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  • iphone menu navigation with buttons help requested

    - by David
    Hi, I'm trying to program an iphone app that will have several different (sub)apps. Ideally, I want to know how to make the main menu for this app look and behave like the iphone's own app menu, but I can't figure it out. If any one knows a package or library that does this, please let me know. Plan B is to mock one using UIButtons, and here is where I'm having problems. Basically, when I press a button that should push a new view, it calls the push method, but I still see the top view. in the app delegate, I have something like: AppViewController *viewController; App1ViewController *app1ViewController; UINavigationController *navController; and in didFinishLaunching method, something like: viewController = [ [ AppViewController alloc ] initWithAppDelegate: self ]; app1ViewController = [ [App1ViewController alloc ] initWithAppDelegate: self ]; navController = [ [ UINavigationController alloc ] initWithRootViewController:viewController]; [window addSubview:viewController.view]; and 2 methods -(void)app1{[ navController pushViewController: app1ViewController animated:YES ];} -(void)back{[ navController popViewControllerAnimated:YES ];} then I have 2 viewcontrollers in AppViewController.h @interface AppViewController : UIViewController { UINavigationController *navController; UIButton *appbtn1, *appbtn2, *appbtn3, *appbtn4; } -(id)initWithAppDelegate:(id)appDelegate; @end @interface App1ViewController : UIViewController { UITextView *textView; UINavigationController *navController; } -(id)initWithAppDelegate:(id)appDelegate; @end and define a loadView for each viewcontroller. However, when I press the app1 button and the app1 method gets called, it says the view hasa been pushed, but my view remains the buttons view, i.e. the root view. If I press the button again, it tells me I can't repush the app1view, the one I can't see. Any ideas? I can post the full code if that helps. Thank you for your time.

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  • A business Case for Enterprise Python

    - by Srirangan
    Hi all, This will not be a "programming" question but more technology / platform related question. I'm trying to figure out whether Python can be a suitable Java alternative for enterprise / web applications. Which are the ideal cases where you would prefer to use Python instead of Java? How would a typical Python web application (databases/sessions/concurrency) perform as compared to a typical Java application? How do specific Python frameworks square up against Java based frameworks (Spring, SEAM, Grails etc.)? For businesses, switching from the Java infrastructure to a Python infrastructure .. is it too hard/expensive/resource intensive/not viable? Also shed some light on the business case for providing a Python + Google AppEngine based solution to the end customer. Will it be cost effective in an typical scenario? Sorry if I am asking too wide a question, I would have liked to keep it specific, but I need your help to evaluate Python as a whole from the perspectives of the programmers, service providing company and end business customer. For an SME, a Python/GoogleAppEngine based technology stack is a clear scalable and affordable platform. But what about a large MNC that already has a lot invested in Java. Thank you so much. I am researching this myself and will gladly share my conclusions here! Thank you, Srirangan

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  • Why do people say that Ruby is slow?

    - by stephen murdoch
    I like Ruby on Rails and I use it for all my web development projects. A few years ago there was a lot of talk about Rails being a memory hog and about how it didn't scale very well but these suggestions were put to bed by Gregg Pollack here. Lately though, I've been hearing people saying that Ruby itself is slow. Why is Ruby considered slow? I do not find Ruby to be slow but then again, I'm just using it to make simple CRUD apps and company blogs. What sort of projects would I need to be doing before I find Ruby becoming slow? Or is this slowness just something that affects all programming languages? What are your options as a Ruby programmer if you want to deal with this "slowness"? Which version of Ruby would best suit an application like Stack Overflow where speed is critical and traffic is intense? The questions are subjective, and I realise that architectural setup (EC2 vs standalone servers etc) makes a big difference but I'd like to hear what people think about Ruby being slow. Finally, I can't find much news on Ruby 2.0 - I take it we're a good few years away from that then?

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  • What's it like being a financial programmer?

    - by Mike
    As a student who's done an internship at a Silicon Valley company(non-financial), I'm curious to know what it's like working for a financial company doing software development. I'd expect the hours to be longer, and the pay to be higher. Specifically, I have the following questions: What's the work/life balance really like? Are you expected to work 80 hours a week most weeks? For those who have worked in non-financial software engineering jobs, how does being a financial software engineer compare in terms of work/life balance? How much does it pay? I'm curious as to starting(i.e. just got a BS) pay, as well as "top out" pay. (I'd prefer concrete numbers - ballpark is fine). Also, bonuses would be useful information. What jobs do financial programmers typically have? Are most just general software engineers, or do people typically have very specialized(i.e. AI or systems) backgrounds? Also, do most programmers have PhDs? Are programmers typically required to be at work, or are financial companies generally flexible about letting programmers work from home? When at work, do programmers have to dress formally? What are the technology environments like? Are finance companies using state-of-the-art hardware and software, or are they generally more conservative in upgrading their equipment? What programming languages are typically used? If VBA(shudder) is used, is it a large part of a finance company's workflow? If you could turn back the clock, would you still be a financial programmer? I'm going to keep this post open a little bit longer to get some more responses.

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  • Is it possible to use OAuth starting from the service provider website?

    - by Brian Armstrong
    I want to let people create apps that use my API and authenticate them with OAuth. Normally this process starts from the consumer service website (say TwitPic) and they request an access token from the service provider (Twitter). The user is then taken to the service provider website where they have to allow/deny access to to the consumer. I'm wondering if it's possible to initiate this process from the service provider website instead. So in this example you would start on Twitter's site, and maybe there is a section marked "do you want to turn on access for TwitPic?". If you click yes, it passes the access token directly to TwitPic which now has access to your account. Basically, fewer steps. I'm looking at the OAuth docs and it looks like the request token is generated on the consumer side and used later to turn it into an access token. So it's not really designed with what I described above in mind, but I thought there might be a way. http://oauth.net/core/1.0/ (Search for "steps") Thanks!

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  • Advice on coding Perl to work like PHP

    - by user272273
    I am first and foremost a perl coder, but like many, also code in PHP for client work, especially web apps. I am finding that I am duplicating a lot of my projects in the two languages, but using different paradigms (e.g. for handling cgi input and session data) or functions. What I would like to do is start to code my Perl in a way which is structured more like PHP, so that I a) am keeping one paradigm in my head b) can more quickly port over scripts from one to the other Specifically, I am asking if people could advise how you might do the following in perl? 1) Reproduce the functionality of $_SESSION, $_GET etc. e.g. by wrapping up the param() method of CGI.pm, a session library? 2) Templating library that is similar to PHP I am used to mixing my code and HTML in the PHP convention. e.g. i <h1>HTML Code here</h1> <? print "Hello World\b"; ?> Can anybody advise on which perl templating engine (and possibly configuration) will allow me to code similarly? 3) PHP function library Anybody know of a library for perl which reproduces a lot of the php inbuilt functions?

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  • How to accurately parse smtp message status code (DSN)?

    - by Geo
    RFC1893 claims that status codes will come in the format below you can read more here. But our bounce management system is having a hard time parsing error status code from bounce messages. We are able to get the raw message, but depending on the email server the code will come in different places. Is there any rule on how to parse this type of messages to obtain better results. We are not looking for the 100% solution but at least 80%. This document defines a new set of status codes to report mail system conditions. These status codes are intended to be used for media and language independent status reporting. They are not intended for system specific diagnostics. The syntax of the new status codes is defined as: status-code = class "." subject "." detail class = "2"/"4"/"5" subject = 1*3digit detail = 1*3digit White-space characters and comments are NOT allowed within a status- code. Each numeric sub-code within the status-code MUST be expressed without leading zero digits. The quote above from the RFC tells one thing but then the text below from a leading tool on bounce management says something different, where I can get a good source of standard status codes: Return Code Description 0 UNDETERMINED - (ie. Recipient Reply) 10 HARD BOUNCE - (ie. User Unknown) 20 SOFT BOUNCE - General 21 SOFT BOUNCE - Dns Failure 22 SOFT BOUNCE - Mailbox Full 23 SOFT BOUNCE - Message Too Large 30 BOUNCE - NO EMAIL ADDRESS. VERY RARE! 40 GENERAL BOUNCE 50 MAIL BLOCK - General 51 MAIL BLOCK - Known Spammer 52 MAIL BLOCK - Spam Detected 53 MAIL BLOCK - Attachment Detected 54 MAIL BLOCK - Relay Denied 60 AUTO REPLY - (ie. Out Of Office) 70 TRANSIENT BOUNCE 80 SUBSCRIBE Request 90 UNSUBSCRIBE/REMOVE Request 100 CHALLENGE-RESPONSE

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  • Outlook style events calendar for project based on MVC framework

    - by Roman
    I need large Calendar (not jQuery datepicker) with possibility to schedule events and show them on calendar. Calendar must support month/week/day views. It is very desirable for Calendar not to reload whole page when view changes (AJAX refresh). It must be easily customizable (CSS themes) and localizable. It should support drag & drop (for scheduled events). Such Calendar must be rendered on client side from JSON data snippet. I know there are too many requirements to find Calendar that matches them all but all they are important. I have found some free open source Calendar controls, but almost all are tightly tuned for ASP.NET but not MVC or have very "heavy" JavaScript codebase. Ideally i see it as jQuery extension but not server side ASP.NET control. The best ready-to-use solution I have found is FullCalendar by Adam Shaw (http://arshaw.com/fullcalendar/). It is jQuery plugin which source code I can change to fit my needs. If you can suggest some better existing solutions I'll be very appreciative.

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  • Should I move big data blobs in JSON or in separate binary connection?

    - by Amagrammer
    QUESTION: Is it better to send large data blobs in JSON for simplicity, or send them as binary data over a separate connection? If the former, can you offer tips on how to optimize the JSON to minimize size? If the latter, is it worth it to logically connect the JSON data to the binary data using an identifier that appears in both, e.g., as "data" : "< unique identifier " in the JSON and with the first bytes of the data blob being < unique identifier ? CONTEXT: My iPhone application needs to receive JSON data over the 3G network. This means that I need to think seriously about efficiency of data transfer, as well as the load on the CPU. Most of the data transfers will be relatively small packets of text data for which JSON is a natural format and for which there is no point in worrying much about efficiency. However, some of the most critical transfers will be big blobs of binary data -- definitely at least 100 kilobytes of data, and possibly closer to 1 megabyte as customers accumulate a longer history with the product. (Note: I will be caching what I can on the iPhone itself, but the data still has to be transferred at least once.) It is NOT streaming data. I will probably use a third-party JSON SDK -- the one I am using during development is here. Thanks

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  • Are there size limitations to the .NET Assembly format?

    - by McKAMEY
    We ran into an interesting issue that I've not experienced before. We have a large scale production ASP.NET 3.5 SP1 Web App Project in Visual Studio 2008 SP1 which gets compiled and deployed using a Website Deployment Project. Everything has worked fine for the last year, until after a check-in yesterday the app started critically failing with BadImageFormatException. The check-in in question doesn't change anything particularly special and the errors are coming from areas of the app not even changed. Using Reflector we inspected the offending methods to find that there were garbage strings in the code (which .NET Reflector humorously interpreted as Chinese characters). We have consistently reproduced this on several machines so it does not appear to be hardware related. Further inspection showed that those garbage strings did not exist in the Assemblies used as inputs to aspnet_merge.exe during deployment. aspnet_merge.exe / Web Deployment Project Output Assemblies Properties: Merge all outputs to a single assembly Merge each individual folder output to its own assembly Merge all pages and control outputs to a single assembly Create a separate assembly for each page and control output In the web deployment project properties if we set the merge options to the first option ("Merge all outputs to a single assembly") we experience the issue, yet all of the other options work perfectly! My question: does anyone know why this is happening? Is there a size-limit to aspnet_merge.exe's capabilities (the resulting merged DLL is around 19.3 MB)? Are there any other known issues with merging the output of WAPs? I would love it if any Assembly format / aspnet_merge.exe gurus know about any such limitations like this. Seems to me like a 25MB Assembly, while big, isn't outrageous.

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  • XSL check param length

    - by AdRock
    I need to check if a param has got a value in it and if it has then do this line otherwise do this line. I've got it working whereas I don't get errors but it's not taking the right branch Here is the template which holds the html in the XSL stylesheet <xsl:call-template name="volunteer_role"> <xsl:with-param name="volrole" select="volunteer/roles" /> </xsl:call-template> and here is the template where there is a choice whether to take this brancg or that brach depending if the param is empty <xsl:template name="volunteer_role"> <xsl:param name="volrole" select="'Not Available'" /> <div class="small bold">ROLES:</div> <div class="large"> <xsl:choose> <xsl:when test="string-length($volrole)!=0"> <xsl:value-of select="$volrole" /> </xsl:when> <xsl:otherwise> <xsl:text> </xsl:text> </xsl:otherwise> </xsl:choose> </div> </xsl:template>

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  • What does "active directory integration" mean in your .NET app?

    - by flipdoubt
    Our marketing department comes back with "active directory integration" being a key customer request, but our company does not seem to have the attention span to (1) decide on what functional changes we want to make toward this end, (2) interview a broad range of customer to identify the most requested functional changes, and (3) still have this be the "hot potato" issue next week. To help me get beyond the broad topic of "active directory integration," what does it mean in your .NET app, both ASP.NET and WinForms? Here are some sample changes I have to consider: When creating and managing users in your app, are administrators presented with a list of all AD users or just a group of AD users? When creating new security groups within your app (we call them Departments, like "Human Resources"), should this create new AD groups? Do administrators assign users to security groups within your app or outside via AD? Does it matter? Is the user signed on to your app by virtue of being signed on to Windows? If not, do you track users with your own user table and some kind of foreign key into AD? What foreign key do you use to link app users to AD users? Do you have to prove your login process protects user passwords? What foreign key do you use to link app security groups to AD security groups? If you have a WinForms component to your app (we have both ASP.NET and WinForms), do you use the Membership Provider in your WinForms app? Currently, our Membership and Role management predates the framework's version, so we do not use the Membership Provider. Am I missing any other areas of functional changes? Followup question Do apps that support "active directory integration" have the ability to authenticate users against more than one domain? Not that one user would authenticate to more than one domain but that different users of the same system would authenticate against different domains.

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  • Kerberos and/or other authentication systems - One time logon for all PHP scripts

    - by devviedev
    I'm managing a set of web apps, almost exclusively written in PHP, and would like to find an authentication platform to build a role-based authorization system on top of. Also, I'd like the authentication system to be extensible to use for, for example, system services (SSH, etc.) Here are some of the main characteristics I'm looking for, in order of importance: Easy PHP implementation (storing/reading easily roles, etc.). Redundant, if possible. If an auth system goes down everyone is not locked out. Has clients for Windows and Mac. Easy web-based administration (adding/removing users/roles, changing passwords). If not, I can build an administration system without too much effort. One-time log on. I'd also like, when an auth token is issued, to store the user's IP address and use that to authorize the user for some non web-based applications. For that reason, I'd like a desktop client to issue the token and revoke tokens when, for example, the user becomes idle at their workstation. I'm thinking Kerberos might be a solution, but what are other options?

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  • C# - parse content away from structure in a binary file

    - by Jeff Godfrey
    Using C#, I need to read a packed binary file created using FORTRAN. The file is stored in an "Unformatted Sequential" format as described here (about half-way down the page in the "Unformatted Sequential Files" section): http://www.tacc.utexas.edu/services/userguides/intel8/fc/f_ug1/pggfmsp.htm As you can see from the URL, the file is organized into "chunks" of 130 bytes or less and includes 2 length bytes (inserted by the FORTRAN compiler) surrounding each chunk. So, I need to find an efficient way to parse the actual file payload away from the compiler-inserted formatting. Once I've extracted the actual payload from the file, I'll then need to parse it up into its varying data types. That'll be the next exercise. My first thoughts are to slurp up the entire file into a byte array using File.ReadAllBytes. Then, just iterate through the bytes, skipping the formatting and transferring the actual data to a second byte array. In the end, that second byte array should contain the actual file contents minus all the formatting, which I'd then need to go back through to get what I need. As I'm fairly new to C#, I thought there might be a better, more accepted way of tackling this. Also, in case it's helpful, these files could be fairly large (say 30MB), though most will be much smaller...

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  • 3 Servers, is this is a cluster?

    - by Andy Barlow
    Hello, At the moment I have one Ubuntu server, 9.10, running with a simple Samba share, a mail server, DNS server and DHCP server. Mostly its just there for file sharing and email server. I also have 2 other servers that are exactly the same hardware and spec as the first, which have an rsync set up to retrieve the shared folders and backs them up. However, if the first server goes down, all of our shares disappear along with our mail and the system must be rebuilt. Also I tend to find if people are downloading a large amount from the file server, no-one can access there emails - especially in the morning when everyone is signing in at once. Would it be more beneficial for me to have all 3 servers, all running the same services, doing the same thing with some sort of cluster with load balancing? I'm not really sure where to begin looking, or how to go about such a setup where 3 servers are all identical, but perhaps one acts as the main load balancer?? If someone can point me in the right direction, or if this simply sounds like one of those Enterprise Cloud's that is now a default setup in Ubuntu Server 9.10+, then I'll go down that route. Cheers in advance. Andy

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  • Apply a recursive CTE on grouped table rows (SQL server 2005).

    - by Evan V.
    Hi all, I have a table (ROOMUSAGE) containing the times people check in and out of rooms grouped by PERSONKEY and ROOMKEY. It looks like this: PERSONKEY | ROOMKEY | CHECKIN | CHECKOUT | ROW ---------------------------------------------------------------- 1 | 8 | 13-4-2010 10:00 | 13-4-2010 11:00 | 1 1 | 8 | 13-4-2010 08:00 | 13-4-2010 09:00 | 2 1 | 1 | 13-4-2010 15:00 | 13-4-2010 16:00 | 1 1 | 1 | 13-4-2010 14:00 | 13-4-2010 15:00 | 2 1 | 1 | 13-4-2010 13:00 | 13-4-2010 14:00 | 3 13 | 2 | 13-4-2010 15:00 | 13-4-2010 16:00 | 1 13 | 2 | 13-4-2010 15:00 | 13-4-2010 16:00 | 2 I want to select just the consecutive rows for each PERSONKEY, ROOMKEY grouping. So the desired resulting table is: PERSONKEY | ROOMKEY | CHECKIN | CHECKOUT | ROW ---------------------------------------------------------------- 1 | 8 | 13-4-2010 10:00 | 13-4-2010 11:00 | 1 1 | 1 | 13-4-2010 15:00 | 13-4-2010 16:00 | 1 1 | 1 | 13-4-2010 14:00 | 13-4-2010 15:00 | 2 1 | 1 | 13-4-2010 13:00 | 13-4-2010 14:00 | 3 13 | 2 | 13-4-2010 15:00 | 13-4-2010 16:00 | 1 I want to avoid using cursors so I thought I would use a recursive CTE. Here is what I came up with: ;with CTE (PERSONKEY, ROOMKEY, CHECKIN, CHECKOUT, ROW) as (select RU.PERSONKEY, RU.ROOMKEY, RU.CHECKIN, RU.CHECKOUT, RU.ROW from ROOMUSAGE RU where RU.ROW = 1 union all select RU.PERSONKEY, RU.ROOMKEY, RU.CHECKIN, RU.CHECKOUT, RU.ROW from ROOMUSAGE RU inner join CTE on RU.ROWNUM = CTE.ROWNUM + 1 where CTE.CHECKIN = RU.CHECKOUT and CTE.PERSONKEY = RU.PERSONKEY and CTE.ROOMKEY = RU.ROOMKEY) This worked OK for very small datasets (under 100 records) but it's unusable on large datasets. I'm thinking that I should somehow apply the cte recursevely on each PERSONKEY, ROOMKEY grouping on my ROOMUSAGE table but I am not sure how to do that. Any help would be much appreciated, Cheers!

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  • Subscription website architecture questions + SQL Server & .NET

    - by chopps
    Hey Guys, I have a few questions about the architecture of a subscription service I am about to embark on and I am looking for some feedback on how best to set it up. I won’t have a large amount of customers as Basecamp, maybe a few hundred and was wondering what would be a solid architecture for setting up the customer sites. I’m running SQL Server and .NET on a dedicated machine. Should create a new database for each customer as to have control and isolation of data or keep them all in one database? I am also thinking of creating a sub-domain for each customer as well so modifications can be made to each site as needed. The customer URLs would look like this: https://customer1.foobar.com https://customer2.foobar.com I am going to have the ability to ‘plug-in’ reports that will be uploaded to the site so each customer can customize as needed. Off the top of my head this necessitates having each sub domain on its own code-base for the uploading of these reports. So on the main site the customer would sign up for their new subscription and I would programmatically create a new directory for the customer from the main code base and then create a sub domain pointing to the new directory for the customer and then finally their database. Does this sound about right? Am I on the right track? How do other such sites accomplish the same thing? Thanks for letting me bend your ear for a bit on this.

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  • How would I make a mouse controlled physics object in Box2D / AS3?

    - by Marty Wallace
    I recently created this tennis game using my own basic physics: http://martywallace.com/sandbox/tennis/ Basically a tennis racquet sticks to your mouse and you can hit the tennis balls upward. The physics aren't that great, and I want to make a more interesting version of this game with milestones and levels in Flash. I am planning to use Box2D because I have moderate experience with it. I'm not sure how to go about creating the racquet - as far as I understand Box2D, the racquet needs a velocity to influence the velocities of the balls when you hit them (so that you can hit them harder or softer upward to keep them up). With that said, I'm assuming I can't just have a kinematic body that will have its position set to the mouse, because it won't affect the velocities of the balls as expected. I've also thought about setting the velocity to the difference between the racquet position and the mouse each frame, but I am concerned that won't provide accurate positioning and am also thinking that the velocity could end up really large if you move the mouse quickly. What is the correct way to have a physics object locked to the mouse but also to have its displacement in the last frame (from where it was to the mouse) affect the balls?

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  • Telephone Number to Geolocation UK

    - by David Toy
    Is there a service that provides latitude and longitude for UK phone numbers? For example: Query: 0141 574 xxx, Returns: (55.8659829, -4.2602205) [Glasgow City Centre] Allow me to stress that I am not looking for a reverse-directory-enquires. I am more interested in 'local area' for things like weather by phone or "Where's my nearest Pizza Shop?" If this service doesn't exist your suggestions on how to implement it or where to get data from would also be incredibly useful. I am aware that Ofcom provides a list of area codes with a place name [1] suitable for geolocation, but I have my concerns about resolution. I see this as a particular problem in smaller towns and rural areas where an area code will cover a large geographical area. Second Example: Area Code: 01555, Ofcom: Lanark However: 01555 860xxx is Crossford (4 miles W of Lanark) 01555 77xxxx is Carluke (5 miles NW) 01555 89xxxx is Lesmahagow (5 miles SW) 01555 840xxx is Carnwath (7 miles NE) Therefore 01555 covers about ~80 sq miles. That's not particularly local. [1] Ofcom Area Code Tool: http://www.ofcom.org.uk/consumer/2009/09/telephone-area-codes-tool/

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  • Foreach is crashing script, but no errors reported.

    - by ILMV
    So I've created this smarty function to get images from my flickr photostream using SimplePie... simple really, or so it should be. The problem I'm having is the foreach will crash the script, this doesn't happen if I put an exit after the closing foreach, of course because of this the rest of my script doesn't execute. The problem also completely subsides if I remove the foreach, I've tested it and it's not the contents of the foreach, but the loop itself. Error reporting is turned on but I don't get any, I also tried messing with the memory_limit, with no luck. Anyone know why this foreach is killing my script? Thanks! function smarty_function_flickr ($params, &$smarty) { require_once('system/library/SimplePie/simplepie.inc'); require_once('system/library/SimplePie/idn/idna_convert.class.php'); $flickr=new flickr(); /** * Set up SimplePie with all default values using shorthand syntax. */ $feed = new SimplePie($params['feed'], 'system/library/SimplePie/cache', '600'); $feed->handle_content_type(); /** * What sizes should we use? * Choices: square, thumb, small, medium, large. */ $thumb = 'square'; $full = 'medium'; $output = array(); $counter=0; // If I comment this foreach out the problem subsides, I know it is not the code within the foreach foreach ($feed->get_items() as $item) { $url = $flickr->image_from_description($item->get_description()); $output[$counter]['title'] = $item->get_title(); $output[$counter]['image'] = $flickr->select_image($url, $full); $output[$counter]['thumb'] = $flickr->select_image($url, $thumb); $counter++; } // Set template variables and template $smarty->assign('flickr',$output); $smarty->display('forms/'.$params['template'].'.tpl'); }

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  • A queue in C using structs and dynamic memory allocation (linked list)

    - by Martin Pugh
    I am tasked with making a queue data structure in C, as a linked list. Our lecturer gave us a large amount of code to implement a stack, but we have to adapt it to create a queue. The code our lecturer gave us ends up not compiling and segfaulting at the exact same point as the code I wrote for the queue. I'm very new to structs, malloc and C in general, so there could be something painfully obvious I've overlooked. Here is the code I am using: #include <stdio.h> #include <stdlib.h> struct node{ int data; //contains the actual data struct node *prev; //pointer to previous node (Closer to front) struct node *next; //pointer to next node (Closer to back) }; typedef struct node *Nodepointer; struct queue{ Nodepointer front; Nodepointer back; }; typedef struct queue *Queuepointer; main(){ Queuepointer myqueue; //create a queue called myqueue init(myqueue); //initialise the queue Nodepointer new = (Nodepointer)malloc(sizeof(struct node)); myqueue->front = new; } int init(Queuepointer q){ q = (Queuepointer)malloc(sizeof(struct queue)); q->front = NULL; q->back = NULL; } The idea is that the queue struct 'contains' the first and last nodes in a queue, and when a node is created, myqueue is updated. However, I cannot even get to that part (pop and push are written but omitted for brevity). The code is segfaulting at the line myqueue->front = new; with the following gdb output: Program received signal SIGSEGV, Segmentation fault. 0x08048401 in main () at queue.c:27 27 myqueue->front = new; Any idea what I'm doing wrong?

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  • List of objects or parallel arrays of properties?

    - by Headcrab
    The question is, basically: what would be more preferable, both performance-wise and design-wise - to have a list of objects of a Python class or to have several lists of numerical properties? I am writing some sort of a scientific simulation which involves a rather large system of interacting particles. For simplicity, let's say we have a set of balls bouncing inside a box so each ball has a number of numerical properties, like x-y-z-coordinates, diameter, mass, velocity vector and so on. How to store the system better? Two major options I can think of are: to make a class "Ball" with those properties and some methods, then store a list of objects of the class, e. g. [b1, b2, b3, ...bn, ...], where for each bn we can access bn.x, bn.y, bn.mass and so on; to make an array of numbers for each property, then for each i-th "ball" we can access it's 'x' coordinate as xs[i], 'y' coordinate as ys[i], 'mass' as masses[i] and so on; To me it seems that the first option represents a better design. The second option looks somewhat uglier, but might be better in terms of performance, and it could be easier to use it with numpy and scipy, which I try to use as much as I can. I am still not sure if Python will be fast enough, so it may be necessary to rewrite it in C++ or something, after initial prototyping in Python. Would the choice of data representation be different for C/C++? What about a hybrid approach, e.g. Python with C++ extension?

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  • Online voice chat: Why client-server model vs. peer-to-peer model?

    - by sstallings
    I am adding online voice chat to a Silverlight app. I've been reviewing current apps, services and SDKs found thru online searches and forums. I'm finding that the majority of these implement a client-server (C/S) model and I'm trying to understand why that model versus a peer-to-peer (PTP) model. To me PTP would be preferable because going direct between peers would be more efficient (fewer IP hops and no processing along the way by a server computer) and no need for a server and its costs and dependencies. I found some products offer the ability to switch from PTP to C/S if the PTP proves insufficient. As I thought more about it, I could see that C/S could be better if there are more than two peers involved in a conversation, then the server (supposedly with more bandwidth) could do a better job of relaying each peers outgoing traffic to the multiple other peers. In C/S many-to-many voice chatting, each peer's upstream broadband (which is where the bottleneck inherently is) would only have to carry each item of voice traffic once, then the server would use its superior bandwidth to relay the message to the multiple other peers. But, in a situation with one-on-one voice chatting it seems that PTP would be best. A server would not reduce each of the two peer's bandwidth requirements and would only add unnecessary overhead, dependency and cost. In one-on-one voice chatting: Am I mistaken on anything above? Would peer-to-peer be best? Would a server provide anything of value that could not be provided by a client-only program? Is there anything else that I should be taking into consideration? And lastly, can you recommend any Silverlight PTP or C/S voice chat products? Thanks in advance for any info.

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  • Abort SAX parsing mid-document?

    - by CSharperWithJava
    I'm parsing a very simple XML schema with a SAX parser in Android. An example file would be <Lists> <List name="foo"> <Note title="note 1" .../> <Note title="note 2" .../> </List> <List name="bar"> <Note title="note 3" .../> </List> </Lists> The ... represents more note data as attributes that aren't important to question. I use a SAX parser to parse the document and only implement the startElement and 'endElement' methods of the HandlerBase to handle Note and List nodes. However, In some cases the files can be very large and take some time to process. I'd like to be able to abort the parsing process at any time (i.e. user presses cancel button). The best way I've come up with is to throw an exception from my startElement method when certain conditions are met (i.e. boolean stopParsing is true). Is there a better way to do this? I've always used DOM style parsers, so I don't fully understand the SAX parser. One final note, I'm running this on Android, so I will have the Parser running on a worker thread to keep the UI responsive. If you know how I can kill the thread safely while the parser is running that would answer my question as well.

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  • How much business logic belongs in RIA services layer?

    - by jkohlhepp
    I have been experimenting recently with Silverlight, RIA Services, and Entity Framework using .NET 4.0. I'm trying to figure out if that stack makes sense for use in any of my upcoming projects. It certainly seems like these technologies can be very productive for developing applications, but I'm struggling to decide how an application on top of this stack should be architected. The main issue I have is that in most of the demos I've seen most of the business logic ends up as DataAnnotations and custom validations in the RIA Services domain service class. This seems inappropriate to me. I view the domain service as basically a glorified web service that happens to make it easy to push information to the client. But most of what I've seen seems to orient the domain service as the main source of business logic in the application. So, my questions: What is the best location for business logic (rules, validations, behaviors, authorization) in an application using this stack? Are there any guidelines published at an architectural level for using this stack? My questions pertain to large, complex, and long-lived applications. Obviously for an application of only a few screens this is less of a concern. Edit: Another thing I meant to mention is that obviously you can make the domain service class stupid, but then you lose a lot of the automagic entity information (e.g. validations) being pushed to the client. And then if you lose that is there any point to using RIA services?

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