] to = new int[]{R.id.text1, R.id.text2}; // Now create a simple cursor adapter and set it to display SimpleCursorAdapter records = new SimpleCursorAdapter(this, R.layout.exset_row, mExsetCursor, from, to); setListAdapter(records); Is there a way to do computation on the data in those rows before I bind it with the SimpleCursorAdapter? I was trying to use an alternative way of doing this by using arraylist and arrayadapter, but that way I dont know to how achieve displaying 2 items in a single row. This is my code for using arrayadapter which only display 1 text in a row instead of 2 textviews in a row: //fill in the array timestamp_arr = new ArrayList<String>(); type_arr = new ArrayList<String>(); fillRecord(); Log.d(TAG,"setting now in recordlist"); setListAdapter(new ArrayAdapter<String>(this, R.layout.list_item,timestamp_arr)); setListAdapter(new ArrayAdapter<String>(this, R.layout.list_item2,type_arr)); It's very obvious that it only displays one textview in a row because I set the second arrayadapter overwrites the first one! I was trying to use R.id.text1 and R.id.text2 for them, but it gave me some errors saying 04-23 01:40:58.658: ERROR/AndroidRuntime(3309): android.content.res.Resources$NotFoundException: Resource ID #0x7f070008 type #0x12 is not valid I believe the second method can achieve this, but I'm not sure how do deal with the layout problems, so if you any suggestions, please post them out. Thank you!!

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• IE and Content-disposition inline vs. extension-token

  - by pinkgothic

  Preamble So IE does Mime-Type sniffing. That part's old news. Suggestions of how to combat it tend to be along the lines of 'supply a content-type IE trusts' (i.e. anything that isn't text/plain or application/octet-stream) or 'add extraneous data at the start of the file that is definitely of the type you're serving'. Now, I'm working on an application that has to allow message attachments (like in e-mails), and we want to close up XSS vectors. IE's mime sniffing is one of those vectors - a text/plain file with html content will trigger as html. Recoding isn't an option at this point, changing the attachments the user has provided can only happen if there is absolutely no doubt about the maliciousness of the file - and someone might want to send HTML as text. Now, Microsoft's MSDN article implies the situation might be easier to fix than advertised: If Internet Explorer knows the Content-Type specified and there is no Content-Disposition data, Internet Explorer performs a "MIME sniff," [...] Great! Except I don't have IE nor current means to reliably install it (I realise this is a fairly sad state for a webdeveloper to be in, I hope to fix this soon) and this is grey theory that I can't quite seem to get confirmed one way or the other. Local sources say that line is hogwash - IE will mime sniff anything that is Content-Disposition: inline / <default> and not specific enough for its tastes in -Type. But what about x-* ('extension-token' in the RFC)? Trying to google for how browsers handle Content-Disposition: <extension-token> hasn't yielded anything (though I may just be doing it wrong, my understanding of Google is seriously slipping lately). I found one question that looked promising, but turned out to be a misunderstanding on side of the thread author, meaning that the train of thought was never actually addressed there. Question(s) Does IE really Mime sniff if you expressly pass Content-Disposition: inline? If so: Does anyone here know how browsers handle Content-Disposition: <extension-token>? If they do this in a way that is for my purposes benign, by presuming it to be synonymous with the default (effectively 'inline', though I hear it's not defined anywhere?), is it specific enough for IE not to Mime sniff? Or am I actually shooting myself in the foot by thinking of pursuing this avenue?

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• PHP-based LaTeX parser -- where to begin?

  - by Alex Basson

  The project: I want to build a LaTeX-to-MathML translator in PHP. Why? Because I'm a mathematician, and I want to publish math on my Drupal site. It doesn't have to translate all of LaTeX, since the basic document-level stuff is ably handled by the CMS and wouldn't be written in LaTeX to begin with; it just has to translate math written in LaTeX into math written in MathML. Although I feel as though I've done my due diligence, this doesn't seem to exist already. Maybe I'm wrong---if you know of something that would serve this purpose, by all means let me know, and thank you in advance. But assuming it doesn't exist, I guess I have to go write it myself. Here's the thing, though: I've never done anything this ambitious. I don't really know where to begin. I've used PHP for years, but just to do the standard "build a CMS with PHP and MySQL"-type of stuff. I've never attempted anything as seemingly sophisticated as translation from one language to another. I'm just dumb enough to consider doing it with regex---after all, LaTeX is a much more formal language, and it doesn't allow for nearly the kinds of pathological edge-cases, as say, HTML. But on the other hand, I'm just smart enough to realize this is probably a terrible idea: now I have two problems, and I sure don't want to end up like this guy. So if that's not the way to go (right?), what is? How should I start thinking about this problem? Am I essentially writing a LaTeX compiler in PHP, and if so, what do I need to know to do that (like, should I just go read the Purple Dragon book first?)? I'm both really excited and pretty intimidated by the prospect of this project, but hey, this is how we all learn to be programmers, right? If something we need doesn't exist, we go and build it, necessity is the mother of... you get the point. Tremendous thanks to everyone in advance for any and all guidance you can offer.

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• Making a Grid in an NSView

  - by Hooligancat

  I currently have an NSView that draws a grid pattern (essentially a guide of horizontal and vertical lines) with the idea being that a user can change the spacing of the grid and the color of the grid. The purpose of the grid is to act as a guideline for the user when lining up objects. Everything works just fine with one exception. When I resize the NSWindow by dragging the resize handle, if my grid spacing is particularly small (say 10 pixels). the drag resize becomes lethargic in nature. My drawRect code for the grid is as follows: -(void)drawRect:(NSRect)dirtyRect { NSRect thisViewSize = [self bounds]; // Set the line color [[NSColor colorWithDeviceRed:0 green:(255/255.0) blue:(255/255.0) alpha:1] set]; // Draw the vertical lines first NSBezierPath * verticalLinePath = [NSBezierPath bezierPath]; int gridWidth = thisViewSize.size.width; int gridHeight = thisViewSize.size.height; int i; while (i < gridWidth) { i = i + [self currentSpacing]; NSPoint startPoint = {i,0}; NSPoint endPoint = {i, gridHeight}; [verticalLinePath setLineWidth:1]; [verticalLinePath moveToPoint:startPoint]; [verticalLinePath lineToPoint:endPoint]; [verticalLinePath stroke]; } // Draw the horizontal lines NSBezierPath * horizontalLinePath = [NSBezierPath bezierPath]; i = 0; while (i < gridHeight) { i = i + [self currentSpacing]; NSPoint startPoint = {0,i}; NSPoint endPoint = {gridWidth, i}; [horizontalLinePath setLineWidth:1]; [horizontalLinePath moveToPoint:startPoint]; [horizontalLinePath lineToPoint:endPoint]; [horizontalLinePath stroke]; } } I suspect this is entirely to do with the way that I am drawing the grid and am open to suggestions on how I might better go about it. I can see where the inefficiency is coming in, drag-resizing the NSWindow is constantly calling the drawRect in this view as it resizes, and the closer the grid, the more calculations per pixel drag of the parent window. I was thinking of hiding the view on the resize of the window, but it doesn't feel as dynamic. I want the user experience to be very smooth without any perceived delay or flickering. Does anyone have any ideas on a better or more efficient method to drawing the grid? All help, as always, very much appreciated.

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• Learning to create beautiful /next-generation GUI

  - by ShaChris23

  I really want to create a stunning-looking GUI desktop application that looks like, for example: Mac OS X interface Picasa desktop client on windows IPhone apps Office 2007 I've mostly been programming GUI using Qt/Swing/WinForm and I'm tired of creating so plain looking GUI, lol. So I was thinking about diving into stuff like: jQuery WPF/C# iPhone SDK Silverlight Adobe Air/Flex Just to get some ideas on how to create really cool looking UI. Does that sound like a good list? Any developers here that could share what platform they use to create very cool looking desktop app? On a sidenote, I really wonder what developers at Apple / Microsoft use to develop their own cool-looking software. EDIT A lot of responses talk about the importance of usability over "cool-looking".. I totally agree that usability and simplicity are the most important aspects of user interface design. I've been doing GUI development for a while now ( 3 years), so that I understand. But using cool-looking UI also improves user experience + it could make big difference on whether or not your software sells. I mean, otherwise why would Microsoft/Apple try to make their OS UI look "cooler" everytime there's a new version? Why would websites like pragprog.com, or versionsapp.com. make their websites look like that? Basically you kill 2 birds with one stone: stunnning-looking UI + super usability (because it looks simple and intuitive). That is what I'm striving for. And as far as I know, I cannot achieve that using Qt/Winform. Most of the books I have read just show you how to make average-looking (read: 1990's) UI. I want to learn how to create cool-looking UI. And the only place I see cool-looking UIs these days are the technology I list above. I'm not enamored with any technology; but I just want to know how things are done in other technology to see if I could apply them to the technology I'm using, or see if I could use those technology in my line of work. An example: if I were to pick between this UI and this UI, I probably would pick the latter, if just based on looks alone. Functionally, they are just the same UI; they both allow you to keep track of your time. They both contain buttons and textboxes, etc. But the fact that they look different, also differentiate them in terms of attractiveness. So in all, I think the "ice on the cake" is very important. I would say it's the thing you strive for after you are certain you have a totally intuitive, usable UI.

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• Binary Search Help

  - by aloh

  Hi, for a project I need to implement a binary search. This binary search allows duplicates. I have to get all the index values that match my target. I've thought about doing it this way if a duplicate is found to be in the middle: Target = G Say there is this following sorted array: B, D, E, F, G, G, G, G, G, G, Q, R S, S, Z I get the mid which is 7. Since there are target matches on both sides, and I need all the target matches, I thought a good way to get all would be to check mid + 1 if it is the same value. If it is, keep moving mid to the right until it isn't. So, it would turn out like this: B, D, E, F, G, G, G, G, G, G (MID), Q, R S, S, Z Then I would count from 0 to mid to count up the target matches and store their indexes into an array and return it. That was how I was thinking of doing it if the mid was a match and the duplicate happened to be in the mid the first time and on both sides of the array. Now, what if it isn't a match the first time? For example: B, D, E, F, G, G, J, K, L, O, Q, R, S, S, Z Then as normal, it would grab the mid, then call binary search from first to mid-1. B, D, E, F, G, G, J Since G is greater than F, call binary search from mid+1 to last. G, G, J. The mid is a match. Since it is a match, search from mid+1 to last through a for loop and count up the number of matches and store the match indexes into an array and return. Is this a good way for the binary search to grab all duplicates? Please let me know if you see problems in my algorithm and hints/suggestions if any. The only problem I see is that if all the matches were my target, I would basically be searching the whole array but then again, if that were the case I still would need to get all the duplicates. Thank you BTW, my instructor said we cannot use Vectors, Hash or anything else. He wants us to stay on the array level and get used to using them and manipulating them.

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• How effective are technical test(s) and is it necessary?

  - by The Elite Gentleman

  Hi everyone, I recently took a Java technical test (for a company who wanted are looking for senior java developers) and, funny enough, I only realised the technical terms of what I've been doing all along after I've written the test. I'm not too IT jargon when it comes to development but I can pretty much code and create solutions unaware that I'm using design pattern (or the specifics of that design pattern) or technology. I learned things such as JMS, Frameworks, etc. while programming at home and having to google stuff online to problems I have. Others e.g. IoC, Surrogates in Databases, etc., I have used extensively without knowing that it had a name for it. Do you think that these technical test are effective and why? What interesting questions did you find that boggled your brains out while the clock kept ticking? Seeing that IT is vastly evolving at a rapid rate, do we have to constantly be updated with new terms that comes out? Some questions I was asked : What object oriented principle is violated by this architectural mechanism for dot notation? Is indexing tables effective for range query or point query search? What is ThreadLocal and what is it used for? Method overloading vs Method overriding. What is the difference between the 2? What is dynamic binding? Now, imagine my poor head trying to understand these jargons (considering I use it almost everyday) PS The question was not a programming question, where you have a problem and write code to solve it. Rather, a thinking type question and you write answers (against the clock). Update I clearly didn't come out clearly as I should have. There are those that are technically "book smart" but with very little hands-on experience and vice versa. So, the question (in connection to what I've asked) is that are these technical test seeking "book smart" people or people with lots of hands-on experience (some who are not that well clued up with too much book-smart jargons). How effective is it then, for companies to look for developers if most of the questions are too terminology-centric? (if that's the correct term, :))

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• How is IObservable<double>.Average supposed to work?

  - by Dan Tao

  Update Looks like Jon Skeet was right (big surprise!) and the issue was with my assumption about the Average extension providing a continuous average (it doesn't). For the behavior I'm after, I wrote a simple ContinuousAverage extension method, the implementation of which I am including here for the benefit of others who may want something similar: public static class ObservableExtensions { private class ContinuousAverager { private double _mean; private long _count; public ContinuousAverager() { _mean = 0.0; _count = 0L; } // undecided whether this method needs to be made thread-safe or not // seems that ought to be the responsibility of the IObservable (?) public double Add(double value) { double delta = value - _mean; _mean += (delta / (double)(++_count)); return _mean; } } public static IObservable<double> ContinousAverage(this IObservable<double> source) { var averager = new ContinuousAverager(); return source.Select(x => averager.Add(x)); } } I'm thinking of going ahead and doing something like the above for the other obvious candidates as well -- so, ContinuousCount, ContinuousSum, ContinuousMin, ContinuousMax ... perhaps ContinuousVariance and ContinuousStandardDeviation as well? Any thoughts on that? Original Question I use Rx Extensions a little bit here and there, and feel I've got the basic ideas down. Now here's something odd: I was under the impression that if I wrote this: var ticks = Observable.FromEvent<QuoteEventArgs>(MarketDataProvider, "MarketTick"); var bids = ticks .Where(e => e.EventArgs.Quote.HasBid) .Select(e => e.EventArgs.Quote.Bid); var bidsSubscription = bids.Subscribe( b => Console.WriteLine("Bid: {0}", b) ); var avgOfBids = bids.Average(); var avgOfBidsSubscription = avgOfBids.Subscribe( b => Console.WriteLine("Avg Bid: {0}", b) ); I would get two IObservable<double> objects (bids and avgOfBids); one would basically be a stream of all the market bids from my MarketDataProvider, the other would be a stream of the average of these bids. So something like this: Bid Avg Bid 1 1 2 1.5 1 1.33 2 1.5 It seems that my avgOfBids object isn't doing anything. What am I missing? I think I've probably misunderstood what Average is actually supposed to do. (This also seems to be the case for all of the aggregate-like extension methods on IObservable<T> -- e.g., Max, Count, etc.)

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• Reading Source Code Aloud

  - by Jon Purdy

  After seeing this question, I got to thinking about the various challenges that blind programmers face, and how some of them are applicable even to sighted programmers. Particularly, the problem of reading source code aloud gives me pause. I have been programming for most of my life, and I frequently tutor fellow students in programming, most often in C++ or Java. It is uniquely aggravating to try to verbally convey the essential syntax of a C++ expression. The speaker must give either an idiomatic translation into English, or a full specification of the code in verbal longhand, using explicit yet slow terms such as "opening parenthesis", "bitwise and", et cetera. Neither of these solutions is optimal. On the one hand, an idiomatic translation is only useful to a programmer who can de-translate back into the relevant programming code—which is not usually the case when tutoring a student. In turn, education (or simply getting someone up to speed on a project) is the most common situation in which source is read aloud, and there is a very small margin for error. On the other hand, a literal specification is aggravatingly slow. It takes far far longer to say "pound, include, left angle bracket, iostream, right angle bracket, newline" than it does to simply type #include <iostream>. Indeed, most experienced C++ programmers would read this merely as "include iostream", but again, inexperienced programmers abound and literal specifications are sometimes necessary. So I've had an idea for a potential solution to this problem. In C++, there is a finite set of keywords—63—and operators—54, discounting named operators and treating compound assignment operators and prefix versus postfix auto-increment and decrement as distinct. There are just a few types of literal, a similar number of grouping symbols, and the semicolon. Unless I'm utterly mistaken, that's about it. So would it not then be feasible to simply ascribe a concise, unique pronunciation to each of these distinct concepts (including one for whitespace, where it is required) and go from there? Programming languages are far more regular than natural languages, so the pronunciation could be standardised. Speakers of any language would be able to verbally convey C++ code, and due to the regularity and fixity of the language, speech-to-text software could be optimised to accept C++ speech with a high degree of accuracy. So my question is twofold: first, is my solution feasible; and second, does anyone else have other potential solutions? I intend to take suggestions from here and use them to produce a formal paper with an example implementation of my solution.

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• Castle ActiveRecord - schema generation without enforcing referential integrity?

  - by Simon

  Hi all, I've just started playing with Castle active record as it seems like a gentle way into NHibernate. I really like the idea of the database schema being generate from my classes during development. I want to do something similar to the following: [ActiveRecord] public class Camera : ActiveRecordBase<Camera> { [PrimaryKey] public int CameraId {get; set;} [Property] public int CamKitId {get; set;} [Property] public string serialNo {get; set;} } [ActiveRecord] public class Tripod : ActiveRecordBase<Tripod> { [PrimaryKey] public int TripodId {get; set;} [Property] public int CamKitId {get; set;} [Property] public string serialNo {get; set;} } [ActiveRecord] public class CameraKit : ActiveRecordBase<CameraKit> { [PrimaryKey] public int CamKitId {get; set;} [Property] public string description {get; set;} [HasMany(Inverse=true, Table="Cameras", ColumnKey="CamKitId")] public IList<Camera> Cameras {get; set;} [HasMany(Inverse=true, Table="Tripods", ColumnKey="CamKitId")] public IList<Camera> Tripods {get; set;} } A camerakit should contain any number of tripods and cameras. Camera kits exist independently of cameras and tripods, but are sometimes related. The problem is, if I use createschema, this will put foreign key constraints on the Camera and Tripod tables. I don't want this, I want to be able to to set CamKitId to null on the tripod and camera tables to indicate that it is not part of a CameraKit. Is there a way to tell activerecord/nhibernate to still see it as related, without enforcing the integrity? I was thinking I could have a cameraKit record in there to indicate "no camera kit", but it seems like oeverkill. Or is my schema wrong? Am I doing something I shouldn't with an ORM? (I've not really used ORMs much) Thanks!

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• How do I redirect a page in php

  - by user225269

  I'm having difficulties in the making the logout code for php to work. When I click on the logout button, it will go back to the home page, but when I click on the back button in the browser. I can still access the previous page, wherein the user must be logged on to access it. So I'm thinking of redirecting to the login page when the user clicks on the back button on the browser. This is my code, in the home page(where in no user is logged in yet. This page is being called by a logout link on the user page. <? session_start(); session_destroy(); ?> <table width="300" border="0" align="center" cellpadding="0" cellspacing="1" bgcolor="#CCCCCC"> <tr> <form name="form1" method="post" action="checklogin.php"> <td> <table width="100%" border="0" cellpadding="3" cellspacing="1" bgcolor="#FFFFFF"> <tr> <td colspan="3"><strong>Member Login </strong></td> </tr> <tr> <td width="78">Username</td> <td width="6">:</td> <td width="294"><input name="myusername" type="text" id="myusername"></td> </tr> <tr> <td>Password</td> <td>:</td> <td><input name="mypassword" type="text" id="mypassword"></td> </tr> <tr> <td>&nbsp;</td> <td>&nbsp;</td> <td><input type="submit" name="Submit" value="Login"></td> </tr> </table> </td> </form> </tr> </table>

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• Best Practice: Legitimate Cross-Site Scripting

  - by Ryan

  While cross-site scripting is generally regarded as negative, I've run into several situations where it's necessary. I was recently working within the confines of a very limiting content management system. I needed to include database code within the page, but the hosting server didn't have anything usable available. I set up a couple barebones scripts on my own server, originally thinking that I could use AJAX to import the contents of my scripts directly into the template of the CMS (thus retaining dynamic images, menu items, CSS, etc.). I was wrong. Due to the limitations of XMLHttpRequest objects, it's not possible to grab content from a different domain. So I thought "iFrame" - even though I'm not a fan of frames, I thought that I could create a frame that matched the width and height of the content, so that it would appear native. Again, I was blocked by cross-site scripting "protections." While I could indeed load a remote file into the iFrame, I couldn't execute JavaScript to modify its size on either the host page or inside the loaded page. In this particular scenario, I wasn't able to point a subdomain to my server. I also couldn't create a script on the CMS server that could proxy content from my server, so my last thought was to use a remote JavaScript. A remote JavaScript works. It breaks when the user has JavaScript disabled, which is a downside; but it works. The "problem" I was having with using a remote JavaScript was that I had to use the JS function document.write() to output any content. Any output that isn't JS causes script errors. In addition to using document.write() for every line, you also have to ensure that the content is escaped - or else you end up with more script errors. My solution was as follows: My script received a GET parameter ("page") and then looked for the file ({$page}.php), and read the contents into a variable. However, I had to use awkward buffering techniques in order to actually execute the included scripts (for things like database interaction) then strip the final content of all line break characters ("\n") followed by escaping all required characters. The end result is that my original script (which outputs JavaScript) accesses seemingly "standard" scripts on my server and converts their standard output to JavaScript for displaying within the CMS template. While this solution works, it seems like there may be a better way to accomplish the same thing. What is the best way to make cross-site scripting work specifically for the purpose of including content from a completely different domain?

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• Using VCL for the web (intraweb) as a trick for adding web interface to a legacy non-tiered (2 tiers

  - by user193655

  My team is maintaining a huge Client Server win32 Delphi application. It is a client/server application (Thick client) that uses DevArt (SDAC) components to connect to SQL Server. The business logic is often "trapped" in Component's event handlers, anyway with some degree of refactoring it is doable to move the business logic in common units (a big part of this work has already been done during refactoring... Maintaing legacy applications someone else wrote is very frustrating, but this is a very common job). Now there is the request of a web interface, I have several options of course, in this question i want to focus on the VCL for the web (intraweb) option. The idea is to use the common code (the same pas files) for both the client/server application and the web application. I heard of many people that moved legacy apps from delphi to intraweb, but here I am trying to keep the Thick client too. The idea is to use common code, may be with some compiler directives to write specific code: {$IFDEF CLIENTSERVER} {here goes the thick client specific code} {$ELSE} {here goes the Intraweb specific code} {$ENDIF} Then another problem is the "migration plan", let's say I have 300 features and on the first release I will have only 50 of them available in the web application. How to keep track of it? I was thinking of (ab)using Delphi interfaces to handle this. For example for the User Authentication I could move all the related code in a procedure and declare an interface like: type IUserAuthentication= interface['{0D57624C-CDDE-458B-A36C-436AE465B477}'] procedure UserAuthentication; end; In this way as I implement the IUserAuthentication interface in both the applications (Thick Client and Intraweb) I know that That feature has been "ported" to the web. Anyway I don't know if this approach makes sense. I made a prototype to simulate the whole process. It works for a "Hello world" application, but I wonder if it makes sense on a large application or this Interface idea is only counter-productive and can backfire. My question is: does this approach make sense? (the Interface idea is just an extra idea, it is not so important as the common code part described above) Is it a viable option? I understand it depends a lot of the kind of application, anyway to be generic my one is in the CRM/Accounting domain, and the number of concurrent users on a single installation is typically less than 20 with peaks of 50. EXTRA COMMENT (UPDATE): I ask this question because since I don't have a n-tier application I see Intraweb as the unique option for having a web application that has common code with the thick client. Developing webservices from the Delphi code makes no sense in my specific case, so the alternative I have is to write the web interface using ASP.NET (duplicating the business logic), but in this case I cannot take advantage of the common code in an easy way. Yes I could use dlls maybe, but my code is not suitable for that.

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• All embedded databases fail to open connections

  - by rsteckly

  Hi, I'm working on a winforms desktop application that needs to store data. I made the really bad decision to try and embed a database. I've tried: SQLite VistaDB SQL Server Compact In each case, I was able to generate a Entity Framework Model over the basic schema I've created. I have an event that adds data that I've been using to test these databases. Well, I kept adding a new record using EF and finding it didn't actually insert a record. In debugging, I checked the context object to see what was happening. It turns out that it is saying "the underlying provider failed to open," or something to that effect. It was not throwing an exception, just not inserting a record. The same thing has happened for all 3 embedded databases--prompting me to get it through my dense head that there has to be something wrong with my configuration. Well, I tried to write some basic sql using a sqlconnection and sqlcommand. This time it throws an exception. In the SQL Server Compact case, it now says: A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: SQL Network Interfaces, error: 26 - Error Locating Server/Instance Specified) I thought perhaps a problem was the path in app.Config. So I changed the connection string to: Note that I simplified the path away from anything that might have spaces and avoided using the Data Directory nonsense that causes problem when the debugging directory does not match the preconfigured value for the data directory. I'm running Windows 7; I thought perhaps it might be an access issue--so I tried running VS 2010 in Administrator mode. No luck. I also installed Sql Server Compact SP2, thinking this might be a bug. No luck. Anyway, I'm ready to pull my hair out. I'm on a tight deadline for this thing and didn't expect to spend the day trying to figure out what is going on.

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• Searches (and general querying) with HBase and/or Cassandra (best practices?)

  - by alexeypro

  I have User model object with quite few fields (properties, if you wish) in it. Say "firstname", "lastname", "city" and "year-of-birth". Each user also gets "unique id". I want to be able to search by them. How do I do that properly? How to do that at all? My understanding (will work for pretty much any key-value storage -- first goes key, then value) u:123456789 = serialized_json_object ("u" as a simple prefix for user's keys, 123456789 is "unique id"). Now, thinking that I want to be able to search by firstname and lastname, I can save in: f:Steve = u:384734807,u:2398248764,u:23276263 f:Alex = u:12324355,u:121324334 so key is "f" - which is prefix for firstnames, and "Steve" is actual firstname. For "u:Steve" we save as value all user id's who are "Steve's". That makes every search very-very easy. Querying by few fields (properties) -- say by firstname (i.e. "Steve") and lastname (i.e. "l:Anything") is still easy - first get list of user ids from "f:Steve", then list from "l:Anything", find crossing user ids, an here you go. Problems (and there are quite a few): Saving, updating, deleting user is a pain. It has to be atomic and consistent operation. Also, if we have size of value limited to some value - then we are in (potential) trouble. And really not of an answer here. Only zipping the list of user ids? Not too cool, though. What id we want to add new field to search by. Eventually. Say by "city". We certainly can do the same way "c:Los Angeles" = ..., "c:Chicago" = ..., but if we didn't foresee all those "search choices" from the very beginning, then we will have to be able to create some night job or something to go by all existing User records and update those "c:CITY" for them... Quite a big job! Problems with locking. User "u:123" updates his name "Alex", and user "u:456" updates his name "Alex". They both have to update "f:Alex" with their id's. That means either we get into overwriting problem, or one update will wait for another (and imaging if there are many of them?!). What's the best way of doing that? Keeping in mind that I want to search by many fields? P.S. Please, the question is about HBase/Cassandra/NoSQL/Key-Value storages. Please please - no advices to use MySQL and "read about" SELECTs; and worry about scaling problems "later". There is a reason why I asked MY question exactly the way I did. :-)

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• The iPhone “phone” doesn’t have the provisioning profile with which the application was signed.

  - by eda

  i have tried everything to fix this provision problem and nothing is working. ive reformated my mac, reinstalled the iphone, ive also dragged the provisions (developer and distribution) onto the organizer, itunes, and xcode. in itunes people say to drag the provisions to the iphone icon but that doesnt work its only able to go under library it shows a blue rectangle for me to drop it there. i just have a newly created dummy app with a 57x57 icon. ive also setup the project with the distribution thing with its distribution provision. when i build i get this: The iPhone “myphone” doesn’t have the provisioning profile with which the application was signed. Click “Install and Run” to install the provisioning profile “distribution” on “myphone” and continue running “helloworld.app”. and it has a button "install and run" ive clicked on that hundreths of times and nothing. in orgranizer i see a tab called console ive cleared it and rebuild the app and there is some output that i dont understand. I'm thinking its my problem whats it mean? Fri Mar 26 11:22:19 unknown misagent[215] <Error>: profile not valid: 0xe8008012 Fri Mar 26 11:22:19 unknown mobile_installationd[206] <Error>: 00808600 install_embedded_profile: Skipping the installation of the embedded profile Fri Mar 26 11:22:20 unknown mobile_installationd[206] <Error>: 00808600 verify_executable: Could not validate signature: e8008015 Fri Mar 26 11:22:20 unknown mobile_installationd[206] <Error>: 00808600 preflight_application_install: Could not verify /var/tmp/install_staging.NEb61T/helloworld.app/helloworld Fri Mar 26 11:22:20 unknown mobile_installationd[206] <Error>: 00808600 install_application: Could not preflight application install Fri Mar 26 11:22:20 unknown mobile_installation_proxy[219] <Error>: handle_install: Installation failed Fri Mar 26 11:22:20 unknown mobile_installationd[206] <Error>: 00808600 handle_install: API failed Fri Mar 26 11:22:20 unknown mobile_installationd[206] <Error>: 00808600 send_message: failed to send mach message of 64 bytes: 10000003 Fri Mar 26 11:22:20 unknown mobile_installationd[206] <Error>: 00808600 send_error: Could not send error response to client Fri Mar 26 11:22:42 unknown misagent[231] <Error>: profile not valid: 0xe8008012 Fri Mar 26 11:22:43 unknown mobile_installationd[206] <Error>: 00809800 install_embedded_profile: Skipping the installation of the embedded profile Fri Mar 26 11:22:43 unknown mobile_installationd[206] <Error>: 00809800 verify_executable: Could not validate signature: e8008015 Fri Mar 26 11:22:43 unknown mobile_installationd[206] <Error>: 00809800 preflight_application_install: Could not verify /var/tmp/install_staging.6M55Ay/helloworld.app/helloworld Fri Mar 26 11:22:43 unknown mobile_installationd[206] <Error>: 00809800 install_application: Could not preflight application install Fri Mar 26 11:22:43 unknown mobile_installation_proxy[235] <Error>: handle_install: Installation failed Fri Mar 26 11:22:43 unknown mobile_installationd[206] <Error>: 00809800 handle_install: API failed Fri Mar 26 11:22:43 unknown mobile_installationd[206] <Error>: 00809800 send_message: failed to send mach message of 64 bytes: 10000003 Fri Mar 26 11:22:43 unknown mobile_installationd[206] <Error>: 00809800 send_error: Could not send error response to client

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• Read email from incoming mail server(POP)

  - by nccsbim071

  Hi, I have used an open source code from codeproject to read email from incoming mail server(POP Server). The code can be found at following location: http://www.codeproject.com/KB/IP/Pop3MimeClient.aspx So far it works fine i can read emails. My objective of using this code was to retrieve emails from POP server and process them. My problem is: If i use gmails pop server "pop.gmail.com" and run the appplication. I get only those emails that i have not retrieved since the last time i run the application. but if i use my clients pop server everytime i run the application i get all the emails in the pop server. for example: If i use gmail pop server: pop.gmail.com I have three emails in the pop server. I haven't run the application. I am running the application for the first time. Application reads the email, this time i will get 3 all the three email. I run the application second time, my application will not read any emails this time because i have already read the 3 existing one. This is fine, this is what i want. Now i send email to pop.gmail.com. I run the application again for the third time, this time i will only get the email that has just arrived that is the fourth one. This is good behaviour, this is what i want. But if i use my clients pop server: No matter how many times i run the application, it reads all the emails in the mail box. This will create problem for me, because i am thinking of building a window service that will read emails from pop server and process them. This service will run continuously. I will process emails in the pop serve then sleep for let's say 1 minute and the process the emails again. If the application downloaded from codeproject reads all the emails all the time, my clients mailbox can have like thousands for email in this mail box, so this would not be feasible for me. Is there some settings that is to be made at my client's pop server that will allow my application to retrieve only those emails that i have not read since last time i run the service or any help Please help, thanks,

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• Stack and queue operations on the same array.

  - by Passonate Learner

  Hi. I've been thinking about a program logic, but I cannot draw a conclusion to my problem. Here, I've implemented stack and queue operations to a fixed array. int A[1000]; int size=1000; int top; int front; int rear; bool StackIsEmpty() { return (top==0); } bool StackPush( int x ) { if ( top >= size ) return false; A[top++] = x; return true; } int StackTop( ) { return A[top-1]; } bool StackPop() { if ( top <= 0 ) return false; A[--top] = 0; return true; } bool QueueIsEmpty() { return (front==rear); } bool QueuePush( int x ) { if ( rear >= size ) return false; A[rear++] = x; return true; } int QueueFront( ) { return A[front]; } bool QueuePop() { if ( front >= rear ) return false; A[front++] = 0; return true; } It is presumed(or obvious) that the bottom of the stack and the front of the queue is pointing at the same location, and vice versa(top of the stack points the same location as rear of the queue). For example, integer 1 and 2 is inside an array in order of writing. And if I call StackPop(), the integer 2 will be popped out, and if I call QueuePop(), the integer 1 will be popped out. My problem is that I don't know what happens if I do both stack and queue operations on the same array. The example above is easy to work out, because there are only two values involved. But what if there are more than 2 values involved? For example, if I call StackPush(1); QueuePush(2); QueuePush(4); StackPop(); StackPush(5); QueuePop(); what values will be returned in the order of bottom(front) from the final array? I know that if I code a program, I would receive a quick answer. But the reason I'm asking this is because I want to hear a logical explanations from a human being, not a computer.

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