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  • Static and default constuctor

    - by Ram
    A non static class can have static as well as default constructor at the same time. What is the difference between these two constructors? When shall I go for only static or static with default constructor?

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  • Creating an instance within the Class itself

    - by didxga
    What's going on when the assignment statement executed at Line 4, does compiler ignore the new operator and keep the foo variable being null or something else happen to handle this awkward moment? public class Foo { // creating an instance before its constructor has been invoked, suppose the "initializing" // gets printed in constructor as a result of the next line, of course it will not print it private Foo foo = new Foo();//Line 4 public Foo() { System.out.println("initializing"); } }

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  • Why is `goog.Disposable.call(this);` necessary?

    - by David Faux
    In this snippet of Google Closure javascript code involving a constructor, why is goog.Disposable.call(this); necessary? Doesn't Foo already inherit from Disposable with goog.inherits(foo, goog.Disposable);? goog.provide('foo'); /** * @constructor */ foo = function(){ goog.Disposable.call(this); } goog.inherits(foo, goog.Disposable); foo.prototype.doSomething = function(){ ... } foo.prototype.disposeInternal = function(){ ... }

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  • java.util.Random zero argument enquiry

    - by deerb
    I am trying to code a game following instructions contained in an OU TMA document which read: In the constructor, write code to assign a new instance of Random to ran which you should create using the Random class's zero argument constructor Will this code work? Random ran = new Random(0) ; I am a relative newbie to Java, and I don't understand exactly what the instructions mean

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  • How to define custom exception class in Java, the easiest way?

    - by yegor256
    I'm trying to define my own exception class the easiest way, and this is what I'm getting: public class MyException extends Exception {} public class Foo { public bar() throws MyException { throw new MyException("try again please"); } } This is what Java compiler says: cannot find symbol: constructor MyException(java.lang.String) I had a feeling that this constructor has to be inherited from java.lang.Exception, isn't it?

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  • c++: see compiled object layout

    - by horsthahn
    Hi, is there a way - much like the way i can see the result of preprocessing when using 'gcc -E' - to see what my objects look like once the compiler compiled them into object files? I am not too good in reading assembler, so an advice to get the results as text would be nice .. or at least a little 'howto read the constructor intructions' or 'howto find the constructor' ... I am talking about gcc/g++, but a solution including msvc would be fine. Thanks!

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  • Multi-Dimensional Array and ArrayIndexOutOfBoundsException

    - by notset
    Hello, I have a strange problem which I can't fix: A field: private boolean[][][] gaps; Constructor (1st line): gaps = new boolean[NOBARRICADES][WIDTH][HEIGHT]; Constructor (2nd line): for (int i = 0; i < NOBARRICADES; i++) { JAVA throws an error for the 2nd line, saying: Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException Does it have anything to do with JAVA syntax (the mistake is in these lines of code) or I should look for the problem somewhere else?

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  • C# dispatcher problem

    - by Bert
    Hi, In the constructor of an object i need to create a WPF mediaElement object: m_videoMedia = new MediaElement(); but the class can also be instantiated from a other thread so i need to use Dispatcher.Invoke(DispatcherPriority.Normal, (Action)(() => { m_videoMedia = new MediaElement(); })); But how can I get the right dispatcher instance in that constructor :s

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  • Determining the calling package

    - by Nachikethas
    I got a package called 1.pm in that the constructor is calling a subroutine which is in the same package. Now if some other classes say 2.pm is calling the constructor defined in 1.pm how can i determine if the subroutine is called from 2.pm ?

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  • What runs before main()?

    - by MikimotoH
    After testing on msvc8, I found: Parse GetCommandLine() to argc and argv Standard C Library initialization C++ Constructor of global variables These three things are called before entering main(). My questions are: Will this execution order be different when I porting my program to different compiler (gcc or armcc), or different platform? What stuff does Standard C Library initialization do? So far I know setlocale() is a must. Is it safe to call standard C functions inside C++ constructor of global variables?

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  • Cannot connect to MySQL over TCP locally - Connection Timeout - Ubuntu 9.04

    - by gav
    I am running Ubuntu and am ultimately trying to connect Tomcat to my MySQL database using JDBC. It has worked previously but after a reboot the instance now fails to connect. Both Tomcat 6 and MySQL 5.0.75 are on the same machine Connection string: jdbc:mysql:///localhost:3306 I can connect to MySQL on the command line using the mysql command The my.cnf file is pretty standard (Available on request) has bind address: 127.0.0.1 I cannot Telnet to the MySQL port despite netstat saying MySQL is listening I have one IpTables rule to forward 80 - 8080 and no firewall I'm aware of. I'm pretty new to this and I'm not sure what else to test. I don't know whether I should be looking in etc/interfaces and if I did what to look for. It's weird because it used to work but after a reboot it's down so I must have changed something.... :). I realise a timeout indicates the server is not responding and I assume it's because the request isn't actually getting through. I installed MySQL via apt-get and Tomcat manually. MySqld processes root@88:/var/log/mysql# ps -ef | grep mysqld root 21753 1 0 May27 ? 00:00:00 /bin/sh /usr/bin/mysqld_safe mysql 21792 21753 0 May27 ? 00:00:00 /usr/sbin/mysqld --basedir=/usr --datadir=/var/lib/mysql --user=mysql --pid-file=/var/run/mysqld/mysqld.pid --skip-external-locking --port=3306 --socket=/var/run/mysqld/mysqld.sock root 21793 21753 0 May27 ? 00:00:00 logger -p daemon.err -t mysqld_safe -i -t mysqld root 21888 13676 0 11:23 pts/1 00:00:00 grep mysqld Netstat root@88:/var/log/mysql# netstat -lnp | grep mysql tcp 0 0 0.0.0.0:3306 0.0.0.0:* LISTEN 21792/mysqld unix 2 [ ACC ] STREAM LISTENING 1926205077 21792/mysqld /var/run/mysqld/mysqld.sock Toy Connection Class root@88:~# cat TestConnect/TestConnection.java import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; public class TestConnection { public static void main(String args[]) throws Exception { Connection con = null; try { Class.forName("com.mysql.jdbc.Driver").newInstance(); System.out.println("Got driver"); con = DriverManager.getConnection( "jdbc:mysql:///localhost:3306", "uname", "pass"); System.out.println("Got connection"); if(!con.isClosed()) System.out.println("Successfully connected to " + "MySQL server using TCP/IP..."); } finally { if(con != null) con.close(); } } } Toy Connection Class Output Note: This is the same error I get from Tomcat. root@88:~/TestConnect# java -cp mysql-connector-java-5.1.12-bin.jar:. TestConnection Got driver Exception in thread "main" com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure The last packet sent successfully to the server was 1 milliseconds ago. The driver has not received any packets from the server. at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) at java.lang.reflect.Constructor.newInstance(Constructor.java:513) at com.mysql.jdbc.Util.handleNewInstance(Util.java:409) at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1122) at TestConnection.main(TestConnection.java:14) Caused by: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server. at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) at java.lang.reflect.Constructor.newInstance(Constructor.java:513) at com.mysql.jdbc.Util.handleNewInstance(Util.java:409) at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1122) at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:344) at com.mysql.jdbc.ConnectionImpl.createNewIO(ConnectionImpl.java:2181) ... 12 more Caused by: java.net.ConnectException: Connection timed out at java.net.PlainSocketImpl.socketConnect(Native Method) ... 13 more Telnet Output root@88:~/TestConnect# telnet localhost 3306 Trying 127.0.0.1... telnet: Unable to connect to remote host: Connection timed out

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  • C#/.NET Little Wonders: Using &lsquo;default&rsquo; to Get Default Values

    - by James Michael Hare
    Once again, in this series of posts I look at the parts of the .NET Framework that may seem trivial, but can help improve your code by making it easier to write and maintain. The index of all my past little wonders posts can be found here. Today’s little wonder is another of those small items that can help a lot in certain situations, especially when writing generics.  In particular, it is useful in determining what the default value of a given type would be. The Problem: what’s the default value for a generic type? There comes a time when you’re writing generic code where you may want to set an item of a given generic type.  Seems simple enough, right?  We’ll let’s see! Let’s say we want to query a Dictionary<TKey, TValue> for a given key and get back the value, but if the key doesn’t exist, we’d like a default value instead of throwing an exception. So, for example, we might have a the following dictionary defined: 1: var lookup = new Dictionary<int, string> 2: { 3: { 1, "Apple" }, 4: { 2, "Orange" }, 5: { 3, "Banana" }, 6: { 4, "Pear" }, 7: { 9, "Peach" } 8: }; And using those definitions, perhaps we want to do something like this: 1: // assume a default 2: string value = "Unknown"; 3:  4: // if the item exists in dictionary, get its value 5: if (lookup.ContainsKey(5)) 6: { 7: value = lookup[5]; 8: } But that’s inefficient, because then we’re double-hashing (once for ContainsKey() and once for the indexer).  Well, to avoid the double-hashing, we could use TryGetValue() instead: 1: string value; 2:  3: // if key exists, value will be put in value, if not default it 4: if (!lookup.TryGetValue(5, out value)) 5: { 6: value = "Unknown"; 7: } But the “flow” of using of TryGetValue() can get clunky at times when you just want to assign either the value or a default to a variable.  Essentially it’s 3-ish lines (depending on formatting) for 1 assignment.  So perhaps instead we’d like to write an extension method to support a cleaner interface that will return a default if the item isn’t found: 1: public static class DictionaryExtensions 2: { 3: public static TValue GetValueOrDefault<TKey, TValue>(this Dictionary<TKey, TValue> dict, 4: TKey key, TValue defaultIfNotFound) 5: { 6: TValue value; 7:  8: // value will be the result or the default for TValue 9: if (!dict.TryGetValue(key, out value)) 10: { 11: value = defaultIfNotFound; 12: } 13:  14: return value; 15: } 16: } 17:  So this creates an extension method on Dictionary<TKey, TValue> that will attempt to get a value using the given key, and will return the defaultIfNotFound as a stand-in if the key does not exist. This code compiles, fine, but what if we would like to go one step further and allow them to specify a default if not found, or accept the default for the type?  Obviously, we could overload the method to take the default or not, but that would be duplicated code and a bit heavy for just specifying a default.  It seems reasonable that we could set the not found value to be either the default for the type, or the specified value. So what if we defaulted the type to null? 1: public static TValue GetValueOrDefault<TKey, TValue>(this Dictionary<TKey, TValue> dict, 2: TKey key, TValue defaultIfNotFound = null) // ... No, this won’t work, because only reference types (and Nullable<T> wrapped types due to syntactical sugar) can be assigned to null.  So what about a calling parameterless constructor? 1: public static TValue GetValueOrDefault<TKey, TValue>(this Dictionary<TKey, TValue> dict, 2: TKey key, TValue defaultIfNotFound = new TValue()) // ... No, this won’t work either for several reasons.  First, we’d expect a reference type to return null, not an “empty” instance.  Secondly, not all reference types have a parameter-less constructor (string for example does not).  And finally, a constructor cannot be determined at compile-time, while default values can. The Solution: default(T) – returns the default value for type T Many of us know the default keyword for its uses in switch statements as the default case.  But it has another use as well: it can return us the default value for a given type.  And since it generates the same defaults that default field initialization uses, it can be determined at compile-time as well. For example: 1: var x = default(int); // x is 0 2:  3: var y = default(bool); // y is false 4:  5: var z = default(string); // z is null 6:  7: var t = default(TimeSpan); // t is a TimeSpan with Ticks == 0 8:  9: var n = default(int?); // n is a Nullable<int> with HasValue == false Notice that for numeric types the default is 0, and for reference types the default is null.  In addition, for struct types, the value is a default-constructed struct – which simply means a struct where every field has their default value (hence 0 Ticks for TimeSpan, etc.). So using this, we could modify our code to this: 1: public static class DictionaryExtensions 2: { 3: public static TValue GetValueOrDefault<TKey, TValue>(this Dictionary<TKey, TValue> dict, 4: TKey key, TValue defaultIfNotFound = default(TValue)) 5: { 6: TValue value; 7:  8: // value will be the result or the default for TValue 9: if (!dict.TryGetValue(key, out value)) 10: { 11: value = defaultIfNotFound; 12: } 13:  14: return value; 15: } 16: } Now, if defaultIfNotFound is unspecified, it will use default(TValue) which will be the default value for whatever value type the dictionary holds.  So let’s consider how we could use this: 1: lookup.GetValueOrDefault(1); // returns “Apple” 2:  3: lookup.GetValueOrDefault(5); // returns null 4:  5: lookup.GetValueOrDefault(5, “Unknown”); // returns “Unknown” 6:  Again, do not confuse a parameter-less constructor with the default value for a type.  Remember that the default value for any type is the compile-time default for any instance of that type (0 for numeric, false for bool, null for reference types, and struct will all default fields for struct).  Consider the difference: 1: // both zero 2: int i1 = default(int); 3: int i2 = new int(); 4:  5: // both “zeroed” structs 6: var dt1 = default(DateTime); 7: var dt2 = new DateTime(); 8:  9: // sb1 is null, sb2 is an “empty” string builder 10: var sb1 = default(StringBuilder()); 11: var sb2 = new StringBuilder(); So in the above code, notice that the value types all resolve the same whether using default or parameter-less construction.  This is because a value type is never null (even Nullable<T> wrapped types are never “null” in a reference sense), they will just by default contain fields with all default values. However, for reference types, the default is null and not a constructed instance.  Also it should be noted that not all classes have parameter-less constructors (string, for instance, doesn’t have one – and doesn’t need one). Summary Whenever you need to get the default value for a type, especially a generic type, consider using the default keyword.  This handy word will give you the default value for the given type at compile-time, which can then be used for initialization, optional parameters, etc. Technorati Tags: C#,CSharp,.NET,Little Wonders,default

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  • testing dao with hibernate genericdao pattern with spring.Headache

    - by black sensei
    Hello good fellas! in my journey of learning hibernate i came across an article on hibernate site. i' learning spring too and wanted to do certain things to discover the flexibility of spring by letting you implement you own session.yes i don't want to use the hibernateTemplate(for experiment). and i'm now having a problem and even the test class.I followed the article on the hibernate site especially the section an "implementation with hibernate" so we have the generic dao interface : public interface GenericDAO<T, ID extends Serializable> { T findById(ID id, boolean lock); List<T> findAll(); List<T> findByExample(T exampleInstance); T makePersistent(T entity); void makeTransient(T entity); } it's implementation in an abstract class that is the same as the one on the web site.Please refer to it from the link i provide.i'll like to save this post to be too long now come my dao's messagedao interface package com.project.core.dao; import com.project.core.model.MessageDetails; import java.util.List; public interface MessageDAO extends GenericDAO<MessageDetails, Long>{ //Message class is on of my pojo public List<Message> GetAllByStatus(String status); } its implementation is messagedaoimpl: public class MessageDAOImpl extends GenericDAOImpl <Message, Long> implements MessageDAO { // mySContainer is an interface which my HibernateUtils implement mySContainer sessionManager; /** * */ public MessageDAOImpl(){} /** * * @param sessionManager */ public MessageDAOImpl(HibernateUtils sessionManager){ this.sessionManager = sessionManager; } //........ plus other methods } here is my HibernatUtils public class HibernateUtils implements SessionContainer { private final SessionFactory sessionFactory; private Session session; public HibernateUtils() { this.sessionFactory = new AnnotationConfiguration().configure().buildSessionFactory(); } public HibernateUtils(SessionFactory sessionFactory) { this.sessionFactory = sessionFactory; } /** * * this is the function that return a session.So i'm free to implements any type of session in here. */ public Session requestSession() { // if (session != null || session.isOpen()) { // return session; // } else { session = sessionFactory.openSession(); // } return session; } } So in my understanding while using spring(will provide the conf), i'ld wire sessionFactory to my HiberbernateUtils and then wire its method RequestSession to the Session Property of the GenericDAOImpl (the one from the link provided). here is my spring config core.xml <bean id="sessionManager" class="com.project.core.dao.hibernate.HibernateUtils"> <constructor-arg ref="sessionFactory" /> </bean> <bean id="messageDao" class="com.project.core.dao.hibernate.MessageDAOImpl"> <constructor-arg ref="sessionManager"/> </bean> <bean id="genericDAOimpl" class="com.project.core.dao.GenericDAO"> <property name="session" ref="mySession"/> </bean> <bean id="mySession" factory-bean="com.project.core.dao.SessionContainer" factory-method="requestSession"/> now my test is this public class MessageDetailsDAOImplTest extends AbstractDependencyInjectionSpringContextTests{ HibernateUtils sessionManager = (HibernateUtils) applicationContext.getBean("sessionManager"); MessageDAO messagedao =(MessageDAO) applicationContext.getBean("messageDao"); static Message[] message = new Message[] { new Message("text",1,"test for dummies 1","1234567890","Pending",new Date()), new Message("text",2,"test for dummies 2","334455669990","Delivered",new Date()) }; public MessageDAOImplTest() { } @Override protected String[] getConfigLocations(){ return new String[]{"file:src/main/resources/core.xml"}; } @Test public void testMakePersistent() { System.out.println("MakePersistent"); messagedao.makePersistent(message[0]); Session session = sessionManager.RequestSession(); session.beginTransaction(); MessageDetails fromdb = ( Message) session.load(Message.class, message[0].getMessageId()); assertEquals(fromdb.getMessageId(), message[0].getMessageId()); assertEquals(fromdb.getDateSent(),message.getDateSent()); assertEquals(fromdb.getGlobalStatus(),message.getGlobalStatus()); assertEquals(fromdb.getNumberOfPages(),message.getNumberOfPages()); } i'm having this error exception in constructor testMakePersistent(java.lang.NullPointerException at com.project.core.dao.hibernate.MessageDAOImplTest) with this stack : at com.project.core.dao.hibernate.MessageDAOImplTest.(MessageDAOImplTest.java:28) at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27) at java.lang.reflect.Constructor.newInstance(Constructor.java:513) at junit.framework.TestSuite.createTest(TestSuite.java:61) at junit.framework.TestSuite.addTestMethod(TestSuite.java:283) at junit.framework.TestSuite.(TestSuite.java:146) at org.apache.tools.ant.taskdefs.optional.junit.JUnitTestRunner.run(JUnitTestRunner.java:481) at org.apache.tools.ant.taskdefs.optional.junit.JUnitTestRunner.launch(JUnitTestRunner.java:1031) at org.apache.tools.ant.taskdefs.optional.junit.JUnitTestRunner.main(JUnitTestRunner.java:888) )) How to actually make this one work.I know this is a lot to stuffs and i'm thanking you for reading it.Please give me a solution.How would you do this? thanks

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  • compile time if && return string reference optimization

    - by Truncheon
    Hi. I'm writing a series classes that inherit from a base class using virtual. They are INT, FLOAT and STRING objects that I want to use in a scripting language. I'm trying to implement weak typing, but I don't want STRING objects to return copies of themselves when used in the following way (instead I would prefer to have a reference returned which can be used in copying): a = "hello "; b = "world"; c = a + b; I have written the following code as a mock example: #include <iostream> #include <string> #include <cstdio> #include <cstdlib> std::string dummy("<int object cannot return string reference>"); struct BaseImpl { virtual bool is_string() = 0; virtual int get_int() = 0; virtual std::string get_string_copy() = 0; virtual std::string const& get_string_ref() = 0; }; struct INT : BaseImpl { int value; INT(int i = 0) : value(i) { std::cout << "constructor called\n"; } INT(BaseImpl& that) : value(that.get_int()) { std::cout << "copy constructor called\n"; } bool is_string() { return false; } int get_int() { return value; } std::string get_string_copy() { char buf[33]; sprintf(buf, "%i", value); return buf; } std::string const& get_string_ref() { return dummy; } }; struct STRING : BaseImpl { std::string value; STRING(std::string s = "") : value(s) { std::cout << "constructor called\n"; } STRING(BaseImpl& that) { if (that.is_string()) value = that.get_string_ref(); else value = that.get_string_copy(); std::cout << "copy constructor called\n"; } bool is_string() { return true; } int get_int() { return atoi(value.c_str()); } std::string get_string_copy() { return value; } std::string const& get_string_ref() { return value; } }; struct Base { BaseImpl* impl; Base(BaseImpl* p = 0) : impl(p) {} ~Base() { delete impl; } }; int main() { Base b1(new INT(1)); Base b2(new STRING("Hello world")); Base b3(new INT(*b1.impl)); Base b4(new STRING(*b2.impl)); std::cout << "\n"; std::cout << b1.impl->get_int() << "\n"; std::cout << b2.impl->get_int() << "\n"; std::cout << b3.impl->get_int() << "\n"; std::cout << b4.impl->get_int() << "\n"; std::cout << "\n"; std::cout << b1.impl->get_string_ref() << "\n"; std::cout << b2.impl->get_string_ref() << "\n"; std::cout << b3.impl->get_string_ref() << "\n"; std::cout << b4.impl->get_string_ref() << "\n"; std::cout << "\n"; std::cout << b1.impl->get_string_copy() << "\n"; std::cout << b2.impl->get_string_copy() << "\n"; std::cout << b3.impl->get_string_copy() << "\n"; std::cout << b4.impl->get_string_copy() << "\n"; return 0; } It was necessary to add an if check in the STRING class to determine whether its safe to request a reference instead of a copy: Script code: a = "test"; b = a; c = 1; d = "" + c; /* not safe to request reference by standard */ C++ code: STRING(BaseImpl& that) { if (that.is_string()) value = that.get_string_ref(); else value = that.get_string_copy(); std::cout << "copy constructor called\n"; } If was hoping there's a way of moving that if check into compile time, rather than run time.

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  • C++0x rvalue references - lvalues-rvalue binding

    - by Doug
    This is a follow-on question to http://stackoverflow.com/questions/2748866/c0x-rvalue-references-and-temporaries In the previous question, I asked how this code should work: void f(const std::string &); //less efficient void f(std::string &&); //more efficient void g(const char * arg) { f(arg); } It seems that the move overload should probably be called because of the implicit temporary, and this happens in GCC but not MSVC (or the EDG front-end used in MSVC's Intellisense). What about this code? void f(std::string &&); //NB: No const string & overload supplied void g1(const char * arg) { f(arg); } void g2(const std::string & arg) { f(arg); } It seems that, based on the answers to my previous question that function g1 is legal (and is accepted by GCC 4.3-4.5, but not by MSVC). However, GCC and MSVC both reject g2 because of clause 13.3.3.1.4/3, which prohibits lvalues from binding to rvalue ref arguments. I understand the rationale behind this - it is explained in N2831 "Fixing a safety problem with rvalue references". I also think that GCC is probably implementing this clause as intended by the authors of that paper, because the original patch to GCC was written by one of the authors (Doug Gregor). However, I don't this is quite intuitive. To me, (a) a const string & is conceptually closer to a string && than a const char *, and (b) the compiler could create a temporary string in g2, as if it were written like this: void g2(const std::string & arg) { f(std::string(arg)); } Indeed, sometimes the copy constructor is considered to be an implicit conversion operator. Syntactically, this is suggested by the form of a copy constructor, and the standard even mentions this specifically in clause 13.3.3.1.2/4, where the copy constructor for derived-base conversions is given a higher conversion rank than other implicit conversions: A conversion of an expression of class type to the same class type is given Exact Match rank, and a conversion of an expression of class type to a base class of that type is given Conversion rank, in spite of the fact that a copy/move constructor (i.e., a user-defined conversion function) is called for those cases. (I assume this is used when passing a derived class to a function like void h(Base), which takes a base class by value.) Motivation My motivation for asking this is something like the question asked in http://stackoverflow.com/questions/2696156/how-to-reduce-redundant-code-when-adding-new-c0x-rvalue-reference-operator-over ("How to reduce redundant code when adding new c++0x rvalue reference operator overloads"). If you have a function that accepts a number of potentially-moveable arguments, and would move them if it can (e.g. a factory function/constructor: Object create_object(string, vector<string>, string) or the like), and want to move or copy each argument as appropriate, you quickly start writing a lot of code. If the argument types are movable, then one could just write one version that accepts the arguments by value, as above. But if the arguments are (legacy) non-movable-but-swappable classes a la C++03, and you can't change them, then writing rvalue reference overloads is more efficient. So if lvalues did bind to rvalues via an implicit copy, then you could write just one overload like create_object(legacy_string &&, legacy_vector<legacy_string> &&, legacy_string &&) and it would more or less work like providing all the combinations of rvalue/lvalue reference overloads - actual arguments that were lvalues would get copied and then bound to the arguments, actual arguments that were rvalues would get directly bound. Questions My questions are then: Is this a valid interpretation of the standard? It seems that it's not the conventional or intended one, at any rate. Does it make intuitive sense? Is there a problem with this idea that I"m not seeing? It seems like you could get copies being quietly created when that's not exactly expected, but that's the status quo in places in C++03 anyway. Also, it would make some overloads viable when they're currently not, but I don't see it being a problem in practice. Is this a significant enough improvement that it would be worth making e.g. an experimental patch for GCC?

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  • how to avoid temporaries when copying weakly typed object

    - by Truncheon
    Hi. I'm writing a series classes that inherit from a base class using virtual. They are INT, FLOAT and STRING objects that I want to use in a scripting language. I'm trying to implement weak typing, but I don't want STRING objects to return copies of themselves when used in the following way (instead I would prefer to have a reference returned which can be used in copying): a = "hello "; b = "world"; c = a + b; I have written the following code as a mock example: #include <iostream> #include <string> #include <cstdio> #include <cstdlib> std::string dummy("<int object cannot return string reference>"); struct BaseImpl { virtual bool is_string() = 0; virtual int get_int() = 0; virtual std::string get_string_copy() = 0; virtual std::string const& get_string_ref() = 0; }; struct INT : BaseImpl { int value; INT(int i = 0) : value(i) { std::cout << "constructor called\n"; } INT(BaseImpl& that) : value(that.get_int()) { std::cout << "copy constructor called\n"; } bool is_string() { return false; } int get_int() { return value; } std::string get_string_copy() { char buf[33]; sprintf(buf, "%i", value); return buf; } std::string const& get_string_ref() { return dummy; } }; struct STRING : BaseImpl { std::string value; STRING(std::string s = "") : value(s) { std::cout << "constructor called\n"; } STRING(BaseImpl& that) { if (that.is_string()) value = that.get_string_ref(); else value = that.get_string_copy(); std::cout << "copy constructor called\n"; } bool is_string() { return true; } int get_int() { return atoi(value.c_str()); } std::string get_string_copy() { return value; } std::string const& get_string_ref() { return value; } }; struct Base { BaseImpl* impl; Base(BaseImpl* p = 0) : impl(p) {} ~Base() { delete impl; } }; int main() { Base b1(new INT(1)); Base b2(new STRING("Hello world")); Base b3(new INT(*b1.impl)); Base b4(new STRING(*b2.impl)); std::cout << "\n"; std::cout << b1.impl->get_int() << "\n"; std::cout << b2.impl->get_int() << "\n"; std::cout << b3.impl->get_int() << "\n"; std::cout << b4.impl->get_int() << "\n"; std::cout << "\n"; std::cout << b1.impl->get_string_ref() << "\n"; std::cout << b2.impl->get_string_ref() << "\n"; std::cout << b3.impl->get_string_ref() << "\n"; std::cout << b4.impl->get_string_ref() << "\n"; std::cout << "\n"; std::cout << b1.impl->get_string_copy() << "\n"; std::cout << b2.impl->get_string_copy() << "\n"; std::cout << b3.impl->get_string_copy() << "\n"; std::cout << b4.impl->get_string_copy() << "\n"; return 0; } It was necessary to add an if check in the STRING class to determine whether its safe to request a reference instead of a copy: Script code: a = "test"; b = a; c = 1; d = "" + c; /* not safe to request reference by standard */ C++ code: STRING(BaseImpl& that) { if (that.is_string()) value = that.get_string_ref(); else value = that.get_string_copy(); std::cout << "copy constructor called\n"; } If was hoping there's a way of moving that if check into compile time, rather than run time.

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  • Silverlight Cream for March 26, 2010 -- #821

    - by Dave Campbell
    In this Issue: Max Paulousky, Christian Schormann, John Papa, Phani Raj, David Anson(-2-, -3-), Brad Abrams(-2-), and Jeff Wilcox(-2-, -3-). Shoutouts: Jeff Wilcox posted his material from mix and some preview TestFramework bits: Unit Testing Silverlight & Windows Phone Applications – talk now online At MIX10, Jeff Wilcox demo'd an app called "Peppermint"... here's the bleeding edge demo: “Peppermint” MIX demo sources Erik Mork and Co. have put out their weekly This Week In Silverlight 3.25.2010 Brad Abrams has all his materials posted for his MIX10 session Mix2010: Search Engine Optimization (SEO) for Microsoft Silverlight... including play-by-play of the demo and all source. Do you use Rooler? Well you should! Watch a video Pete Brown did with Pete Blois on Expression Blend, Windows Phone, Rooler Interested in Silverlight and XNA for WP7? Me too! Michael Klucher has a post outlining the two: Silverlight and XNA Framework Game Development and Compatibility From SilverlightCream.com: Modularity in Silverlight Applications - An Issue With ModuleInitializeException Max Paulousky has a truly ugly error trace listed by way of not having a reference listed, and the obvious simple solution. Next time he'll talk about the difficult situations. Using SketchFlow to Prototype for Windows Phone Christian Schormann has a tutorial up on using Expression Blend to develop for WP7 ... who better than Christian for that task?? Silverlight TV 18: WCF RIA Services Validation John Papa held forth with Nikhil Kothari on WCF RIA Services and validation just prior to MIX10, and was posted yesterday. Building SL3 applications using OData client Library with Vs 2010 RC Phani Raj walks through building an OData consumer in SL3, the first problem you're going to hit, and the easy solution to it. Tip: When creating a DependencyProperty, follow the handy convention of "wrapper+register+static+virtual" David Anson has a couple more of his 'Tips' up... this first is about Dependency Properties again... having a good foundation for all your Dependency Properties is a great way to avoid problems. Tip: Do not assign DependencyProperty values in a constructor; it prevents users from overriding them In the next post, David Anson talks about not assigning Dependency Property values in a constructor and gives one of the two ways to get around doing so. Tip: Set DependencyProperty default values in a class's default style if it's more convenient In his latest post, David Anson gives the second way to avoid setting a Dependency Property value in the constructor. Silverlight 4 + RIA Services - Ready for Business: Search Engine Optimization (SEO) Brad Abrams Abrams adds SEO to the tutorial series he's doing. He begins with his PDC09 session material on the subject and then takes off on a great detailed tutorial all with source. Silverlight 4 + RIA Services - Ready for Business: Localizing Business Application Brad Abrams then discusses localization and Silverlight in another detailed tutorial with all code included. Silverlight Toolkit and the Windows Phone: WrapPanel, and a few others Jeff Wilcox has a few WP7 posts I'm going to push today. This first is from earlier this week and is about using the Toolkit in WP7 and better than that, he includes the bits you need if all you want is the WrapPanel Data binding user settings in Windows Phone applications In the next one from yesterday, Jeff Wilcox demonstrates saving some user info in Isolated Storage to improve the user experience, and shares all the necessary plumbing files, and other external links as well. Displaying 2D QR barcodes in Windows Phone applications In a post from today, Jeff Wilcox ported his Silverlight 2D QR Barcode app from last year into WP7 ... just very cool... get the source and display your Microsoft Tag. Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone    MIX10

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  • Unable to build my c++ code with g++ 4.6.3

    - by Mriganka
    I am facing multiple issues with building my c++ code on Ubuntu 12.04. This code was building and running fine on RH Enterprise. I am using g++ 4.6.3. Here's the output of g++ -v. g++ -v Using built-in specs. COLLECT_GCC=g++ COLLECT_LTO_WRAPPER=/usr/lib/gcc/i686-linux-gnu/4.6/lto-wrapper Target: i686-linux-gnu Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro 4.6.3-1ubuntu5' --with-bugurl=file:///usr/share/doc/gcc-4.6/README.Bugs --enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.6 --enable-shared --enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.6 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object --enable-plugin --enable-objc-gc --enable-targets=all --disable-werror --with-arch-32=i686 --with-tune=generic --enable-checking=release --build=i686-linux-gnu --host=i686-linux-gnu --target=i686-linux-gnu Thread model: posix gcc version 4.6.3 (Ubuntu/Linaro 4.6.3-1ubuntu5) Here's a sample of my code: #include "Word.h" #include < string> using namespace std; pthread_mutex_t Word::_lock = PTHREAD_MUTEX_INITIALIZER; Word::Word(): _occurrences(1) { memset(_buf, 0, 25); } Word::Word(char *str): _occurrences(1) { memset(_buf, 0, 25); if (str != NULL) { strncpy(_buf, str, strlen(str)); } } g++ -c -ansi or g++ -c -std=c++98 or g++ -c -std=c++03, none of these options are able to build the code correctly. I get the following compilation errors: mriganka@ubuntu:~/WordCount$ make g++ -c -g -ansi Word.cpp -o Word.o Word.cpp: In constructor ‘Word::Word()’: Word.cpp:10:21: error: ‘memset’ was not declared in this scope Word.cpp: In constructor ‘Word::Word(char*)’: Word.cpp:16:21: error: ‘memset’ was not declared in this scope Word.cpp:19:34: error: ‘strlen’ was not declared in this scope Word.cpp:19:35: error: ‘strncpy’ was not declared in this scope Word.cpp: In member function ‘void Word::operator=(const Word&)’: Word.cpp:37:42: error: ‘strlen’ was not declared in this scope Word.cpp:37:43: error: ‘strncpy’ was not declared in this scope Word.cpp: In copy constructor ‘Word::Word(const Word&)’: Word.cpp:44:21: error: ‘memset’ was not declared in this scope Word.cpp:45:52: error: ‘strlen’ was not declared in this scope Word.cpp:45:53: error: ‘strncpy’ was not declared in this scope So basically g++ 4.6.3 on Ubuntu 12.04 is not able to recognize the standard c++ headers. And I am not finding a way out of this situation. Second problem: In order to make progress, I included < string.h instead of < string. But now I am facing linking errors with my message queue and pthread library functions. Here's the error that I am getting: mriganka@ubuntu:~/WordCount$ make g++ -c -g -ansi Word.cpp -o Word.o g++ -lrt -I/usr/lib/i386-linux-gnu Word.o HashMap.o main.o -o word_count main.o: In function `main': /home/mriganka/WordCount/main.cpp:75: undefined reference to `pthread_create' /home/mriganka/WordCount/main.cpp:90: undefined reference to `mq_open' /home/mriganka/WordCount/main.cpp:93: undefined reference to `mq_getattr' /home/mriganka/WordCount/main.cpp:113: undefined reference to `mq_send' /home/mriganka/WordCount/main.cpp:123: undefined reference to `pthread_join' /home/mriganka/WordCount/main.cpp:129: undefined reference to `mq_close' /home/mriganka/WordCount/main.cpp:130: undefined reference to `mq_unlink' main.o: In function `count_words(void*)': /home/mriganka/WordCount/main.cpp:151: undefined reference to `mq_open' /home/mriganka/WordCount/main.cpp:154: undefined reference to `mq_getattr' /home/mriganka/WordCount/main.cpp:162: undefined reference to `mq_timedreceive' collect2: ld returned 1 exit status Here's my makefile: CC=g++ CFLAGS=-c -g -ansi LDFLAGS=-lrt INC=-I/usr/lib/i386-linux-gnu SOURCES=Word.cpp HashMap.cpp main.cpp OBJECTS=$(SOURCES:.cpp=.o) EXECUTABLE=word_count all: $(SOURCES) $(EXECUTABLE) $(EXECUTABLE): $(OBJECTS) $(CC) $(LDFLAGS) $(INC) -pthread $(OBJECTS) -o $@ .cpp.o: $(CC) $(CFLAGS) $< -o $@ clean: rm -f *.o word_count Please help me to resolve both the issues. I searched online relentlessly for any solution of these problems, but no one seems to have encountered these issues.

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  • std::map for storing static const Objects

    - by Sean M.
    I am making a game similar to Minecraft, and I am trying to fine a way to keep a map of Block objects sorted by their id. This is almost identical to the way that Minecraft does it, in that they declare a bunch of static final Block objects and initialize them, and then the constructor of each block puts a reference of that block into whatever the Java equivalent of a std::map is, so there is a central place to get ids and the Blocks with those ids. The problem is, that I am making my game in C++, and trying to do the exact same thing. In Block.h, I am declaring the Blocks like so: //Block.h public: static const Block Vacuum; static const Block Test; And in Block.cpp I am initializing them like so: //Block.cpp const Block Block::Vacuum = Block("Vacuum", 0, 0); const Block Block::Test = Block("Test", 1, 0); The block constructor looks like this: Block::Block(std::string name, uint16 id, uint8 tex) { //Check for repeat ids if (IdInUse(id)) { fprintf(stderr, "Block id %u is already in use!", (uint32)id); throw std::runtime_error("You cannot reuse block ids!"); } _id = id; //Check for repeat names if (NameInUse(name)) { fprintf(stderr, "Block name %s is already in use!", name); throw std::runtime_error("You cannot reuse block names!"); } _name = name; _tex = tex; //fprintf(stdout, "Using texture %u\n", _tex); _transparent = false; _solidity = 1.0f; idMap[id] = this; nameMap[name] = this; } And finally, the maps that I'm using to store references of Blocks in relation to their names and ids are declared as such: std::map<uint16, Block*> Block::idMap = std::map<uint16, Block*>(); //The map of block ids std::map<std::string, Block*> Block::nameMap = std::map<std::string, Block*>(); //The map of block names The problem comes when I try to get the Blocks in the maps using a method called const Block* GetBlock(uint16 id), where the last line is return idMap.at(id);. This line returns a Block with completely random values like _visibility = 0xcccc and such like that, found out through debugging. So my question is, is there something wrong with the blocks being declared as const obejcts, and then stored at pointers and accessed later on? The reason I cant store them as Block& is because that makes a copy of the Block when it is entered, so the block wouldn't have any of the attributes that could be set afterwards in the constructor of any child class, so I think I need to store them as a pointer. Any help is greatly appreciated, as I don't fully understand pointers yet. Just ask if you need to see any other parts of the code.

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  • Adding custom interfaces to your mock instance.

    - by mehfuzh
    Previously, i made a post  showing how you can leverage the dependent interfaces that is implemented by JustMock during the creation of mock instance. It could be a informative post that let you understand how JustMock behaves internally for class or interfaces implement other interfaces into it. But the question remains, how you can add your own custom interface to your target mock. In this post, i am going to show you just that. Today, i will not start with a dummy class as usual rather i will use two most common interfaces in the .NET framework  and create a mock combining those. Before, i start i would like to point out that in the recent release of JustMock we have extended the Mock.Create<T>(..) with support for additional settings though closure. You can add your own custom interfaces , specify directly the real constructor that should be called or even set the behavior of your target. Doing a fast forward directly to the point,  here goes the test code for create a creating a mock that contains the mix for ICloneable and IDisposable using the above mentioned changeset. var myMock = Mock.Create<IDisposable>(x => x.Implements<ICloneable>()); var myMockAsClonable = myMock as ICloneable; bool isCloned = false;   Mock.Arrange(() => myMockAsClonable.Clone()).DoInstead(() => isCloned = true);   myMockAsClonable.Clone();   Assert.True(isCloned);   Here, we are creating the target mock for IDisposable and also implementing ICloneable. Finally, using the “as” for getting the ICloneable reference accordingly arranging it, acting on it and asserting if the expectation is met properly. This is a very rudimentary example, you can do the same for a given class: var realItem = Mock.Create<RealItem>(x => {     x.Implements<IDisposable>();     x.CallConstructor(() => new RealItem(0)); }); var iDispose = realItem as IDisposable;     iDispose.Dispose(); Here, i am also calling the real constructor for RealItem class.  This is to mention that you can implement custom interfaces only for non-sealed classes or less it will end up with a proper exception. Also, this feature don’t require any profiler, if you are agile or running it inside silverlight runtime feel free to try it turning off the JM add-in :-). TIP :  Ability to  specify real constructor could be a useful productivity boost in cases for code change and you can re-factor the usage just by one click with your favorite re-factor tool.   That’s it for now and hope that helps Enjoy!!

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  • Bug in Delphi XE RegularExpressions Unit

    - by Jan Goyvaerts
    Using the new RegularExpressions unit in Delphi XE, you can iterate over all the matches that a regex finds in a string like this: procedure TForm1.Button1Click(Sender: TObject); var RegEx: TRegEx; Match: TMatch; begin RegEx := TRegex.Create('\w+'); Match := RegEx.Match('One two three four'); while Match.Success do begin Memo1.Lines.Add(Match.Value); Match := Match.NextMatch; end end; Or you could save yourself two lines of code by using the static TRegEx.Match call: procedure TForm1.Button2Click(Sender: TObject); var Match: TMatch; begin Match := TRegEx.Match('One two three four', '\w+'); while Match.Success do begin Memo1.Lines.Add(Match.Value); Match := Match.NextMatch; end end; Unfortunately, due to a bug in the RegularExpressions unit, the static call doesn’t work. Depending on your exact code, you may get fewer matches or blank matches than you should, or your application may crash with an access violation. The RegularExpressions unit defines TRegEx and TMatch as records. That way you don’t have to explicitly create and destroy them. Internally, TRegEx uses TPerlRegEx to do the heavy lifting. TPerlRegEx is a class that needs to be created and destroyed like any other class. If you look at the TRegEx source code, you’ll notice that it uses an interface to destroy the TPerlRegEx instance when TRegEx goes out of scope. Interfaces are reference counted in Delphi, making them usable for automatic memory management. The bug is that TMatch and TGroupCollection also need the TPerlRegEx instance to do their work. TRegEx passes its TPerlRegEx instance to TMatch and TGroupCollection, but it does not pass the instance of the interface that is responsible for destroying TPerlRegEx. This is not a problem in our first code sample. TRegEx stays in scope until we’re done with TMatch. The interface is destroyed when Button1Click exits. In the second code sample, the static TRegEx.Match call creates a local variable of type TRegEx. This local variable goes out of scope when TRegEx.Match returns. Thus the reference count on the interface reaches zero and TPerlRegEx is destroyed when TRegEx.Match returns. When we call MatchAgain the TMatch record tries to use a TPerlRegEx instance that has already been destroyed. To fix this bug, delete or rename the two RegularExpressions.dcu files and copy RegularExpressions.pas into your source code folder. Make these changes to both the TMatch and TGroupCollection records in this unit: Declare FNotifier: IInterface; in the private section. Add the parameter ANotifier: IInterface; to the Create constructor. Assign FNotifier := ANotifier; in the constructor’s implementation. You also need to add the ANotifier: IInterface; parameter to the TMatchCollection.Create constructor. Now try to compile some code that uses the RegularExpressions unit. The compiler will flag all calls to TMatch.Create, TGroupCollection.Create and TMatchCollection.Create. Fix them by adding the ANotifier or FNotifier parameter, depending on whether ARegEx or FRegEx is being passed. With these fixes, the TPerlRegEx instance won’t be destroyed until the last TRegEx, TMatch, or TGroupCollection that uses it goes out of scope or is used with a different regular expression.

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  • JPedal Action for Converting PDF to JavaFX

    - by Geertjan
    The question of the day comes from Mark Stephens, from JPedal (JPedal is the leading 100% Java PDF library, providing a Java PDF viewer, PDF to image conversion, PDF printing or adding PDF search and PDF extraction features), in the form of a screenshot: The question is clear. By looking at the annotations above, you can see that Mark has an ActionListener that has been bound to the right-click popup menu on PDF files. Now he needs to get hold of the file to which the Action has been bound. How, oh  how, can one get hold of that file? Well, it's simple. Leave everything you see above exactly as it is but change the Java code section to this: public final class PDF2JavaFXContext implements ActionListener {     private final DataObject context;     public PDF2JavaFXContext(DataObject context) {         this.context = context;     }     public void actionPerformed(ActionEvent ev) {         FileObject fo = context.getPrimaryFile();         File theFile = FileUtil.toFile(fo);         //do something with your file...     } } The point is that the annotations at the top of the class bind the Action to either Actions.alwaysEnabled, which is a factory method for creating always-enabled Actions, or Actions.context, which is a factory method for creating context-sensitive Actions. How does the Action get bound to the factory method? The annotations are converted, when the module is compiled, into XML registration entries in the "generated-layer.xml", which you can find in your "build" folder, in the Files window, after building the module. In Mark's case, since the Action should be context-sensitive to PDF files, he needs to bind his PDF2JavaFXContext ActionListener (which should probably be named "PDF2JavaFXActionListener", since the class is an ActionListener) to Actions.context. All he needs to do that is pass in the object he wants to work with into the constructor of the ActionListener. Now, when the module is built, the annotation processor is going to take the annotations and convert them to XML registration entries, but the constructor will also be checked to see whether it is empty or not. In this case, the constructor isn't empty, hence the Action should be context-sensitive and so the ActionListener is bound to Actions.context. The Actions.context will do all the enablement work for Mark, so that he will not need to provide any code for enabling/disabling the Action. The Action will be enabled whenever a DataObject is selected. Since his Action is bound to Nodes in the Projects window that represent PDF files, the Action will always be enabled whenever Mark right-clicks on a PDF Node, since the Node exposes its own DataObject. Once Mark has access to the DataObject, he can get the underlying FileObject via getPrimaryFile and he can then convert the FileObject to a java.io.File via FileUtil.getConfigFile. Once he's got the java.io.File, he can do with it whatever he needs. Further reading: http://bits.netbeans.org/dev/javadoc/

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  • concurrency::extent<N> from amp.h

    - by Daniel Moth
    Overview We saw in a previous post how index<N> represents a point in N-dimensional space and in this post we'll see how to define the N-dimensional space itself. With C++ AMP, an N-dimensional space can be specified with the template class extent<N> where you define the size of each dimension. From a look and feel perspective, you'd expect the programmatic interface of a point type and size type to be similar (even though the concepts are different). Indeed, exactly like index<N>, extent<N> is essentially a coordinate vector of N integers ordered from most- to least- significant, BUT each integer represents the size for that dimension (and hence cannot be negative). So, if you read the description of index, you won't be surprised with the below description of extent<N> There is the rank field returning the value of N you passed as the template parameter. You can construct one extent from another (via the copy constructor or the assignment operator), you can construct it by passing an integer array, or via convenience constructor overloads for 1- 2- and 3- dimension extents. Note that the parameterless constructor creates an extent of the specified rank with all bounds initialized to 0. You can access the components of the extent through the subscript operator (passing it an integer). You can perform some arithmetic operations between extent objects through operator overloading, i.e. ==, !=, +=, -=, +, -. There are operator overloads so that you can perform operations between an extent and an integer: -- (pre- and post- decrement), ++ (pre- and post- increment), %=, *=, /=, +=, –= and, finally, there are additional overloads for plus and minus (+,-) between extent<N> and index<N> objects, returning a new extent object as the result. In addition to the usual suspects, extent offers a contains function that tests if an index is within the bounds of the extent (assuming an origin of zero). It also has a size function that returns the total linear size of this extent<N> in units of elements. Example code extent<2> e(3, 4); _ASSERT(e.rank == 2); _ASSERT(e.size() == 3 * 4); e += 3; e[1] += 6; e = e + index<2>(3,-4); _ASSERT(e == extent<2>(9, 9)); _ASSERT( e.contains(index<2>(8, 8))); _ASSERT(!e.contains(index<2>(8, 9))); grid<N> Our upcoming pre-release bits also have a similar type to extent, grid<N>. The way you create a grid is by passing it an extent, e.g. extent<3> e(4,2,6); grid<3> g(e); I am not going to dive deeper into grid, suffice for now to think of grid<N> simply as an alias for the extent<N> object, that you create when you encounter a function that expects a grid object instead of an extent object. Usage The extent class on its own simply defines the size of the N-dimensional space. We'll see in future posts that when you create containers (arrays) and wrappers (array_views) for your data, it is an extent<N> object that you'll need to use to create those (and use an index<N> object to index into them). We'll also see that it is a grid<N> object that you pass to the new parallel_for_each function that I'll cover in the next post. Comments about this post by Daniel Moth welcome at the original blog.

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