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  • Cannot use String.Empty as a default value for an optional parameter in C# - then what's the point?

    - by Mikeyg36
    I am reading Effective C# by Bill Wagner. In Item 14 - Minimize Duplicate Initialization Logic, he shows the following example of using the new optional parameters feature in a constructor: public MyClass(int initialCount = 0, string name = "") Notice that he used "" instead of string.Empty. He comments: You'll note [in an example above] that the second constructor specified "" for the default value on the name parameter, rather than the more customary string.Empty. That's because string.Empty is not a compile-time constant. It is a static property defined in the string class. Because it is not a compile constant, you cannot use it for the default value for a parameter. If we cannot use the string.Empty static in all situations, then doesn't that defeat the purpose of it? I thought that we would use it to be sure that we have a system-independent means of referring to the empty string. Is my understanding wrong? Thanks.

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  • What is the best method of assessment for computer science students?

    - by Gavimoss
    This question is a bit more philosophical so feel free to remove if you like but it's been bugging me for the last 4 years! As a final year student I find that exams can be often be passed with a couple of days of cramming, without necessarily retaining or understanding the content i.e. a regurgitation of lecture notes is often enough to gain high marks. A friend of mine is about to graduate with an honours degree whose final year evaluation was based solely on practical work (a project, assignment marks and the creation of a poster) yet all of this work could have been completed by a third party. Personally I don't think either of these methods of assessment is sufficient as I am currently on track for a 1st class honours in artificial intelligence and computer science and believe this is mostly due to my skill in passing exams not my skill as a programmer or my vast in depth knowledge of any of the subjects I have "studied". Surely there is a better way to assess our skills - isn't there?

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  • php require class call from inside method

    - by jera
    from my understanding, require pastes code into the calling php file. what if you were requiring from inside a method...it would paste the entire code/class inside the method, blocking the next statement in the method. eg. function test() { require 'pathtosomeclasscode'; somestatement; // any code after the require is blocked. } how do i get around this, to be able to require code where-ever, without it being pasted in that exact spot? Thanks in advance for your help.

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  • Simple explaination of Arraylists

    - by Jeremy
    I'm new to programming and I'm looking for a simple answer to build my foundation of understanding Arrays. I've used google and searched this site. After a bit of trial and error I get how to make and reference Arrays like thing[3] gets you the fourth thing in the thing array(since 0 is the first). which lets me do something like thing[3].getStupidNumber() to get the StupidNumber of the 4th thing in the thing array. Then I get to ArrayLists which seem to have much more utility but I cant make logical sense of them like Arrays. When i search I cant find this or word this correctly and thus far everything else I've learned clicked easily. so say I make an ArrayList thing with 5 things in it. how do i get to the .getStupidNumber() method inside the fourth thing, if possible? I think if I learn this I can learn the rest on my own. Thanks!

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  • WM6x IMAPIAdviseSink::OnNotify threading issues

    - by violet313
    specifically WM6x, winCE5x Now my current understanding from trawling the msdn etal is that the IMAPIAdviseSink::OnNotify callback can be made from any old thread; from (ce)mapi or perhaps even from a third-party service provider. Under WM6x, i cannot seem to coax an in-thread response by invoking HrThisThreadAdviseSink, since while this function is declared in mapiutil.h, a definition appears not to exist (in cemapi.lib or wherever??) ~But i notice that all the OnNotify callbacks i receive derive from windows messages that i am receiving on my thread (=looks to me like an in-thread implementation in any case under cemapi)... So, can anyone confirm that this is infact always the case -or am i just getting lucky right now? ah, i should add that my advise source is IMAPISession::Advise erm i should also say that i might have cross-posted this on the msdn forum -but they're mostly numptys over there,,

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  • Passing values across pages ASP.net

    - by GigaPr
    Hi i need to pass a long list of Ids from one page to another, i was thinking of using querystring but taking in consideration that the number of ids to be passed may reach 300 i think is not a good idea. an option from my understanding may be the use of session, this seems to me an optimal solution in my case but on the other hand I can certainly clear the session when the user performs a certain action and the list of ids is not longer needed, but if the user leaves the page without performing any action i want to clear the session, how can i do it? If multiple users are using the same functionality do i need the session's items to be confused or the session is for a single user? I am working in asp.net c# Thanks

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  • identify documents from results of mahout clustering

    - by Tejas
    I am using mahout to cluster text documents indexed using solr. I have used the "text" field in the document to form vectors. Then I used the k-means driver in mahout for clustering and then the clusterdumper utility to dump the results. I am having difficulty in understanding the output results from the dumper. I could see the clusters formed with term vectors in those clusters. But how do I extract the documents from these clusters. I want the result to be the input documents appearing in different clusters.

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  • Why is volatile not considered useful in multithreaded C or C++ programming?

    - by Michael E
    As demonstrated in this answer I recently posted, I seem to be confused about the utility (or lack thereof) of volatile in multi-threaded programming contexts. My understanding is this: any time a variable may be changed outside the flow of control of a piece of code accessing it, that variable should be declared to be volatile. Signal handlers, I/O registers, and variables modified by another thread all constitute such situations. So, if you have a global int foo, and foo is read by one thread and set atomically by another thread (probably using an appropriate machine instruction), the reading thread sees this situation in the same way it sees a variable tweaked by a signal handler or modified by an external hardware condition and thus foo should be declared volatile (or, for multithreaded situations, accessed with memory-fenced load, which is probably a better a solution). How and where am I wrong?

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  • TypeError: Error #1009 Actionscript 3 help.

    - by matt_t
    I am extremely frustrated. I'm following a tutorial and mimicing it on my own. I've been able to sort out most of the errors so far but this one has me stumped. I have tried replacing all of the class files with the tutorial specimen ones but i still get the error. TypeError: Error #1009: Cannot access a property or method of a null object reference. at com.senocular.utils::KeyObject/construct() at com.senocular.utils::KeyObject() at com.asgamer.basics1::Ship() at com.asgamer.basics1::Engine() Now, not really understanding the error properly I paste dumped the files online for you to look at. Ship class: textbin.com/78z35 Engine class: textbin.com/32b24 KeyObject class: textbin.com/p2725 As the error still occured when using the specimen class files I really have no idea where to begin. I will gladly try out any suggestions (although later on, i'm tired now ;). Thanks very much.

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  • Perl, creating a hash of hashes.

    - by Mike
    Based on my current understanding of hashes in Perl, I would expect this code to print "hello world." It instead prints nothing. %a=(); %b=(); $b{str} = "hello"; $a{1}=%b; $b=(); $b{str} = "world"; $a{2}=%b; print "$a{1}{str} $a{2}{str}"; I assume that a hash is just like an array, so why can't I make a hash contain another?

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  • Database permissions and ORMs

    - by Jonn
    I've been using .NET's Entity Framework a lot lately and have absolutely no wish to go back to using Stored Procedures. Been shocked though that the company I'm building this project for had a policy where applications were only given accounts that only had permissions to access stored procedures! Apparently, they believe that there's a security risk involved in allowing applications to access the tables/views directly. I don't get this. My first question is, can someone enlighten me as to what kind of security risk applications having direct access to the database may pose? AND If that's the case, are there any other ORM solutions that can provide a workaround to this (I can't think of any logical possibility atm) that would allow me to circumvent the restrictions on the user account to be assigned to me? OR is my understanding that I'd need direct permissions for the tables and views wrong?

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  • Ruby on Rails- :symbols, @iVars and "strings" - oh my!

    - by Meltemi
    New to Rails and trying to get my head around when/why to use :symbols, @ivars , "strings" within the framework. I think I understand the differences between them conceptually only one :symbol instance per project one @ivar per instance multiple "strings" - as they are created whenever referenced (?) Feel free to correct me! The main confusion comes from understanding the rules & conventions of what Rails expects - where and WHY? I'm sure there's an "Ah ha!" moment coming but I haven't had it yet...as it seems pretty arbitrary to me (coming from C/Obj-C). -thx

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  • YUI and/or jQuery for a new project?

    - by Hortitude
    If I am starting a new project how should I pick between using YUI 2, YUI 3 and jQuery? I know there are a bunch of questions/answers already about can you use them together, but I am trying to figure out what criteria I should be thinking about to make my decision. Are they overlapping? Is one better at GUI and the other better at internals? Do they play well together? My understanding from other questions is that they can live in different namespaces, so they can live together, but that doesn't necessarily mean that it is good to use both. Thanks!

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  • Question about domain models & their visibility...

    - by Another SO User
    I was involved in an interesting debate about the visibility of domain models & was wondering if people here have any good guidance. Per my understanding of MDA, we need not expose the domain model throughout the application layers & tiers The reason being that any change to the domain model has an impact in the overall application The wise thing to do would be to expose light-weight object (DTO's) which are a small sub-set of the domain model to abstract the actual model On the flip side, any change to the domain model would mean changing various DTO's throughout the application for the change to be visible, while if we do expose the domain model, then the change is in a single location Hope to see some comments & thoughts about this. Appreciate all the help!

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  • How to see contents of deployed datasource?

    - by callisto
    I've inherited a project (without a handy handover) that contains reports published to a Reporting Server (2005). MY SSRS knowledge is 4 years stale, so I need your help. I need to edit one of the published reports, is this possible? I also want to peek into the Data Source on the RS, coz that's probably where I can change stuff. I'll add more info as I get a better understanding of what exactly to ask. EDIT: I found a project for some of the reports, opened up in VS2005 BI. Still, how do see where the Data Source gets its data? It brins back 56 fields but I dont know which tables/stored procs/queries are used to get these.

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  • Hibernate / MySQL Bulk insert problem

    - by Marty Pitt
    I'm having trouble getting Hibernate to perform a bulk insert on MySQL. I'm using Hibernate 3.3 and MySQL 5.1 At a high level, this is what's happening: @Transactional public Set<Long> doUpdate(Project project, IRepository externalSource) { List<IEntity> entities = externalSource.loadEntites(); buildEntities(entities, project); persistEntities(project); } public void persistEntities(Project project) { projectDAO.update(project); } This results in n log entries (1 for every row) as follows: Hibernate: insert into ProjectEntity (name, parent_id, path, project_id, state, type) values (?, ?, ?, ?, ?, ?) I'd like to see this get batched, so the update is more performant. It's possible that this routine could result in tens-of-thousands of rows generated, and a db trip per row is a killer. Why isn't this getting batched? (It's my understanding that batch inserts are supposed to be default where appropriate by hibernate).

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  • AJAX XMLHttpRequest POST X-Domain

    - by Tom
    Hi Guys, I am sending an AJAX request using POST over X-Domain for a widget we are producing for our website. The problem we are facing is that this is getting blocked. My question is - for "modern browsers" [Chrome, Safari, FF, IE8] - it is my understanding that setting "Access-Control" headers Access-Control-Allow-Origin: http://www.test.com Access-Control-Allow-Methods: POST, GET, OPTIONS Access-Control-Allow-Headers: * Access-Control-Max-Age: 1728000 Will allow these "POST" requests to work ? But for IE7 we need to implement some "custom" JSONP solution? Am I correct in this ?

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  • Why is new showat attribute required when using code generation?

    - by Patrick Karcher
    When I generate code using T4 templates in Visual Studio 2010, I get the following error for each of my asp controls when I try to compile: Control "ddState" is missing required attribute "showat". I have never gotten this error in previous versions of .NET. Further, I don't get this error when I manually construct my pages either by dragging/dropping, nor do I get it when I type out the control text myself. When I generate code, I have to manually add showat="client" to my tag for the compiler to be happy. It was my understanding that I never had to explicitly specify this tag. The following: <asp:dropdownlist id="ddState" runat="server" showat="client" /> solves the problem. Why do I have to add this to generated code but not other times? (It's a VS-2010 webforms project, using VB, in case that makes a difference.)

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  • replacing data.frame element-wise operations with data.table (that used rowname)

    - by Harold
    So lets say I have the following data.frames: df1 <- data.frame(y = 1:10, z = rnorm(10), row.names = letters[1:10]) df2 <- data.frame(y = c(rep(2, 5), rep(5, 5)), z = rnorm(10), row.names = letters[1:10]) And perhaps the "equivalent" data.tables: dt1 <- data.table(x = rownames(df1), df1, key = 'x') dt2 <- data.table(x = rownames(df2), df2, key = 'x') If I want to do element-wise operations between df1 and df2, they look something like dfRes <- df1 / df2 And rownames() is preserved: R> head(dfRes) y z a 0.5 3.1405463 b 1.0 1.2925200 c 1.5 1.4137930 d 2.0 -0.5532855 e 2.5 -0.0998303 f 1.2 -1.6236294 My poor understanding of data.table says the same operation should look like this: dtRes <- dt1[, !'x', with = F] / dt2[, !'x', with = F] dtRes[, x := dt1[,x,]] setkey(dtRes, x) (setkey optional) Is there a more data.table-esque way of doing this? As a slightly related aside, more generally, I would have other columns such as factors in each data.table and I would like to omit those columns while doing the element-wise operations, but still have them in the result. Does this make sense? Thanks!

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  • What are some Servlet Container pros and cons for a Solr installation?

    - by danieltalsky
    The SolrInstall wiki page lists seven different server / Servlet Containers compatible with Solr: Tomcat Jetty Resin JBoss WebSphere Weblogic Glassfish I'm sure that "best" is subjective, so I'll just say my criteria are: easiest to set up, best for search performance with a smallish, infrequently-updated dataset, and with the fewest number of gotchas. Jetty and Tomcat both have apt-get solr packages, so they're clearly the frontrunners for some. Jetty is used in the demo install, but there's some notes that Jetty has some difficulties handling Unicode in some cases. Tomcat is a common choice but my understanding is that it's not as lightweight and has a lot of features not needed by Solr. Is it worth considering any of the others? Are there some important pro's and cons I should be aware of?

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  • Can an application's Service ever run in a different process?

    - by kpdvx
    If an application begins a Service via bindService or startService, will this Service object ever run from a process different from that of the application? I ask because many Android example projects begin a service and communicate to them using IPC which seems wholly unnecessary considering that, according to the Android Service documentation, "... services, like other application objects, run in the main thread of their hosting process." IPC, AIDL, and the IBinder interface only seem useful if connecting to a Service started by an application other than your own. Is this a correct or fair understanding?

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  • Variable loss in redirected bash while loop

    - by James Hadley
    I have the following code for ip in $(ifconfig | awk -F ":" '/inet addr/{split($2,a," ");print a[1]}') do bytesin=0; bytesout=0; while read line do if [[ $(echo ${line} | awk '{print $1}') == ${ip} ]] then increment=$(echo ${line} | awk '{print $4}') bytesout=$((${bytesout} + ${increment})) else increment=$(echo ${line} | awk '{print $4}') bytesin=$((${bytesin} + ${increment})) fi done < <(pmacct -s | grep ${ip}) echo "${ip} ${bytesin} ${bytesout}" >> /tmp/bwacct.txt done Which I would like to print the incremented values to bwacct.txt, but instead the file is full of zeroes: 91.227.223.66 0 0 91.227.221.126 0 0 127.0.0.1 0 0 My understanding of Bash is that a redirected for loop should preserve variables. What am I doing wrong?

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  • .NET platform independant sync framework

    - by Quandary
    Question: I need to synchronize a few ActionScript files from my computer to a network share (backup). I saw a quick fix would be using Microsoft Sync Framework for this, and write a windows service. My problem is I also use Linux, and before I start with MS vendor lockin, is there any sync framework/library/whatever I could use that works accross platform? Or does the MS sync framework work on Linux, too? It is my understanding that it is a wrapper around some com objects, thus it wouldn't work. All I need is synchronizing files. So never mind the database part, although it would be nice to have it, too.

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  • JPA and aggregate functions. How do I use the result of the query?

    - by Bogdan
    Hey guys, I'm new to ORM stuff and I need some help understanding something. Let's assume I have the following standard SQL query: SELECT *, COUNT(test.testId) AS noTests FROM inspection LEFT JOIN test ON inspection.inspId = test.inspId GROUP BY inspection.inspId which I want to use in JPA. I have an Inspection entity with a one-to-many relationship to a Test entity. (an inspection has many tests) I tried writing this in JPQL: Query query = em.createQuery("SELECT insp, COUNT(???what???) FROM Inspection insp LEFT JOIN insp.testList " + "GROUP BY insp.inspId"); 1) How do I write the COUNT clause? I'd have to apply count to elements from the test table but testList is a collection, so I can't do smth like COUNT(insp.testList.testId) 2) Assuming 1 is resolved, what type of object will be returned. It will definitely not be an Inspection object... How do I use the result?

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  • Creating a computer with pencil and paper [closed]

    - by Justian Meyer
    This concept has been brought to my attention before, but many people might know it from this popular comic here, where he uses stones instead of points on a paper. This concept is so abstract to me. A full-functioning computer that can manage algorithms, input, output, etc. without electricity? Surely, it's difficult to visualize because my definition of a computer is not exactly what the word sounds like COMPUTE-ER. Can someone help me bring the concept to light - the understanding, how to make one, etc? It seems like it'd be an interesting read, although I think I wouldn't be able to make it do anything. Many thanks in advance for responses. I've tried searching Google, but all I got were ways to diagram code and chart ideas. -.Justian.

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