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• Apache Not Accepting a Path in My Home Folder

  - by Promather

  I have trying to set up an Apache site to use a folder in my home folder without any success. I exactly followed the steps in this page: https://help.ubuntu.com/community/ApacheMySQLPHP yet I did not succeed; I keep getting error 403, which says that the server doesn't have permission to access the requested page. I searched forums and many suggested changing the permission of the folder. I went straight away and set the permission to 777, but that didn't solve the problem. I made another search and somebody gave me a clue, which is that it could be because my home folder is encrypted. I believe this could be the problem, but: What is the relation between encryption and Apache? I suppose Apache server is requesting the file from the system, rather than trying to access the file bytes! Is there anyway to solve this problem? I don't want to move the folder to /var/www because I am using this Apache for testing, so I want whatever change I make to be immediately reflected, rather than having to copy files which is error prone.

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• "Public" nested classes or not

  - by Frederick

  Suppose I have a class 'Application'. In order to be initialised it takes certain settings in the constructor. Let's also assume that the number of settings is so many that it's compelling to place them in a class of their own. Compare the following two implementations of this scenario. Implementation 1: class Application { Application(ApplicationSettings settings) { //Do initialisation here } } class ApplicationSettings { //Settings related methods and properties here } Implementation 2: class Application { Application(Application.Settings settings) { //Do initialisation here } class Settings { //Settings related methods and properties here } } To me, the second approach is very much preferable. It is more readable because it strongly emphasises the relation between the two classes. When I write code to instantiate Application class anywhere, the second approach is going to look prettier. Now just imagine the Settings class itself in turn had some similarly "related" class and that class in turn did so too. Go only three such levels and the class naming gets out out of hand in the 'non-nested' case. If you nest, however, things still stay elegant. Despite the above, I've read people saying on StackOverflow that nested classes are justified only if they're not visible to the outside world; that is if they are used only for the internal implementation of the containing class. The commonly cited objection is bloating the size of containing class's source file, but partial classes is the perfect solution for that problem. My question is, why are we wary of the "publicly exposed" use of nested classes? Are there any other arguments against such use?

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• Problem with sfRemember cookie / sfGuard Remember me

  - by Tom

  I'm using Symfony 1.4 with Doctrine. Sorry if this is a silly question but what exactly does one need to build on top of the sfDoctrineGuardPlugin to get the "remember me" functionality working? When I login a user, the sfRemember cookie is created with the default 15-day lifetime, and the remember key is saved in the plugin's sf_guard_remember_key table. Without any tweaks to the plugin, the sfGuardSecurityUser SignIn() method creates the cookie, but the Signout() method erases it, leaving no cookie unless you're logged in! Signin(): sfContext::getInstance()->getResponse()->setCookie($remember_cookie, $key, time() + $expiration_age); Signout(): sfContext::getInstance()->getResponse()->setCookie($remember_cookie, '', time() - $expiration_age); I can see that the database table saves the cookie as a relation of sf_guard_user, but that's not much good if the cookie is gone.... I'd be grateful if someone could tell me what I'm missing here, and ideally, if I prevent the Signout() method from removing the cookie, do I need to write code to read the cookie myself or is this automated somewhere/somehow? I've got box-standard Symfony 1.4 and sfDoctrineGuardPlugin installations. It all just seems totally wrong and the documentation on this is non-existent. Any help would appreciated.

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• NSOutlineview - strange behavior after reloading data

  - by matei

  I have a NSOutlineView which loads data from a data source. The table is displayed in a panel. The items shown in the table are items which belong to an object (the relation is one-to many between the object and the items). I have a list of objects in a combo box (in fact a NSPopupButton), and when I select another object in the combo box, I want it's items to be shown in the table (the NSOutlineView). I managed to do all this , however when I select another object from the combo box, not all of it's items are displayed. I have put some logging messages in the data source and it seems that there are some items that are being returned from the data source , but are not shown in the table (and are not queried for children). Now the strange part is that when I click the main window (as I said, all that I described here is in a NSPanel loaded on top of the window) , all the data is displayed correctly. It seems as if clicking the main window triggers something in the NSOutlineView that makes it display the missing items, but I can't tell what it is.

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• PostgreSQL - Why are some queries on large datasets so incredibly slow

  - by Brad Mathews

  Hello, I have two types of queries I run often on two large datasets. They run much slower than I would expect them to. The first type is a sequential scan updating all records: Update rcra_sites Set street = regexp_replace(street,'/','','i') rcra_sites has 700,000 records. It takes 22 minutes from pgAdmin! I wrote a vb.net function that loops through each record and sends an update query for each record (yes, 700,000 update queries!) and it runs in less than half the time. Hmmm.... The second type is a simple update with a relation and then a sequential scan: Update rcra_sites as sites Set violations='No' From narcra_monitoring as v Where sites.agencyid=v.agencyid and v.found_violation_flag='N' narcra_monitoring has 1,700,000 records. This takes 8 minutes. The query planner refuses to use my indexes. The query runs much faster if I start with a set enable_seqscan = false;. I would prefer if the query planner would do its job. I have appropriate indexes, I have vacuumed and analyzed. I optimized my shared_buffers and effective_cache_size best I know to use more memory since I have 4GB. My hardware is pretty darn good. I am running v8.4 on Windows 7. Is PostgreSQL just this slow? Or am I still missing something? Thanks! Brad

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• Using ReadOnlyCollection preventing me from setting up a bi-directional many-to-many relationship

  - by Kevin Pang

  I'm using NHibernate to persist a many-to-many relation between Users and Networks. I've set up both the User and Network class as follows, exposing each's collections as ReadOnlyCollections to prevent direct access to the underlying lists. I'm trying to make sure that the only way a User can be added to a Network is by using its "JoinNetwork" function. However, I can't seem to figure out how to add the User to the Network's list of users since its collection is readonly. public class User { private ISet<Network> _Networks = new HashedSet<Network>(); public ReadOnlyCollection<Network> Networks { get { return new List<Network>(_Networks).AsReadOnly(); } } public void JoinNetwork(Network network) { _Networks.Add(network); // How do I add the current user to the Network's list of users? } } public class Network { private ISet<User> _Users = new HashedSet<User>(); public ReadOnlyCollection<User> Users { get { return new List<User>(_Users).AsReadOnly(); } } }

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• How to use Common Table Expression and check no duplication in sqlserver

  - by vodkhang

  I have a table references to itself. User table: id, username, managerid and managerid links back to id Now, I want to get all the managers including direct manager, manager of direct manager, so on and so forth... The problem is that I do not want to have a unstop recursive sql. So, I want to check if an id alreay in a list, I will not include it anymore. Here is my sql for that: with --the relation for all the subparts of ozsolar including itself all_managers (id, username, managerid, idlist) as ( --seed that is the ozsola part select u1.id, u1.username, u1.managerid, ' ' from users u1, users u2 where u1.id = u2.managerid and u2.id = 6 UNION ALL select u.id, u.username, u.managerid, idlist + ' ' + u.id from all_managers a, users u where a.managerid = u.id and charindex(cast(u.id as nvarchar(5)), idlist) != 0 ) --select the total number of subparts and group by subpart select id, username from all_managers; The problem is that in this line: select u1.id, u1.username, u1.managerid, ' ' The sqlserver complains with me that I can not put ' ' as the initialized for idlist. nvarchar(40) does not work as well. I do not know how to declare it inside a common table expression like this one. Usually, in db2, I can just put varchar(40)

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• CSS3 Gradients and border-radius leading to extraneous background in webkit

  - by iamfriendly

  Hello all, After my 1st question with relation to CSS3 gradients in which I was recreating an 'inner glow' I've now got to the point where I'm not so happy with the way in which webkit renders the effect. Basically, if you give an element a background colour and apply a border radius to it, webkit lets the background colour "bleed" out to fill the surrounding box (making it look a bit awful) To reproduce the undesirable effect, try something like the following section#featured footer p a { color: rgb(255,255,255); text-shadow: 1px 1px 1px rgba(0,0,0,0.6); text-decoration: none; padding: 5px 10px; border-radius: 15px; -moz-border-radius: 15px; -webkit-border-radius: 15px; background: rgb(98,99,100); -moz-box-shadow: inset 0 0 8px rgba(0,0,0, 0.25); -webkit-box-shadow: inset 0 0 8px rgba(0,0,0, 0.25); } You can see an example of this here: http://iamfriendly.clients.friendlygp.com/ Apparently this appears to be a Windows-only problem, so for those on a Mac, here's a screenshot: (Check the 'carry on reading' button) You'll notice that in Safari/Chrome (the latest available public downloads as well as the latest nightlies as far as I can tell), you get a rather ugly background colour bleed. However, in Firefox, you should be able to see what I'm after. If you're in Internet Explorer, woe betide you. Does anyone know of a technique which will allow me to produce the 'correct' effect? Is there a CSS Property which I've missed that tells webkit to only have the background within the border-radius'd part of the containing box. I could potentially use an image, but I'm really trying to avoid it. Naturally, as we're dealing with CSS3 and the landscape is continually changing, I might just have to 'lump' it and revert to an image. However, if anyone can suggest an alternative I would be very much appreciative!

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• PLPGSQL : How to return a record from function executed by INSERT/UPDATE rule?

  - by seas

  Do the following scheme for my database: create sequence data_sequence; create table data_table { id integer primary key; field varchar(100); }; create view data_view as select id, field from data_table; create function data_insert(_new data_view) returns data_view as $$declare _id integer; _result data_view%rowtype; begin _id := nextval('data_sequence'); insert into data_table(id, field) values(_id, _new.field); select * into _result from data_view where id = _id; return _result; end; $$ language plpgsql; create rule insert as on insert to data_view do instead select data_insert(new); Then type in psql: insert into data_view(field) values('abc'); Would like to see something like: id | field ----+--------- 1 | abc Instead see: data_insert ------------- (1, "abc") Is it possible to fix this somehow? Thanks for any ideas. Ultimate idea is to use this in other functions, so that I could obtain id of just inserted record without selecting for it from scratch. Something like: insert into data_view(field) values('abc') returning id into my_variable would be nice but doesn't work with error: ERROR: cannot perform INSERT RETURNING on relation "data_view" HINT: You need an unconditional ON INSERT DO INSTEAD rule with a RETURNING clause. I don't really understand that HINT. I use PostgreSQL 8.4.

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• MVC design question for forms

  - by kenny99

  Hi, I'm developing an app which has a large amount of related form data to be handled. I'm using a MVC structure and all of the related data is represented in my models, along with the handling of data validation from form submissions. I'm looking for some advice on a good way to approach laying out my controllers - basically I will have a huge form which will be broken down into manageable categories (similar to a credit card app) where the user progresses through each stage/category filling out the answers. All of these form categories are related to the main relation/object, but not to each other. Does it make more sense to have each subform/category as a method in the main controller class (which will make that one controller fairly massive), or would it be better to break each category into a subclass of the main controller? It may be just for neatness that the second approach is better, but I'm struggling to see much of a difference between either creating a new method for each category (which communicates with the model and outputs errors/success) or creating a new controller to handle the same functionality. Thanks in advance for any guidance!

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• MySQL & PHP - Creating Multiple Parent Child Relations

  - by Ashok

  Hi, I'm trying to build a navigation system using categories table with hierarchies. Normally, the table would be defined as follows: id (int) - Primary key name (varchar) - Name of the Category parentid (int) - Parent ID of this Category referenced to same table (Self Join) But the catch is that I require that a category can be child to multiple parent categories.. Just like a Has and Belongs to Many (HABTM) relation. I know that if there are two tables, categories & items, we use a join table categories_items to list the HABTM relations. But here i'm not having two tables but only table but should somehow show HABTM relations to itself. Is this be possible using a single table? If yes, How? If not possible, what rules (table naming, fields) should I follow while creating the additional join table? I'm trying to achieve this using CakePHP, If someone can provide CakePHP solution for this problem, that would be awesome. Even if that's not possible, any solution about creating join table is appreciated. Thanks for your time.

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• How to log correct context with Threadpool threads using log4net?

  - by myotherme

  I am trying to find a way to log useful context from a bunch of threads. The problem is that a lot of code is dealt with on Events that are arriving via threadpool threads (as far as I can tell) so their names are not in relation to any context. The problem can be demonstrated with the following code: class Program { private static readonly log4net.ILog log = log4net.LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType); static void Main(string[] args) { new Thread(TestThis).Start("ThreadA"); new Thread(TestThis).Start("ThreadB"); Console.ReadLine(); } private static void TestThis(object name) { var nameStr = (string)name; Thread.CurrentThread.Name = nameStr; log4net.ThreadContext.Properties["ThreadContext"] = nameStr; log4net.LogicalThreadContext.Properties["LogicalThreadContext"] = nameStr; log.Debug("From Thread itself"); ThreadPool.QueueUserWorkItem(x => log.Debug("From threadpool Thread: " + nameStr)); } } The Conversion pattern is: %date [%thread] %-5level %logger [%property] - %message%newline The output is like so: 2010-05-21 15:08:02,357 [ThreadA] DEBUG LogicalContextTest.Program [{LogicalThreadContext=ThreadA, log4net:HostName=xxx, ThreadContext=ThreadA}] - From Thread itself 2010-05-21 15:08:02,357 [ThreadB] DEBUG LogicalContextTest.Program [{LogicalThreadContext=ThreadB, log4net:HostName=xxx, ThreadContext=ThreadB}] - From Thread itself 2010-05-21 15:08:02,404 [7] DEBUG LogicalContextTest.Program [{log4net:HostName=xxx}] - From threadpool Thread: ThreadA 2010-05-21 15:08:02,420 [16] DEBUG LogicalContextTest.Program [{log4net:HostName=xxx}] - From threadpool Thread: ThreadB As you can see the last two rows have no Names of useful information to distinguish the 2 threads, other than manually adding the name to the message (which I want to avoid). How can I get the Name/Context into the log for the threadpool threads without adding it to the message at every call?

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• How to insert an Array/Objet into SQL (bestpractice)

  - by Jason

  I need to store three items as an array in a single column and be able to quickly/easily modify that data in later functions. [---YOU CAN SKIP THIS PART IF YOU TRUST ME--] To be clear, I love and use x_ref tables all the time but an x_ref doesn't work here because this is not a one-to-many relationship. I am making a project management tool that among other things, assigns a user to a project and assigns hours to that project on a weekly basis, per user, sometimes for weeks many weeks into the future. Of course there are many projects, a project can have many team members, a team member can be involved with many projects at one time BUT its not one-to-many because a team member can be working many weeks on the same project but have different hours for different weeks. In other words, each object really is unique. Also/finally, this data can be changed at any time by any team-member - hence it needs to be easily to manipulate. Basically, I need to handle three values (the team member, the week we're talking about, and how many hours) dropped into a project row in the projects table (under the column for project team members) and treated as one item - a team member - that will actually be part of a larger array of all the team members involved on the project. [--END SKIP, START READING HERE :) --] So assuming that the application's general schema and relation tables aren't total crap and that we are in fact up against a wall in this one case to use an array/object as a value for this column, is there a best practice for that? Like a particular SQL data-type? A particular object/array format? CSV? JSON? XML? Most of the app is in C# but (for very odd reasons that I won't explain) we could really use any environment if there is a particular one that handles this well. For the moment, I am thinking either (webservice + JS/JSON) or PHP unserialize/serialize (but I am bit sketched out by the PHP solution because it seems a bit cumbersome when using ajax?) Thoughts anyone?

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• Switch between multiple views while respecting orientation

  - by zoul

  Hello! I have an MVC application with a single model and several views (something like skins). I want the user to be able to switch the views and I can’t get it working with interface orientation. The most simple approach looks like this: - (void) switchToADifferentView: (UIView*) newView { // self is a descendant of UIViewController self.view = newView; } This does not work because the incoming view does not get rotated according to current orientation (until the next orientation change, test case). Is there a way to force the orientation on a view? It looks like the system is trying really hard to keep the interface controls for itself. (Or is it as simple as setting the right transform by hand?) I figured I’d better not switch the views directly and switch controllers instead. This makes sense, as it makes the initial code simpler. But how do I switch controllers that have no “navigation relation” between them? I guess I could use presentModalViewController:, but that seems like a hack. Same goes for navigation controller. If I exchange the controllers by hand, I get the wrong orientation again: - (void) switchToAController: (id) incoming { [currentController.view removeFromSuperview]; [window addSubview:incoming.view]; // does not respect current orientation } Now how the heck do I simply exchange the current controller for another one? Again, the controllers are something like “skins” operating above a shared model, so it really makes no sense to pretend that skin A is a “modal” dialog above skin B or that they’re a part of a navigation stack.

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• whats wrong with this ruby hash?

  - by yaya3

  I'm pretty new to ruby, I keep getting the following error: in gem_original_require': ./helpers/navigation.rb:28: odd number list for Hash (SyntaxError) Any help appreciated... module Sinatra::Navigation def navigation @navigation nav = { primary[0] = { :title => "cheddar", :active => false, :children => { { :title => "cheese", :active => false }, { :title => "ham", :active => false } } }, primary[1] = { :title => "gorgonzola", :active => false, :children => { { :title => "What is the cheese?", :active => false }, { :title => "What cheese", :active => false }, { :title => "What does the cheese tell us?", :active => false, :children => { { :title => "Cheessus", :active => false }, { :title => "The impact of different cheeses / characteristics for cheese in relation to CHSE outcomes", :active => false } } } } } }

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• python NameError: name '<anything>' is not defined (but it is!)

  - by BenjaminGolder

  Note: Solved. It turned out that I was importing a previous version of the same module. It is easy to find similar topics on StackOverflow, where someone ran into a NameError. But most of the questions deal with specific modules and the solution is often to update the module. In my case, I am trying to import a function from a module that I wrote myself. The module is named InfraPy, and it is definitely on sys.path. One particular function (called listToText) in InfraPy returns a NameError, but only when I try to import it into another script. Inside InfraPy, under if __name__=='__main__':, the listToText function works just fine. From InfraPy I can import other functions with no problems. Including from InfraPy import * in my script does not return any errors until I try to use the listToText function. How can this occur? How can importing one particular function return a NameError, while importing all the other functions in the same module works fine? Using python 2.6 on MacOSX 10.6, also encountered the same error running the script on Windows 7, using IronPython 2.6 for .NET 4.0 Thanks. If there are other details you think would be helpful in solving this, I'd be happy to provide them. As requested, here is the function definition inside of InfraPy: def listToText(inputList, folder=None, outputName='list.txt'): ''' Creates a text file from a list (with each list item on a separate line). May be placed in any given folder, but will otherwise be created in the working directory of the python interpreter. ''' fname = outputName if folder != None: fname = folder+'/'+fname f = open(fname, 'w') for file in inputList: f.write(file+'\n') f.close() This function is defined above and outside of if __name__=='__main__': I've tried moving InfraPy around in relation to the script. The most baffling situation is that when InfraPy is in the same folder as the script, and I import using from InfraPy import listToText, I receive this error: NameError: name listToText is not defined. Again, the other functions import fine, they are all defined outside of if __name__=='__main__': in InfraPy.

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• db:migrate creates sequences but doesn't alter table?

  - by RewbieNewbie

  Hello, I have a migration that creates a postres sequence for auto incrementing a primary identifier, and then executes a statement for altering the column and specifying the default value: execute 'CREATE SEQUENCE "ServiceAvailability_ID_seq";' execute <<-SQL ALTER TABLE "ServiceAvailability" ALTER COLUMN "ID" set DEFAULT NEXTVAL('ServiceAvailability_ID_seq'); SQL If I run db:migrate everything seems to work, in that no errors are returned, however, if I run the rails application I get: Mnull value in column "ID" violates not-null constraint I have discovered by executing the sql statement in the migration manually, that this error is because the alter statement isn't working, or isn't being executed. If I manually execute the following statement: CREATE SEQUENCE "ServiceAvailability_ID_seq; I get: error : ERROR: relation "serviceavailability_id_seq" already exists Which means the migration successfully created the sequence! However, if I manually run: ALTER TABLE "ServiceProvider" ALTER COLUMN "ID" set DEFAULT NEXTVAL('ServiceProvider_ID_seq'); SQL It runs successfully and creates the default NEXTVAL. So the question is, why is the migration file creating the sequence with the first execute statement, but not altering the table in the second execute? (Remembering, no errors are output on running db:migrate) Thank you and apologies for tl:dr

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• Creating form using Generic_inlineformset_factory from the Model Form

  - by Prateek

  hello dear all, I wanted to create a edit form with the help of ModelForm. and my models contain a Generic relation b/w classes, so if any one could suggest me the view and a bit of template for the purpose I would be very thankful, as I am new to the language. My models look like:- class Employee(Person): nickname = models.CharField(_('nickname'), max_length=25, null=True, blank=True) blood_type = models.CharField(_('blood group'), max_length=3, null=True, blank=True, choices=BLOOD_TYPE_CHOICES) marital_status = models.CharField(_('marital status'), max_length=1, null=True, blank=True, choices=MARITAL_STATUS_CHOICES) nationality = CountryField(_('nationality'), default='IN', null=True, blank=True) about = models.TextField(_('about'), blank=True, null=True) dependent = models.ManyToManyField(Dependent, through='DependentRelationship') pan_card_number = models.CharField(_('PAN card number'), max_length=50, blank=True, null=True) policy_number = models.CharField(_('policy number'), max_length=50, null=True, blank=True) # code specific details user = models.OneToOneField(User, blank=True, null=True, verbose_name=_('user')) class Person(models.Model): """Person model""" title = models.CharField(_('title'), max_length=20, null=True, blank=True) first_name = models.CharField(_('first name'), max_length=100) middle_name = models.CharField(_('middle name'), max_length=100, null=True, blank=True) last_name = models.CharField(_('last name'), max_length=100, null=True, blank=True) suffix = models.CharField(_('suffix'), max_length=20, null=True, blank=True) slug = models.SlugField(_('slug'), max_length=50, unique=True) class PhoneNumber(models.Model) : phone_number = generic.GenericRelation('PhoneNumber') email_address = generic.GenericRelation('EmailAddress') address = generic.GenericRelation('Address') date_of_birth = models.DateField(_('date of birth'), null=True, blank=True) gender = models.CharField(_('gender'), max_length=1, null=True, blank=True, choices=GENDER_CHOICES) content_type = models.ForeignKey(ContentType, If anyone could suggest me a link or so. it would be a great help........

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• Templates, and C++ operator for logic: B contained by set A

  - by James Morris

  In C++, I'm looking to implement an operator for selecting items in a list (of type B) based upon B being contained entirely within A. In the book "the logical design of digital computers" by Montgomery Phister jr (published 1958), p54, it says: F11 = A + ~B has two interesting and useful associations, neither of them having much to do with computer design. The first is the logical notation of implication... The second is notation of inclusion... This may be expressed by a familiar looking relation, B < A; or by the statement "B is included in A"; or by the boolean equation F11= A + ~B = 1. My initial implementation was in C. Callbacks were given to the list to use for such operations. An example being a list of ints, and a struct containting two ints, min and max, for selection purposes. There, selection would be based upon B = A-min && B <= A-max. Using C++ and templates, how would you approach this after having implemented a generic list in C using void pointers and callbacks? Is using < as an over-ridden operator for such purposes... <ugh> evil? </ugh> (or by using a class B for the selection criteria, implementing the comparison by overloading ?)

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• Why does my GridSplitter not work at all?

  - by Crippledsmurf

  I'm migrating a WinForms app to WPF. Everything has gone well so far except in relation to my attempts to use GridSplitter which I can never seam to make resize anything at run-time. To make sure it wasn't just my code I attempted to compile the GridSplitter sample from LearnWPF.com and it doesn't appear to work either. I am expecting to see the standard resize cursor when I mouse over the splitter which doesn't happen, and as far as I can see there is no other visual representation of the splitter in the window either. What am I missing here? <Window x:Class="UI.Test" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="Test" Height="300" Width="300"> <Grid> <Grid> <Grid.ColumnDefinitions> <ColumnDefinition /> <ColumnDefinition /> </Grid.ColumnDefinitions> <StackPanel Background="#feca00" Grid.Column="0"> <TextBlock FontSize="35" Foreground="#58290A" TextWrapping="Wrap">Left Hand Side</TextBlock> </StackPanel> <GridSplitter/> <Border CornerRadius="10" BorderBrush="#58290A" BorderThickness="5" Grid.Column="1"> <TextBlock FontSize="25" Margin="20" Foreground="#FECA00" TextWrapping="Wrap">Right Hand Side</TextBlock> </Border> </Grid>

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• Hibernate ManyToMany and superclass mapping problem

  - by Jesus Benito

  Hi all, I need to create a relation in Hibernate, linking three tables: Survey, User and Group. The Survey can be visible to a User or to a Group, and a Group is form of several Users. My idea was to create a superclass for User and Group, and create a ManyToMany relationship between that superclass and Survey. My problem is that Group, is not map to a table, but to a view, so I can't split the fields of Group among several tables -which would happen if I created a common superclass-. I thought about creating a common interface, but mapping to them is not allowed. I will probably end up going for a two relations solution (Survey-User and Survey-Group), but I don't like too much that approach. I thought as well about creating a table that would look like: Survey Id | ElementId | Type ElementId would be the Group or UserId, and the type... the type of it. Does anyone know how to achieve it using hibernate annotations? Any other ideas? Thanks a lot

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• General many-to-many relationship problem ( Postgresql )

  - by David

  Hi, i have two tables: CREATE TABLE "public"."auctions" ( "id" VARCHAR(255) NOT NULL, "auction_value_key" VARCHAR(255) NOT NULL, "ctime" TIMESTAMP WITHOUT TIME ZONE NOT NULL, "mtime" TIMESTAMP WITHOUT TIME ZONE NOT NULL, CONSTRAINT "pk_XXXX2" PRIMARY KEY("id"), ); and CREATE TABLE "public"."auction_values" ( "id" NUMERIC DEFAULT nextval('default_seq'::regclass) NOT NULL, "fk_auction_value_key" VARCHAR(255) NOT NULL, "key" VARCHAR(255) NOT NULL, "value" TEXT, "ctime" TIMESTAMP WITHOUT TIME ZONE NOT NULL, "mtime" TIMESTAMP WITHOUT TIME ZONE NOT NULL, CONSTRAINT "pk_XXXX1" PRIMARY KEY("id"), ); if i want to create a many-to-many relationship on the auction_value_key like this: ALTER TABLE "public"."auction_values" ADD CONSTRAINT "auction_values_fk" FOREIGN KEY ("fk_auction_value_key") REFERENCES "public"."auctions"("auction_value_key") ON DELETE NO ACTION ON UPDATE NO ACTION NOT DEFERRABLE; i get this SQL error: ERROR: there is no unique constraint matching given keys for referenced table "auctions" Question: As you might see, i want "auction_values" to be be "reused" by different auctions without duplicating them for every auction... So i don't want a key relation on the "id" field in the auctions table... Am i thinking wrong here or what is the deal? ;) Thanks

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• Examples of monoids/semigroups in programming

  - by jkff

  It is well-known that monoids are stunningly ubiquitous in programing. They are so ubiquitous and so useful that I, as a 'hobby project', am working on a system that is completely based on their properties (distributed data aggregation). To make the system useful I need useful monoids :) I already know of these: Numeric or matrix sum Numeric or matrix product Minimum or maximum under a total order with a top or bottom element (more generally, join or meet in a bounded lattice, or even more generally, product or coproduct in a category) Set union Map union where conflicting values are joined using a monoid Intersection of subsets of a finite set (or just set intersection if we speak about semigroups) Intersection of maps with a bounded key domain (same here) Merge of sorted sequences, perhaps with joining key-equal values in a different monoid/semigroup Bounded merge of sorted lists (same as above, but we take the top N of the result) Cartesian product of two monoids or semigroups List concatenation Endomorphism composition. Now, let us define a quasi-property of an operation as a property that holds up to an equivalence relation. For example, list concatenation is quasi-commutative if we consider lists of equal length or with identical contents up to permutation to be equivalent. Here are some quasi-monoids and quasi-commutative monoids and semigroups: Any (a+b = a or b, if we consider all elements of the carrier set to be equivalent) Any satisfying predicate (a+b = the one of a and b that is non-null and satisfies some predicate P, if none does then null; if we consider all elements satisfying P equivalent) Bounded mixture of random samples (xs+ys = a random sample of size N from the concatenation of xs and ys; if we consider any two samples with the same distribution as the whole dataset to be equivalent) Bounded mixture of weighted random samples Which others do exist?

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• Database design for a media server containing movies, music, tv and everything in between?

  - by user364114

  In the near future I am attempting to design a media server as a personal project. MY first consideration to get the project underway is architecture, it will certainly be web based but more specifically than that I am looking for suggestions on the database design. So far I am considering something like the following, where I am using [] to represent a table, the first text is the table name to give an idea of purpose and the items within {} would be fields of the table. Also not, fid is functional id referencing some other table. [Item {id, value/name, description, link, type}] - this could be any entity, single song or whole music album, game, movie - almost see this as a recursive relation, ie. a song is an item but an album that song is part of is also an item or for example a tv season is an item, with multiple items being tv episodes [Type {id, fid, mime type, etc}] - file type specific information - could identify how code handles streaming/sending this item to a user [Location {id, fid, path to file?}] [Users {id, username, email, password, ...? }] - user account information [UAC {id, fid, acess level}] - i almost feel its more flexible to seperate access control permissions form the user accounts themselves [ItemLog {id, fid, fid2, timestamp}] - fid for user id, and fid2 for item id - this way we know what user access what when [UserLog {id, fid, timestamp}] -both are logs for access, whether login or last item access [Quota {id, fid, cap}] - some sort of way to throttle users from queing up the entire site and letting it download ... Suggestions or comments are welcome as the hope is that this project will be a open source project once some code is laid out.

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• gridviev add new row problem

  - by Dominating

  My relation is from two tables - table A and table B. B has fk ID pointing to A.ID. In gridview for sourse i have choosen A. When I append new row in A its ok.. But with this action I want to add new row in B too and init it with some values which are copies from row number Row given as argument in PasteCopy private void PasteCopy(int Row) { XPDataTableObject forCopy = gridView1.GetRow(Row) as XPDataTableObject; gridViewEcnMaster.AddNewRow(); XPDataTableObject toCopy = gridView1.GetRow(GridControl.NewItemRowHandle) as XPDataTableObject; SetA(forCopy);// working SetB(ref toCopy, forCopy); XPDataTableObject toCopy1 = gridView1.GetFocusedRow() as XPDataTableObject; XPCollection historyForCopy = toCopy1.GetMemberValue("FK___B__ID") as XPCollection; foreach (XPDataTableObject item in historyForCopy) { MessageBox.Show(item.GetMemberValue("USER").ToString()); } } public void SetB(ref XPDataTableObject toCopy, XPDataTableObject forCopy) { XPCollection historyToCopy = toCopy.GetMemberValue("FK__B__ID") as XPCollection; XPCollection historyForCopy = forCopy.GetMemberValue("FK__B__ID") as XPCollection; XPClassInfo cinfo = session.GetClassInfo(typeof(SPM_ECN_DataSet.BDataTable)); foreach (XPDataTableObject item in historyForCopy) { XPDataTableObject historyRecord = new XPDataTableObject(session, cinfo); historyRecord.SetMemberValue("USER", GetCurWinUser().ToString()); historyRecord.SetMemberValue("ID", forCopy.GetMemberValue("ID"));//if not set == null historyToCopy.Add(historyRecord); } } public void SetA(XPDataTableObject forCopy) { gridView1.SetFocusedRowCellValue("VERSION", 1); } What is wrong with this? why its locking all my application after i do this?

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