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• What exactly is a reentrant function?

  - by eSKay

  Most of the times, the definition of reentrance is quoted from Wikipedia: A computer program or routine is described as reentrant if it can be safely called again before its previous invocation has been completed (i.e it can be safely executed concurrently). To be reentrant, a computer program or routine: Must hold no static (or global) non-constant data. Must not return the address to static (or global) non-constant data. Must work only on the data provided to it by the caller. Must not rely on locks to singleton resources. Must not modify its own code (unless executing in its own unique thread storage) Must not call non-reentrant computer programs or routines. How is safely defined? If a program can be safely executed concurrently, does it always mean that it is reentrant? What exactly is the common thread between the six points mentioned that I should keep in mind while checking my code for reentrant capabilities? Also, Are all recursive functions reentrant? Are all thread-safe functions reentrant? Are all recursive and thread-safe functions reentrant? While writing this question, one thing comes to mind: Are the terms like reentrance and thread safety absolute at all i.e. do they have fixed concrete definations? For, if they are not, this question is not very meaningful. Thanks!

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• Boost's "cstdint" Usage

  - by patt0h

  Boost's C99 stdint implementation is awfully handy. One thing bugs me, though. They dump all of their typedefs into the boost namespace. This leaves me with three choices when using this facility: Use "using namespace boost" Use "using boost::[u]<type><width>_t" Explicitly refer to the target type with the boost:: prefix; e.g., boost::uint32_t foo = 0; Option ? 1 kind of defeats the point of namespaces. Even if used within local scope (e.g., within a function), things like function arguments still have to be prefixed like option ? 3. Option ? 2 is better, but there are a bunch of these types, so it can get noisy. Option ? 3 adds an extreme level of noise; the boost:: prefix is often = to the length of the type in question. My question is: What would be the most elegant way to bring all of these types into the global namespace? Should I just write a wrapper around boost/cstdint.hpp that utilizes option ? 2 and be done with it? Also, wrapping the header like so didn't work on VC++ 10 (problems with standard library headers): namespace Foo { #include <boost/cstdint.hpp> using namespace boost; } using namespace Foo; Even if it did work, I guess it would cause ambiguity problems with the ::boost namespace.

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• horizontal uiview's controls unresponsive.. or how to foul up a view hierarchy

  - by Oldmicah

  Hello all, I'm working on an app that has two sections, a config section and a results section. My config section needs to be 2 separate views (horizontal and vert, and yes, I can hear the intake of breath from here), with one rotatable view for the results. b/c of layout restraints and a lot of pain around rotation, I'm not using a navigation controller. I've been experiencing the joys of rotation experimentation and have settled upon keeping my views contained as subviews of my view controller. i.e. view controller.view.subviews = configH, configV, and results. I then use the controller.view bringSubviewToFront to bring the either the configH, configV, or the result view to the front. Rotation works-queue(humor intended) the angelic choirs... almost. What's happening is that my configV button's are responsive, but when the device (or simulator) is rotated, my configH controls are not. (configV is the second subview added, but the first one to be brought to the front because app comes up in portrait mode) The controls on the results view also work. Plan B was to assign the controller.view to configH, configV, or results. All of my controls now work, but rotation is now fouled up. Question 1: Is there a better way to do this? (a horizontal and vertical config view and a rotatable results view) Question 2: Does the above suggest a design issue, or is it more likely that my addled brain is just missing something in my own code. (nothing from the peanut gallery please) many thanks!

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• What are the arguments against the inclusion of server side scripting in JavaScript code blocks?

  - by James Wiseman

  I've been arguing for some time against embedding server-side tags in JavaScript code, but was put on the spot today by a developer who seemed unconvinced The code in question was a legacy ASP application, although this is largely unimportant as it could equally apply to ASP.NET or PHP (for example). The example in question revolved around the use of a constant that they had defined in ServerSide code. 'VB Const MY_CONST: MY_CONST = 1 If sMyVbVar = MY_CONST Then 'Do Something End If //JavaScript if (sMyJsVar === "<%= MY_CONST%>"){ //DoSomething } My standard arguments against this are: Script injection: The server-side tag could include code that can break the JavaScript code Unit testing. Harder to isolate units of code for testing Code Separation : We should keep web page technologies apart as much as possible. The reason for doing this was so that the developer did not have to define the constant in two places. They reasoned that as it was a value that they controlled, that it wasn't subject to script injection. This reduced my justification for (1) to "We're trying to keep the standards simple, and defining exception cases would confuse people" The unit testing and code separation arguments did not hold water either, as the page itself was a horrible amalgam of HTML, JavaScript, ASP.NET, CSS, XML....you name it, it was there. No code that was every going to be included in this page could possibly be unit tested. So I found myself feeling like a bit of a pedant insisting that the code was changed, given the circumstances. Are there any further arguments that might support my reasoning, or am I, in fact being a bit pedantic in this insistence?

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• Comparing lists in Standard ML

  - by user1050640

  I am extremely new to SML and we just got out first programming assignment for class and I need a little insight. The question is: write an ML function, called minus: int list * int list -> int list, that takes two non-decreasing integer lists and produces a non-decreasing integer list obtained by removing the elements from the first input list which are also found in the second input list. For example, minus( [1,1,1,2,2], [1,1,2,3] ) = [1,2] minus( [1,1,2,3],[1,1,1,2,2] ) = [3] Here is my attempt at answering the question. Can anyone tell me what I am doing incorrectly? I don't quite understand parsing lists. fun minus(xs,nil) = [] | minus(nil,ys) = [] | minus(x::xs,y::ys) = if x=y then minus(xs,ys) else x :: minus(x,ys); Here is a fix I just did, I think this is right now? fun minus(L1,nil) = L1 | minus(nil,L2) = [] | minus(L1,L2) = if hd(L1) > hd(L2) then minus(L1,tl(L2)) else if hd(L1) = hd(L2) then minus(tl(L1),tl(L2)) else hd(L1) :: minus(tl(L1), L2);

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• How does one implement storage/retrieval of smart-search/mailbox features?

  - by humble_coder

  Hi All, I have a question regarding implementation of smart-search features. For example, consider something like "smart mailboxes" in various email applications. Let's assume you have your data (emails) stored in a database and, depending on the field for which the query will be created, you present different options to the end user. At the moment let's assume the Subject, Verb, Object approach… For instance, say you have the following: SUBJECTs: message, to_address, from_address, subject, date_received VERBs: contains, does_not_contain, is_equal_to, greater_than, less_than OBJECTs: ??????? Now, in case it isn't clear, I want a table structure (although I'm not opposed to an external XMLesque file of some sort) to store (and later retrieve/present) my criteria for smart searches/mailboxes for later use. As an example, using SVO I could easily store then reconstruct a query for "date between two dates" -- simply use "date greater than" AND "date less than". However, what if, in the same smart search, I wanted a "between" OR'ed with another criterion? You can see that it might get out of hand -- not necessarily in the query creation (as that is rather simplistic), but in the option presentation and storage mechanism. Perhaps I need to think more on a more granular level. Perhaps I need to simply allow the user to select AND or OR for each entry independently instead of making it an ALL OR NOTHING type smart search (i.e. instead of MATCH ALL or MATCH ANY, I need to simply allow them to select -- I just don't want it to turn into a Hydra). Any input would be most appreciated. My apologies if the question is a bit incoherent. It is late, and I my brain is toast. Best.

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• Document management, SCM ?

  - by tsunade

  Hello, This might not be a hard core programming question, but it's related to some of the tools used by programmers I suspect. So we're a bunch of people each with a bunch of documents and a bunch of different computers on a bunch of operating systems (well, only 2, linux and windows). The best way these documents can be stored/managed is if they were available offline (the laptop might not always be online) but also synchronized between all the machines. Having a server with extra reliable storage be a "base repository" seems like a good idea to me. Using a SCM comes to my mind and I've tried Subversion, and it seems to be a good thing that it uses a centralized repository - but: When checking out the total size of the checkout is roughly double the original size. Big files or big repositories seem to slow it down. Also I've tried rsync, which might work - but it's a bit rough when it comes to the potential conflict. Finally I've tried Unison (which is a wrapping of rsync, I think) and while it works it becomes horribly slow for the big directories we have here since it has to scan everything. So the question is - is there a SCM tool out there that is actually practial to use for a big bunch of both small and big files? If thats a NO - does anyone know other tools that do this job? Thanks for reading :)

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• minimum L sum in a mxn matrix - 2

  - by hilal

  Here is my first question about maximum L sum and here is different and hard version of it. Problem : Given a mxn *positive* integer matrix find the minimum L sum from 0th row to the m'th row . L(4 item) likes chess horse move Example : M = 3x3 0 1 2 1 3 2 4 2 1 Possible L moves are : (0 1 2 2), (0 1 3 2) (0 1 4 2) We should go from 0th row to the 3th row with minimum sum I solved this with dynamic-programming and here is my algorithm : 1. Take a mxn another Minimum L Moves Sum array and copy the first row of main matrix. I call it (MLMS) 2. start from first cell and look the up L moves and calculate it 3. insert it in MLMS if it is less than exists value 4. Do step 2. until m'th row 5. Choose the minimum sum in the m'th row Let me explain on my example step by step: M[ 0 ][ 0 ] sum(L1 = (0, 1, 2, 2)) = 5 ; sum(L2 = (0,1,3,2)) = 6; so MLMS[ 0 ][ 1 ] = 6 sum(L3 = (0, 1, 3, 2)) = 6 ; sum(L4 = (0,1,4,2)) = 7; so MLMS[ 2 ][ 1 ] = 6 M[ 0 ][ 1 ] sum(L5 = (1, 0, 1, 4)) = 6; sum(L6 = (1,3,2,4)) = 10; so MLMS[ 2 ][ 2 ] = 6 ... the last MSLS is : 0 1 2 4 3 6 6 6 6 Which means 6 is the minimum L sum that can be reach from 0 to the m. I think it is O(8*(m-1)*n) = O(m*n). Is there any optimal solution or dynamic-programming algorithms fit this problem? Thanks, sorry for long question

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• UITableView superClass for delegate?

  - by fuzzygoat

  A quick question, I am setting a delegate for UITableView and I have a question regarding setting the delegate and dataSource properties. I have noticed that the properties for delegate and dataSource are not available, I was thinking that adopting the protocols would make them available. But I am now thinking that I maybe have the superclass for my delegate class wrong. Currently I have: -(void)viewDidLoad { TestDelegate *tempDelegate = [[TestDelegate alloc] init]; [self setMyDelegate:tempDelegate]; // setDelegate // setDataSource [tempDelegate release]; [super viewDidLoad]; } My interface for TestDelegate looks like: @interface TestDelegate : NSObject <UITableViewDelegate, UITableViewDataSource> { NSArray *listData; int myCounter; } Can I ask if the above should be: @interface TestDelegate : UITableView <UITableViewDelegate, UITableViewDataSource> { NSArray *listData; int myCounter; } gary EDIT: I think it might be right as NSObject, I have a viewtableView in IB, thats what I will need to connect my delegate class to. I added to tableView in IB so maybe I just need to make it available in Xcode.

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• Entity Framework - Many to Many Subquery

  - by Jorin

  I asked a question about this previously but my database structure has changed, and while it made other things simpler, now this part is more complicated. Here is the previous question. At the time, my EF Context had a UsersProjects object because there were other properties. Now that I've simplified that table, it is just the keys, so all my EF context knows about is Users and Projects and the M2M relationship between them. There is no more UsersProjects as far as EF knows. So my goal is to say "show me all the users who are working on projects with me." in SQL, this would go something like: SELECT * FROM Users INNER JOIN UsersProjects ON Users.ID=UsersProjects.UserID WHERE ProjectID IN (SELECT ProjectID FROM UsersProjects WHERE UserID=@UserID) and I started in EF with something like this: var myProjects = (from p in edmx.Projects where p.Users.Contains(edmx.Users.FirstOrDefault(u => u.Email == UserEmail)) orderby p.Name select p).ToList(); var associatedUsers = (from u in edmx.Users where myProjects.Contains(?????????) //where myProjects.Any(????????) select u); The trick is finding what to put in the ????????. Anyone help here?

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• Facebook SSO authorize in safari but not in facebook app

  - by Pedro Calero

  My problem: I has developed an app with Facebook SSO in my iPhone/iPad. It was working OK. But I have changed the certificate of my app (so now it has new app ID). I also have changed the "iOS pack ID" property in Facebook: I deleted the old app ID and I added the new one. But now my app doesn't do the Facebook SSO when Facebook app is installed. It does it OK when Facebook app is not installed and it uses Safari. I have read this question and this question that say the problem is the "iOS pack ID" and app ID don't match. I have checked it a lot of times, and it is the same. I have put the old app ID in the "iOS pack ID" property of Facebook, but it still doesn't work. I don't know if Facebook take a time to check if my app ID is valid, and how they show the result. I have been a lot of time with this issue. It seem like the problem is the iOS pack ID is not exactly the app ID, but it is not the problem: they are exactly the same. Thank you very much.

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• Give More Prominence To DIV or <P> That Is After Floating DIV

  - by Aahan Krish

  Consider this HTML: <div id="entry-content"> <div id="my-300px-ad">AD CODE HERE</div> <p><img src="file.jpg" alt="file" /></p> <p>SOME TEXT</p> <p>SOME MORE TEXT</p> </div> Now, consider that the div#my-300px-ad is floating right. Would it be possible for me to have the image in the next paragraph show up before the ad so that the TEXT in its following paragraphs can wrap around the ad? For example, like this: Why so...? The thing is, due to various reasons (including Google) I want to avoid placing an ad in BETWEEN the post's content. CSS only I am sure that something like this would be possible with some JavaScript code. But I am looking for a CSS-based solution only. (Cross-browser compatibility, = IE8) Please note that ONLY the CSS of div#my-300px-ad can be changed. Nothing else should be touched as this is not a static HTML page, besides they are articles. PS: It was hard to frame a one-line question for this. Please feel free to edit the question's title if it can be made more clear.

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• How does DateTime.Now affect query plan caching in SQL Server?

  - by Bill Paetzke

  Question: Does passing DateTime.Now as a parameter to a proc prevent SQL Server from caching the query plan? If so, then is the web app missing out on huge performance gains? Possible Solution: I thought DateTime.Today.AddDays(1) would be a possible solution. It would pass the same end-date to the sql proc (per day). And the user would still get the latest data. Please speak to this as well. Given Example: Let's say we have a stored procedure. It reports data back to a user on a webpage. The user can set a date range. If the user sets today's date as the "end date," which includes today's data, the web app passes DateTime.Now to the sql proc. Let's say that one user runs a report--5/1/2010 to now--over and over several times. On the webpage, the user sees 5/1/2010 to 5/4/2010. But the web app passes DateTime.Now to the sql proc as the end date. So, the end date in the proc will always be different, although the user is querying a similar date range. Assume the number of records in the table and number of users are large. So any performance gains matter. Hence the importance of the question. Example proc and execution (if that helps to understand): CREATE PROCEDURE GetFooData @StartDate datetime @EndDate datetime AS SELECT * FROM Foo WHERE LogDate >= @StartDate AND LogDate < @EndDate Here's a sample execution using DateTime.Now: EXEC GetFooData '2010-05-01', '2010-05-04 15:41:27' -- passed in DateTime.Now Here's a sample execution using DateTime.Today.AddDays(1) EXEC GetFooData '2010-05-01', '2010-05-05' -- passed in DateTime.Today.AddDays(1) The same data is returned for both procs, since the current time is: 2010-05-04 15:41:27.

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• Why adding custom objects to List<T> in ApplicationSettingsBase via constructor doesn't work?

  - by BadNinja

  This is pretty closely related to another SO question. Using the example below, could someone explain to me why adding a new List<Foo> where each of Foo's properties are explicitly set causes the ApplicationSettingsBase.Save() method to correctly store the data, whereas adding a new Foo to the list via a constructor (where the constructor sets the property values) does not work? Thanks! public class Foo { public Foo(string blah, string doh) { this.Blah = blah; this.Doh = doh; } public Foo() { } public string Blah { get; set; } public string Doh { get; set; } } public sealed class MySettings : ApplicationSettingsBase { [UserScopedSetting] public List<Foo> MyFoos { get { return (List<Foo>)this["MyFoos"]; } set { this["MyFoos"] = value; } } } // Here's the question... private void button1_Click(object sender, EventArgs e) { MySettings mySettings = new MySettings(); // Adding new Foo's to the list like this doesn't work. List<Foo> theList = new List<Foo>() { new Foo("doesn't","work") }; // But doing it like this DOES work. List<Foo> theList = new List<Foo>() { new Foo() {Blah = "DOES", Doh = "work"} }; mySettings.MyFoos = theList; mySettings.Save(); }

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• Where do objects merge/join data in a 3-tier model?

  - by BerggreenDK

  Its probarbly a simple 3-tier problem. I just want to make sure we use the best practice for this and I am not that familiary with the structures yet. We have the 3 tiers: GUI: ASP.NET for Presentation-layer (first platform) BAL: Business-layer will be handling the logic on a webserver in C#, so we both can use it for webforms/MVC + webservices DAL: LINQ to SQL in the Data-layer, returning BusinessObjects not LINQ. DB: The SQL will be Microsoft SQL-server/Express (havent decided yet). Lets think of setup where we have a database of [Persons]. They can all have multiple [Address]es and we have a complete list of all [PostalCode] and corresponding citynames etc. The deal is that we have joined a lot of details from other tables. {Relations}/[tables] [Person]:1 --- N:{PersonAddress}:M --- 1:[Address] [Address]:N --- 1:[PostalCode] Now we want to build the DAL for Person. How should the PersonBO look and when does the joins occure? Is it a business-layer problem to fetch all citynames and possible addressses pr. Person? or should the DAL complete all this before returning the PersonBO to the BAL ? Class PersonBO { public int ID {get;set;} public string Name {get;set;} public List<AddressBO> {get;set;} // Question #1 } // Q1: do we retrieve the objects before returning the PersonBO and should it be an Array instead? or is this totally wrong for n-tier/3-tier?? Class AddressBO { public int ID {get;set;} public string StreetName {get;set;} public int PostalCode {get;set;} // Question #2 } // Q2: do we make the lookup or just leave the PostalCode for later lookup? Can anyone explain in what order to pull which objects? Constructive criticism is very welcome. :o)

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• Using Dispose on a Singleton to Cleanup Resources

  - by ImperialLion

  The question I have might be more to do with semantics than with the actual use of IDisposable. I am working on implementing a singleton class that is in charge of managing a database instance that is created during the execution of the application. When the application closes this database should be deleted. Right now I have this delete being handled by a Cleanup() method of the singleton that the application calls when it is closing. As I was writing the documentation for Cleanup() it struck me that I was describing what a Dispose() method should be used for i.e. cleaning up resources. I had originally not implemented IDisposable because it seemed out of place in my singleton, because I didn't want anything to dispose the singleton itself. There isn't currently, but in the future might be a reason that this Cleanup() might be called but the singleton should will need to still exist. I think I can include GC.SuppressFinalize(this); in the Dispose method to make this feasible. My question therefore is multi-parted: 1) Is implementing IDisposable on a singleton fundamentally a bad idea? 2) Am I just mixing semantics here by having a Cleanup() instead of a Dispose() and since I'm disposing resources I really should use a dispose? 3) Will implementing 'Dispose()' with GC.SuppressFinalize(this); make it so my singleton is not actually destroyed in the case I want it to live after a call to clean-up the database.

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• How do I create a class repository in Java and do I really need it?

  - by Roman

  I have a large number of objects which are identified by names (strings). So, I would like to have a kind of mapping from object name to the class instances. I was told that in this situation I can use a "repository" class which works like that: Server myServer = ServerRepository.getServer("NameOfServer"); So, if there is already an object (sever) with the "NameOfServer" it will be returned by the "getServer". If such an object does not exist yet, it will be created and returned by the "getServer". So, my question is how to program such a "repository" class? In this class I have to be able to check if there is an instance of a given class such that it has a given value of a given field. How can I do it? I need to have a kind of loop over all existing object of a given class? Another part of my question is why I cannot use associative arrays (associative container, map, mapping, dictionary, finite map)? (I am not sure how do you call it in Java) In more details, I have an "array" which maps names of objects to objects. So, whenever I create a new object, I add a new element to the array: myArray["NameOfServer"] = new Server("NameOfServer").

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• php form submit and the resend infromation screen

  - by Para

  Hello, I want to ask a best practice question. Suppose I have a form in php with 3 fields say name, email and comment. I submit the form via POST. In PHP I try and insert the date into the database. Suppose the insertion fails. I should now show the user an error and display the form filled in with the data he previously inserted so he can correct his error. Showing the form in it's initial state won't do. So I display the form and the 3 fields are now filled in from PHP with echo or such. Now if I click refresh I get a message saying "Are you sure you want to resend information?". OK. Suppose after I insert the data I don't carry on but I redirect to the same page but with the necessary parameters in the query string. This makes the message go away but I have to carry 3 parameters in the query string. So my question is: How is it better to do this? I want to not carry around lots of parameters in the query string but also not get that error. How can this be done? Should I use cookies to store the form information.

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• problem configure JBoss to work with JNDI(2)

  - by Spiderman

  in continuation to the question from last week: http://stackoverflow.com/questions/2828237/problem-configure-jboss-to-work-with-jndi I'm trying to bind datasource in JBoss and use it in my application. In my struggling, I already managed to avoid the javax.naming.NameNotFoundException by: 1. using in java new InitialContext().lookup(connection); instead of new JndiObjectFactoryBean().setJndiName(connection); 2. changing the connection name from: 'jndi-name' to 'java:jndi-name' Now the problem is that the datasouce that I get from the lookup is null. I created the datsource file: <datasources> <local-tx-datasource> <jndi-name>bilby</jndi-name> <connection-url>jdbc:oracle:myURL</connection-url> <driver-class>oracle.jdbc.OracleDriver </driver-class> <user-name>myUsername</user-name> <password>myPassword</password> <exception-sorter-class- name>org.jboss.resource.adapter.jdbc.vendor.OracleExceptionSorter</exception-sorter-class-name> <metadata> <type-mapping>Oracle9i</type-mapping> </metadata> </local-tx-datasource> </datasources> and put it under \server\default\deploy\oracle-ds.xml I get during runtime the line: 18:37:56,560 INFO [ConnectionFactoryBindingService] Bound ConnectionManager 'jb oss.jca:service=DataSourceBinding,name=bilby' to JNDI name 'java:bilby' So my question is - why do I get null as my datasource???

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• Treating differential operator as algebraic entity

  - by chappar

  I know that this question is offtopic and don't belong here. But i didn't know somewhere else to ask. So here is the question. I was reading e:the story of a number by Eli Maor, where he treats differential operator as just like any algebraic entity. For example if we have a differential equation like y’’ + 5y’ - 6y = 0. This can be treaed as (D^2 + 5D – 6)y = 0. So, either y = 0 (trivial solution) or (D^2 + 5D – 6) = 0. Factoring out above equation we get (D-1)(D+6)= 0 with solutions as D = 1 and D = -6. Since D does not have any meaning on its own, multiplying by y on both the sides we get Dy = y and Dy = -6y for which the solutions are Ae^x and Be^-6x. Combining these 2 solutions we get Ae^x + Be^-6x. Now my doubt is this approach break when we have an equation like D^2y = 0. Which means y = 0 (again trivial) or D^2 = 0 which means D = 0. Now Dy = y*0 = 0. That means y = C ( a constant). The actual answer should be Cx. I know that it is stupidity to treat D^2 = 0 as D = 0, it led me to doubt the entire process of treating differential equation as algebraic equation. Can someone throw light on this? Or any other site where i might get answer?

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• Understanding how software testing works and what to test.

  - by RHaguiuda

  Intro: I've seen lots of topics here on SO about software testing and other terms I don't understand. Problem: As a beginner developer I, unfortunately, have no idea how software testing works, not even how to test a simple function. This is a shame, but thats the truth. I also hope this question can help others beginners developers too. Question: Can you help me to understand this subject a little bit more? Maybe some questions to start would help: When I develop a function, how should I test it? For example: when working with a sum function, should I test every input value possible or just some limits? How about testing functions with strings as parameters? In a big program, do I have to test every single piece of code of it? When you guys program do you test every code written? How automated test works and how can I try one? How tools for automated testing works and what they do? I`ve heard about unit testing. Can I have a brief explanation on this? What is a testing framework? If possible please post some code with examples to clarify the ideas. Any help on this topic is very welcome! Thanks.

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• Exporting de-aggregated data

  - by Ben

  I'm currently working on a data export feature for a survey application. We are using SQL2k8. We store data in a normalized format: QuestionId, RespondentId, Answer. We have a couple other tables that define what the question text is for the QuestionId and demographics for the RespondentId... Currently I'm using some dynamic SQL to generate a pivot that joins the question table to the answer table and creates an export, its working... The problem is that it seems slow and we don't have that much data (less than 50k respondents). Right now I'm thinking "why am I 'paying' to de-aggregate the data for each query? Why don't I cache that?" The data being exported is based on dynamic criteria. It could be "give me respondents that completed on x date (or range)" or "people that like blue", etc. Because of that, I think I have to cache at the respondent level, find out what respondents are being exported and then select their combined cached de-aggregated data. To me the quick and dirty fix is a totally flat table, RespondentId, Question1, Question2, etc. The problem is, we have multiple clients and that doesn't scale AND I don't want to have to maintain the flattened table as the survey changes. So I'm thinking about putting an XML column on the respondent table and caching the results of a SELECT * FROM Data FOR XML AUTO WHERE RespondentId = x. With that in place, I would then be able to get my export with filtering and XML calls into the XML column. What are you doing to export aggregated data in a flattened format (CSV, Excel, etc)? Does this approach seem ok? I worry about the cost of XML functions on larger result sets (think SELECT RespondentId, XmlCol.value('//data/question_1', 'nvarchar(50)') AS [Why is there air?], XmlCol.RinseAndRepeat)... Is there a better technology/approach for this? Thanks!

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• ControlCollection extension method optimization

  - by Johan Leino

  Hi, got question regarding an extension method that I have written that looks like this: public static IEnumerable<T> FindControlsOfType<T>(this ControlCollection instance) where T : class { T control; foreach (Control ctrl in instance) { if ((control = ctrl as T) != null) { yield return control; } foreach (T child in FindControlsOfType<T>(ctrl.Controls)) { yield return child; } } } public static IEnumerable<T> FindControlsOfType<T>(this ControlCollection instance, Func<T, bool> match) where T : class { return FindControlsOfType<T>(instance).Where(match); } The idea here is to find all controls that match a specifc criteria (hence the Func<..) in the controls collection. My question is: Does the second method (that has the Func) first call the first method to find all the controls of type T and then performs the where condition or does the "runtime" optimize the call to perform the where condition on the "whole" enumeration (if you get what I mean). secondly, are there any other optimizations that I can do to the code to perform better. An example can look like this: var checkbox = this.Controls.FindControlsOfType<MyCustomCheckBox>( ctrl => ctrl.CustomProperty == "Test" ) .FirstOrDefault();

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• select all values from a dimension for which there are facts in all other dimensions

  - by ideasculptor

  I've tried to simplify for the purposes of asking this question. Hopefully, this will be comprehensible. Basically, I have a fact table with a time dimension, another dimension, and a hierarchical dimension. For the purposes of the question, let's assume the hierarchical dimension is zip code and state. The other dimension is just descriptive. Let's call it 'customer' Let's assume there are 50 customers. I need to find the set of states for which there is at least one zip code in which EVERY customer has at least one fact row for each day in the time dimension. If a zip code has only 49 customers, I don't care about it. If even one of the 50 customers doesn't have a value for even 1 day in a zip code, I don't care about it. Finally, I also need to know which zip codes qualified the state for selection. Note, there is no requirement that every zip code have a full data set - only that at least one zip code does. I don't mind making multiple queries and doing some processing on the client side. This is a dataset that only needs to be generated once per day and can be cached. I don't even see a particularly clean way to do it with multiple queries short of simply brute-force iteration, and there are a heck of a lot of 'zip codes' in the data set (not actually zip codes, but the there are approximately 100,000 entries in the lower level of the hierarchy and several hundred in the top level, so zipcode-state is a reasonable analogy)

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• C# class can not disguise to be another class because GetType method cannot be override

  - by zinking

  there is a statement in the CLR via C# saying in C#, one class cannot disguise to be another, because GetType is virutal and thus it cannot be override but I think in C# we can still hide the parent implementation of GetType. I must missed something if I hide the base GetType implementation then I can disguise my class to be another class, is that correct? The key here is not whether GetType is virutal or not, the question is can we disguise one class to be another in C# Following is the NO.4 answer from the possible duplicate, so My question is more on this. is this kind of disguise possible, if so, how can we say that we can prevent class type disguise in C# ? regardless of the GetType is virtual or not While its true that you cannot override the object.GetType() method, you can use "new" to overload it completely, thereby spoofing another known type. This is interesting, however, I haven't figured out how to create an instance of the "Type" object from scratch, so the example below pretends to be another type. public class NotAString { private string m_RealString = string.Empty; public new Type GetType() { return m_RealString.GetType(); } } After creating an instance of this, (new NotAString()).GetType(), will indeed return the type for a string. share|edit|flag answered Mar 15 at 18:39 Dr Snooze 213 By almost anything that looks at GetType has an instance of object, or at the very least some base type that they control or can reason about. If you already have an instance of the most derived type then there is no need to call GetType on it. The point is as long as someone uses GetType on an object they can be sure it's the system's implementation, not any other custom definition. – Servy Mar 15 at 18:54 add comment

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