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  • Consuming JSON stream into AWS Database on the cheap

    - by wjl
    I'm working on a project that needs to consume a JSON stream (approximately 1MB / minute), and parse and insert objects into a database. Amazon's DynamoDB or SimpleDB seem like attractive options for this. Is there a web service that can run a very simple script to eat the data and put it in a database? I could use a worker on Heroku or Elastic Beanstalk, or even pure EC2, but I'd like to find a service that's much cheaper, due to the very low amount of bandwidth and CPU required. (Sorry for the crappy tags. I'm not even sure where to categorize this question.)

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  • What are some easy techniques to scan books for new information?

    - by aditya menon
    I find it irresistible to keep purchasing cheap programming and technical e-books in fields such as Drupal, PHP, etc., and also compulsively download free material made available such as those from Microsoft's developer blog... The main problem with the large library I've developed is that there are many chapters (especially the first few) in these books packed with information I already know, but with helpful tidbits hidden in between. The logical step would be to skip those chapters and read the ones I don't seem to know anything about, but I'm afraid I may lose out on really important information this way. But naturally it is tedious to have to read about variables, functions and objects all over again when you are trying to know more about the Registry pattern, for example. It's hard to research on the net for this, because my question itself seems vague and difficult to formulate into a single search query. I need people-advice - what do you do in this situation?

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  • Acceptable GC frequency for a SlimDX/Windows/.NET game?

    - by Rei Miyasaka
    I understand that the Windows GC is much better than the Xbox/WP7 GC, being that it's generational and multithreaded -- so I don't need to worry quite as much about avoiding memory allocation. SlimDX even has some unavoidable functions that generate some amount of garbage (specifically, MapSubresource creates DataBoxes), yet people don't seem to be too upset about it. I'd like to use some functional paradigms to write my code too, which also means creating objects like closures and monads. I know premature optimization isn't a good thing, but are there rules of thumb or metrics that I can follow to know whether I need to cut down on allocations? Is, say, one gen 0 GC per frame too much? One thing that has me stumped is object promotions. Gen 0 GCs will supposedly finish within a millisecond or two, but if I'm understanding correctly, it's the gen 1 and 2 promotions that start to hurt. I'm not too sure how I can predict/prevent these.

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  • Immutable Method Java

    - by Chris Okyen
    In Java, there is the final keyword in lieu of the const keyword in c and c++. In the latter languages their is mutable and immutable methods such as stated in one answer by Johannes Schaub - litb the question how-many-and-which-are-the-uses-of-const-in-ce Use const to tell others methods won't change the logical state of this object. struct SmartPtr { int getCopies() const { return mCopiesMade; } }ptr1; ... int var = ptr.getCopies(); // returns mCopiesMade and is specified that to not modify objects state. How is this performed in Java?

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  • Changes to the LINQ-to-StreamInsight Dialect

    - by Roman Schindlauer
    In previous versions of StreamInsight (1.0 through 2.0), CepStream<> represents temporal streams of many varieties: Streams with ‘open’ inputs (e.g., those defined and composed over CepStream<T>.Create(string streamName) Streams with ‘partially bound’ inputs (e.g., those defined and composed over CepStream<T>.Create(Type adapterFactory, …)) Streams with fully bound inputs (e.g., those defined and composed over To*Stream – sequences or DQC) The stream may be embedded (where Server.Create is used) The stream may be remote (where Server.Connect is used) When adding support for new programming primitives in StreamInsight 2.1, we faced a choice: Add a fourth variety (use CepStream<> to represent streams that are bound the new programming model constructs), or introduce a separate type that represents temporal streams in the new user model. We opted for the latter. Introducing a new type has the effect of reducing the number of (confusing) runtime failures due to inappropriate uses of CepStream<> instances in the incorrect context. The new types are: IStreamable<>, which logically represents a temporal stream. IQStreamable<> : IStreamable<>, which represents a queryable temporal stream. Its relationship to IStreamable<> is analogous to the relationship of IQueryable<> to IEnumerable<>. The developer can compose temporal queries over remote stream sources using this type. The syntax of temporal queries composed over IQStreamable<> is mostly consistent with the syntax of our existing CepStream<>-based LINQ provider. However, we have taken the opportunity to refine certain aspects of the language surface. Differences are outlined below. Because 2.1 introduces new types to represent temporal queries, the changes outlined in this post do no impact existing StreamInsight applications using the existing types! SelectMany StreamInsight does not support the SelectMany operator in its usual form (which is analogous to SQL’s “CROSS APPLY” operator): static IEnumerable<R> SelectMany<T, R>(this IEnumerable<T> source, Func<T, IEnumerable<R>> collectionSelector) It instead uses SelectMany as a convenient syntactic representation of an inner join. The parameter to the selector function is thus unavailable. Because the parameter isn’t supported, its type in StreamInsight 1.0 – 2.0 wasn’t carefully scrutinized. Unfortunately, the type chosen for the parameter is nonsensical to LINQ programmers: static CepStream<R> SelectMany<T, R>(this CepStream<T> source, Expression<Func<CepStream<T>, CepStream<R>>> streamSelector) Using Unit as the type for the parameter accurately reflects the StreamInsight’s capabilities: static IQStreamable<R> SelectMany<T, R>(this IQStreamable<T> source, Expression<Func<Unit, IQStreamable<R>>> streamSelector) For queries that succeed – that is, queries that do not reference the stream selector parameter – there is no difference between the code written for the two overloads: from x in xs from y in ys select f(x, y) Top-K The Take operator used in StreamInsight causes confusion for LINQ programmers because it is applied to the (unbounded) stream rather than the (bounded) window, suggesting that the query as a whole will return k rows: (from win in xs.SnapshotWindow() from x in win orderby x.A select x.B).Take(k) The use of SelectMany is also unfortunate in this context because it implies the availability of the window parameter within the remainder of the comprehension. The following compiles but fails at runtime: (from win in xs.SnapshotWindow() from x in win orderby x.A select win).Take(k) The Take operator in 2.1 is applied to the window rather than the stream: Before After (from win in xs.SnapshotWindow() from x in win orderby x.A select x.B).Take(k) from win in xs.SnapshotWindow() from b in     (from x in win     orderby x.A     select x.B).Take(k) select b Multicast We are introducing an explicit multicast operator in order to preserve expression identity, which is important given the semantics about moving code to and from StreamInsight. This also better matches existing LINQ dialects, such as Reactive. This pattern enables expressing multicasting in two ways: Implicit Explicit var ys = from x in xs          where x.A > 1          select x; var zs = from y1 in ys          from y2 in ys.ShiftEventTime(_ => TimeSpan.FromSeconds(1))          select y1 + y2; var ys = from x in xs          where x.A > 1          select x; var zs = ys.Multicast(ys1 =>     from y1 in ys1     from y2 in ys1.ShiftEventTime(_ => TimeSpan.FromSeconds(1))     select y1 + y2; Notice the product translates an expression using implicit multicast into an expression using the explicit multicast operator. The user does not see this translation. Default window policies Only default window policies are supported in the new surface. Other policies can be simulated by using AlterEventLifetime. Before After xs.SnapshotWindow(     WindowInputPolicy.ClipToWindow,     SnapshotWindowInputPolicy.Clip) xs.SnapshotWindow() xs.TumblingWindow(     TimeSpan.FromSeconds(1),     HoppingWindowOutputPolicy.PointAlignToWindowEnd) xs.TumblingWindow(     TimeSpan.FromSeconds(1)) xs.TumblingWindow(     TimeSpan.FromSeconds(1),     HoppingWindowOutputPolicy.ClipToWindowEnd) Not supported … LeftAntiJoin Representation of LASJ as a correlated sub-query in the LINQ surface is problematic as the StreamInsight engine does not support correlated sub-queries (see discussion of SelectMany). The current syntax requires the introduction of an otherwise unsupported ‘IsEmpty()’ operator. As a result, the pattern is not discoverable and implies capabilities not present in the server. The direct representation of LASJ is used instead: Before After from x in xs where     (from y in ys     where x.A > y.B     select y).IsEmpty() select x xs.LeftAntiJoin(ys, (x, y) => x.A > y.B) from x in xs where     (from y in ys     where x.A == y.B     select y).IsEmpty() select x xs.LeftAntiJoin(ys, x => x.A, y => y.B) ApplyWithUnion The ApplyWithUnion methods have been deprecated since their signatures are redundant given the standard SelectMany overloads: Before After xs.GroupBy(x => x.A).ApplyWithUnion(gs => from win in gs.SnapshotWindow() select win.Count()) xs.GroupBy(x => x.A).SelectMany(     gs =>     from win in gs.SnapshotWindow()     select win.Count()) xs.GroupBy(x => x.A).ApplyWithUnion(gs => from win in gs.SnapshotWindow() select win.Count(), r => new { r.Key, Count = r.Payload }) from x in xs group x by x.A into gs from win in gs.SnapshotWindow() select new { gs.Key, Count = win.Count() } Alternate UDO syntax The representation of UDOs in the StreamInsight LINQ dialect confuses cardinalities. Based on the semantics of user-defined operators in StreamInsight, one would expect to construct queries in the following form: from win in xs.SnapshotWindow() from y in MyUdo(win) select y Instead, the UDO proxy method is referenced within a projection, and the (many) results returned by the user code are automatically flattened into a stream: from win in xs.SnapshotWindow() select MyUdo(win) The “many-or-one” confusion is exemplified by the following example that compiles but fails at runtime: from win in xs.SnapshotWindow() select MyUdo(win) + win.Count() The above query must fail because the UDO is in fact returning many values per window while the count aggregate is returning one. Original syntax New alternate syntax from win in xs.SnapshotWindow() select win.UdoProxy(1) from win in xs.SnapshotWindow() from y in win.UserDefinedOperator(() => new Udo(1)) select y -or- from win in xs.SnapshotWindow() from y in win.UdoMacro(1) select y Notice that this formulation also sidesteps the dynamic type pitfalls of the existing “proxy method” approach to UDOs, in which the type of the UDO implementation (TInput, TOuput) and the type of its constructor arguments (TConfig) need to align in a precise and non-obvious way with the argument and return types for the corresponding proxy method. UDSO syntax UDSO currently leverages the DataContractSerializer to clone initial state for logical instances of the user operator. Initial state will instead be described by an expression in the new LINQ surface. Before After xs.Scan(new Udso()) xs.Scan(() => new Udso()) Name changes ShiftEventTime => AlterEventStartTime: The alter event lifetime overload taking a new start time value has been renamed. CountByStartTimeWindow => CountWindow

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  • Programming language features that help to catch bugs early

    - by Christian Neumanns
    Do you know any programming language features that help to detect bugs early in the software development process - ideally at compile-time or else as early as possible at run-time? Examples of well-known and effective bug-reducing features are: Static typing and generic types: type incompatibility errors are detected by the compiler Design by Contract (TM), also called Contract Programming: invalid values are quickly detected at runtime (through preconditions, postconditions and class invariants) Unit testing I ask this question in the context of improving an object-oriented programming language (called Obix) which has been designed from the ground up to 'make it easy to quickly write reliable code'. Besides the features mentioned above this language also incorporates other Fail-fast features such as: Objects are immutable by default Void (null) values are not allowed by default The aim is to add more Fail-fast concepts to the language. If you know other features which help to write less error-prone code then please let us know. Thank you.

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  • OpenGL Shading Program Object Memory Requirement

    - by Hans Wurst
    gDEbugger states that OpenGL's program objects only occupy an insignificant amount of memory. How much is this actually? I don't know if the stuff I looked up in mesa is actually that I was looking for but it requires 16KB [Edit: false, confusing struct names, less than 1KB immediate, some further behind pointers] per program object. Not quite insignificant. So is it recommended to create a unique program object for each object of the scene? Or to share a single program object and set the scene's object's custom variables just before its draw call?

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  • Variable declaration versus assignment syntax

    - by rwallace
    Working on a statically typed language with type inference and streamlined syntax, and need to make final decision about syntax for variable declaration versus assignment. Specifically I'm trying to choose between: // Option 1. Create new local variable with :=, assign with = foo := 1 foo = 2 // Option 2. Create new local variable with =, assign with := foo = 1 foo := 2 Creating functions will use = regardless: // Indentation delimits blocks square x = x * x And assignment to compound objects will do likewise: sky.color = blue a[i] = 0 Which of options 1 or 2 would people find most convenient/least surprising/otherwise best?

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  • Where to store shaders

    - by Mark Ingram
    I have an OpenGL renderer which has a Scene member variable. The Scene object can contain N SceneObjects. I use these SceneObjects for storing the vertex position and any transforms. My question is, where should shaders be stored in this arrangement? I guess they need to be in a central location because multiple objects can use the same shader. But then each object needs access to the shader because it needs to set attributes into the shader. Does anyone have any advice?

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  • For Programmers familiar with ACM API? Drawing Initials [closed]

    - by user71992
    Possible Duplicate: For Programmers familiar with ACM API? Drawing Initials I came across an exercise (in the book "The Art and Science of Java" by Eric Roberts) that requires using only GArc and GLine classes to create a lettering library which draws your initials on the canvas. This should be made independent of the GLabel class. I'd like to know the correct approach to use in solving this problem. I'm not sure what I have so far is good enough (I'm thinking it's too long). The questions requires that I use a good Top-Down approach. Here's my code so far: //Passes letters to GLetter objects and draws them on the canvas package artScienceJavaExercises.chapter8; import acm.program.*; //import acm.graphics.*; public class DrawInitials extends GraphicsProgram{ public void init(){ resize(400,400); } public void run(){ //String let = readLine("Letter?: "); letter = new GLetter("l"); add(letter, (getWidth()-letter.getWidth()*2)/2, (getHeight()-letter.getHeight())/2); add(new GLetter("o"), (letter.getX()+letter.getWidth()), letter.getY()); } private GLetter letter; } //GLetter Class package artScienceJavaExercises.chapter8; import acm.graphics.*; import java.awt.*; public class GLetter extends GCompound{ private static final int ONE_THIRD = 30; private static final int ROW_2_HEIGHT = 40; private GArc[] arc = new GArc[4]; private GLine[] line = new GLine[24]; public GLetter(String s){ line[0] = new GLine(0,0, ONE_THIRD, 0); line[1] = new GLine(ONE_THIRD,0, ONE_THIRD*2, 0); line[2] = new GLine(ONE_THIRD*2,0, ONE_THIRD*3, 0); line[3] = new GLine(0,0, 0,ONE_THIRD); line[4] = new GLine(ONE_THIRD,0, ONE_THIRD, ONE_THIRD); line[5] = new GLine(ONE_THIRD*2,0, ONE_THIRD*2, ONE_THIRD); line[6] = new GLine(ONE_THIRD*3,0, ONE_THIRD*3, ONE_THIRD); line[7] = new GLine(0,ONE_THIRD, ONE_THIRD*2, ONE_THIRD); line[8] = new GLine(ONE_THIRD,ONE_THIRD, ONE_THIRD*2, ONE_THIRD); line[9] = new GLine(ONE_THIRD*2,ONE_THIRD, ONE_THIRD*3, ONE_THIRD); line[10] = new GLine(0,ONE_THIRD, 0, ONE_THIRD+ROW_2_HEIGHT); line[11] = new GLine(ONE_THIRD, ONE_THIRD, ONE_THIRD, ONE_THIRD+ROW_2_HEIGHT); line[12] = new GLine(ONE_THIRD*2,ONE_THIRD, ONE_THIRD*2, ONE_THIRD+ROW_2_HEIGHT); line[13] = new GLine(ONE_THIRD*3,ONE_THIRD, ONE_THIRD*3, ONE_THIRD+ROW_2_HEIGHT); line[14] = new GLine(0, ONE_THIRD+ROW_2_HEIGHT, ONE_THIRD, ONE_THIRD+ROW_2_HEIGHT); line[15] = new GLine(ONE_THIRD, ONE_THIRD+ROW_2_HEIGHT, ONE_THIRD*2, ONE_THIRD+ROW_2_HEIGHT); line[16] = new GLine(ONE_THIRD*2, ONE_THIRD+ROW_2_HEIGHT, ONE_THIRD*3, ONE_THIRD+ROW_2_HEIGHT); line[17] = new GLine(0, ONE_THIRD+ROW_2_HEIGHT, 0, ONE_THIRD*2+ROW_2_HEIGHT); line[18] = new GLine(ONE_THIRD, ONE_THIRD+ROW_2_HEIGHT, ONE_THIRD, ONE_THIRD*2+ROW_2_HEIGHT); line[19] = new GLine(ONE_THIRD*2, ONE_THIRD+ROW_2_HEIGHT, ONE_THIRD*2, ONE_THIRD*2+ROW_2_HEIGHT); line[20] = new GLine(ONE_THIRD*3, ONE_THIRD+ROW_2_HEIGHT, ONE_THIRD*3, ONE_THIRD*2+ROW_2_HEIGHT); line[21] = new GLine(0,ONE_THIRD*2+ROW_2_HEIGHT, ONE_THIRD, ONE_THIRD*2+ROW_2_HEIGHT); line[22] = new GLine(ONE_THIRD, ONE_THIRD*2+ROW_2_HEIGHT, ONE_THIRD*2, ONE_THIRD*2+ROW_2_HEIGHT); line[23] = new GLine(ONE_THIRD*2,ONE_THIRD*2+ROW_2_HEIGHT, ONE_THIRD*3, ONE_THIRD*2+ROW_2_HEIGHT); for(int i = 0; i<line.length; i++){ add(line[i]); line[i].setColor(Color.BLACK); line[i].setVisible(false); } arc[0] = new GArc(getWidth(), getHeight(), 106.699, 49.341); arc[1] = new GArc(getWidth(), getHeight(), 23.96, 49.341); arc[2] = new GArc(getWidth(), getHeight(), -23.96, -49.341); arc[3] = new GArc(0,0,getWidth(), getHeight(), -106.699, -49.341); for(int i = 0; i<arc.length; i++){ add(arc[i],0,0); arc[i].setColor(Color.BLACK); arc[i].setVisible(false); } paintLetter(s); } private void paintLetter(String s){ if (s.equalsIgnoreCase("l")){ turnOn(line[3]); turnOn(line[10]); turnOn(line[17]); turnOn(line[21]); turnOn(line[22]); turnOn(line[23]); } else if(s.equalsIgnoreCase("o")){ for(int i = 0; i<4; ++i){ turnOn(arc[i]); } turnOn(line[1]); turnOn(line[10]); turnOn(line[13]); turnOn(line[22]); } } private void turnOn(GObject g){ g.setVisible(true); } } I created a class (GLetter.java) with arrays for GArc and GLine objects. They are positioned in certain ways thereby turning certain Glines and/or GArcs on or off (changing visiblity) would create a pattern for a letter. This Gletter uses the if/else statements to determine which pattern to create - this makes me feel my code is too long. There is another class (DrawInitials.java) that simulates a GraphicsProgram and allows the user to pass certain letters as arguments to the GLetter object. I've used 'L' and 'O' as examples. However, I posted this because I'm not sure I'm using the right approach. That's why I need your help. I feel MY CODE IS TOO LONG! The code above is not the complete project...it only draws letters 'L' and 'O' for now.

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  • 2D object-aligned bounding-box intersection test

    - by AshleysBrain
    Hi all, I have two object-aligned bounding boxes (i.e. not axis aligned, they rotate with the object). I'd like to know if two object-aligned boxes overlap. (Edit: note - I'm using an axis-aligned bounding box test to quickly discard distant objects, so it doesn't matter if the quad routine is a little slower.) My boxes are stored as four x,y points. I've searched around for answers, but I can't make sense of the variable names and algorithms in examples to apply them to my particular case. Can someone help show me how this would be done, in a clear and simple way? Thanks. (The particular language isn't important, C-style pseudo code is OK.)

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  • Should I use both WCF and ASP.NET Web API

    - by Mithir
    We already have a WCF API with basichttpbinding. Some of the calls have complex objects in both the response and request. We need to add RESTful abilities to the API. at first I tried adding a webHttp endpoint, but I got At most one body parameter can be serialized without wrapper elements If I made it Wrapped it wasn't pure as I need it to be. I got to read this, and this (which states "ASP.NET Web API is the new way to build RESTful service on .NET"). So my question is, should I make 2 APIs(2 different projects)? one for SOAP with WCF and one RESTful with ASP.NET Web API? is there anything wrong architecturally speaking with this approach?

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  • Is true multithreading really necessary?

    - by Jonathan Graef
    So yeah, I'm creating a programming language. And the language allows multiple threads. But, all threads are synchronized with a global interpreter lock, which means only one thread is allowed to execute at a time. The only way to get the threads to switch off is to explicitly tell the current thread to wait, which allows another thread to execute. Parallel processing is of course possible by spawning multiple processes, but the variables and objects in one process cannot be accessed from another. However the language does have a fairly efficient IPC interface for communicating between processes. My question is: Would there ever be a reason to have multiple, unsynchronized threads within a single process (thus circumventing the GIL)? Why not just put thread.wait() statements in key positions in the program logic (presuming thread.wait() isn't a CPU hog, of course)? I understand that certain other languages that use a GIL have processor scheduling issues (cough Python), but they have all been resolved.

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  • Using SMO to drop a SQL Database

    - by ybbest
    SQL Server Management Objects(SMO) is the API you can use to manipulate the sql server,like create databse and delete database. To get more details you can check the msdn documentation. There are 2 ways you can drop a database 1. You could create a Database object and call Drop method: Dim database As Database = New Database(Your database name) database.Drop() 2.However if you have existing connections to the database ,attempting to drop it using the above method will fail.Recall that when you try to drop the database from management studio ,you can tick the check box to close all the connections before drop the database.It is not so obvious , but you can do the exact same thing using SMO: Dim server As Server= New Server(ServerConn) server.KillAllProcesses(Your database name) server.KillDatabase(Your database name)

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  • PostgreSQL, Ubuntu, NetBeans IDE (Part 3)

    - by Geertjan
    To complete the picture, let's use the traditional (that is, old) Hibernate mechanism, i.e., via XML files, rather than via the annotations shown yesterday. It's definitely trickier, with many more places where typos can occur, but that's why it's the old mechanism. I do not recommend this approach. I recommend the approach shown yesterday. The other players in this scenario include PostgreSQL, as outlined in the previous blog entries in this series. Here's the structure of the module, replacing the code shown yesterday: Here's the Employee class, notice that it has no annotations: import java.io.Serializable; import java.util.Date; public class Employees implements Serializable {         private int employeeId;     private String firstName;     private String lastName;     private Date dateOfBirth;     private String phoneNumber;     private String junk;     public int getEmployeeId() {         return employeeId;     }     public void setEmployeeId(int employeeId) {         this.employeeId = employeeId;     }     public String getFirstName() {         return firstName;     }     public void setFirstName(String firstName) {         this.firstName = firstName;     }     public String getLastName() {         return lastName;     }     public void setLastName(String lastName) {         this.lastName = lastName;     }     public Date getDateOfBirth() {         return dateOfBirth;     }     public void setDateOfBirth(Date dateOfBirth) {         this.dateOfBirth = dateOfBirth;     }     public String getPhoneNumber() {         return phoneNumber;     }     public void setPhoneNumber(String phoneNumber) {         this.phoneNumber = phoneNumber;     }     public String getJunk() {         return junk;     }     public void setJunk(String junk) {         this.junk = junk;     } } And here's the Hibernate configuration file: <?xml version="1.0"?> <!DOCTYPE hibernate-configuration PUBLIC       "-//Hibernate/Hibernate Configuration DTD 3.0//EN"     "http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd"> <hibernate-configuration>     <session-factory>         <property name="hibernate.connection.driver_class">org.postgresql.Driver</property>         <property name="hibernate.connection.url">jdbc:postgresql://localhost:5432/smithdb</property>         <property name="hibernate.connection.username">smith</property>         <property name="hibernate.connection.password">smith</property>         <property name="hibernate.connection.pool_size">1</property>         <property name="hibernate.default_schema">public"</property>         <property name="hibernate.transaction.factory_class">org.hibernate.transaction.JDBCTransactionFactory</property>         <property name="hibernate.current_session_context_class">thread</property>         <property name="hibernate.dialect">org.hibernate.dialect.PostgreSQLDialect</property>         <property name="hibernate.show_sql">true</property>         <mapping resource="org/db/viewer/employees.hbm.xml"/>     </session-factory> </hibernate-configuration> Next, the Hibernate mapping file: <?xml version="1.0"?> <!DOCTYPE hibernate-mapping PUBLIC       "-//Hibernate/Hibernate Mapping DTD 3.0//EN"       "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> <hibernate-mapping>     <class name="org.db.viewer.Employees"            table="employees"            schema="public"            catalog="smithdb">         <id name="employeeId" column="employee_id" type="int">             <generator class="increment"/>         </id>         <property name="firstName" column="first_name" type="string" />         <property name="lastName" column="last_name" type="string" />         <property name="dateOfBirth" column="date_of_birth" type="date" />         <property name="phoneNumber" column="phone_number" type="string" />         <property name="junk" column="junk" type="string" />             </class>     </hibernate-mapping> Then, the HibernateUtil file, for providing access to the Hibernate SessionFactory: import java.net.URL; import org.hibernate.cfg.AnnotationConfiguration; import org.hibernate.SessionFactory; public class HibernateUtil {     private static final SessionFactory sessionFactory;         static {         try {             // Create the SessionFactory from standard (hibernate.cfg.xml)             // config file.             String res = "org/db/viewer/employees.cfg.xml";             URL myURL = Thread.currentThread().getContextClassLoader().getResource(res);             sessionFactory = new AnnotationConfiguration().configure(myURL).buildSessionFactory();         } catch (Throwable ex) {             // Log the exception.             System.err.println("Initial SessionFactory creation failed." + ex);             throw new ExceptionInInitializerError(ex);         }     }         public static SessionFactory getSessionFactory() {         return sessionFactory;     }     } Finally, the "createKeys" in the ChildFactory: @Override protected boolean createKeys(List list) {     Session session = HibernateUtil.getSessionFactory().getCurrentSession();     Transaction transac = null;     try {         transac = session.beginTransaction();         Query query = session.createQuery("from Employees");         list.addAll(query.list());     } catch (HibernateException he) {         Exceptions.printStackTrace(he);         if (transac != null){             transac.rollback();         }     } finally {         session.close();     }     return true; } Note that Constantine Drabo has a similar article here. Run the application and the result should be the same as yesterday.

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  • C#/.NET Little Wonders: Constraining Generics with Where Clause

    - by James Michael Hare
    Back when I was primarily a C++ developer, I loved C++ templates.  The power of writing very reusable generic classes brought the art of programming to a brand new level.  Unfortunately, when .NET 1.0 came about, they didn’t have a template equivalent.  With .NET 2.0 however, we finally got generics, which once again let us spread our wings and program more generically in the world of .NET However, C# generics behave in some ways very differently from their C++ template cousins.  There is a handy clause, however, that helps you navigate these waters to make your generics more powerful. The Problem – C# Assumes Lowest Common Denominator In C++, you can create a template and do nearly anything syntactically possible on the template parameter, and C++ will not check if the method/fields/operations invoked are valid until you declare a realization of the type.  Let me illustrate with a C++ example: 1: // compiles fine, C++ makes no assumptions as to T 2: template <typename T> 3: class ReverseComparer 4: { 5: public: 6: int Compare(const T& lhs, const T& rhs) 7: { 8: return rhs.CompareTo(lhs); 9: } 10: }; Notice that we are invoking a method CompareTo() off of template type T.  Because we don’t know at this point what type T is, C++ makes no assumptions and there are no errors. C++ tends to take the path of not checking the template type usage until the method is actually invoked with a specific type, which differs from the behavior of C#: 1: // this will NOT compile! C# assumes lowest common denominator. 2: public class ReverseComparer<T> 3: { 4: public int Compare(T lhs, T rhs) 5: { 6: return lhs.CompareTo(rhs); 7: } 8: } So why does C# give us a compiler error even when we don’t yet know what type T is?  This is because C# took a different path in how they made generics.  Unless you specify otherwise, for the purposes of the code inside the generic method, T is basically treated like an object (notice I didn’t say T is an object). That means that any operations, fields, methods, properties, etc that you attempt to use of type T must be available at the lowest common denominator type: object.  Now, while object has the broadest applicability, it also has the fewest specific.  So how do we allow our generic type placeholder to do things more than just what object can do? Solution: Constraint the Type With Where Clause So how do we get around this in C#?  The answer is to constrain the generic type placeholder with the where clause.  Basically, the where clause allows you to specify additional constraints on what the actual type used to fill the generic type placeholder must support. You might think that narrowing the scope of a generic means a weaker generic.  In reality, though it limits the number of types that can be used with the generic, it also gives the generic more power to deal with those types.  In effect these constraints says that if the type meets the given constraint, you can perform the activities that pertain to that constraint with the generic placeholders. Constraining Generic Type to Interface or Superclass One of the handiest where clause constraints is the ability to specify the type generic type must implement a certain interface or be inherited from a certain base class. For example, you can’t call CompareTo() in our first C# generic without constraints, but if we constrain T to IComparable<T>, we can: 1: public class ReverseComparer<T> 2: where T : IComparable<T> 3: { 4: public int Compare(T lhs, T rhs) 5: { 6: return lhs.CompareTo(rhs); 7: } 8: } Now that we’ve constrained T to an implementation of IComparable<T>, this means that our variables of generic type T may now call any members specified in IComparable<T> as well.  This means that the call to CompareTo() is now legal. If you constrain your type, also, you will get compiler warnings if you attempt to use a type that doesn’t meet the constraint.  This is much better than the syntax error you would get within C++ template code itself when you used a type not supported by a C++ template. Constraining Generic Type to Only Reference Types Sometimes, you want to assign an instance of a generic type to null, but you can’t do this without constraints, because you have no guarantee that the type used to realize the generic is not a value type, where null is meaningless. Well, we can fix this by specifying the class constraint in the where clause.  By declaring that a generic type must be a class, we are saying that it is a reference type, and this allows us to assign null to instances of that type: 1: public static class ObjectExtensions 2: { 3: public static TOut Maybe<TIn, TOut>(this TIn value, Func<TIn, TOut> accessor) 4: where TOut : class 5: where TIn : class 6: { 7: return (value != null) ? accessor(value) : null; 8: } 9: } In the example above, we want to be able to access a property off of a reference, and if that reference is null, pass the null on down the line.  To do this, both the input type and the output type must be reference types (yes, nullable value types could also be considered applicable at a logical level, but there’s not a direct constraint for those). Constraining Generic Type to only Value Types Similarly to constraining a generic type to be a reference type, you can also constrain a generic type to be a value type.  To do this you use the struct constraint which specifies that the generic type must be a value type (primitive, struct, enum, etc). Consider the following method, that will convert anything that is IConvertible (int, double, string, etc) to the value type you specify, or null if the instance is null. 1: public static T? ConvertToNullable<T>(IConvertible value) 2: where T : struct 3: { 4: T? result = null; 5:  6: if (value != null) 7: { 8: result = (T)Convert.ChangeType(value, typeof(T)); 9: } 10:  11: return result; 12: } Because T was constrained to be a value type, we can use T? (System.Nullable<T>) where we could not do this if T was a reference type. Constraining Generic Type to Require Default Constructor You can also constrain a type to require existence of a default constructor.  Because by default C# doesn’t know what constructors a generic type placeholder does or does not have available, it can’t typically allow you to call one.  That said, if you give it the new() constraint, it will mean that the type used to realize the generic type must have a default (no argument) constructor. Let’s assume you have a generic adapter class that, given some mappings, will adapt an item from type TFrom to type TTo.  Because it must create a new instance of type TTo in the process, we need to specify that TTo has a default constructor: 1: // Given a set of Action<TFrom,TTo> mappings will map TFrom to TTo 2: public class Adapter<TFrom, TTo> : IEnumerable<Action<TFrom, TTo>> 3: where TTo : class, new() 4: { 5: // The list of translations from TFrom to TTo 6: public List<Action<TFrom, TTo>> Translations { get; private set; } 7:  8: // Construct with empty translation and reverse translation sets. 9: public Adapter() 10: { 11: // did this instead of auto-properties to allow simple use of initializers 12: Translations = new List<Action<TFrom, TTo>>(); 13: } 14:  15: // Add a translator to the collection, useful for initializer list 16: public void Add(Action<TFrom, TTo> translation) 17: { 18: Translations.Add(translation); 19: } 20:  21: // Add a translator that first checks a predicate to determine if the translation 22: // should be performed, then translates if the predicate returns true 23: public void Add(Predicate<TFrom> conditional, Action<TFrom, TTo> translation) 24: { 25: Translations.Add((from, to) => 26: { 27: if (conditional(from)) 28: { 29: translation(from, to); 30: } 31: }); 32: } 33:  34: // Translates an object forward from TFrom object to TTo object. 35: public TTo Adapt(TFrom sourceObject) 36: { 37: var resultObject = new TTo(); 38:  39: // Process each translation 40: Translations.ForEach(t => t(sourceObject, resultObject)); 41:  42: return resultObject; 43: } 44:  45: // Returns an enumerator that iterates through the collection. 46: public IEnumerator<Action<TFrom, TTo>> GetEnumerator() 47: { 48: return Translations.GetEnumerator(); 49: } 50:  51: // Returns an enumerator that iterates through a collection. 52: IEnumerator IEnumerable.GetEnumerator() 53: { 54: return GetEnumerator(); 55: } 56: } Notice, however, you can’t specify any other constructor, you can only specify that the type has a default (no argument) constructor. Summary The where clause is an excellent tool that gives your .NET generics even more power to perform tasks higher than just the base "object level" behavior.  There are a few things you cannot specify with constraints (currently) though: Cannot specify the generic type must be an enum. Cannot specify the generic type must have a certain property or method without specifying a base class or interface – that is, you can’t say that the generic must have a Start() method. Cannot specify that the generic type allows arithmetic operations. Cannot specify that the generic type requires a specific non-default constructor. In addition, you cannot overload a template definition with different, opposing constraints.  For example you can’t define a Adapter<T> where T : struct and Adapter<T> where T : class.  Hopefully, in the future we will get some of these things to make the where clause even more useful, but until then what we have is extremely valuable in making our generics more user friendly and more powerful!   Technorati Tags: C#,.NET,Little Wonders,BlackRabbitCoder,where,generics

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  • Hadoop and Object Reuse, Why?

    - by Andrew White
    In Hadoop, objects passed to reducers are reused. This is extremely surprising and hard to track down if you're not expecting it. Furthermore, the original tracker for this "feature" doesn't offer any evidence that this change actually improved performance (unless I missed it). It would speed up the system substantially if we reused the keys and values [...] but I think it is worth doing. This seems completely counter to this very popular answer. Is there some credence to the Hadoop developer's claim? Is there something "special" about Hadoop that would invalidate the notion of object creation being cheap?

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  • What's the best way to create animations when doing Android development?

    - by Adam Smith
    I'm trying to create my first Android game and I'm currently trying to figure out (with someone that will do the drawings and another programmer) what the best way to create animation is. (Animations such as a character moving, etc.) At first, the designer said that she could draw objects/characters and animate them with flash so she didn't have to draw every single frame of an action. The other programmer and I don't know Flash too much so I suggested extracting all the images from the Flash animation and making them appear one after the other when the animation is to start. He said that would end up taking too much resource on the CPU and I tend to agree, but I don't really see how we're supposed to make smooth animations without it being too hard on the hardware and, if possible, not have the designer draw every single frame on Adobe Illustrator. Can an experienced Android game developper help me balance this out so we can move on to other parts of the game as I have no idea what the best way to create animations is.

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  • When is a Use Case layer needed?

    - by Meta-Knight
    In his blog post The Clean Architecture Uncle Bob suggests a 4-layer architecture. I understand the separation between business rules, interfaces and infrastructure, but I wonder if/when it's necessary to have separate layers for domain objects and use cases. What added value will it bring, compared to just having the uses cases as "domain services" in the domain layer? The only useful info I've found on the web about a use case layer is an article by Martin Fowler, who seems to contradict Uncle Bob about its necessity: At some point I may run into the problems, and then I'll make a Use Case Controller - but only then. And even when I do that I rarely consider the Use Case Controllers to occupy a separate layer in the system architecture. Edit: I stumbled upon a video of Uncle Bob's Architecture: The Lost Years keynote, in which he explains this architecture in depth. Very informative.

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  • [PHP] Version Changes: How considerable are the compatibility issues in project?

    - by AdityaGameProgrammer
    For example if we consider ActionScript2.0(based on Objects but programming does not implement much OOP ) vs 3.0(highly OOP) its like a whole new scripting language in the sense of approach, programming style,features you get the idea. In PHP we can see current versions going from 3-5. brief version changes Question :Developers who work on PHP is it easy to migrate from version to version? Question :Are there any extensive compatibility issues, forward or backward? Question :Does your project stick to a particular version till the end ? Question :Does the programming style ,approach change from version to version? Question :If you had to get started on PHP to contribute to a project built earlier versions, would learning the latest version be counterproductive towards this aim? Some related topics i had come across on SE How should I be keeping track of php script version/changes? What is happening to PHP 6? It would be Really helpful in understanding if you could answer this topic directly to the questions put forth.

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  • Align tetrahedrons

    - by thedeadlybutter
    I'm currently generating tetrahedron meshes in Unity When a player clicks the side of a mesh, a new one spawns aligned with it, like this. I'm not sure how nor can I find any information on implementing a tetra hedron grid. I tried playing around with the vertices until I realized I need to adjust position & rotation. Any ideas? EDIT: To be clear, the second image was manually placed objects in the Unity Editor. I'm looking to make an algorithm that places the meshes correctly.

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  • Embed IF text parser in another game?

    - by DragonFax
    Are there any existing interactive fiction text parsing engines that I can embed in another game or application? I'm looking to use something as a library. I can pass it the available objects and verbs from my own side. It will parse the sentences from the user and give me back some sort of structure/AST describing what the user asked for. Then my own code can then act upon that request. I don't need something SIRI level. The simple sentences and actions that current IF games support is fine. But I'm not looking to write a whole text/sentence parser myself. This isn't an If game and I can't write it entirely in an interactive-fiction language like inform 7. Unfortunatly, I can't seem to find any examples of anyone using the text parsing capabilities of these engines without writing the entire game in that engine's language.

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  • Push or Pull Input Data In the Game Logic?

    - by Qua
    In the process of preparing my game for networking I'm adding a layer of seperation between the physical input (mouse/keyboard) and the actual game "engine"/logic. All input that has any relation to the game logic is wrapped inside action objects such as BuildBuildingAction. I was thinking of having an action processing layer that would determine what to do with the input. This layer could then be set up to either just pass the actions locally to the game engine or send it via sockets to the network server depending on whether the game was single- or multiplayer. In network games it would make sense that the player's actions should be sent to the server, but should the game logic be pulling (polling?) the data through some sort of interface or should the action processing layer be adding the actions to an input queue in the game logic code?

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  • how to save a png as a smaller file but the same resolution?

    - by Radek
    not sure what stackexchange site is the best for this question. I have a scanned jpg file with below properties and size 8.5MB pixel dimension: 2468 × 3484 pixels print size: 208.96 × 294.98 millimeters resolution: 300 × 300 ppi I need to save the file as png while the size cannot be bigger than 4MB. The most important is that the size of picture must remain the same. I mean that the object size in the picture must stay the same. Could anybody tell me what is used to define the size of the objects in the picture?

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  • Calculating 3D camera positions from a video

    - by Geotarget
    I need to calculate the 3D camera position and rotation for each frame in a given video. This is typically used for motion-tracking, and to insert 3D objects into a video. I'm currently using VideoTrace to calculate this for me, and I'm getting the data exported as a 3DS Maxscript file. However when I try to use the 3D camera rotations, I'm getting strange errors in my 3D calculations, as if there is an error with the 3x3 rotation matrices. Can you spot any error with the data itself? Or is it my other calculations that are erroneous? frame 1 rotation=(matrix3[-0.011938, 0.756018, -0.654442][-0.382040, -0.608284, -0.695727][-0.924068, 0.241718, 0.296091][0, 0, 0]).rotationpart position=[-0.767177, 0.308723, -0.232722] fov=57.352135 frame 2 rotation=(matrix3[-0.460922, -0.726580, -0.509541][-0.200163, 0.644491, -0.737947][ 0.864572, -0.238145, -0.442495][0, 0, 0]).rotationpart position=[-0.856630, 0.198654, -0.243853] fov=57.352135

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