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  • Declarative programming vs. Imperative programming

    - by EpsilonVector
    I feel very comfortable with Imperative programming. I never have trouble expressing algorithmically what I want the computer to do once I figured out what is it that I want it to do. But when it comes to languages like SQL or Relational Algebra I often get stuck because my head is too used to Imperative programming. For example, suppose you have the relations band(bandName, bandCountry), venue(venueName, venueCountry), plays(bandName, venueName), and I want to write a query that says: all venueNames such that for every bandCountry there's a band from that country that plays in venue of that name. In my mind I immediately go "for each venueName iterate over all the bandCountries and for each bandCountry get the list of bands that come from it. If none of them play in venueName, go to next venueName. Else, at the end of the bandCountries iteration add venueName to the set of good venueNames". ...but you can't talk like that in SQL and I actually need to think about how to formulate this, with the intuitive Imperative solution constantly nagging in the back of my head. Did anybody else had this problem? How did you overcome this? Did you figured out a paradigm shift? Made a map from Imperative concepts to SQL concepts to translate Imperative solutions into Declarative ones? Read a good book? PS I'm not looking for a solution to the above query, I did solve it.

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  • Imperative Programming v/s Declarative Programming v/s Functional Programming

    - by kaleidoscope
    Imperative Programming :: Imperative programming is a programming paradigm that describes computation in terms of statements that change a program state. In much the same way as the imperative mood in natural languages expresses commands to take action, imperative programs define sequences of commands for the computer to perform. The focus is on what steps the computer should take rather than what the computer will do (ex. C, C++, Java). Declarative Programming :: Declarative programming is a programming paradigm that expresses the logic of a computation without describing its control flow. It attempts to minimize or eliminate side effects by describing what the program should accomplish, rather than describing how to go about accomplishing it. The focus is on what the computer should do rather than how it should do it (ex. SQL). A  C# example of declarative v/s. imperative programming is LINQ. With imperative programming, you tell the compiler what you want to happen, step by step. For example, let's start with this collection, and choose the odd numbers: List<int> collection = new List<int> { 1, 2, 3, 4, 5 }; With imperative programming, we'd step through this, and decide what we want: List<int> results = new List<int>(); foreach(var num in collection) {     if (num % 2 != 0)           results.Add(num); } Here’s what we are doing: *Create a result collection *Step through each number in the collection *Check the number, if it's odd, add it to the results With declarative programming, on the other hand, we write the code that describes what you want, but not necessarily how to get it var results = collection.Where( num => num % 2 != 0); Here, we're saying "Give us everything where it's odd", not "Step through the collection. Check this item, if it's odd, add it to a result collection." Functional Programming :: Functional programming is a programming paradigm that treats computation as the evaluation of mathematical functions and avoids state and mutable data. It emphasizes the application of functions.Functional programming has its roots in the lambda calculus. It is a subset of declarative languages that has heavy focus on recursion. Functional programming can be a mind-bender, which is one reason why Lisp, Scheme, and Haskell have never really surpassed C, C++, Java and COBOL in commercial popularity. But there are benefits to the functional way. For one, if you can get the logic correct, functional programming requires orders of magnitude less code than imperative programming. That means fewer points of failure, less code to test, and a more productive (and, many would say, happier) programming life. As systems get bigger, this has become more and more important. To know more : http://stackoverflow.com/questions/602444/what-is-functional-declarative-and-imperative-programming http://msdn.microsoft.com/en-us/library/bb669144.aspx http://en.wikipedia.org/wiki/Imperative_programming   Technorati Tags: Ranjit,Imperative Programming,Declarative programming,Functional Programming

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  • Building Tag Cloud Declarative ADF Component

    - by Arunkumar Ramamoorthy
    When building a website, there could a requirement to add a tag cloud to let the users know the popular tags (or terms) used in the site. In this blog, we would build a simple declarative component to be used as tag cloud in the page. To start with, we would first create the declarative component, which could display the tag cloud. We will do that by creating a new custom application from the new gallery. Give a name for the app and the project and from the new gallery, let us create a new ADF Declarative Component We need to specify the name for the declarative component, attributes in it etc. as follows For displaying the tags as cloud, we need to pass the content to this component. So, we will create an attribute to hold the values for the tag. Let us name it as "value" and make it as java.lang.String  type. Once after this, to hold the component, we need to create a tag library. This can be done by clicking on the Add Tag Library button. Clicking on OK buttons in all the open dialogs would create a declarative component for us. Now, we need to display the tag cloud based on the value passed to the component. To do that, we assume that the value is a Tree Binding and has two attributes in it, say "Name" and "Weight". To make a tag cloud, we would put together the "Name" in a loop and set it's font size based on the "Weight". After putting our logic to work, here is how the source look Attributes added to the declarative components can be retrieved by using #{attrs.<attribute_name>}. Now, we need to deploy this project as ADF Library Jar file, so that this can be distributed to the consuming applications. We'll select ADF Library Jar as type and create the profile. We would be getting the jar file after deployment. To test the functionality, we could create a simple Fusion Web Application. To add our custom component to the consuming application, we can create a file system connection pointing to the location where the jar file is and add it or, add through the project properties of the ViewController project. Now, our custom component has been added to the consuming application. We could test that by creating a VO in the model project with a query like, select 'Faces' as Name,25 as Weight from dual union all select 'ADF', 15 from dual  union all select 'ADFdi', 30 from dual union all select 'BC4J', 20 from dual union all select 'EJB', 40 from dual union all select 'WS', 35 from dual Add this VO to the AppModule, so that it would be exposed to the data control. Then, we could create a jspx page, and add a tree binding to the VO created. We can now see our Tag Cloud declarative component is available in the component palette.  It can be inserted from the component palette to our page and set it's value property to CollectionModel of the tree binding created. Now that we've created the Declarative component and added that to our page successfully, we can run the page to see how it looks. As per the query, the Tags are displayed in different fonts, based on their weight.

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  • suggestions for declarative GUI programming in Java

    - by Jason S
    I wonder if there are any suggestions for declarative GUI programming in Java. (I abhor visual-based GUI creator/editor software, but am getting a little tired of manually instantiating JPanels and Boxes and JLabels and JLists etc.) That's my overall question, but I have two specific questions for approaches I'm thinking of taking: JavaFX: is there an example somewhere of a realistic GUI display (e.g. not circles and rectangles, but listboxes and buttons and labels and the like) in JavaFX, which can interface with a Java sourcefile that accesses and updates various elements? Plain Old Swing with something to parse XUL-ish XML: has anyone invented a declarative syntax (like XUL) for XML for use with Java Swing? I suppose it wouldn't be hard to do, to create some code based on STaX which reads an XML file, instantiates a hierarchy of Swing elements, and makes the hierarchy accessible through some kind of object model. But I'd rather use something that's well-known and documented and tested than to try to invent such a thing myself. JGoodies Forms -- not exactly declarative, but kinda close & I've had good luck with JGoodies Binding. But their syntax for Form Layout seems kinda cryptic. edit: lots of great answers here! (& I added #3 above) I'd be especially grateful for hearing any experiences any of you have had with using one of these frameworks for real-world applications. p.s. I did try a few google searches ("java gui declarative"), just didn't quite know what to look for.

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  • How to better start learning programming - with imperative or declarative languages?

    - by user712092
    Someone is interested in learning to program. What language paradigm should I recomend him - imperative or declarative? And what programming language should he start with? I think that declarative because it is closer to math. And I would say that Prolog might be the best start because it is based on logic and programs are short. On the other hand at school we started learning from imperative languages and I am not sure whether there is a benefit to start with them instead of declarive ones. Thanks. :)

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  • E: Sub-process /usr/bin/dpkg returned an error code (1)

    - by Joel
    I cant install or uppdate anything on my system 12.04 I get the error... installArchives() failed: dpkg: error processing libqt4-xmlpatterns (--configure): libqt4-xmlpatterns:amd64 4:4.8.1-0ubuntu4.2 cannot be configured because libqt4-xmlpatterns:i386 is in a different version (4:4.8.1-0ubuntu4.3) dpkg: error processing libqt4-xmlpatterns:i386 (--configure): libqt4-xmlpatterns:i386 4:4.8.1-0ubuntu4.3 cannot be configured because libqt4-xmlpatterns:amd64 is in a different version (4:4.8.1-0ubuntu4.2) dpkg: dependency problems prevent configuration of libqt4-declarative:i386: libqt4-declarative:i386 depends on libqt4-xmlpatterns (= 4:4.8.1-0ubuntu4.3); however: Package libqt4-xmlpatterns:i386 is not configured yet. dpkg: error processing libqt4-declarative:i386 (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of libqt4-declarative: libqt4-declarative depends on libqt4-xmlpatterns (= 4:4.8.1-0ubuntu4.3); however: Version of libqt4-xmlpatterns on system is 4:4.8.1-0ubuntu4.2. dpkg: error processing libqt4-declarative (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of libqtgui4:i386: libqtgui4:i386 depends on libqt4-declarative (= 4:4.8.1-0ubuntu4.3); however: Package libqt4-declarative:i386 is not configured yet. dpkg: error processing libqtgui4:i386 (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of libqtgui4: No apport report written because the error message indicates its a followup error from a previous failure. No apport report written because the error message indicates its a followup error from a previous failure. No apport report written because MaxReports is reached already No apport report written because MaxReports is reached already No apport report written because MaxReports is reached already No apport report written because MaxReports is reached already libqtgui4 depends on libqt4-declarative (= 4:4.8.1-0ubuntu4.3); however: Package libqt4-declarative is not configured yet. dpkg: error processing libqtgui4 (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of libqt4-designer: libqt4-designer depends on libqtgui4 (= 4:4.8.1-0ubuntu4.3); however: Package libqtgui4 is not configured yet. dpkg: error processing libqt4-designer (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of libqt4-designer:i386: libqt4-designer:i386 depends on libqtgui4 (= 4:4.8.1-0ubuntu4.3); however: Package libqtgui4:i386 is not configured yet. dpkg: error processing libqt4-designer:i386 (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of libqt4-opengl: libqt4-opengl depends on libqtgui4 (= 4:4.8.1-0ubuntu4.3); however: Package libqtgui4 is not configured yet. dpkg: error processing libqt4-opengl (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of libqt4-opengl:i386: libqt4-opengl:i386 depends on libqtgui4 (= 4:4.8.1-0ubuntu4.3); however: Package libqtgui4:i386 is not configured yet. dpkg: error processing libqt4-opengl:i386 (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of libqt4-qt3support: libqt4-qt3support depends on libqt4-designer (= 4:4.8.1-0ubuntu4.3); however: Package libqt4-designer is not configured yet. libqt4-qt3support depends on libqtgui4 (= 4:4.8.1-0ubuntu4.3); however: Package libqtgui4 is not configured yet. dpkg: error processing libqt4-qt3support (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of libqt4-qt3support:i386: libqt4-qt3support:i386 depends on libqt4-designer (= 4:4.8.1-0ubuntu4.3); however: Package libqt4-designer:i386 is not configured yet. libqt4-qt3support:i386 depends on libqtgui4 (= 4:4.8.1-0ubuntu4.3); however: Package libqtgui4:i386 is not configured yet. dpkg: error processing libqt4-qt3support:i386 (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of libqt4-scripttools:i386: libqt4-scripttools:i386 depends on libqtgui4 (= 4:4.8.1-0ubuntu4.3); however: Package libqtgui4:i386 is not configured yet. dpkg: error processing libqt4-scripttools:i386 (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of libqt4-svg: libqt4-svg depends on libqtgui4 (= 4:4.8.1-0ubuntu4.3); however: Package libqtgui4 is not configured yet. dpkg: error processing libqt4-svg (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of libqt4-svg:i386: libqt4-svg:i386 depends on libqtgui4 (= 4:4.8.1-0ubuntu4.3); however: Package libqtgui4:i386 is not configured yet. dpkg: error processing libqt4-svg:i386 (--configure): dependency problems - leaving unconfigured Errors were encountered while processing: libqt4-xmlpatterns libqt4-xmlpatterns:i386 libqt4-declarative:i386 libqt4-declarative libqtgui4:i386 libqtgui4 libqt4-designer libqt4-designer:i386 libqt4-opengl libqt4-opengl:i386 libqt4-qt3support libqt4-qt3support:i386 libqt4-scripttools:i386 libqt4-svg libqt4-svg:i386 Error in function: dpkg: dependency problems prevent configuration of libqt4-declarative: libqt4-declarative depends on libqt4-xmlpatterns (= 4:4.8.1-0ubuntu4.3); however: Version of libqt4-xmlpatterns on system is 4:4.8.1-0ubuntu4.2. dpkg: error processing libqt4-declarative (--configure): dependency problems - leaving unconfigured dpkg: error processing libqt4-xmlpatterns (--configure): libqt4-xmlpatterns:amd64 4:4.8.1-0ubuntu4.2 cannot be configured because libqt4-xmlpatterns:i386 is in a different version (4:4.8.1-0ubuntu4.3) dpkg: error processing libqt4-xmlpatterns:i386 (--configure): libqt4-xmlpatterns:i386 4:4.8.1-0ubuntu4.3 cannot be configured because libqt4-xmlpatterns:amd64 is in a different version (4:4.8.1-0ubuntu4.2) dpkg: dependency problems prevent configuration of libqtgui4: libqtgui4 depends on libqt4-declarative (= 4:4.8.1-0ubuntu4.3); however: Package libqt4-declarative is not configured yet. dpkg: error processing libqtgui4 (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of libqt4-declarative:i386: libqt4-declarative:i386 depends on libqt4-xmlpatterns (= 4:4.8.1-0ubuntu4.3); however: Package libqt4-xmlpatterns:i386 is not configured yet. dpkg: error processing libqt4-declarative:i386 (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of libqt4-svg: libqt4-svg depends on libqtgui4 (= 4:4.8.1-0ubuntu4.3); however: Package libqtgui4 is not configured yet. dpkg: error processing libqt4-svg (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of libqt4-opengl: libqt4-opengl depends on libqtgui4 (= 4:4.8.1-0ubuntu4.3); however: Package libqtgui4 is not configured yet. dpkg: error processing libqt4-opengl (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of libqt4-designer: libqt4-designer depends on libqtgui4 (= 4:4.8.1-0ubuntu4.3); however: Package libqtgui4 is not configured yet. dpkg: error processing libqt4-designer (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of libqt4-qt3support: libqt4-qt3support depends on libqt4-designer (= 4:4.8.1-0ubuntu4.3); however: Package libqt4-designer is not configured yet. libqt4-qt3support depends on libqtgui4 (= 4:4.8.1-0ubuntu4.3); however: Package libqtgui4 is not configured yet. dpkg: error processing libqt4-qt3support (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of libqtgui4:i386: libqtgui4:i386 depends on libqt4-declarative (= 4:4.8.1-0ubuntu4.3); however: Package libqt4-declarative:i386 is not configured yet. dpkg: error processing libqtgui4:i386 (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of libqt4-svg:i386: libqt4-svg:i386 depends on libqtgui4 (= 4:4.8.1-0ubuntu4.3); however: Package libqtgui4:i386 is not configured yet. dpkg: error processing libqt4-svg:i386 (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of libqt4-opengl:i386: libqt4-opengl:i386 depends on libqtgui4 (= 4:4.8.1-0ubuntu4.3); however: Package libqtgui4:i386 is not configured yet. dpkg: error processing libqt4-opengl:i386 (--configure): dependency problems - leaving unconfigured dpkg: dependency problems prevent configuration of libqt4-designer:i386: joel@Joel-PC:~$ sudo apt-get install -f [sudo] password for joel: Läser paketlistor... Färdig Bygger beroendeträd Läser tillståndsinformation... Färdig Korrigerar beroenden.... Färdig Följande paket har installerats automatiskt och är inte längre nödvändiga: kde-l10n-sv language-pack-kde-sv-base language-pack-kde-zh-hans-base calligra-l10n-engb calligra-l10n-sv calligra-l10n-zhcn language-pack-kde-en kde-l10n-engb language-pack-kde-sv language-pack-zh-hans-base kde-l10n-zhcn language-pack-zh-hans language-pack-kde-zh-hans language-pack-kde-en-base Använd "apt-get autoremove" för att ta bort dem. Följande ytterligare paket kommer att installeras: libqt4-xmlpatterns Följande paket kommer att uppgraderas: libqt4-xmlpatterns 1 att uppgradera, 0 att nyinstallera, 0 att ta bort och 22 att inte uppgradera. 15 är inte helt installerade eller borttagna. Behöver hämta 0 B/1 033 kB arkiv. Efter denna åtgärd kommer ytterligare 0 B utrymme användas på disken. Vill du fortsätta [J/n]? J dpkg: fel vid hantering av libqt4-xmlpatterns (--configure): libqt4-xmlpatterns:amd64 4:4.8.1-0ubuntu4.2 cannot be configured because libqt4-xmlpatterns:i386 is in a different version (4:4.8.1-0ubuntu4.3) dpkg: fel vid hantering av libqt4-xmlpatterns:i386 (--configure): libqt4-xmlpatterns:i386 4:4.8.1-0ubuntu4.3 cannot be configured because libqt4-xmlpatterns:amd64 is in a different version (4:4.8.1-0ubuntu4.2) dpkg: beroendeproblem förhindrar konfigurering av libqt4-declarative:i386: libqt4-declarative:i386 är beroende av libqt4-xmlpatterns (= 4:4.8.1-0ubuntu4.3), men: Paketet libqt4-xmlpatterns:i386 har inte konfigurerats ännu. dpkg: fel vid hantering av libqt4-declarative:i386 (--configure): beroendeproblem - lämnar okonfigurerad dpkg: beroendeproblem förhindrar konfigurering av libqt4-declarative: libqt4-declarative är beroende av libqt4-xmlpatterns (= 4:4.8.1-0ubuntu4.3), men: Versionen av libqt4-xmlpatterns på systemet är 4:4.8.1-0ubuntu4.2. dpkg: fel vid hantering av libqt4-declarative (--configure): beroendeproblem - lämnar okonfigurerad dpkg: beroendeproblem förhindrar konfigurering av libqtgui4:i386: libqtgui4:i386 är beroende av libqt4-declarative (= 4:4.8.1-0ubuntu4.3), men: Paketet libqt4-declarative:i386 har inte konfigurerats ännu. dpkg: fel vid hantering av libqtgui4:i386 (--configure): beroendeproblem - lämnar okonfigurerad dpkg: beroendeproblem förhindrar koIngen apport-rapport skrevs därför att felmeddelandet indikerar att det är ett efterföljande fel från ett tidigare problem. Ingen apport-rapport skrevs därför att felmeddelandet indikerar att det är ett efterföljande fel från ett tidigare problem. Ingen apport-rapport skrevs därför att felmeddelandet indikerar att det är ett efterföljande fel från ett tidigare problem. Ingen apport-rapport skrevs därför att felmeddelandet indikerar att det är ett efterföljande fel från ett tidigare problem. Ingen apport-rapport skrevs därför att felmeddelandet indikerar att det är ett efterföljande fel från ett tidigare problem. Ingen apport-rapport skrevs därför att felmeddelandet indikerar att det är ett efterföljande fel från ett tidigare problem. nfigurering av libqtgui4: libqtgui4 är beroende av libqt4-declarative (= 4:4.8.1-0ubuntu4.3), men: Paketet libqt4-declarative har inte konfigurerats ännu. dpkg: fel vid hantering av libqtgui4 (--configure): beroendeproblem - lämnar okonfigurerad dpkg: beroendeproblem förhindrar konfigurering av libqt4-designer: libqt4-designer är beroende av libqtgui4 (= 4:4.8.1-0ubuntu4.3), men: Paketet libqtgui4 har inte konfigurerats ännu. dpkg: fel vid hantering av libqt4-designer (--configure): beroendeproblem - lämnar okonfigurerad dpkg: beroendeproblem förhindrar konfigurering av libqt4-designer:i386: libqt4-designer:i386 är beroende av libqtgui4 (= 4:4.8.1-0ubuntu4.3), men: Paketet libqtgui4:i386 har inte konfigurerats ännu. dpkg: fel vid hantering av libqt4-designer:i386 (--configure): beroendeproblem - lämnar okonfigurerad dpkg: beroendeproblem förhindrar konfigurering av libqt4-opengl: libqt4-opengl är beroende av libqtgui4 (= 4:4.8.1-0ubuntu4.3), men: Paketet libqtgui4 har inte konfigurerats ännu. dpkg: fel vid hantering av libqt4-opengl (--configure): beroendeproblem - lämnar okonfigurerad dpkg: beroendeproblem förhindrar konfigurering av libqt4-opengl:i386: libqt4-opengl:i386 är beroende av libqtgui4 (= 4:4.8.1-0ubuntu4.3), men: Paketet libqtgui4:i386 har inte konfigurerats ännu. dpkg: fel vid hantering av libqt4-opengl:i386 (--configure): beroendeproblem - lämnar okonfigurerad dpkg: beroendeproblem förhindrar konfigurering av libqt4-qt3support: libqt4-qt3support är beroende av libqt4-designer (= 4:4.8.1-0ubuntu4.3), men: Paketet libqt4-designer har inte konfigurerats ännu. libqt4-qt3support är beroende av libqtgui4 (= 4:4.8.1-0ubuntu4.3), men: Paketet libqtgui4 har inte konfigurerats ännu. dpkg: fel vid hantering av libqt4-qt3support (--configure): beroendeproblem - lämnar okonfigurerad dpkg: beroendeproblem förhindrar konfigurering av libqt4-qt3support:i386: libqt4-qt3support:i386 är beroende av libqt4-designer (= 4:4.8.1-0ubuntu4.3), men: Paketet libqt4-designer:i386 har inte konfigurerats ännu. libqt4-qt3support:i386 är beroende av libqtgui4 (= 4:4.8.1-0ubuntu4.3), men: Paketet libqtgui4:i386 har inte konfigurerats ännu. dpkg: fel vid hantering av libqt4-qt3support:i386 (--configure): beroendeproblem - lämnar okonfigurerad dpkg: beroendeproblem förhindrar konfigurering av libqt4-scripttools:i386: libqt4-scripttools:i386 är beroende av libqtgui4 (= 4:4.8.1-0ubuntu4.3), men: Paketet libqtgui4:i386 har inte konfigurerats ännu. dpkg: fel vid hantering av libqt4-scripttools:i386 (--configure): beroendeproblem - lämnar okonfigurerad dpkg: beroendeproblem förhindrar konfigurering av libqt4-svg: libqt4-svg är beroende av libqtgui4 (= 4:4.8.1-0ubuntu4.3), men: Paketet libqtgui4 har inte konfigurerats ännu. dpkg: fel vid hantering av libqt4-svg (--configure): beroendeproblem - lämnar okonfigurerad dpkg: beroendeproblem förhindrar konfigurering av libqt4-svg:i386: libqt4-svg:i386 är beroende av libqtgui4 (= 4:4.8.1-0ubuntu4.3), men: Paketet libqtgui4:i386 har inte konfigurerats ännu. dpkg: fel vid hantering av libqt4-svg:i386 (--configure): beroendeproblem - lämnar okonfigurerad Fel uppstod vid hantering: libqt4-xmlpatterns libqt4-xmlpatterns:i386 libqt4-declarative:i386 libqt4-declarative libqtgui4:i386 libqtgui4 libqt4-designer libqt4-designer:i386 libqt4-opengl libqt4-opengl:i386 libqt4-qt3support libqt4-qt3support:i386 libqt4-scripttools:i386 libqt4-svg libqt4-svg:i386 E: Sub-process /usr/bin/dpkg returned an error code (1)

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  • Declarative authorization and the if_attribute not working...

    - by ro
    I've been having almost the same issues as Victor Martin (you can see the questions asked here). I've got declarative authorization working for just about everything that doesn't involve using conditionals. E.g. has_permission_on :users, :to => [:edit, :update, :destroy] do if_attribute :user => is { current_user } end Are there any common pitfalls with Declarative Authorization? I'm using authlogic and I'm suspicious the 'current_user' method in the application controller might be the source of the problem.

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  • SQLAlchemy declarative syntax with autoload in Pylons

    - by Juliusz Gonera
    I would like to use autoload to use an existings database. I know how to do it without declarative syntax (model/_init_.py): def init_model(engine): """Call me before using any of the tables or classes in the model""" t_events = Table('events', Base.metadata, schema='events', autoload=True, autoload_with=engine) orm.mapper(Event, t_events) Session.configure(bind=engine) class Event(object): pass This works fine, but I would like to use declarative syntax: class Event(Base): __tablename__ = 'events' __table_args__ = {'schema': 'events', 'autoload': True} Unfortunately, this way I get: sqlalchemy.exc.UnboundExecutionError: No engine is bound to this Table's MetaData. Pass an engine to the Table via autoload_with=<someengine>, or associate the MetaData with an engine via metadata.bind=<someengine> The problem here is that I don't know where to get the engine from (to use it in autoload_with) at the stage of importing the model (it's available in init_model()). I tried adding meta.Base.metadata.bind(engine) to environment.py but it doesn't work. Anyone has found some elegant solution?

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  • Fun with Declarative Components

    - by [email protected]
    Use case background I have been asked on a number of occasions if our selectOneChoice component could allow random text to be entered, as well as having a list of selections available. Unfortunately, the selectOneChoice component only allows entry via the dropdown selection list and doesn't allow text entry. I was thinking of possible solutions and thought that this might make a good example for using a declarative component.My initial idea My first thought was to use an af:inputText to allow the text entry, and an af:selectOneChoice with mode="compact" for the selections. To get it to layout horizontally, we would want to use an af:panelGroupLayout with layout="horizontal". To get the label for this to line up correctly, we'll need to wrap the af:panelGroupLayout with an af:panelLabelAndMessage. This is the basic structure: <af:panelLabelAndMessage> <af:panelGroupLayout layout="horizontal"> <af:inputText/> <af:selectOneChoice mode="compact"/> </af:panelgroupLayout></af:panelLabelAndMessage> Make it into a declarative component One of the steps to making a declarative component is deciding what attributes we want to be able to specify. To keep this example simple, let's just have: 'label' (the label of our declarative component)'value' (what we want to bind to the value of the input text)'items' (the select items in our dropdown) Here is the initial declarative component code (saved as file "inputTextWithChoice.jsff"): <?xml version='1.0' encoding='UTF-8'?><!-- Copyright (c) 2008, Oracle and/or its affiliates. All rights reserved. --><jsp:root xmlns:jsp="http://java.sun.com/JSP/Page" version="2.1" xmlns:f="http://java.sun.com/jsf/core" xmlns:af="http://xmlns.oracle.com/adf/faces/rich"> <jsp:directive.page contentType="text/html;charset=utf-8"/> <af:componentDef var="attrs" componentVar="comp"> <af:xmlContent> <component xmlns="http://xmlns.oracle.com/adf/faces/rich/component"> <description>Input text with choice component.</description> <attribute> <description>Label</description> <attribute-name>label</attribute-name> <attribute-class>java.lang.String</attribute-class> </attribute> <attribute> <description>Value</description> <attribute-name>value</attribute-name> <attribute-class>java.lang.Object</attribute-class> </attribute> <attribute> <description>Choice Select Items Value</description> <attribute-name>items</attribute-name> <attribute-class>[[Ljavax.faces.model.SelectItem;</attribute-class> </attribute> </component> </af:xmlContent> <af:panelLabelAndMessage id="myPlm" label="#{attrs.label}" for="myIt"> <af:panelGroupLayout id="myPgl" layout="horizontal"> <af:inputText id="myIt" value="#{attrs.value}" partialTriggers="mySoc" label="myIt" simple="true" /> <af:selectOneChoice id="mySoc" label="mySoc" simple="true" mode="compact" value="#{attrs.value}" autoSubmit="true"> <f:selectItems id="mySIs" value="#{attrs.items}" /> </af:selectOneChoice> </af:panelGroupLayout> </af:panelLabelAndMessage> </af:componentDef></jsp:root> By having af:inputText and af:selectOneChoice both have the same value, then (assuming that this passed in as an EL expression) selecting something in the selectOneChoice will update the value in the af:inputText. To use this declarative component in a jspx page: <af:declarativeComponent id="myItwc" viewId="inputTextWithChoice.jsff" label="InputText with Choice" value="#{demoInput.choiceValue}" items="#{demoInput.selectItems}" /> Some problems arise At first glace, this seems to be functioning like we want it to. However, there is a side effect to having the af:inputText and af:selectOneChoice share a value, if one changes, so does the other. The problem here is that when we update the af:inputText to something that doesn't match one of the selections in the af:selectOneChoice, the af:selectOneChoice will set itself to null (since the value doesn't match one of the selections) and the next time the page is submitted, it will submit the null value and the af:inputText will be empty. Oops, we don't want that. Hmm, what to do. Okay, how about if we make sure that the current value is always available in the selection list. But, lets not render it if the value is empty. We also need to add a partialTriggers attribute so that this gets updated when the af:inputText is changed. Plus, we really don't want to select this item so let's disable it. <af:selectOneChoice id="mySoc" partialTriggers="myIt" label="mySoc" simple="true" mode="compact" value="#{attrs.value}" autoSubmit="true"> <af:selectItem id="mySI" label="Selected:#{attrs.value}" value="#{attrs.value}" disabled="true" rendered="#{!empty attrs.value}"/> <af:separator id="mySp" /> <f:selectItems id="mySIs" value="#{attrs.items}" /></af:selectOneChoice> That seems to be working pretty good. One minor issue that we probably can't do anything about is that when you enter something in the inputText and then click on the selectOneChoice, the popup is displayed, but then goes away because it has been replaced via PPR because we told it to with the partialTriggers="myIt". This is not that big a deal, since if you are entering something manually, you probably don't want to select something from the list right afterwards. Making it look like a single component. Now, let's play around a bit with the contentStyle of the af:inputText and the af:selectOneChoice so that the compact icon will layout inside the af:inputText, making it look more like an af:selectManyChoice. We need to add some padding-right to the af;inputText so there is space for the icon. These adjustments were for the Fusion FX skin. <af:inputText id="myIt" partialTriggers="mySoc" autoSubmit="true" contentStyle="padding-right: 15px;" value="#{attrs.value}" label="myIt" simple="true" /><af:selectOneChoice id="mySoc" partialTriggers="myIt" contentStyle="position: relative; top: -2px; left: -19px;" label="mySoc" simple="true" mode="compact" value="#{attrs.value}" autoSubmit="true"> <af:selectItem id="mySI" label="Selected:#{attrs.value}" value="#{attrs.value}" disabled="true" rendered="#{!empty attrs.value}"/> <af:separator id="mySp" /> <f:selectItems id="mySIs" value="#{attrs.items}" /></af:selectOneChoice> There you have it, a declarative component that allows for suggested selections, but also allows arbitrary text to be entered. This could be used for search field, where the 'items' attribute could be populated with popular searches. Lines of java code written: 0

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  • sqlalchemy relation through another (declarative)

    - by clayg
    Is anyone familiar with ActiveRecord's "has_many :through" relations for models? I'm not really a Rails guy, but that's basically what I'm trying to do. As a contrived example consider Projects, Programmers, and Assignments: from sqlalchemy import create_engine from sqlalchemy.orm import sessionmaker from sqlalchemy import Column, ForeignKey from sqlalchemy.types import Integer, String, Text from sqlalchemy.orm import relation from sqlalchemy.ext.declarative import declarative_base Base = declarative_base() class Assignment(Base): __tablename__ = 'assignment' id = Column(Integer, primary_key=True) description = Column(Text) programmer_id = Column(Integer, ForeignKey('programmer.id')) project_id = Column(Integer, ForeignKey('project.id')) def __init__(self, description=description): self.description = description def __repr__(self): return '<Assignment("%s")>' % self.description class Programmer(Base): __tablename__ = 'programmer' id = Column(Integer, primary_key=True) name = Column(String(64)) assignments = relation("Assignment", backref='programmer') def __init__(self, name=name): self.name = name def __repr__(self): return '<Programmer("%s")>' % self.name class Project(Base): __tablename__ = 'project' id = Column(Integer, primary_key=True) name = Column(String(64)) description = Column(Text) assignments = relation("Assignment", backref='project') def __init__(self, name=name, description=description): self.name = name self.description = description def __repr__(self): return '<Project("%s", "%s...")>' % (self.name, self.description[:10]) engine = create_engine('sqlite://') Base.metadata.create_all(engine) Session = sessionmaker(bind=engine) session = Session() Projects have many Assignments. Programmers have many Assignments. (understatement?) But in my office at least, Programmers also have many Projects - I'd like this relationship to be inferred through the Assignments assigned to the Programmer. I'd like the Programmer model to have a attribute "projects" which will return a list of Projects associated to the Programmer through the Assignment model. me = session.query(Programmer).filter_by(name='clay').one() projects = session.query(Project).\ join(Project.assignments).\ join(Assignment.programmer).\ filter(Programmer.id==me.id).all() How can I describe this relationship clearly and simply using the sqlalchemy declarative syntax? Thanks!

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  • What are some good practices when trying to teach declarative programming to imperative programmers?

    - by ChaosPandion
    I offered to do a little bit training in F# at my company and they seemed to show some interest. They are generally VB6 and C# programmers who don't follow programming with too much passion. That being said I feel like it is easier to write correct code when you think in a functional matter so they should definitely get some benefit out of it. Can anyone offer up some advice on how I should approach this? Ideas Don't focus on the syntax, instead focus on how this language and the idioms it promotes can be used. Try and think of examples that are a pain to write in an imperative fashion but translates to elegant code when written in a declarative fashion.

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  • what is the difference between declarative and imperative programming

    - by Brad
    I have been searching the web looking for a definition for declarative and imperative programming that would shed some light for me. However the language used at some of the resources that I have found is daunting - for instance at wikipedia. Does any one have a real world example that they could show me that might bring some perspective to this subject...perhaps in c# thanks

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  • if_attribute on declarative authorization

    - by Victor Martins
    I have a many-to-many relationship like this: A user has_many organizations through affiliations and vice-versa. I'm using declarative organizations and I only want a user to edit a particular organization if he is affiliated and the affiliationtype attribute of affiliation is a particular value. So affiliations has 3 columns , user_id, organization_id and affiliationtype_id I can do: o = Organization.find(:first) o.affiliatons[0].user and get the user now I wish to do this: has_permission_on [:organizations], :to => :edit do if_attribute (...) end That if_attribute should see if the current user is the organization.affiliation[?].user and if the organization.affiliation[?].affiliationtype_id = "3" I hope this is syntax issue ... I really need to get this working.

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  • Is there a declarative language for data definitions?

    - by Jekke
    Reading about WPF and thinking about my application's data store at the same time led me to wonder if there are any languages or tools that allow you to define relational data in a declarative way? A shallow Google search suggests no such thing exists. Yet it seems so obviously useful. The kind of tool I have in mind would declaratively describe (at least) entities, relationships and views is a platform-agnostic way that would act as an abstraction layer between data-driven applications and their datastores. Does any such tool exist?

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  • declarative authorization and has_and_belongs_to_many

    - by Michael Balsiger
    Hi, I have a little problem with declarative-authorization. I have a User and Role Model with a has_and_belongs_to_many association. I've created a Role named :moderator in my authorization_rules.rb Is it possible that a User with the Role Moderator only gets the Users that have the Moderator Role assigned to it?? -- User.with_permissions_to(:index) I thought it would be possible like that: role :moderator do has_permission_on :users, :to => :index do if_attribute :roles => contains { ????? } end end I also created a named_scope in my User Model because I thought it would help... class User has_and_belongs_to_many :roles named_scope :by_role, lambda { |role| { :include => :roles, :conditions => {"roles.name" => role} } } end Does anyone knows if it's possible to do this with declarative_authorization? Thanks for your help!

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  • OSGI Declarative Services (DS): What is a good way of using service component instances

    - by Christoph
    I am just getting started with OSGI and Declarative Services (DS) using Equinox and Eclipse PDE. I have 2 Bundles, A and B. Bundle A exposes a component which is consumed by Bundle B. Both bundles also expose this service to the OSGI Service registry again. Everything works fine so far and Equinox is wireing the components together, which means the Bundle A and Bundle B are instanciated by Equinox (by calling the default constructor) and then the wireing happens using the bind / unbind methods. Now, as Equinox is creating the instances of those components / services I would like to know what is the best way of getting this instance? So assume there is third class class which is NOT instantiated by OSGI: Class WantsToUseComponentB{ public void doSomethingWithComponentB(){ // how do I get componentB??? Something like this maybe? ComponentB component = (ComponentB)someComponentRegistry.getComponent(ComponentB.class.getName()); } I see the following options right now: 1. Use a ServiceTracker in the Activator to get the Service of ComponentBundleA.class.getName() (I have tried that already and it works, but it seems to much overhead to me) and make it available via a static factory methods public class Activator{ private static ServiceTracker componentBServiceTracker; public void start(BundleContext context){ componentBServiceTracker = new ServiceTracker(context, ComponentB.class.getName(),null); } public static ComponentB getComponentB(){ return (ComponentB)componentBServiceTracker.getService(); }; } 2. Create some kind of Registry where each component registers as soon as the activate() method is called. public ComponentB{ public void bind(ComponentA componentA){ someRegistry.registerComponent(this); } or public ComponentB{ public void activate(ComponentContext context){ someRegistry.registerComponent(this); } } } 3. Use an existing registry inside osgi / equinox which has those instances? I mean OSGI is already creating instances and wires them together, so it has the objects already somewhere. But where? How can I get them? Conclusion Where does the class WantsToUseComponentB (which is NOT a Component and NOT instantiated by OSGI) get an instance of ComponentB from? Are there any patterns or best practises? As I said I managed to use a ServiceTracker in the Activator, but I thought that would be possible without it. What I am looking for is actually something like the BeanContainer of Springframework, where I can just say something like Container.getBean(ComponentA.BEAN_NAME). But I don't want to use Spring DS. I hope that was clear enough. Otherwise I can also post some source code to explain in more detail. Thanks Christoph UPDATED: Answer to Neil's comment: Thanks for clarifying this question against the original version, but I think you still need to state why the third class cannot be created via something like DS. Hmm don't know. Maybe there is a way but I would need to refactor my whole framework to be based on DS, so that there are no "new MyThirdClass(arg1, arg2)" statements anymore. Don't really know how to do that, but I read something about ComponentFactories in DS. So instead of doing a MyThirdClass object = new MyThirdClass(arg1, arg2); I might do a ComponentFactory myThirdClassFactory = myThirdClassServiceTracker.getService(); // returns a if (myThirdClassFactory != null){ MyThirdClass object = objectFactory.newInstance(); object.setArg1("arg1"); object.setArg2("arg2"); } else{ // here I can assume that some service of ComponentA or B went away so MyThirdClass Componenent cannot be created as there are missing dependencies? } At the time of writing I don't know exactly how to use the ComponentFactories but this is supposed to be some kind of pseudo code :) Thanks Christoph

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  • rails declarative authorization, permit all actions for controller?

    - by SooDesuNe
    using the delcarative_authorization gem for rails, is there a shortcut to allow a role access to all controller actions? privileges do # default privilege hierarchies to facilitate RESTful Rails apps privilege :manage, :includes => [:create, :read, :update, :delete] end isn't sufficient, because I have more controlling methods than just CRUD in my controllers. Something like: role :foo do has_permission_on :bar, :to =>[:all] end would be perfect, but I'm not finding it in the docs.

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  • C++ Declarative Parsing Serialization

    - by Martin York
    Looking at Java and C# they manage to do some wicked processing based on special languaged based anotation (forgive me if that is the incorrect name). In C++ we have two problems with this: 1) There is no way to annotate a class with type information that is accessable at runtime. 2) Parsing the source to generate stuff is way to complex. But I was thinking that this could be done with some template meta-programming to achieve the same basic affect as anotations (still just thinking about it). Like char_traits that are specialised for the different types an xml_traits template could be used in a declaritive way. This traits class could be used to define how a class is serialised/deserialized by specializing the traits for the class you are trying to serialize. Example Thoughs: template<typename T> struct XML_traits { typedef XML_Empty Children; }; template<> struct XML_traits<Car> { typedef boost::mpl::vector<Body,Wheels,Engine> Children; }; template<typename T> std::ostream& Serialize(T const&) { // my template foo is not that strong. // but somthing like this. boost::mpl::for_each<typename XML_Traits<T>::Children,Serialize>(data); } template<> std::ostream& Serialize<XML_Empty>(T const&) { /* Do Nothing */ } My question is: Has anybody seen any projects/decumentation (not just XML) out there that uses techniques like this (template meta-programming) to emulate the concept of annotation used in languges like Java and C# that can then be used in code generation (to effectively automate the task by using a declaritive style). At this point in my research I am looking for more reading material and examples.

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  • Declarative View Objects (VOs) for better ADF performance

    - by Shay Shmeltzer
    Just got back from ODTUG's kscope13 conference which had a lot of good deep ADF content. In one of my session I ran out of time to do one of my demos, so I wanted to share it here instead. This is a demo of how Declarative View Objects can increase your application's performance. For those who are not familiar with declarative VOs, those are VOs that don't actually specify a hard coded query. Instead ADF creates their query at runtime, and it does it based on the data that is requested in your UI layer. This can be a huge saver of both DB resources and network resources. More in the documentation. Here is a quick example that shows you how using such a VO can automatically switch to a simpler SQL instead of a complex join when needed. (note while I demo with 11.1.2.* the feature is there in 11.1.1.* versions also). The demo also shows you how you can monitor the SQL that ADF BC issues to the database using the WebLogic logging feature in JDeveloper. As a side note, I would have loved to see more ADF developers attending Kscope. This demo was part of the "ADF intro" track at Kscope, In the advanced ADF track you would have been treated to a full tuning session about ADF with lots of other tips. Consider attending Kscope next year - it is going to be in Seattle this time.

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  • Parallelism in .NET – Part 6, Declarative Data Parallelism

    - by Reed
    When working with a problem that can be decomposed by data, we have a collection, and some operation being performed upon the collection.  I’ve demonstrated how this can be parallelized using the Task Parallel Library and imperative programming using imperative data parallelism via the Parallel class.  While this provides a huge step forward in terms of power and capabilities, in many cases, special care must still be given for relative common scenarios. C# 3.0 and Visual Basic 9.0 introduced a new, declarative programming model to .NET via the LINQ Project.  When working with collections, we can now write software that describes what we want to occur without having to explicitly state how the program should accomplish the task.  By taking advantage of LINQ, many operations become much shorter, more elegant, and easier to understand and maintain.  Version 4.0 of the .NET framework extends this concept into the parallel computation space by introducing Parallel LINQ. Before we delve into PLINQ, let’s begin with a short discussion of LINQ.  LINQ, the extensions to the .NET Framework which implement language integrated query, set, and transform operations, is implemented in many flavors.  For our purposes, we are interested in LINQ to Objects.  When dealing with parallelizing a routine, we typically are dealing with in-memory data storage.  More data-access oriented LINQ variants, such as LINQ to SQL and LINQ to Entities in the Entity Framework fall outside of our concern, since the parallelism there is the concern of the data base engine processing the query itself. LINQ (LINQ to Objects in particular) works by implementing a series of extension methods, most of which work on IEnumerable<T>.  The language enhancements use these extension methods to create a very concise, readable alternative to using traditional foreach statement.  For example, let’s revisit our minimum aggregation routine we wrote in Part 4: double min = double.MaxValue; foreach(var item in collection) { double value = item.PerformComputation(); min = System.Math.Min(min, value); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Here, we’re doing a very simple computation, but writing this in an imperative style.  This can be loosely translated to English as: Create a very large number, and save it in min Loop through each item in the collection. For every item: Perform some computation, and save the result If the computation is less than min, set min to the computation Although this is fairly easy to follow, it’s quite a few lines of code, and it requires us to read through the code, step by step, line by line, in order to understand the intention of the developer. We can rework this same statement, using LINQ: double min = collection.Min(item => item.PerformComputation()); Here, we’re after the same information.  However, this is written using a declarative programming style.  When we see this code, we’d naturally translate this to English as: Save the Min value of collection, determined via calling item.PerformComputation() That’s it – instead of multiple logical steps, we have one single, declarative request.  This makes the developer’s intentions very clear, and very easy to follow.  The system is free to implement this using whatever method required. Parallel LINQ (PLINQ) extends LINQ to Objects to support parallel operations.  This is a perfect fit in many cases when you have a problem that can be decomposed by data.  To show this, let’s again refer to our minimum aggregation routine from Part 4, but this time, let’s review our final, parallelized version: // Safe, and fast! double min = double.MaxValue; // Make a "lock" object object syncObject = new object(); Parallel.ForEach( collection, // First, we provide a local state initialization delegate. () => double.MaxValue, // Next, we supply the body, which takes the original item, loop state, // and local state, and returns a new local state (item, loopState, localState) => { double value = item.PerformComputation(); return System.Math.Min(localState, value); }, // Finally, we provide an Action<TLocal>, to "merge" results together localState => { // This requires locking, but it's only once per used thread lock(syncObj) min = System.Math.Min(min, localState); } ); Here, we’re doing the same computation as above, but fully parallelized.  Describing this in English becomes quite a feat: Create a very large number, and save it in min Create a temporary object we can use for locking Call Parallel.ForEach, specifying three delegates For the first delegate: Initialize a local variable to hold the local state to a very large number For the second delegate: For each item in the collection, perform some computation, save the result If the result is less than our local state, save the result in local state For the final delegate: Take a lock on our temporary object to protect our min variable Save the min of our min and local state variables Although this solves our problem, and does it in a very efficient way, we’ve created a set of code that is quite a bit more difficult to understand and maintain. PLINQ provides us with a very nice alternative.  In order to use PLINQ, we need to learn one new extension method that works on IEnumerable<T> – ParallelEnumerable.AsParallel(). That’s all we need to learn in order to use PLINQ: one single method.  We can write our minimum aggregation in PLINQ very simply: double min = collection.AsParallel().Min(item => item.PerformComputation()); By simply adding “.AsParallel()” to our LINQ to Objects query, we converted this to using PLINQ and running this computation in parallel!  This can be loosely translated into English easily, as well: Process the collection in parallel Get the Minimum value, determined by calling PerformComputation on each item Here, our intention is very clear and easy to understand.  We just want to perform the same operation we did in serial, but run it “as parallel”.  PLINQ completely extends LINQ to Objects: the entire functionality of LINQ to Objects is available.  By simply adding a call to AsParallel(), we can specify that a collection should be processed in parallel.  This is simple, safe, and incredibly useful.

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  • Procedural, Semi-Procedural and Declarative Programming in SQL

    A lot of the time, the key to making SQL databases perform well is to take a break from the keyboard and rethink the way of approaching the problem; and rethinking in terms of a set-based declarative approach. Joe takes a simple discussion abut a problem with a UDF to illustrate the point that ingrained procedural reflexes can often prevent us from seeing simpler set-based techniques.

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  • Procedural, Semi-Procedural and Declarative Programming in SQL

    A lot of the time, the key to making SQL databases perform well is to take a break from the keyboard and rethink the way of approaching the problem; and rethinking in terms of a set-based declarative approach. Joe takes a simple discussion abut a problem with a UDF to illustrate the point that ingrained procedural reflexes can often prevent us from seeing simpler set-based techniques.

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  • Web Services Example - Part 1: Declarative

    - by Denis T
    In this edition of the ADF Mobile blog we'll tackle part 1 of our Web Service examples. In this posting we'll take a look at using a declarative SOAP Web Service. Getting the sample code: Just click here to download a zip of the entire project. You can unzip it and load it into JDeveloper and deploy it either to iOS or Android. Please follow the previous blog posts if you need help getting JDeveloper or ADF Mobile installed. Defining our Web Service: First off, we should mention that this sample code is using a public web service provided free by CDYNE Corporation that provides weather forecasts by zipcode. Sometimes this service goes down so please ensure you know it's up before reporting this example isn't working. Let's take a look at the web service.  We created this by using the "Web Service Data Control" from the New Gallery and using this link to this wsdl:  "http://wsf.cdyne.com/WeatherWS/Weather.asmx?WSDL"   This web service has several methods but we're interested in GetCityForecastByZIP which takes a single string parameter for the zipcode and the second method, GetWeatherInformation that enumerates all possible forecast descriptions and associated image URLs.  The latter we'll use in the next edition but we included it here for completeness. Defing the Application: After adding a feature to the adfmf-feature.xml file, we added a taskflow to host the application flow.  This comprises of a home screen with a list with items for each method in the web service, "Forecast by Zip" and "Weather Info".  In this application we've also decided to hide the navigation bar since there is only one feature in the application. Forecast by Zip: The "Forecast By ZIP" option first presents the user with a screen where they can enter a zipcode and when the "Search" button is tapped, it executes the GetCityForecastByZIP method.  This is done by binding an Action binding to that method. The easiest way to accomplish this is to just drag & drop the method from the Data Control palette to the AMX page and drop it as a button and let the framework hook it up for you.  There is an inputText component on the page that is bound to a pageFlowScope variable called "zip".  This is used as the parameter to the Action binding when it is executed.  Because the actionListener attribute of the commandButton executes the Web Service each time, we ensure that the method is invoked every time the button is clicked. Weather Info: Unlike the previous method, this time instead of explictly executing the web service method we are using deferred invocation.  What this means is that we will bind to the results of the method and the framework will execute the method when it the data is required to be rendered.  We do this by simply doing a drag & drop of the results of the GetWeatherInformation to the AMX page.  When the page is rendered and the bindings are resolved the framework invokes the method.  This executes the method only when it is needed and fills the Data Control provider.  Because we never re-execute the method, you can click from Home to Weather Info and back many times and the web service is only ever invoked once. Issues and Possible Improvements: One thing you will quickly realize with this example is that the error handling is done by the framework for you. For simple examples this is fine but for real applications you'll want to customize these error messages.  With the declarative invocation of web services, this is difficult.  This is one aspect we'll address in the second installment of the web service examples where we will show you how to do programmatic invocation which allows you better error handling. Another issue you will notice with this example is that we can enumerate the weather information but there isn't an easy way to use that information to show the corresponding description and image as part of the forecast results.  We'll show you how to do this in the next example.

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  • Metro: Declarative Data Binding

    - by Stephen.Walther
    The goal of this blog post is to describe how declarative data binding works in the WinJS library. In particular, you learn how to use both the data-win-bind and data-win-bindsource attributes. You also learn how to use calculated properties and converters to format the value of a property automatically when performing data binding. By taking advantage of WinJS data binding, you can use the Model-View-ViewModel (MVVM) pattern when building Metro style applications with JavaScript. By using the MVVM pattern, you can prevent your JavaScript code from spinning into chaos. The MVVM pattern provides you with a standard pattern for organizing your JavaScript code which results in a more maintainable application. Using Declarative Bindings You can use the data-win-bind attribute with any HTML element in a page. The data-win-bind attribute enables you to bind (associate) an attribute of an HTML element to the value of a property. Imagine, for example, that you want to create a product details page. You want to show a product object in a page. In that case, you can create the following HTML page to display the product details: <!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>Application1</title> <!-- WinJS references --> <link href="//Microsoft.WinJS.0.6/css/ui-dark.css" rel="stylesheet"> <script src="//Microsoft.WinJS.0.6/js/base.js"></script> <script src="//Microsoft.WinJS.0.6/js/ui.js"></script> <!-- Application1 references --> <link href="/css/default.css" rel="stylesheet"> <script src="/js/default.js"></script> </head> <body> <h1>Product Details</h1> <div class="field"> Product Name: <span data-win-bind="innerText:name"></span> </div> <div class="field"> Product Price: <span data-win-bind="innerText:price"></span> </div> <div class="field"> Product Picture: <br /> <img data-win-bind="src:photo;alt:name" /> </div> </body> </html> The HTML page above contains three data-win-bind attributes – one attribute for each product property displayed. You use the data-win-bind attribute to set properties of the HTML element associated with the data-win-attribute. The data-win-bind attribute takes a semicolon delimited list of element property names and data source property names: data-win-bind=”elementPropertyName:datasourcePropertyName; elementPropertyName:datasourcePropertyName;…” In the HTML page above, the first two data-win-bind attributes are used to set the values of the innerText property of the SPAN elements. The last data-win-bind attribute is used to set the values of the IMG element’s src and alt attributes. By the way, using data-win-bind attributes is perfectly valid HTML5. The HTML5 standard enables you to add custom attributes to an HTML document just as long as the custom attributes start with the prefix data-. So you can add custom attributes to an HTML5 document with names like data-stephen, data-funky, or data-rover-dog-is-hungry and your document will validate. The product object displayed in the page above with the data-win-bind attributes is created in the default.js file: (function () { "use strict"; var app = WinJS.Application; app.onactivated = function (eventObject) { if (eventObject.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.launch) { var product = { name: "Tesla", price: 80000, photo: "/images/TeslaPhoto.png" }; WinJS.Binding.processAll(null, product); } }; app.start(); })(); In the code above, a product object is created with a name, price, and photo property. The WinJS.Binding.processAll() method is called to perform the actual binding (Don’t confuse WinJS.Binding.processAll() and WinJS.UI.processAll() – these are different methods). The first parameter passed to the processAll() method represents the root element for the binding. In other words, binding happens on this element and its child elements. If you provide the value null, then binding happens on the entire body of the document (document.body). The second parameter represents the data context. This is the object that has the properties which are displayed with the data-win-bind attributes. In the code above, the product object is passed as the data context parameter. Another word for data context is view model.  Creating Complex View Models In the previous section, we used the data-win-bind attribute to display the properties of a simple object: a single product. However, you can use binding with more complex view models including view models which represent multiple objects. For example, the view model in the following default.js file represents both a customer and a product object. Furthermore, the customer object has a nested address object: (function () { "use strict"; var app = WinJS.Application; app.onactivated = function (eventObject) { if (eventObject.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.launch) { var viewModel = { customer: { firstName: "Fred", lastName: "Flintstone", address: { street: "1 Rocky Way", city: "Bedrock", country: "USA" } }, product: { name: "Bowling Ball", price: 34.55 } }; WinJS.Binding.processAll(null, viewModel); } }; app.start(); })(); The following page displays the customer (including the customer address) and the product. Notice that you can use dot notation to refer to child objects in a view model such as customer.address.street. <!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>Application1</title> <!-- WinJS references --> <link href="//Microsoft.WinJS.0.6/css/ui-dark.css" rel="stylesheet"> <script src="//Microsoft.WinJS.0.6/js/base.js"></script> <script src="//Microsoft.WinJS.0.6/js/ui.js"></script> <!-- Application1 references --> <link href="/css/default.css" rel="stylesheet"> <script src="/js/default.js"></script> </head> <body> <h1>Customer Details</h1> <div class="field"> First Name: <span data-win-bind="innerText:customer.firstName"></span> </div> <div class="field"> Last Name: <span data-win-bind="innerText:customer.lastName"></span> </div> <div class="field"> Address: <address> <span data-win-bind="innerText:customer.address.street"></span> <br /> <span data-win-bind="innerText:customer.address.city"></span> <br /> <span data-win-bind="innerText:customer.address.country"></span> </address> </div> <h1>Product</h1> <div class="field"> Name: <span data-win-bind="innerText:product.name"></span> </div> <div class="field"> Price: <span data-win-bind="innerText:product.price"></span> </div> </body> </html> A view model can be as complicated as you need and you can bind the view model to a view (an HTML document) by using declarative bindings. Creating Calculated Properties You might want to modify a property before displaying the property. For example, you might want to format the product price property before displaying the property. You don’t want to display the raw product price “80000”. Instead, you want to display the formatted price “$80,000”. You also might need to combine multiple properties. For example, you might need to display the customer full name by combining the values of the customer first and last name properties. In these situations, it is tempting to call a function when performing binding. For example, you could create a function named fullName() which concatenates the customer first and last name. Unfortunately, the WinJS library does not support the following syntax: <span data-win-bind=”innerText:fullName()”></span> Instead, in these situations, you should create a new property in your view model that has a getter. For example, the customer object in the following default.js file includes a property named fullName which combines the values of the firstName and lastName properties: (function () { "use strict"; var app = WinJS.Application; app.onactivated = function (eventObject) { if (eventObject.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.launch) { var customer = { firstName: "Fred", lastName: "Flintstone", get fullName() { return this.firstName + " " + this.lastName; } }; WinJS.Binding.processAll(null, customer); } }; app.start(); })(); The customer object has a firstName, lastName, and fullName property. Notice that the fullName property is defined with a getter function. When you read the fullName property, the values of the firstName and lastName properties are concatenated and returned. The following HTML page displays the fullName property in an H1 element. You can use the fullName property in a data-win-bind attribute in exactly the same way as any other property. <!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>Application1</title> <!-- WinJS references --> <link href="//Microsoft.WinJS.0.6/css/ui-dark.css" rel="stylesheet"> <script src="//Microsoft.WinJS.0.6/js/base.js"></script> <script src="//Microsoft.WinJS.0.6/js/ui.js"></script> <!-- Application1 references --> <link href="/css/default.css" rel="stylesheet"> <script src="/js/default.js"></script> </head> <body> <h1 data-win-bind="innerText:fullName"></h1> <div class="field"> First Name: <span data-win-bind="innerText:firstName"></span> </div> <div class="field"> Last Name: <span data-win-bind="innerText:lastName"></span> </div> </body> </html> Creating a Converter In the previous section, you learned how to format the value of a property by creating a property with a getter. This approach makes sense when the formatting logic is specific to a particular view model. If, on the other hand, you need to perform the same type of formatting for multiple view models then it makes more sense to create a converter function. A converter function is a function which you can apply whenever you are using the data-win-bind attribute. Imagine, for example, that you want to create a general function for displaying dates. You always want to display dates using a short format such as 12/25/1988. The following JavaScript file – named converters.js – contains a shortDate() converter: (function (WinJS) { var shortDate = WinJS.Binding.converter(function (date) { return date.getMonth() + 1 + "/" + date.getDate() + "/" + date.getFullYear(); }); // Export shortDate WinJS.Namespace.define("MyApp.Converters", { shortDate: shortDate }); })(WinJS); The file above uses the Module Pattern, a pattern which is used through the WinJS library. To learn more about the Module Pattern, see my blog entry on namespaces and modules: http://stephenwalther.com/blog/archive/2012/02/22/windows-web-applications-namespaces-and-modules.aspx The file contains the definition for a converter function named shortDate(). This function converts a JavaScript date object into a short date string such as 12/1/1988. The converter function is created with the help of the WinJS.Binding.converter() method. This method takes a normal function and converts it into a converter function. Finally, the shortDate() converter is added to the MyApp.Converters namespace. You can call the shortDate() function by calling MyApp.Converters.shortDate(). The default.js file contains the customer object that we want to bind. Notice that the customer object has a firstName, lastName, and birthday property. We will use our new shortDate() converter when displaying the customer birthday property: (function () { "use strict"; var app = WinJS.Application; app.onactivated = function (eventObject) { if (eventObject.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.launch) { var customer = { firstName: "Fred", lastName: "Flintstone", birthday: new Date("12/1/1988") }; WinJS.Binding.processAll(null, customer); } }; app.start(); })(); We actually use our shortDate converter in the HTML document. The following HTML document displays all of the customer properties: <!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>Application1</title> <!-- WinJS references --> <link href="//Microsoft.WinJS.0.6/css/ui-dark.css" rel="stylesheet"> <script src="//Microsoft.WinJS.0.6/js/base.js"></script> <script src="//Microsoft.WinJS.0.6/js/ui.js"></script> <!-- Application1 references --> <link href="/css/default.css" rel="stylesheet"> <script src="/js/default.js"></script> <script type="text/javascript" src="js/converters.js"></script> </head> <body> <h1>Customer Details</h1> <div class="field"> First Name: <span data-win-bind="innerText:firstName"></span> </div> <div class="field"> Last Name: <span data-win-bind="innerText:lastName"></span> </div> <div class="field"> Birthday: <span data-win-bind="innerText:birthday MyApp.Converters.shortDate"></span> </div> </body> </html> Notice the data-win-bind attribute used to display the birthday property. It looks like this: <span data-win-bind="innerText:birthday MyApp.Converters.shortDate"></span> The shortDate converter is applied to the birthday property when the birthday property is bound to the SPAN element’s innerText property. Using data-win-bindsource Normally, you pass the view model (the data context) which you want to use with the data-win-bind attributes in a page by passing the view model to the WinJS.Binding.processAll() method like this: WinJS.Binding.processAll(null, viewModel); As an alternative, you can specify the view model declaratively in your markup by using the data-win-datasource attribute. For example, the following default.js script exposes a view model with the fully-qualified name of MyWinWebApp.viewModel: (function () { "use strict"; var app = WinJS.Application; app.onactivated = function (eventObject) { if (eventObject.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.launch) { // Create view model var viewModel = { customer: { firstName: "Fred", lastName: "Flintstone" }, product: { name: "Bowling Ball", price: 12.99 } }; // Export view model to be seen by universe WinJS.Namespace.define("MyWinWebApp", { viewModel: viewModel }); // Process data-win-bind attributes WinJS.Binding.processAll(); } }; app.start(); })(); In the code above, a view model which represents a customer and a product is exposed as MyWinWebApp.viewModel. The following HTML page illustrates how you can use the data-win-bindsource attribute to bind to this view model: <!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>Application1</title> <!-- WinJS references --> <link href="//Microsoft.WinJS.0.6/css/ui-dark.css" rel="stylesheet"> <script src="//Microsoft.WinJS.0.6/js/base.js"></script> <script src="//Microsoft.WinJS.0.6/js/ui.js"></script> <!-- Application1 references --> <link href="/css/default.css" rel="stylesheet"> <script src="/js/default.js"></script> </head> <body> <h1>Customer Details</h1> <div data-win-bindsource="MyWinWebApp.viewModel.customer"> <div class="field"> First Name: <span data-win-bind="innerText:firstName"></span> </div> <div class="field"> Last Name: <span data-win-bind="innerText:lastName"></span> </div> </div> <h1>Product</h1> <div data-win-bindsource="MyWinWebApp.viewModel.product"> <div class="field"> Name: <span data-win-bind="innerText:name"></span> </div> <div class="field"> Price: <span data-win-bind="innerText:price"></span> </div> </div> </body> </html> The data-win-bindsource attribute is used twice in the page above: it is used with the DIV element which contains the customer details and it is used with the DIV element which contains the product details. If an element has a data-win-bindsource attribute then all of the child elements of that element are affected. The data-win-bind attributes of all of the child elements are bound to the data source represented by the data-win-bindsource attribute. Summary The focus of this blog entry was data binding using the WinJS library. You learned how to use the data-win-bind attribute to bind the properties of an HTML element to a view model. We also discussed several advanced features of data binding. We examined how to create calculated properties by including a property with a getter in your view model. We also discussed how you can create a converter function to format the value of a view model property when binding the property. Finally, you learned how to use the data-win-bindsource attribute to specify a view model declaratively.

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