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  • Multiple-File Template Implementation

    - by Maxpm
    With normal functions, the declaration and definition are often separated across multiple files like so: // Foo.h namespace Foo { void Bar(); } . // Foo.cpp #include "Foo.h" void Foo::Bar() { cout << "Inside function." << endl; } It is my understanding that this cannot be done with templates. The declaration and definition must not be separate because the appropriate form of the template is created "on-demand" when needed. So, how and where are templates typically defined in a multiple-file project like this? My intuition is that it would be in Foo.cpp because that's where the "meat" of functions normally is, but on the other hand it's the header file that's going to be included.

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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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  • Rails + simple role system through associative table

    - by user202411
    So I have the Ninja model which has many Hovercrafts through ninja_hovercrafts (which stores the ninja_id and the hovercraft_id). It is of my understanding that this kind of arrangement should be set in a way that the associative table stores only enough information to bind two different classes. But I'd like to use the associative table to work as a very streamlined authorization hub on my application. So i'd also like this table to inform my system if this binding makes the ninja the pilot or co-pilot of a given hovercraft, through a "role" field in the table. My questions are: Is this ugly? Is this normal? Are there methods built into rails that would help me to automagically create Ninjas and Hovercrafts associations WITH the role? For exemple, could I have a nested form to create both ninjas and hcs in a way that the role field in ninjas_hovercrafts would be also filled? If managing my application roles this way isn't a good idea, whats the non-resource heavy alternative (my app is being designed trying to avoid scalability problems such as excessive joins, includes, etc) thank you

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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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  • 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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  • JVM specification and Java compiler code useful for SCJP preparation ?

    - by BenoitParis
    I'm preparing the SCJP exam with the almost official study book ("SCJP Sun Certified Programmer for Java 6 Exam 310-065") I understand that Java programming is writting code that fulfills a certain high-level contract; So that Java can stay platform-independent. However, I have trouble understanding and remembering things when it comes to highly specific SCJP items (and they are numerous) The book stays high-level and does not provide examples of how one compiler would handle things. This is the same thing for runtime issues (JVM level): things are too much abstract for me. Rules often seems arbitrary and therefore, with no well defined purpose, are difficult to remember. Or maybe it's that sometimes I just don't get the underlying purpose. And here is the question: Would a JVM specification and/or some java compiler code help in preparing the SCJP? Have you had the need for such material or is the book sufficient enough? Also, please share the resources you used, apart from the book.

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  • Value was either too large or too small for an Int16 error

    - by Barlow Tucker
    I am working on fixing a bug in VB that is giving this error. I am new to VB, so there is some syntax that I am not fully understanding. The code that is throwing the error says: .Row(itemIndex).Item("parentIndex") = CLng(oID) + 1000000 I understand that adding 1000000 is too much for an int16. I can't change that value (not right now anyway). What I don't understand, and can't seem to find, is what .Row is referring too. Any ideas?

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  • Vim and clang_complete, how to explicitly compile my code

    - by puller
    I use Vim with clang_complete for omnicompletion. The plugin is automatically triggered when I need completion, e.g., after I type . or -> to access an object members or methods (see attached screenshot). The plugin works really nice, however I would need a way to trigger it manually (i.e. to compile my code for syntax checking). This is useful for two reasons: Static syntax checking Clear previous errors which have been fixed (which otherwise will remain in their buffer). See the two screenshots below for a better understanding. Any help is appreciated. Thanks. Screenshot 1 Screenshot 2

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  • Copy of Access mdb database being updated by live database

    - by James
    I'm trying to compute statistics for data held in an Access .mdb database. In order to avoid interfering with the live database, I'm working from a copy which I made by simply using copy-paste in Windows Explorer. The copy resides in the same directory, but with a different name. I'm using R and RODBC to connect to the copy of the file. The strange thing is that new data that is being updated on the original live database is appearing in my queries. This is despite the file timestamps of the copy not changing at all. It is also causing some slowdown in the live database. My understanding is that the .mdb files are standalone, or is this not the case? Should I have copied the database in a different way?

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  • Problem with dependencies in m2eclipse

    - by MH
    Hi, I have a problem with m2eclipse and Nexus. Normally, when you create a new Maven Project in Eclipse, you can select an Archetype like maven-archetype-quickstart from the Nexus Indexer. Unfortunately, the Nexus Indexer doesn't show anything at all. But the worst part about all this is, that the "Add Dependency" menue doesn't work. (For a better understanding: By clicking on the "Dependencies" tab, you can usually click on a button in order to enter a groupId or artifactId. That's the menue what I am talking about. If I enter for example "junit", it shows no search results.) Does anybody know this issue? How could I fix it? Thanks a million in advance for any help.

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  • How can I speed up line by line reading of an ASCII file? (C++)

    - by Jon
    Here's a bit of code that is a considerable bottleneck after doing some measuring: //----------------------------------------------------------------------------- // Construct dictionary hash set from dictionary file //----------------------------------------------------------------------------- void constructDictionary(unordered_set<string> &dict) { ifstream wordListFile; wordListFile.open("dictionary.txt"); string word; while( wordListFile >> word ) { if( !word.empty() ) { dict.insert(word); } } wordListFile.close(); } I'm reading in ~200,000 words and this takes about 240 ms on my machine. Is the use of ifstream here efficient? Can I do better? I'm reading about mmap() implementations but I'm not understanding them 100%. The input file is simply text strings with *nix line terminations.

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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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  • 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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  • what the java command's -jar option really does

    - by JBoy
    Does the -jar option of the java command also compile the sources before running the main method? I believe so but i would like to have a better understanding of the internal process, from the man page you can clearly see a small workflow sequence: -jar Execute a program encapsulated in a JAR file. The first argument is the name of a JAR file instead of a startup class name. In order for this option to work, the manifest of the JAR file must contain a line of the form Main-Class: classname. Here, classname identifies the class having the public static void main(String[] args) method that serves as your application's starting point. See the Jar tool reference page and the Jar trail of the Java Tutorial @ But it does not mention that it compiles the sources.

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  • Why are my margins still collapsing?

    - by Brandon Dorsey
    My code in this "Fiddle" shows that I have adjacent elements which vertical margins are collapsing on one another. I understand that due to the nature of vertical margins in css, the largest of the two is chosen, In my case the p tag. What I am having trouble with is trying to break the margins by using a 1px border or 1px padding. I've seen it work with other workarounds such as position:absolute or float method. I am not understanding why using 1px border or padding is not working properly to give me 15px of space.

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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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  • 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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  • 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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  • 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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  • How to write a simple usb driver?

    - by ScReYm0
    I make this treat because you are closing my other before i get my answer. Here is my answer clear and exactly what i want to do! I wanna create a usb driver, so my own C application be able to get into my flash drive and take information from the imported flash drive. OS: Windows Please don't close it again I still cant find my answer... more details I start my app/which contains my USB driver/ i plug-in my flash and its shows in Explorer that this drive is plugged and it is accessible, while that's happening, my app is checking that file data.txt EXIST if that file exist, program run next function, if not program, my program runs down/exit/! I hope that this helps understanding my idea...

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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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  • C99 strict aliasing rules in C++ (GCC)

    - by Checkers
    As far as I understand, GCC supports all of its C99 features in C++. But how is C99 strict aliasing handled in C++ code? I know that casting with C casts between unrelated types is not strict-aliasing-safe and may generate incorrect code, but what about C++? Since strict aliasing is not part of C++ standard (is that correct?), GCC must be specifying the semantics itself. I figure const_cast and static_cast cast between related types, hence they are safe, while reinterpret_cast can break strict aliasing rules. Is this a correct understanding?

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  • Replacing a C++ ActiveX component with a .NET implementation?

    - by Leon Breedt
    I have existing managed and unmanaged software using an ActiveX component supplied by a third party to perform some communications, but it is now required that this communication be routed through my application. Ideally I'd be able to install a .NET component which will expose exactly the same interface, and will be usable as a drop-in replacement. However, I am running into the limits of my understanding of COM, which admittedly is quite minimal. How best to ensure that my implementation of the interface is 100% binary compatible with the existing object? How do I ensure that applications use my implementation of the interface instead of the legacy implementation? Is it simply a matter of registering my implementation, and unregistering the legacy one? How do I ensure it's a "drop-in" replacement, and requires no changes to existing software? How do I ensure unmanaged code can use it without issue? Note: I am able to require that .NET 4.0 be used, if that will make things simpler.

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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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  • 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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