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• MVC design pattern in complex iPad app: is one fat controller acceptable?

  - by nutsmuggler

  I am building a complex iPad application; think of it as a scrapbook. For the purpose of this question, let's consider a page with two images over it. My main view displays my doc data rendered as a single UIImage; this because I need to do some global manipulation over them. This is my DisplayView. When editing I need to instantiate an EditorView with my two images as subviews; this way I can interact with a single image, (rotate it, scale it, move it). When editing is triggered, I hide my DisplayView and show my EditorView. In a iPhone app, I'd associate each main view (that is, a view filling the screen) to a view controller. The problem is here there is just one view controller; I've considered passing the EditorView via a modal view controller, but it's not an option (there a complex layout with a mask covering everything and palettes over it; rebuilding it in the EditorView would create duplicate code). Presently the EditorView incorporates some logic (loads data from the model, invokes some subviews for fine editing, saves data back to the model); EditorView subviews also incorporate some logic (I manipulate images and pass them back to the main EditorView). I feel this logic belongs more to a controller. On the other hand, I am not sure making my only view controller so fat a good idea. What is the best, cocoa-ish implementation of such a class structure? Feel free to ask for clarifications. Cheers.

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• Keeping video viewing statistics breakdown by video time in a database

  - by Septagram

  I need to keep a number of statistics about the videos being watched, and one of them is what parts of the video are being watched most. The design I came up with is to split the video into 256 intervals and keep the floating-point number of views for each of them. I receive the data as a number of intervals the user watched continuously. The problem is how to store them. There are two solutions I see. Row per every video segment Let's have a database table like this: CREATE TABLE `video_heatmap` ( `id` int(11) NOT NULL AUTO_INCREMENT, `video_id` int(11) NOT NULL, `position` tinyint(3) unsigned NOT NULL, `views` float NOT NULL, PRIMARY KEY (`id`), UNIQUE KEY `idx_lookup` (`video_id`,`position`) ) ENGINE=MyISAM Then, whenever we have to process a number of views, make sure there are the respective database rows and add appropriate values to the views column. I found out it's a lot faster if the existence of rows is taken care of first (SELECT COUNT(*) of rows for a given video and INSERT IGNORE if they are lacking), and then a number of update queries is used like this: UPDATE video_heatmap SET views = views + ? WHERE video_id = ? AND position >= ? AND position < ? This seems, however, a little bloated. The other solution I came up with is Row per video, update in transactions A table will look (sort of) like this: CREATE TABLE video ( id INT NOT NULL AUTO_INCREMENT, heatmap BINARY (4 * 256) NOT NULL, ... ) ENGINE=InnoDB Then, upon every time a view needs to be stored, it will be done in a transaction with consistent snapshot, in a sequence like this: If the video doesn't exist in the database, it is created. A row is retrieved, heatmap, an array of floats stored in the binary form, is converted into a form more friendly for processing (in PHP). Values in the array are increased appropriately and the array is converted back. Row is changed via UPDATE query. So far the advantages can be summed up like this: First approach Stores data as floats, not as some magical binary array. Doesn't require transaction support, so doesn't require InnoDB, and we're using MyISAM for everything at the moment, so there won't be any need to mix storage engines. (only applies in my specific situation) Doesn't require a transaction WITH CONSISTENT SNAPSHOT. I don't know what are the performance penalties of those. I already implemented it and it works. (only applies in my specific situation) Second approach Is using a lot less storage space (the first approach is storing video ID 256 times and stores position for every segment of the video, not to mention primary key). Should scale better, because of InnoDB's per-row locking as opposed to MyISAM's table locking. Might generally work faster because there are a lot less requests being made. Easier to implement in code (although the other one is already implemented). So, what should I do? If it wasn't for the rest of our system using MyISAM consistently, I'd go with the second approach, but currently I'm leaning to the first one. But maybe there are some reasons to favour one approach or another?

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• How can I tell when the Text of a System.Windows.Forms.GroupBox wraps to the next line?

  - by fre0n

  I'm creating a GroupBox at runtime and setting its Text property. Usually, the text is only on one line, but sometimes it wraps. The problem is that the controls contained in the GroupBox cover up the GroupBox's text. What I'd like to do is determine if and when the text wraps. Specifically, I'd like to determine how much extra height the wrapped text takes up as compared to a single line. That way, I can reposition the GroupBox's controls and adjust its height. Initially, I thought I'd do this by calling the GroupBox's CreateGraphics() method, and using the Graphics to measure the string. Something like this: private void SetGroupBoxText(GroupBox grp, string text) { const int somePadding = 10; Graphics g = grp.CreateGraphics(); SizeF textSize = g.MeasureString(text, grp.Font); if (textSize.Width > (grp.Width - somePadding)) { // Adjust height, etc. } } The problem is that the size generated by g.MeasureString(text, grp.Font) doesn't seem to be accurate. I determined that it wasn't accurate by putting enough of a single character to cause a wrap, then measuring the resulting string. For example, it took 86 pipes (|) to until a wrap happened. When I measured that string, its width was ~253. And it took 16 capital W's to force a wrap - its string had a width of ~164. These were the two extremes that I tested. My GroupBox's width was 189. (a's took 29 and had a width of ~180, O's took 22 and had a width of ~189) Does anyone have any ideas? (hacks, WinAPI, etc. are welcome solutions)

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• open a text file only if not opened alread (open in NotePad)

  - by Mr_Green

  In my project, I am trying to open a text file. Well the below code works but when the user click the button again and again, many files are being opened. (which I dont want) System.Diagnostics.Process.Start(filePath); I also tried Link , File.Open and File.OpenText which are not opening the text file and also not showing any error (tried with try catch block) File.Open(filePath); (or) File.OpenText(filePath); (or) FileStream fileStream = new FileStream(filePath, FileMode.Open); I also tried this: (ERROR : Cannot be accessed with instance reference qualify with a type name instead) System.Diagnostics.Process proc = new System.Diagnostics.Process(); proc.Start(filePath); /*red scribbles here*/ proc.WaitForExit(); How to show only one instance of the Text file(.txt). am I doing something wrong in my attempts? please suggest. EDIT: I want to open other text files afterwards but not the same and also the application should be accessible after opening a text file(or many). I have only one form.

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• Pass a variable from the source file to an included file in PHP

  - by Alpha1

  For my website I want to store the general format of the site in a single PHP file in a single location, and each of the different pages content in the local location of the page. I then want to pass the title and content address to the included file via a variable. However I can't get the included format file to read the variables storing the title and content data. AKA, the called file for the individual page would be: <?php $title = 'Some Title'; $source_file = 'content.php'; readfile('http:...../format.php'); ?> The format file would be: <html> ... <title> <?php echo $title; ?> </title> ... <?php include($source_file); ?> ... I recall reading somewhere I need to include something to get the variables at the start of the format file, however I can't remember what it is or find where I found that information.

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• Running Ubuntu off a USB drive?

  - by Solignis

  I was wondering if a USB 2.0 Thumb drive has enough bandwidth to act as a primary system drive in an Ubuntu Linux server. More specifically an SAN server. I am running an iSCSI target, ZFS and NFS-kernel-server, BIND9 (Slave), and Openldap (Slave). I was thinking of resorting to a thumb drive because my new motherboard only has 4 SATA ports and I have 5 disks. 4 (ZFS Pool) 1 (System). And unless I get an expansion card there is no way to get more SATA ports. This "server" leans more twords a home server. I use in my lab with my VMware server. It provides storage, or atleast it did until it died. Would it still be better to go with the SATA hard disk?

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• Working with Java using methods and arrays [closed]

  - by jordan

  Hi i'm a newb at java and for one of my labs I have to create a instant messenger client with these requirements: add buddyList instance variable add IMClient constructor to create ArrayList addBuddy method removeBuddy method findBuddy method printBuddyList method what's the best way to go about this? so far I have this: public class IMClient { private String userId; // User id private String password; // Password private int status; // Status code for user: 1 - Online, 2 - Off-line, 3 - Away public IMClient(String userId, String password, int status) { super(); this.userId = userId; this.password = password; this.status = status; } // Returns true if password as a parameter matches password instance variable. public boolean checkPassword(String password) { return this.password.equals(password); } public String toString() { StringBuffer buf = new StringBuffer(100); buf.append(" User id: "); buf.append(userId); buf.append(" Password: "); buf.append(password); buf.append(" Status: "); buf.append(status); return buf.toString(); } public String getUserId() { return userId; } public void setUserId(String userId) { this.userId = userId; } public String getPassword() { return password; } public void setPassword(String password) { this.password = password; } public int getStatus() { return status; } public void setStatus(int status) { this.status = status; } public static void main(String[] args) { } }

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• Does IE completely ignore cache control headers for AJAX requests?

  - by Joshua Hayworth

  Hello there, I've got, what I would consider, a simple test web site. A single page with a single button. Here is a copy of the source I'm working with if you would like to download it and play with it. When that button is clicked, it creates a JavaScript timer that executes once a second. When the timer function is executed, An AJAX call is made to retrieve a text value. That text value is then placed into the DOM. What's my problem? IE Caching. Crack open Task Manager and watch what happens to the iexplorer.exe process (IE 8.0.7600.16385 for me) while the timer in that page is executing. See the memory and handle count getting larger? Why is that happening when, by all accounts, I have caching turned off. I've got the jQuery cache option set to false in $.ajaxSetup. I've got the CacheControl header set to no-cache and no-store. The Expires header is set to DateTime.Now.AddDays(-1). The headers are set in both the page code-behind as well as the HTTP Handler's response. Anybody got any ideas as to how I could prevent IE from caching the results of the AJAX call? Here is what the iexplorer.exe process looks like in ProcessMonitor. I believe that the activity shown in this picture is exactly what I'm attempting to prevent.

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• Changing pointer of self

  - by rob5408

  I have an object that I alloc/init like normal just to get a instance. Later in my application I want to load state from disk for that object. I figure I could unarchive my class (which conforms to NSCoding) and just swap where my instance points to. To this end I use this code... NSString* pathForDataFile = [self pathForDataFile]; if([[NSFileManager defaultManager] fileExistsAtPath:pathForDataFile] == YES) { NSLog(@"Save file exists"); NSData *data = [[NSMutableData alloc] initWithContentsOfFile:pathForDataFile]; NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data]; [data release]; Person *tempPerson = [unarchiver decodeObjectForKey:@"Person"]; [unarchiver finishDecoding]; [unarchiver release]; if (tempPerson) { [self release]; self = [tempPerson retain]; } } Now when I sprinkled some NSLogs throughout my application I noticed self.person: <Person: 0x3d01a10> (After I create the object with alloc/init) self: <Person: 0x3d01a10> (At the start of this method) tempPerson: <Person: 0x3b1b880> (When I create the tempPerson) self: <Person: 0x3b1b880> (after i point self to the location of the tempPerson) self.person: <Person: 0x3d01a10> (After the method back in the main program) What am I missing?

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• multiple models in Rails with a shared interface

  - by dfondente

  I'm not sure of the best structure for a particular situation in Rails. We have several types of workshops. The administration of the workshops is the same regardless of workshop type, so the data for the workshops is in a single model. We collect feedback from participants about the workshops, and the questionnaire is different for each type of workshop. I want to access the feedback about the workshop from the workshop model, but the class of the associated model will depend on the type of workshop. If I was doing this in something other than Rails, I would set up an abstract class for WorkshopFeedback, and then have subclasses for each type of workshop: WorkshopFeedbackOne, WorkshopFeedbackTwo, WorkshopFeedbackThree. I'm unsure how to best handle this with Rails. I currently have: class Workshop < ActiveRecord::Base has_many :workshop_feedbacks end class Feedback < ActiveRecord::Base belongs_to :workshop has_many :feedback_ones has_many :feedback_twos has_many :feedback_threes end class FeedbackOne < ActiveRecord::Base belongs_to :feedback end class FeedbackTwo < ActiveRecord::Base belongs_to :feedback end class FeedbackThree < ActiveRecord::Base belongs_to :feedback end This doesn't seem like to the cleanest way to access the feedback from the workshop model, as accessing the correct feedback will require logic investigating the Workshop type and then choosing, for instance, @workshop.feedback.feedback_one. Is there a better way to handle this situation? Would it be better to use a polymorphic association for feedback? Or maybe using a Module or Mixin for the shared Feedback interface? Note: I am avoiding using Single Table Inheritance here because the FeedbackOne, FeedbackTwo, FeedbackThree models do not share much common data, so I would end up with a large sparsely populated table with STI.

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• pass a pointer of a class

  - by small_potato

  Say I have Class1 and Class2 and I want a shallow copy constructor for Class1. Class1 has a member variable, which is a pointer pointing to a Class2 instance. Also I have to be able to change the Class2 ptr is pointing at. in header file: class Class1 { Class2* ptr; ... } in source file: Class1::Class1() { ptr = new Class2(); } ...... Class2* Class1::Exchange(Class2* newClass2) { Class2* temp; ptr = newClass2; return temp; } ...... Now say Class1 original; Class1 shallowCopy(original); Class2* newClass2 = new Class2(); Class2* oldClass2; oldClass2 = orignal.Exchange(newClass2); delete oldClass2; now I want is associate original.ptr with shallowCopy.ptr, when I implement the shallow copy constructor, how do I make sure these two pointer always point at the same Class2? I mean in the class above, the oldClass2 is deleted, so ptr of shallowCopy is pointing at nothing. If I don't delete oldClass2, ptrs of original and shallowCopy are pointing at different Class2 instance.

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• Is it possible to have WAMP run httpd.exe as user [myself] instead of local SYSTEM?

  - by Olivier H

  Hello! I run a django application over apache with mod_wsgi, using WAMP. A certain URL allows me to stream the content of image files, the paths of which are stored in database. The files can be located whether on local machine or under network drive (\my\network\folder). With the development server (manage.py runserver), I have no trouble at all reading and streaming the files. With WAMP, and with network drive files, I get a IOError : obviously because the httpd instance does not have read permission on said drive. In the task manager, I see that httpd.exe is run by SYSTEM. I would like to tell WAMP to run the server as [myself] as I have read and write permissions on the shared folder. (eventually, the production server should be run by a 'www-admin' user having the permissions) Mapping the network shared folder on a drive letter (Z: for instance) does not solve this at all. The User/Group directives in httpd.conf do not seem to have any kind of influence on Apache's behaviour. I've also regedited : I tried to duplicate the HKLM[...]\wampapache registry key under HK_CURRENT_USER\ and rename the original key, but then the new key does not seem to be found when I cmd this > httpd.exe -n wampapache -k start or when I run WAMP. I've run out of ideas :) Has anybody ever had the same issue?

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• Word frequency tally script is too slow

  - by Dave Jarvis

  Background Created a script to count the frequency of words in a plain text file. The script performs the following steps: Count the frequency of words from a corpus. Retain each word in the corpus found in a dictionary. Create a comma-separated file of the frequencies. The script is at: http://pastebin.com/VAZdeKXs Problem The following lines continually cycle through the dictionary to match words: for i in $(awk '{if( $2 ) print $2}' frequency.txt); do grep -m 1 ^$i\$ dictionary.txt >> corpus-lexicon.txt; done It works, but it is slow because it is scanning the words it found to remove any that are not in the dictionary. The code performs this task by scanning the dictionary for every single word. (The -m 1 parameter stops the scan when the match is found.) Question How would you optimize the script so that the dictionary is not scanned from start to finish for every single word? The majority of the words will not be in the dictionary. Thank you!

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• Hyper-V: determine the guest's name given the GUID

  - by syneticon-dj

  How would I go about determining the guest's name given its GUID or vice-versa, preferably with only the Hyper-V/Server Core stock install at hands? Rationale: I am in favor of having a repository of dirty tricks to revert to when in great need. To immediately quiesce all (storage) operations of a VM guest without losing the state, I used to run kill 17 <all VM's virtual processes> (signaling SIGSTOP) and resumed afterwards using kill 19 <all VM's virtual processes> (signaling SIGCONT) in ESXi/vSphere shell. I tried the same technique with Hyper-V using Process Explorer's "Suspend" functionality on the vmwp.exe processes and it seemed to work. I have yet to find a way for easily identifying the processes to suspend, though - the vmwp command line is only listing a GUID.

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• Purpose of singletons in programming

  - by thecoshman

  This is admittedly a rather loose question. My current understanding of singletons is that they are a class that you set up in such a way that only one instance is ever created. This sounds a lot like a static class to me. The main differnce being that with a static class you don't / can't instance it, you just use it such as Math.pi(). With a singletong class, you would still need to do something like singleton mySingleton = new singleton(); mysingleton.set_name("foo"); singleton otherSingleton = new singleton(); // correct me if i am wrong, but mysingleton == othersingleton right now, yes? // this the following should happen? otherSingleston.set_name("bar"); mysingleton.report_name(); // will output "bar" won't it? Please note, I am asking this language independently, more about the concept. So I am not so worried about actually how to coed such a class, but more why you would wan't to and what thing you would need to consider.

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• Using an unencoded key vs a real Key, benefits?

  - by user246114

  Hi, I am reading the docs for Key generation in app engine. I'm not sure what effect using a simple String key has over a real Key. For example, when my users sign up, they must supply a unique username: class User { /** Key type = unencoded string. */ @PrimaryKey private String name; } now if I understand the docs correctly, I should still be able to generate named keys and entity groups using this, right?: // Find an instance of this entity: User user = pm.findObjectById(User.class, "myusername"); // Create a new obj and put it in same entity group: Key key = new KeyFactory.Builder( User.class.getSimpleName(), "myusername") .addChild(Goat.class.getSimpleName(), "baa").getKey(); Goat goat = new Goat(); goat.setKey(key); pm.makePersistent(goat); the Goat instance should now be in the same entity group as that User, right? I mean there's no problem with leaving the User's primary key as just the raw String? Is there a performance benefit to using a Key though? Should I update to: class User { /** Key type = unencoded string. */ @PrimaryKey private Key key; } // Generate like: Key key = KeyFactory.createKey( User.class.getSimpleName(), "myusername"); user.setKey(key); it's almost the same thing, I'd still just be generating the Key using the unique username anyway, Thanks

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• Detecting the axis of rotation from a pointcloud

  - by tfinniga

  I'm trying to auto-detect the axis of rotation on a 3d pointcloud. In other words, if I took a small 3d pointcloud, chose a single axis of rotation, and make several copies of the points at different rotation angles, then I get a larger pointcloud. The input to my algorithm is the larger pointcloud, and the desired output is the single axis of symmetry. And eventually I'm going to compute the correspondences between points that are rotations of each other. The size of the larger pointcloud is on the order of 100K points, and the number of rotational copies made is unknown. The rotation angles in my case have constant deltas, but don't necessarily span 360 degrees. For example, I might have 0, 20, 40, 60. Or I might have 0, 90, 180, 270. But I won't have 0, 13, 78, 212 (or if I do, I don't care to detect it). This seems like a computer vision problem, but I'm having trouble figuring out how to precisely find the axis. The input will generally be very clean, close to float accuracy.

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• Rapid Opening and Closing System.IO.StreamWriter in C#

  - by ccomet

  Suppose you have a file that you are programmatically logging information into with regards to a process. Kinda like your typical debug Console.WriteLine, but due to the nature of the code you're testing, you don't have a console to write onto so you have to write it somewhere like a file. My current program uses System.IO.StreamWriter for this task. My question is about the approach to using the StreamWriter. Is it better to open just one StreamWriter instance, do all of the writes, and close it when the entire process is done? Or is it a better idea to open a new StreamWriter instance to write a line into the file, then immediately close it, and do this for every time something needs to be written in? In the latter approach, this would probably be facilitated by a method that would do just that for a given message, rather than bloating the main process code with excessive amounts of lines. But having a method to aid in that implementation doesn't necessarily make it the better choice. Are there significant advantages to picking one approach or the other? Or are they functionally equivalent, leaving the choice on the shoulders of the programmer?

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• Parallelizing L2S Entity Retrieval

  - by MarkB

  Assuming a typical domain entity approach with SQL Server and a dbml/L2S DAL with a logic layer on top of that: In situations where lazy loading is not an option, I have settled on a convention where getting a list of entities does not also get each item's child entities (no loading), but getting a single entity does (eager loading). Since getting a single entity also gets children, it causes a cascading effect in which each child then gets its children too. This sounds bad, but as long as the model is not too deep, I usually don't see performance problems that outweigh the benefits of the ease of use. So if I want to get a list in which each of the items is fully hydrated with children, I combine the GetList and GetItem methods. So I'll get a list and then loop through it getting each item with the full cascade. Even this is generally acceptable in many of the projects I've worked on - but I have recently encountered situations with larger models and/or more data in which it needs to be more efficient. I've found that partitioning the loop and executing it on multiple threads yields excellent results. In my first experiment with a list of 50 items from one particular project, I did 5 threads of 10 items each and got a 3X improvement in time. Of course, the mileage will vary depending on the project but all else being equal this is clearly a big opportunity. However, before I go further, I was wondering what others have done that have already been through this. What are some good approaches to parallelizing this type of thing?

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• Why would one want to use the public constructors on Boolean and similar immutable classes?

  - by Robert J. Walker

  (For the purposes of this question, let us assume that one is intentionally not using auto(un)boxing, either because one is writing pre-Java 1.5 code, or because one feels that autounboxing makes it too easy to create NullPointerExceptions.) Take Boolean, for example. The documentation for the Boolean(boolean) constructor says: Note: It is rarely appropriate to use this constructor. Unless a new instance is required, the static factory valueOf(boolean) is generally a better choice. It is likely to yield significantly better space and time performance. My question is, why would you ever want to get a new instance in the first place? It seems like things would be simpler if constructors like that were private. For example, if they were, you could write this with no danger (even if myBoolean were null): if (myBoolean == Boolean.TRUE) It'd be safe because all true Booleans would be references to Boolean.TRUE and all false Booleans would be references to Boolean.FALSE. But because the constructors are public, someone may have used them, which means that you have to write this instead: if (Boolean.TRUE.equals(myBoolean)) But where it really gets bad is when you want to check two Booleans for equality. Something like this: if (myBooleanA == myBooleanB) ...becomes this: if ( (myBooleanA == null && myBooleanB == null) || (myBooleanA == null && myBooleanA.equals(myBooleanB)) ) I can't think of any reason to have separate instances of these objects which is more compelling than not having to do the nonsense above. What say you?

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• Handling large (object) datasets with PHP

  - by Aron Rotteveel

  I am currently working on a project that extensively relies on the EAV model. Both entities as their attributes are individually represented by a model, sometimes extending other models (or at least, base models). This has worked quite well so far since most areas of the application only rely on filtered sets of entities, and not the entire dataset. Now, however, I need to parse the entire dataset (IE: all entities and all their attributes) in order to provide a sorting/filtering algorithm based on the attributes. The application currently consists of aproximately 2200 entities, each with aproximately 100 attributes. Every entity is represented by a single model (for example Client_Model_Entity) and has a protected property called $_attributes, which is an array of Attribute objects. Each entity object is about 500KB, which results in an incredible load on the server. With 2000 entities, this means a single task would take 1GB of RAM (and a lot of CPU time) in order to work, which is unacceptable. Are there any patterns or common approaches to iterating over such large datasets? Paging is not really an option, since everything has to be taken into account in order to provide the sorting algorithm.

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• Unable to format/add a partition to Windows XP

  - by sma

  I recently add a 1T disk to an XP machine. I found the disk in the "disk management", I click "initialize" to init it, then creates a primary partition with size 950G, then select quick format to format the disk, the "disk management" will then complains: The disk configuration operation did not complete. Check the system event log for more information on the error. Verify the status of your storage devices before retrying. If that does not solve the problem, close the disk management console, then restart disk management or restart the computer. What could be the reason?

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• How does Haskell do pattern matching without us defining an Eq on our data types?

  - by devoured elysium

  I have defined a binary tree: data Tree = Null | Node Tree Int Tree and have implemented a function that'll yield the sum of the values of all its nodes: sumOfValues :: Tree -> Int sumOfValues Null = 0 sumOfValues (Node Null v Null) = v sumOfValues (Node Null v t2) = v + (sumOfValues t2) sumOfValues (Node t1 v Null) = v + (sumOfValues t1) sumOfValues (Node t1 v t2) = v + (sumOfValues t1) + (sumOfValues t2) It works as expected. I had the idea of also trying to implement it using guards: sumOfValues2 :: Tree -> Int sumOfValues2 Null = 0 sumOfValues2 (Node t1 v t2) | t1 == Null && t2 == Null = v | t1 == Null = v + (sumOfValues2 t2) | t2 == Null = v + (sumOfValues2 t1) | otherwise = v + (sumOfValues2 t1) + (sumOfValues2 t2) but this one doesn't work because I haven't implemented Eq, I believe: No instance for (Eq Tree) arising from a use of `==' at zzz3.hs:13:3-12 Possible fix: add an instance declaration for (Eq Tree) In the first argument of `(&&)', namely `t1 == Null' In the expression: t1 == Null && t2 == Null In a stmt of a pattern guard for the definition of `sumOfValues2': t1 == Null && t2 == Null The question that has to be made, then, is how can Haskell make pattern matching without knowing when a passed argument matches, without resorting to Eq?

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• Django - Weird behaviour of sessions variables with Apache

  - by Étienne Loks

  In a Menu class with Section children, each Section has an available attribute. This attribute is initialized during the instance creation. The process of getting the availability is not trivial, so I stock a Menu instance for each user in a session variable. With the Django embedded webserver this works well. But when I deploy the application on an Apache webserver I can observe a very weird behavior. Once authentified, a click on a link or a refreshment of the page and the availability of each Section seems to be forgotten (empty menu but in the log file I can see that all Sections are here) then a new refresh on the page the availability is back, a new refresh the menu disappears once again, etc. There is no cache activated on the web server. The menu is initialized in a context processor. def get_base_context(request): if 'MENU' not in request.session or \ not request.session['MENU'].childs or\ request.session['MENU'].user != request.user: _menu = Menu(request.user) _menu.init() request.session['MENU'] = _menu (...) I have no idea what could cause such a behavior. Any clue?

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• iphone: memory problems after refactor

  - by agilpwc

  I had a NIB with several view controllers in it. I modified the code and used Interface Builder decomose interface to get all the view controllers in their own Nib. But now with empty core data database, I'm getting "message sent to deallocated instance" errors. Here is the code flow: From the RootViewController this is called: if (self.dogController == nil) { DogViewController *controller = [[DogViewController alloc] initWithNibName:@"DogViewController" bundle:nil]; self.dogController = controller; [controller release]; } self.dogController.managedObjectContext = self.managedObjectContext; [self.navigationController pushViewController:self.dogController animated:YES]; Then in a dogController a button is pressed to insert a new object and the following code is excuted and the error hits on the save, according to the trace NSManagedObjectContext *context = [self.fetchedResultsController managedObjectContext]; NSEntityDescription *entity = [[self.fetchedResultsController fetchRequest] entity]; NSManagedObject *newManagedObject = [NSEntityDescription insertNewObjectForEntityForName:[entity name] inManagedObjectContext:context]; // If appropriate, configure the new managed object. [newManagedObject setValue:[NSDate date] forKey:@"birthDate"]; [newManagedObject setValue:@"-" forKey:@"callName"]; // Save the context. NSError *error = nil; if (![context save:&error]) { Then the error produced in the console is * -[JudgeViewController numberOfSectionsInTableView:]: message sent to deallocated instance 0x598e580 I'm racking my brain for hours and I can't figure out where my minor changes made something messed up. Any ideas?

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