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  • How to implement a unit converter in java

    - by Mohit Deshpande
    How could I possibly implement a unit converter in Java??? I was thinking of having a abstract base class: public abstract class Unit { ... public void ConvertTo(Unit unit); } Then having each class like Meter Kilometer Inch Centimeter Millimeter ... derive from that base Unit class. All the units of length would be in a package called com.unitconverter.distance, then a package, com.unitconverter.energy, for energy etc. etc. So is this the best way to implement a unit converter? Or is there a better or more easier way?

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  • Cannot instantiate abstract class or interface : problem while persisting

    - by sammy
    i have a class campaign that maintains a list of AdGroupInterfaces. im going to persist its implementation @Entity @Table(name = "campaigns") public class Campaign implements Serializable,Comparable<Object>,CampaignInterface { private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; @OneToMany ( cascade = {CascadeType.ALL}, fetch = FetchType.EAGER, targetEntity=AdGroupInterface.class ) @org.hibernate.annotations.Cascade( value = org.hibernate.annotations.CascadeType.DELETE_ORPHAN ) @org.hibernate.annotations.IndexColumn(name = "CHOICE_POSITION") private List<AdGroupInterface> AdGroup; public Campaign() { super(); } public List<AdGroupInterface> getAdGroup() { return AdGroup; } public void setAdGroup(List<AdGroupInterface> adGroup) { AdGroup = adGroup; } public void set1AdGroup(AdGroupInterface adGroup) { if(AdGroup==null) AdGroup=new LinkedList<AdGroupInterface>(); AdGroup.add(adGroup); } } AdGroupInterface's implementation is AdGroups. when i add an adgroup to the list in campaign, campaign c; c.getAdGroupList().add(new AdGroups()), etc and save campaign it says"Cannot instantiate abstract class or interface :" AdGroupInterface its not recognizing the implementation just before persisting... Whereas Persisting adGroups separately works. when it is a member of another entity, it doesnt get persisted. import java.io.Serializable; import java.util.List; import javax.persistence.*; @Entity @DiscriminatorValue("1") @Table(name = "AdGroups") public class AdGroups implements Serializable,Comparable,AdGroupInterface{ /** * */ private static final long serialVersionUID = 1L; private Long Id; private String Name; private CampaignInterface Campaign; private MonetaryValue DefaultBid; public AdGroups(){ super(); } public AdGroups( String name, CampaignInterface campaign) { super(); this.Campaign=new Campaign(); Name = name; this.Campaign = campaign; DefaultBid = defaultBid; AdList=adList; } @Id @GeneratedValue(strategy = GenerationType.IDENTITY) @Column(name="AdGroup_Id") public Long getId() { return Id; } public void setId(Long id) { Id = id; } @Column(name="AdGroup_Name") public String getName() { return Name; } public void setName(String name) { Name = name; } @ManyToOne @JoinColumn (name="Cam_ID", nullable = true,insertable = false) public CampaignInterface getCampaign() { return Campaign; } public void setCampaign(CampaignInterface campaign) { this.Campaign = campaign; } } what am i missing?? please look into it ...

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  • Series of abstract classes and NHibernate

    - by Chris Cowdery-Corvan
    Hello, and first off thanks for your time to look at this. For a research project I'm working on, I have a somewhat complex design (which I've been given) to persist to a database via NHibernate. Here's an example of the class hierarchy: TransitStrategy, TransportationCompany and TransportationLocation are all abstract classes. The XML configuration I have is presently: <?xml version="1.0" encoding="utf-8" ?> <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="Vacationizer" namespace="Vacationizer.Domain.Transit"> <class name="TransitStrategy"> <id name="TransitStrategyId"> <generator class="guid" /> </id> <property name="Restrictions" /> <joined-subclass name="Flight" table="Flight_TransitStrategy"> <key column="TransitStrategyId" /> <property name="DepartingAirport" /> <property name="ArrivingAirport" /> <property name="Airline" /> <property name="FlightNumber" /> <property name="FlightArrivalTime" /> <property name="FlightDepartureTime" /> </joined-subclass> <joined-subclass name="RentalCar" table="RentalCar_TransitStrategy"> <key column="TransitStrategyId" /> <property name="RentalCarBranch" /> <property name="CarMake" /> <property name="CarModel" /> <property name="CarYear" /> <property name="CarColor" /> <property name="RentalBegins" /> <property name="RentalEnds" /> </joined-subclass> </class> <?xml version="1.0" encoding="utf-8" ?> <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="Vacationizer" namespace="Vacationizer.Domain.Transit"> <class name="TransportationCompany"> <id name="TransportationCompanyId"> <generator class="guid" /> </id> <property name="Name" /> <property name="Reviews" /> <property name="Website" /> <property name="Photo" /> <joined-subclass name="Airline" table="Airline_TransportationCompany"> <key column="TransportationLocationId" /> </joined-subclass> <joined-subclass name="RentalCarAgency" table="RentalCarAgency_TransportationCompany"> <key column="TransportationLocationId" /> </joined-subclass> </class> <?xml version="1.0" encoding="utf-8" ?> <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="Vacationizer" namespace="Vacationizer.Domain.Transit"> <class name="TransportationLocation"> <id name="TransportationLocationId"> <generator class="guid" /> </id> <property name="Name" /> <property name="Image" /> <property name="Geolocation" /> <property name="Reviews" /> <!-- <property name="HoursOpen" />--> <property name="PhoneNumber" /> <property name="FaxNumber" /> <joined-subclass name="Airport" table="Airport_TransportationLocation"> <key column="TransportationLocationId" /> <property name="AirportCode" /> <property name="Website" /> </joined-subclass> <joined-subclass name="RentalCarBranch" table="RentalCarBranch_TransportationLocation"> <key column="TransitStrategyId" /> <property name="Agency" /> </joined-subclass> </class> However, whenever I try to use this schema I get this error/stack trace: ------ Test started: Assembly: Vacationizer.Tests.dll ------ TestCase 'M:Vacationizer.Tests.VacationRepository_Fixture.TestFixtureSetUp' failed: Could not compile the mapping document: Vacationizer.Mappings.TransitStrategy.hbm.xml NHibernate.MappingException: Could not compile the mapping document: Vacationizer.Mappings.TransitStrategy.hbm.xml ---> NHibernate.MappingException: Problem trying to set property type by reflection ---> NHibernate.MappingException: class Vacationizer.Domain.Transit.RentalCar, Vacationizer, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null not found while looking for property: RentalCarBranch ---> NHibernate.PropertyNotFoundException: Could not find a getter for property 'RentalCarBranch' in class 'Vacationizer.Domain.Transit.RentalCar' at NHibernate.Properties.BasicPropertyAccessor.GetGetter(Type type, String propertyName) at NHibernate.Util.ReflectHelper.ReflectedPropertyClass(String className, String name, String accessorName) --- End of inner exception stack trace --- at NHibernate.Util.ReflectHelper.ReflectedPropertyClass(String className, String name, String accessorName) at NHibernate.Mapping.SimpleValue.SetTypeUsingReflection(String className, String propertyName, String accesorName) --- End of inner exception stack trace --- at NHibernate.Mapping.SimpleValue.SetTypeUsingReflection(String className, String propertyName, String accesorName) at NHibernate.Cfg.XmlHbmBinding.ClassBinder.CreateProperty(IValue value, String propertyName, String className, XmlNode subnode, IDictionary`2 inheritedMetas) at NHibernate.Cfg.XmlHbmBinding.ClassBinder.PropertiesFromXML(XmlNode node, PersistentClass model, IDictionary`2 inheritedMetas, UniqueKey uniqueKey, Boolean mutable, Boolean nullable, Boolean naturalId) at NHibernate.Cfg.XmlHbmBinding.JoinedSubclassBinder.HandleJoinedSubclass(PersistentClass model, XmlNode subnode, IDictionary`2 inheritedMetas) at NHibernate.Cfg.XmlHbmBinding.ClassBinder.PropertiesFromXML(XmlNode node, PersistentClass model, IDictionary`2 inheritedMetas, UniqueKey uniqueKey, Boolean mutable, Boolean nullable, Boolean naturalId) at NHibernate.Cfg.XmlHbmBinding.RootClassBinder.Bind(XmlNode node, HbmClass classSchema, IDictionary`2 inheritedMetas) at NHibernate.Cfg.XmlHbmBinding.MappingRootBinder.AddRootClasses(XmlNode parentNode, IDictionary`2 inheritedMetas) at NHibernate.Cfg.XmlHbmBinding.MappingRootBinder.Bind(XmlNode node) at NHibernate.Cfg.Configuration.AddValidatedDocument(NamedXmlDocument doc) --- End of inner exception stack trace --- at NHibernate.Cfg.Configuration.LogAndThrow(Exception exception) at NHibernate.Cfg.Configuration.AddValidatedDocument(NamedXmlDocument doc) at NHibernate.Cfg.Configuration.ProcessMappingsQueue() at NHibernate.Cfg.Configuration.AddDocumentThroughQueue(NamedXmlDocument document) at NHibernate.Cfg.Configuration.AddXmlReader(XmlReader hbmReader, String name) at NHibernate.Cfg.Configuration.AddInputStream(Stream xmlInputStream, String name) at NHibernate.Cfg.Configuration.AddResource(String path, Assembly assembly) at NHibernate.Cfg.Configuration.AddAssembly(Assembly assembly) at NHibernate.Cfg.Configuration.AddAssembly(String assemblyName) at NHibernate.Cfg.Configuration.DoConfigure(IHibernateConfiguration hc) at NHibernate.Cfg.Configuration.Configure() VacationRepository_Fixture.cs(24,0): at Vacationizer.Tests.VacationRepository_Fixture.TestFixtureSetUp() 0 passed, 1 failed, 0 skipped, took 8.38 seconds (Ad hoc). Any ideas on how I can implement this differently? Thanks very much!

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  • Java inheritance question

    - by Milos
    I have an abstract class Airplane, and two classes PassengerAirplane and CargoAirplane, which extend class Airplane. I also have an interface Measurable, and two classes that implement it - People and Containers. So, Airplane can do many things on its own, and there is a method which allows measurable things to be added to the airplane (called addAMeasurableThing). The only difference between PassengerAirplane/CargoAirplane and just an Airplane is that addAMeasurableThing should only accept People / Containers, and not any kind Measurable things. How do I implement this? I tried doing: Airplane class: public abstract Airplane addAMeasurableThing (Measurable m, int position); PassengerAirplane class: public Airplane addAMeasurableThing (Measurable m, int position) { if (m instanceof People)... CargoAirplane class: public Airplane addAMeasurableThing (Measurable m, int position) { if (m instanceof Containers)... But when I was debugging it, I've noticed that addAMeasurableThing in the CargoAirplane class never gets called, because both methods have the same signature. So how can the appropriate PassengerAirplane/CargoAirplane's addAMeasurableThing be called, depending on the type of Measurable thing that is being passed on? Thanks!

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  • Problems Allocating Objects of Derived Class Where Base Class has Abstract Virtual Functions

    - by user1743901
    I am trying to get this Zombie/Human agent based simulation running, but I am having problems with these derived classes (Human and Zombie) who have parent class "Creature". I have 3 virtual functions declared in "Creature" and all three of these are re-declared AND DEFINED in both "Human" and "Zombie". But for some reason when I have my program call "new" to allocate memory for objects of type Human or Zombie, it complains about the virtual functions being abstract. Here's the code: definitions.h #ifndef definitions_h #define definitions_h class Creature; class Item; class Coords; class Grid { public: Creature*** cboard; Item*** iboard; int WIDTH; int HEIGHT; Grid(int WIDTHVALUE, int HEIGHTVALUE); void FillGrid(); //initializes grid object with humans and zombies void Refresh(); //calls Creature::Die(),Move(),Attack(),Breed() on every square void UpdateBuffer(char** buffer); bool isEmpty(int startx, int starty, int dir); char CreatureType(int xcoord, int ycoord); char CreatureType(int startx, int starty, int dir); }; class Random { public: int* rptr; void Print(); Random(int MIN, int MAX, int LEN); ~Random(); private: bool alreadyused(int checkthis, int len, int* rptr); bool isClean(); int len; }; class Coords { public: int x; int y; int MaxX; int MaxY; Coords() {x=0; y=0; MaxX=0; MaxY=0;} Coords(int X, int Y, int WIDTH, int HEIGHT) {x=X; y=Y; MaxX=WIDTH; MaxY=HEIGHT; } void MoveRight(); void MoveLeft(); void MoveUp(); void MoveDown(); void MoveUpRight(); void MoveUpLeft(); void MoveDownRight(); void MoveDownLeft(); void MoveDir(int dir); void setx(int X) {x=X;} void sety(int Y) {y=Y;} }; class Creature { public: bool alive; Coords Location; char displayletter; Creature() {Location.x=0; Location.y=0;} Creature(int i, int j) {Location.setx(i); Location.sety(j);} virtual void Attack() =0; virtual void AttackCreature(Grid G, int attackdirection) =0; virtual void Breed() =0; void Die(); void Move(Grid G); int DecideSquare(Grid G); void MoveTo(Grid G, int dir); }; class Human : public Creature { public: bool armed; //if armed, chances of winning fight increased for next fight bool vaccinated; //if vaccinated, no chance of getting infected int bitecount; //if a human is bitten, bite count is set to a random number int breedcount; //if a human goes x steps without combat, will breed if next to a human int starvecount; //if a human does not eat in x steps, will die Human() {displayletter='H';} Human(int i, int j) {displayletter='H';} void Attack(Grid G); void AttackCreature(Grid G, int attackdirection); void Breed(Grid G); //will breed after x steps and next to human int DecideAttack(Grid G); }; class Zombie : public Creature { public: Zombie() {displayletter='Z';} Zombie(int i, int j) {displayletter='Z';} void Attack(Grid G); void AttackCreature(Grid G, int attackdirection); void Breed() {} //does nothing int DecideAttack(Grid G); void AttackCreature(Grid G, int attackdirection); }; class Item { }; #endif definitions.cpp #include <cstdlib> #include "definitions.h" Random::Random(int MIN, int MAX, int LEN) //constructor { len=LEN; rptr=new int[LEN]; //allocate array of given length for (int i=0; i<LEN; i++) { int random; do { random = rand() % (MAX-MIN+1) + MIN; } while (alreadyused(random,LEN,rptr)); rptr[i]=random; } } bool Random::alreadyused(int checkthis, int len, int* rptr) { for (int i=0; i<len; i++) { if (rptr[i]==checkthis) return 1; } return 0; } Random::~Random() { delete rptr; } Grid::Grid(int WIDTHVALUE, int HEIGHTVALUE) { WIDTH = WIDTHVALUE; HEIGHT = HEIGHTVALUE; //builds 2d array of creature pointers cboard = new Creature**[WIDTH]; for(int i=0; i<WIDTH; i++) { cboard[i] = new Creature*[HEIGHT]; } //builds 2d array of item pointers iboard = new Item**[WIDTH]; for (int i=0; i<WIDTH; i++) { iboard[i] = new Item*[HEIGHT]; } } void Grid::FillGrid() { /* For each creature pointer in grid, randomly selects whether to initalize as zombie, human, or empty square. This methodology can be changed to initialize different creature types with different probabilities */ int random; for (int i=0; i<WIDTH; i++) { for (int j=0; j<HEIGHT; j++) { Random X(1,100,1); //create a single random integer from [1,100] at X.rptr random=*(X.rptr); if (random < 20) cboard[i][j] = new Human(i,j); else if (random < 40) cboard[i][j] = new Zombie(i,j); else cboard[i][j] = NULL; } } //at this point every creature pointer should be pointing to either //a zombie, human, or NULL with varying probabilities } void Grid::UpdateBuffer(char** buffer) { for (int i=0; i<WIDTH; i++) { for (int j=0; j<HEIGHT; j++) { if (cboard[i][j]) buffer[i][j]=cboard[i][j]->displayletter; else buffer[i][j]=' '; } } } bool Grid::isEmpty(int startx, int starty, int dir) { Coords StartLocation(startx,starty,WIDTH,HEIGHT); switch(dir) { case 1: StartLocation.MoveUp(); if (cboard[StartLocation.x][StartLocation.y]) return 0; case 2: StartLocation.MoveUpRight(); if (cboard[StartLocation.x][StartLocation.y]) return 0; case 3: StartLocation.MoveRight(); if (cboard[StartLocation.x][StartLocation.y]) return 0; case 4: StartLocation.MoveDownRight(); if (cboard[StartLocation.x][StartLocation.y]) return 0; case 5: StartLocation.MoveDown(); if (cboard[StartLocation.x][StartLocation.y]) return 0; case 6: StartLocation.MoveDownLeft(); if (cboard[StartLocation.x][StartLocation.y]) return 0; case 7: StartLocation.MoveLeft(); if (cboard[StartLocation.x][StartLocation.y]) return 0; case 8: StartLocation.MoveUpLeft(); if (cboard[StartLocation.x][StartLocation.y]) return 0; } return 1; } char Grid::CreatureType(int xcoord, int ycoord) { if (cboard[xcoord][ycoord]) //if there is a creature at location xcoord,ycoord return (cboard[xcoord][ycoord]->displayletter); else //if pointer at location xcoord,ycoord is null, return null char return '\0'; } char Grid::CreatureType(int startx, int starty, int dir) { Coords StartLocation(startx,starty,WIDTH,HEIGHT); switch(dir) { case 1: StartLocation.MoveUp(); if (cboard[StartLocation.x][StartLocation.y]) return (cboard[StartLocation.x][StartLocation.y]->displayletter); case 2: StartLocation.MoveUpRight(); if (cboard[StartLocation.x][StartLocation.y]) return (cboard[StartLocation.x][StartLocation.y]->displayletter); case 3: StartLocation.MoveRight(); if (cboard[StartLocation.x][StartLocation.y]) return (cboard[StartLocation.x][StartLocation.y]->displayletter); case 4: StartLocation.MoveDownRight(); if (cboard[StartLocation.x][StartLocation.y]) return (cboard[StartLocation.x][StartLocation.y]->displayletter); case 5: StartLocation.MoveDown(); if (cboard[StartLocation.x][StartLocation.y]) return (cboard[StartLocation.x][StartLocation.y]->displayletter); case 6: StartLocation.MoveDownLeft(); if (cboard[StartLocation.x][StartLocation.y]) return (cboard[StartLocation.x][StartLocation.y]->displayletter); case 7: StartLocation.MoveLeft(); if (cboard[StartLocation.x][StartLocation.y]) return (cboard[StartLocation.x][StartLocation.y]->displayletter); case 8: StartLocation.MoveUpLeft(); if (cboard[StartLocation.x][StartLocation.y]) return (cboard[StartLocation.x][StartLocation.y]->displayletter); } //if function hasn't returned by now, square being looked at is pointer to null return '\0'; //return null char } void Coords::MoveRight() {(x==MaxX)? (x=0):(x++);} void Coords::MoveLeft() {(x==0)? (x=MaxX):(x--);} void Coords::MoveUp() {(y==0)? (y=MaxY):(y--);} void Coords::MoveDown() {(y==MaxY)? (y=0):(y++);} void Coords::MoveUpRight() {MoveUp(); MoveRight();} void Coords::MoveUpLeft() {MoveUp(); MoveLeft();} void Coords::MoveDownRight() {MoveDown(); MoveRight();} void Coords::MoveDownLeft() {MoveDown(); MoveLeft();} void Coords::MoveDir(int dir) { switch(dir) { case 1: MoveUp(); break; case 2: MoveUpRight(); break; case 3: MoveRight(); break; case 4: MoveDownRight(); break; case 5: MoveDown(); break; case 6: MoveDownLeft(); break; case 7: MoveLeft(); break; case 8: MoveUpLeft(); break; case 0: break; } } void Creature::Move(Grid G) { int movedir=DecideSquare(G); MoveTo(G,movedir); } int Creature::DecideSquare(Grid G) { Random X(1,8,8); //X.rptr now points to 8 unique random integers from [1,8] for (int i=0; i<8; i++) { int dir=X.rptr[i]; if (G.isEmpty(Location.x,Location.y,dir)) return dir; } return 0; } void Creature::MoveTo(Grid G, int dir) { Coords OldLocation=Location; Location.MoveDir(dir); G.cboard[Location.x][Location.y]=this; //point new location to this creature G.cboard[OldLocation.x][OldLocation.y]=NULL; //point old location to NULL } void Creature::Die() { if (!alive) { delete this; this=NULL; } } void Human::Breed(Grid G) { if (!breedcount) { Coords BreedLocation=Location; Random X(1,8,8); for (int i=0; i<8; i++) { BreedLocation.MoveDir(X.rptr[i]); if (!G.cboard[BreedLocation.x][BreedLocation.y]) { G.cboard[BreedLocation.x][BreedLocation.y])=new Human(BreedLocation.x,BreedLocation.y); return; } } } } int Human::DecideAttack(Grid G) { Coords AttackLocation=Location; Random X(1,8,8); int attackdir; for (int i=0; i<8; i++) { attackdir=X.rptr[i]; switch(G.CreatureType(Location.x,Location.y,attackdir)) { case 'H': break; case 'Z': return attackdir; case '\0': break; default: break; } } return 0; //no zombies! } int AttackRoll(int para1, int para2) { //outcome 1: Zombie wins, human dies //outcome 2: Human wins, zombie dies //outcome 3: Human wins, zombie dies, but human is bitten Random X(1,100,1); int roll= *(X.rptr); if (roll < para1) return 1; else if (roll < para2) return 2; else return 3; } void Human::AttackCreature(Grid G, int attackdirection) { Coords AttackLocation=Location; AttackLocation.MoveDir(attackdirection); int para1=33; int para2=33; if (vaccinated) para2=101; //makes attackroll > para 2 impossible, never gets infected if (armed) para1-=16; //reduces chance of zombie winning fight int roll=AttackRoll(para1,para2); //outcome 1: Zombie wins, human dies //outcome 2: Human wins, zombie dies //outcome 3: Human wins, zombie dies, but human is bitten switch(roll) { case 1: alive=0; //human (this) dies return; case 2: G.cboard[AttackLocation.x][AttackLocation.y]->alive=0; return; //zombie dies case 3: G.cboard[AttackLocation.x][AttackLocation.y]->alive=0; //zombie dies Random X(3,7,1); //human is bitten bitecount=*(X.rptr); return; } } int Zombie::DecideAttack(Grid G) { Coords AttackLocation=Location; Random X(1,8,8); int attackdir; for (int i=0; i<8; i++) { attackdir=X.rptr[i]; switch(G.CreatureType(Location.x,Location.y,attackdir)) { case 'H': return attackdir; case 'Z': break; case '\0': break; default: break; } } return 0; //no zombies! } void Zombie::AttackCreature(Grid G, int attackdirection) { int reversedirection; if (attackdirection < 9 && attackdirection>0) { (attackdirection<5)? (reversedirection=attackdirection+4):(reversedirection=attackdirection-4); } else reversedirection=0; //this should never happen //when a zombie attacks a human, the Human::AttackZombie() function is called //in the "reverse" direction, utilizing that function that has already been written Coords ZombieLocation=Location; Coords HumanLocation=Location; HumanLocation.MoveDir(attackdirection); if (G.cboard[HumanLocation.x][HumanLocation.y]) //if there is a human there, which there should be G.cboard[HumanLocation.x][HumanLocation.y]->AttackCreature(G,reversedirection); } void Zombie::Attack(Grid G) { int attackdirection=DecideAttack(G); AttackCreature(G,attackdirection); } main.cpp #include <cstdlib> #include <iostream> #include "definitions.h" using namespace std; int main(int argc, char *argv[]) { Grid G(500,500); system("PAUSE"); return EXIT_SUCCESS; }

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  • c# - what approach can I use to extend a group of classes that include implemented methods? (see des

    - by Greg
    Hi, I want to create an extendible package I am writing that has Topology, Node & Relationship classes. The idea is these base classes would have the various methods in them necessary to base graph traversal methods etc. I would then like to be able to reuse this by extending the package. For example the base requirements might see Relationship with a parentNode & childNode. Topology would have a List of Nodes and List of Relationships. Topology would have methods like FindChildren(int depth). Then the usage would be to extend these such that additional attributes for Node and Relationships could be added etc. QUESTION - What would be the best approach to package & expose the base level classes/methods? (it's kind of like a custom collection but with multiple facets). Would the following concepts come into play: Interfaces - would this be a good idea to have ITopology, INode etc, or is this not required as the user would extend these classes anyway? Abstract Classes - would the base classes be abstract classes Custom Generic Collection - would some approach using this concept assist (but how would this work if there are the 3 different classes) thanks

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  • How can this Ambient Context become null?

    - by Mark Seemann
    Can anyone help me explain how TimeProvider.Current can become null in the following class? public abstract class TimeProvider { private static TimeProvider current = DefaultTimeProvider.Instance; public static TimeProvider Current { get { return TimeProvider.current; } set { if (value == null) { throw new ArgumentNullException("value"); } TimeProvider.current = value; } } public abstract DateTime UtcNow { get; } public static void ResetToDefault() { TimeProvider.current = DefaultTimeProvider.Instance; } } Observations All unit tests that directly reference TimeProvider also invokes ResetToDefault() in their Fixture Teardown. There is no multithreaded code involved. Once in a while, one of the unit tests fail because TimeProvider.Current is null (NullReferenceException is thrown). This only happens when I run the entire suite, but not when I just run a single unit test, suggesting to me that there is some subtle test interdependence going on. It happens approximately once every five or six test runs. When a failure occurs, it seems to be occuring in the first executed tests that involves TimeProvider.Current. More than one test can fail, but only one fails in a given test run. FWIW, here's the DefaultTimeProvider class as well: public class DefaultTimeProvider : TimeProvider { private readonly static DefaultTimeProvider instance = new DefaultTimeProvider(); private DefaultTimeProvider() { } public override DateTime UtcNow { get { return DateTime.UtcNow; } } public static DefaultTimeProvider Instance { get { return DefaultTimeProvider.instance; } } } I suspect that there's some subtle interplay going on with static initialization where the runtime is actually allowed to access TimeProvider.Current before all static initialization has finished, but I can't quite put my finger on it. Any help is appreciated.

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  • Is there a way to make sure classes implementing an Interface implement static methods?

    - by Tobias Kienzler
    Frist of all, I read erickson's usefull reply to "Why can’t I define a static method in a Java interface?". This question is not about the "why" but about the "how then?". So basically I want one Interface to provide both usual methods and e.g. a getSimilarObject method. For (a made up) example public interface ParametricFunction { /** @return f(x) using the parameters */ static abstract public double getValue(double x, double[] parameters); /** @return The function's name */ static abstract public String getName(); } and then public class Parabola implements ParametricFunction { /** @return f(x) = parameters[0] * x² + parameters[1] * x + parameters[2] */ static public double getValue(double x, double[] parameters) { return ( parameters[2] + x*(parameters[1] + x*parameters[0])); } static public String getName() { return "Parabola"; } } Since this is not allowed in the current Java standard, what is the closest thing to this? The idea behind this is putting several ParametricFunction's in a package and use Reflection to list them all, allowing the user to pick e.g. which one to plot. Obviously one could provide a loader class containing an array of the available ParametricFunction's, but every time a new one is implemented one has to remember adding it there, too.

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  • Efficient 4x4 matrix inverse (affine transform)

    - by Budric
    Hi, I was hoping someone can point out an efficient formula for 4x4 affine matrix transform. Currently my code uses cofactor expansion and it allocates a temporary array for each cofactor. It's easy to read, but it's slower than it should be. Note, this isn't homework and I know how to work it out manually using 4x4 co-factor expansion, it's just a pain and not really an interesting problem for me. Also I've googled and came up with a few sites that give you the formula already (http://www.euclideanspace.com/maths/algebra/matrix/functions/inverse/fourD/index.htm). However this one could probably be optimized further by pre-computing some of the products. I'm sure someone came up with the "best" formula for this at one point or another? Thanks.

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  • subscript for a join (\bowtie) operation in LyX/LaTeX

    - by Amir Rachum
    I'm using LyX to write some Relational Algebra queries. I'm using the \bowtie symbol for the join operation but when I try to put a text in subscript directly under the symbol, I get the following error: ...a_{\t{pId}}\t{person}\right)\bowtie\limits {\t{pId}{1}=\t{pId}_{2}... I'm ignoring this misplaced \limits or \nolimits command. Anyone knows how to do what I want? Preferably in LyX, but ERT code snippets will also be appreciated. Thanks! Edit: \t is a macro for \text.

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  • What is a Delphi version of the C++ header for the DVP7010B video card DLL?

    - by grzegorz1
    I need help with converting c++ header file to delphi. I spent several days on this problem without success. Below is the original header file and my Delphi translation. C++ header #if _MSC_VER > 1000 #pragma once #endif // _MSC_VER > 1000 #ifdef DVP7010BDLL_EXPORTS #define DVP7010BDLL_API __declspec(dllexport) #else #define DVP7010BDLL_API __declspec(dllimport) #endif #define MAXBOARDS 4 #define MAXDEVS 4 #define ID_NEW_FRAME 37810 #define ID_MUX0_NEW_FRAME 37800 #define ID_MUX1_NEW_FRAME 37801 #define ID_MUX2_NEW_FRAME 37802 #define ID_MUX3_NEW_FRAME 37803 typedef enum { SUCCEEDED = 1, FAILED = 0, SDKINITFAILED = -1, PARAMERROR = -2, NODEVICES = -3, NOSAMPLE = -4, DEVICENUMERROR = -5, INPUTERROR = -6, // VERIFYHWERROR = -7 } Res; typedef enum tagAnalogVideoFormat { Video_None = 0x00000000, Video_NTSC_M = 0x00000001, Video_NTSC_M_J = 0x00000002, Video_PAL_B = 0x00000010, Video_PAL_M = 0x00000200, Video_PAL_N = 0x00000400, Video_SECAM_B = 0x00001000 } AnalogVideoFormat; typedef enum { SIZEFULLPAL=0, SIZED1, SIZEVGA, SIZEQVGA, SIZESUBQVGA } VideoSize; typedef enum { STOPPED = 1, RUNNING = 2, UNINITIALIZED = -1, UNKNOWNSTATE = -2 } CapState; class IDVP7010BDLL { public: int AdvDVP_CreateSDKInstence(void **pp); virtual int AdvDVP_InitSDK() PURE; virtual int AdvDVP_CloseSDK() PURE; virtual int AdvDVP_GetNoOfDevices(int *pNoOfDevs) PURE; virtual int AdvDVP_Start(int nDevNum, int SwitchingChans, HWND Main, HWND hwndPreview) PURE; virtual int AdvDVP_Stop(int nDevNum) PURE; virtual int AdvDVP_GetCapState(int nDevNum) PURE; virtual int AdvDVP_IsVideoPresent(int nDevNum, BOOL* VPresent) PURE; virtual int AdvDVP_GetCurFrameBuffer(int nDevNum, int VMux, long* bufSize, BYTE* buf) PURE; virtual int AdvDVP_SetNewFrameCallback(int nDevNum, int callback) PURE; virtual int AdvDVP_GetVideoFormat(int nDevNum, AnalogVideoFormat* vFormat) PURE; virtual int AdvDVP_SetVideoFormat(int nDevNum, AnalogVideoFormat vFormat) PURE; virtual int AdvDVP_GetFrameRate(int nDevNum, int *nFrameRate) PURE; virtual int AdvDVP_SetFrameRate(int nDevNum, int SwitchingChans, int nFrameRate) PURE; virtual int AdvDVP_GetResolution(int nDevNum, VideoSize *Size) PURE; virtual int AdvDVP_SetResolution(int nDevNum, VideoSize Size) PURE; virtual int AdvDVP_GetVideoInput(int nDevNum, int* input) PURE; virtual int AdvDVP_SetVideoInput(int nDevNum, int input) PURE; virtual int AdvDVP_GetBrightness(int nDevNum, int input, long *pnValue) PURE; virtual int AdvDVP_SetBrightness(int nDevNum, int input, long nValue) PURE; virtual int AdvDVP_GetContrast(int nDevNum, int input, long *pnValue) PURE; virtual int AdvDVP_SetContrast(int nDevNum, int input, long nValue) PURE; virtual int AdvDVP_GetHue(int nDevNum, int input, long *pnValue) PURE; virtual int AdvDVP_SetHue(int nDevNum, int input, long nValue) PURE; virtual int AdvDVP_GetSaturation(int nDevNum, int input, long *pnValue) PURE; virtual int AdvDVP_SetSaturation(int nDevNum, int input, long nValue) PURE; virtual int AdvDVP_GPIOGetData(int nDevNum, int DINum, BOOL* value) PURE; virtual int AdvDVP_GPIOSetData(int nDevNum, int DONum, BOOL value) PURE; }; Delphi unit IDVP7010BDLL_h; interface uses Windows, Messages, SysUtils, Classes; //{$if _MSC_VER > 1000} //pragma once //{$endif} // _MSC_VER > 1000 {$ifdef DVP7010BDLL_EXPORTS} //const DVP7010BDLL_API = __declspec(dllexport); {$else} //const DVP7010BDLL_API = __declspec(dllimport); {$endif} const MAXDEVS = 4; MAXMUXS = 4; ID_NEW_FRAME = 37810; ID_MUX0_NEW_FRAME = 37800; ID_MUX1_NEW_FRAME = 37801; ID_MUX2_NEW_FRAME = 37802; ID_MUX3_NEW_FRAME = 37803; // TRec SUCCEEDED = 1; FAILED = 0; SDKINITFAILED = -1; PARAMERROR = -2; NODEVICES = -3; NOSAMPLE = -4; DEVICENUMERROR = -5; INPUTERROR = -6; // TRec // TAnalogVideoFormat Video_None = $00000000; Video_NTSC_M = $00000001; Video_NTSC_M_J = $00000002; Video_PAL_B = $00000010; Video_PAL_M = $00000200; Video_PAL_N = $00000400; Video_SECAM_B = $00001000; // TAnalogVideoFormat // TCapState STOPPED = 1; RUNNING = 2; UNINITIALIZED = -1; UNKNOWNSTATE = -2; // TCapState type TCapState = Longint; TRes = Longint; TtagAnalogVideoFormat = DWORD; TAnalogVideoFormat = TtagAnalogVideoFormat; PAnalogVideoFormat = ^TAnalogVideoFormat; TVideoSize = ( SIZEFULLPAL, SIZED1, SIZEVGA, SIZEQVGA, SIZESUBQVGA); PVideoSize = ^TVideoSize; P_Pointer = ^Pointer; TIDVP7010BDLL = class function AdvDVP_CreateSDKInstence(pp: P_Pointer): integer; virtual; stdcall; abstract; function AdvDVP_InitSDK():Integer; virtual; stdcall; abstract; function AdvDVP_CloseSDK():Integer; virtual; stdcall; abstract; function AdvDVP_GetNoOfDevices(pNoOfDevs : PInteger) :Integer; virtual; stdcall; abstract; function AdvDVP_Start(nDevNum : Integer; SwitchingChans : Integer; Main : HWND; hwndPreview: HWND ) :Integer; virtual; stdcall; abstract; function AdvDVP_Stop(nDevNum : Integer ):Integer; virtual; stdcall; abstract; function AdvDVP_GetCapState(nDevNum : Integer ):Integer; virtual; stdcall; abstract; function AdvDVP_IsVideoPresent(nDevNum : Integer; VPresent : PBool) :Integer; virtual; stdcall; abstract; function AdvDVP_GetCurFrameBuffer(nDevNum : Integer; VMux : Integer; bufSize : PLongInt; buf : PByte) :Integer; virtual; stdcall; abstract; function AdvDVP_SetNewFrameCallback(nDevNum : Integer; callback : Integer ) :Integer; virtual; stdcall; abstract; function AdvDVP_GetVideoFormat(nDevNum : Integer; vFormat : PAnalogVideoFormat) :Integer; virtual; stdcall; abstract; function AdvDVP_SetVideoFormat(nDevNum : Integer; vFormat : TAnalogVideoFormat ) :Integer; virtual; stdcall; abstract; function AdvDVP_GetFrameRate(nDevNum : Integer; nFrameRate : Integer) :Integer; virtual; stdcall; abstract; function AdvDVP_SetFrameRate(nDevNum : Integer; SwitchingChans : Integer; nFrameRate : Integer) :Integer; virtual; stdcall; abstract; function AdvDVP_GetResolution(nDevNum : Integer; Size : PVideoSize) :Integer; virtual; stdcall; abstract; function AdvDVP_SetResolution(nDevNum : Integer; Size : TVideoSize ) :Integer; virtual; stdcall; abstract; function AdvDVP_GetVideoInput(nDevNum : Integer; input : PInteger) :Integer; virtual; stdcall; abstract; function AdvDVP_SetVideoInput(nDevNum : Integer; input : Integer) :Integer; virtual; stdcall; abstract; function AdvDVP_GetBrightness(nDevNum : Integer; input: Integer; pnValue : PLongInt) :Integer; virtual; stdcall; abstract; function AdvDVP_SetBrightness(nDevNum : Integer; input: Integer; nValue : LongInt) :Integer; virtual; stdcall; abstract; function AdvDVP_GetContrast(nDevNum : Integer; input: Integer; pnValue : PLongInt) :Integer; virtual; stdcall; abstract; function AdvDVP_SetContrast(nDevNum : Integer; input: Integer; nValue : LongInt) :Integer; virtual; stdcall; abstract; function AdvDVP_GetHue(nDevNum : Integer; input: Integer; pnValue : PLongInt) :Integer; virtual; stdcall; abstract; function AdvDVP_SetHue(nDevNum : Integer; input: Integer; nValue : LongInt) :Integer; virtual; stdcall; abstract; function AdvDVP_GetSaturation(nDevNum : Integer; input: Integer; pnValue : PLongInt) :Integer; virtual; stdcall; abstract; function AdvDVP_SetSaturation(nDevNum : Integer; input: Integer; nValue : LongInt) :Integer; virtual; stdcall; abstract; function AdvDVP_GPIOGetData(nDevNum : Integer; DINum:Integer; value : PBool) :Integer; virtual; stdcall; abstract; function AdvDVP_GPIOSetData(nDevNum : Integer; DONum:Integer; value : Boolean) :Integer; virtual; stdcall; abstract; end; function IDVP7010BDLL : TIDVP7010BDLL ; stdcall; implementation function IDVP7010BDLL; external 'DVP7010B.dll'; end.

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  • Need help converting a C++ header file to delphi

    - by grzegorz1
    I need help with converting c++ header file to delphi. I spent several days on this problem without success. Below is the original header file and my Delphi translation. ///////////////////////// C++ header file //////////////////////////////////// if _MSC_VER 1000 pragma once endif // _MSC_VER 1000 ifdef DVP7010BDLL_EXPORTS define DVP7010BDLL_API __declspec(dllexport) else define DVP7010BDLL_API __declspec(dllimport) endif define MAXBOARDS 4 define MAXDEVS 4 define ID_NEW_FRAME 37810 define ID_MUX0_NEW_FRAME 37800 define ID_MUX1_NEW_FRAME 37801 define ID_MUX2_NEW_FRAME 37802 define ID_MUX3_NEW_FRAME 37803 typedef enum { SUCCEEDED = 1, FAILED = 0, SDKINITFAILED = -1, PARAMERROR = -2, NODEVICES = -3, NOSAMPLE = -4, DEVICENUMERROR = -5, INPUTERROR = -6, // VERIFYHWERROR = -7 } Res; typedef enum tagAnalogVideoFormat { Video_None = 0x00000000, Video_NTSC_M = 0x00000001, Video_NTSC_M_J = 0x00000002, Video_PAL_B = 0x00000010, Video_PAL_M = 0x00000200, Video_PAL_N = 0x00000400, Video_SECAM_B = 0x00001000 } AnalogVideoFormat; typedef enum { SIZEFULLPAL=0, SIZED1, SIZEVGA, SIZEQVGA, SIZESUBQVGA } VideoSize; typedef enum { STOPPED = 1, RUNNING = 2, UNINITIALIZED = -1, UNKNOWNSTATE = -2 } CapState; class IDVP7010BDLL { public: int AdvDVP_CreateSDKInstence(void **pp); virtual int AdvDVP_InitSDK() PURE; virtual int AdvDVP_CloseSDK() PURE; virtual int AdvDVP_GetNoOfDevices(int *pNoOfDevs) PURE; virtual int AdvDVP_Start(int nDevNum, int SwitchingChans, HWND Main, HWND hwndPreview) PURE; virtual int AdvDVP_Stop(int nDevNum) PURE; virtual int AdvDVP_GetCapState(int nDevNum) PURE; virtual int AdvDVP_IsVideoPresent(int nDevNum, BOOL* VPresent) PURE; virtual int AdvDVP_GetCurFrameBuffer(int nDevNum, int VMux, long* bufSize, BYTE* buf) PURE; virtual int AdvDVP_SetNewFrameCallback(int nDevNum, int callback) PURE; virtual int AdvDVP_GetVideoFormat(int nDevNum, AnalogVideoFormat* vFormat) PURE; virtual int AdvDVP_SetVideoFormat(int nDevNum, AnalogVideoFormat vFormat) PURE; virtual int AdvDVP_GetFrameRate(int nDevNum, int *nFrameRate) PURE; virtual int AdvDVP_SetFrameRate(int nDevNum, int SwitchingChans, int nFrameRate) PURE; virtual int AdvDVP_GetResolution(int nDevNum, VideoSize *Size) PURE; virtual int AdvDVP_SetResolution(int nDevNum, VideoSize Size) PURE; virtual int AdvDVP_GetVideoInput(int nDevNum, int* input) PURE; virtual int AdvDVP_SetVideoInput(int nDevNum, int input) PURE; virtual int AdvDVP_GetBrightness(int nDevNum, int input, long *pnValue) PURE; virtual int AdvDVP_SetBrightness(int nDevNum, int input, long nValue) PURE; virtual int AdvDVP_GetContrast(int nDevNum, int input, long *pnValue) PURE; virtual int AdvDVP_SetContrast(int nDevNum, int input, long nValue) PURE; virtual int AdvDVP_GetHue(int nDevNum, int input, long *pnValue) PURE; virtual int AdvDVP_SetHue(int nDevNum, int input, long nValue) PURE; virtual int AdvDVP_GetSaturation(int nDevNum, int input, long *pnValue) PURE; virtual int AdvDVP_SetSaturation(int nDevNum, int input, long nValue) PURE; virtual int AdvDVP_GPIOGetData(int nDevNum, int DINum, BOOL* value) PURE; virtual int AdvDVP_GPIOSetData(int nDevNum, int DONum, BOOL value) PURE; }; /////////////////// delphi /////////////////////////////////////// unit IDVP7010BDLL_h; interface uses Windows, Messages, SysUtils, Classes; //{$if _MSC_VER 1000} //pragma once //{$endif} // _MSC_VER 1000 {$ifdef DVP7010BDLL_EXPORTS} //const DVP7010BDLL_API = __declspec(dllexport); {$else} //const DVP7010BDLL_API = __declspec(dllimport); {$endif} const MAXDEVS = 4; MAXMUXS = 4; ID_NEW_FRAME = 37810; ID_MUX0_NEW_FRAME = 37800; ID_MUX1_NEW_FRAME = 37801; ID_MUX2_NEW_FRAME = 37802; ID_MUX3_NEW_FRAME = 37803; // TRec SUCCEEDED = 1; FAILED = 0; SDKINITFAILED = -1; PARAMERROR = -2; NODEVICES = -3; NOSAMPLE = -4; DEVICENUMERROR = -5; INPUTERROR = -6; // TRec // TAnalogVideoFormat Video_None = $00000000; Video_NTSC_M = $00000001; Video_NTSC_M_J = $00000002; Video_PAL_B = $00000010; Video_PAL_M = $00000200; Video_PAL_N = $00000400; Video_SECAM_B = $00001000; // TAnalogVideoFormat // TCapState STOPPED = 1; RUNNING = 2; UNINITIALIZED = -1; UNKNOWNSTATE = -2; // TCapState type TCapState = Longint; TRes = Longint; TtagAnalogVideoFormat = DWORD; TAnalogVideoFormat = TtagAnalogVideoFormat; PAnalogVideoFormat = ^TAnalogVideoFormat; TVideoSize = ( SIZEFULLPAL, SIZED1, SIZEVGA, SIZEQVGA, SIZESUBQVGA); PVideoSize = ^TVideoSize; P_Pointer = ^Pointer; TIDVP7010BDLL = class function AdvDVP_CreateSDKInstence(pp: P_Pointer): integer; virtual; stdcall; abstract; function AdvDVP_InitSDK():Integer; virtual; stdcall; abstract; function AdvDVP_CloseSDK():Integer; virtual; stdcall; abstract; function AdvDVP_GetNoOfDevices(pNoOfDevs : PInteger) :Integer; virtual; stdcall; abstract; function AdvDVP_Start(nDevNum : Integer; SwitchingChans : Integer; Main : HWND; hwndPreview: HWND ) :Integer; virtual; stdcall; abstract; function AdvDVP_Stop(nDevNum : Integer ):Integer; virtual; stdcall; abstract; function AdvDVP_GetCapState(nDevNum : Integer ):Integer; virtual; stdcall; abstract; function AdvDVP_IsVideoPresent(nDevNum : Integer; VPresent : PBool) :Integer; virtual; stdcall; abstract; function AdvDVP_GetCurFrameBuffer(nDevNum : Integer; VMux : Integer; bufSize : PLongInt; buf : PByte) :Integer; virtual; stdcall; abstract; function AdvDVP_SetNewFrameCallback(nDevNum : Integer; callback : Integer ) :Integer; virtual; stdcall; abstract; function AdvDVP_GetVideoFormat(nDevNum : Integer; vFormat : PAnalogVideoFormat) :Integer; virtual; stdcall; abstract; function AdvDVP_SetVideoFormat(nDevNum : Integer; vFormat : TAnalogVideoFormat ) :Integer; virtual; stdcall; abstract; function AdvDVP_GetFrameRate(nDevNum : Integer; nFrameRate : Integer) :Integer; virtual; stdcall; abstract; function AdvDVP_SetFrameRate(nDevNum : Integer; SwitchingChans : Integer; nFrameRate : Integer) :Integer; virtual; stdcall; abstract; function AdvDVP_GetResolution(nDevNum : Integer; Size : PVideoSize) :Integer; virtual; stdcall; abstract; function AdvDVP_SetResolution(nDevNum : Integer; Size : TVideoSize ) :Integer; virtual; stdcall; abstract; function AdvDVP_GetVideoInput(nDevNum : Integer; input : PInteger) :Integer; virtual; stdcall; abstract; function AdvDVP_SetVideoInput(nDevNum : Integer; input : Integer) :Integer; virtual; stdcall; abstract; function AdvDVP_GetBrightness(nDevNum : Integer; input: Integer; pnValue : PLongInt) :Integer; virtual; stdcall; abstract; function AdvDVP_SetBrightness(nDevNum : Integer; input: Integer; nValue : LongInt) :Integer; virtual; stdcall; abstract; function AdvDVP_GetContrast(nDevNum : Integer; input: Integer; pnValue : PLongInt) :Integer; virtual; stdcall; abstract; function AdvDVP_SetContrast(nDevNum : Integer; input: Integer; nValue : LongInt) :Integer; virtual; stdcall; abstract; function AdvDVP_GetHue(nDevNum : Integer; input: Integer; pnValue : PLongInt) :Integer; virtual; stdcall; abstract; function AdvDVP_SetHue(nDevNum : Integer; input: Integer; nValue : LongInt) :Integer; virtual; stdcall; abstract; function AdvDVP_GetSaturation(nDevNum : Integer; input: Integer; pnValue : PLongInt) :Integer; virtual; stdcall; abstract; function AdvDVP_SetSaturation(nDevNum : Integer; input: Integer; nValue : LongInt) :Integer; virtual; stdcall; abstract; function AdvDVP_GPIOGetData(nDevNum : Integer; DINum:Integer; value : PBool) :Integer; virtual; stdcall; abstract; function AdvDVP_GPIOSetData(nDevNum : Integer; DONum:Integer; value : Boolean) :Integer; virtual; stdcall; abstract; end; function IDVP7010BDLL : TIDVP7010BDLL ; stdcall; implementation function IDVP7010BDLL; external 'DVP7010B.dll'; end.

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  • Translate C# code into AST?

    - by Erik Forbes
    Is it currently possible to translate C# code into an Abstract Syntax Tree? Edit: some clarification; I don't necessarily expect the compiler to generate the AST for me - a parser would be fine, although I'd like to use something "official." Lambda expressions are unfortunately not going to be sufficient given they don't allow me to use statement bodies, which is what I'm looking for.

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  • AST generation for a an application developed both in visual basic and c#

    - by Dev
    Hi, I'm currently understanding one application developed both in visual basic and c#. Running through the code is getting tough as code is around 50KLOC. So i'm planning for generation of AST (abstract syntax tree). Will it be possible to generate for both language together. Atleast a call graph generation will be helpful (but can't find any tool which works for both languages) Please let me know if this question is confusing. Thanks in Advance Dev

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  • How to initialize List<E> in empty class constructor?

    - by Nazgulled
    Hi, The following code obviously doesn't work because List<E> is abstract: public class MyList { private List<E> list; public MyList() { this.list = new List<E>(); } } How can I initialize MyList class with an empty constructor if I need the list variable to be a LinkedList or a ArrayList depending on my needs?

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  • UiElement from abstract class

    - by plotnick
    I placed a control into a grid. let's say the control is derived from public class 'ButBase' which is derived in its turn from System.Windows.Controls.Button. The code normally compiles and app works just fine. But there's something really annoying. When you try to switch to xaml-design tab it will say 'The document root element is not supported by the visual designer', which is normal and I'm totally okay with that, but the thing is, that all the xaml code is underlined and VS2010 says: 'Cannot create an instance of ButBase' although still normally compiles and able to run. I've tried the same code in VS2008, it said that needs to see a public parameterless constructor in the ButBase, and even after I put one it showed the same error. What do I miss here?

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  • Designing a fluid Javascript interface to abstract away the asynchronous nature of AJAX

    - by Anurag
    How would I design an API to hide the asynchronous nature of AJAX and HTTP requests, or basically delay it to provide a fluid interface. To show an example from Twitter's new Anywhere API: // get @ded's first 20 statuses, filter only the tweets that // mention photography, and render each into an HTML element T.User.find('ded').timeline().first(20).filter(filterer).each(function(status) { $('div#tweets').append('<p>' + status.text + '</p>'); }); function filterer(status) { return status.text.match(/photography/); } vs this (asynchronous nature of each call is clearly visible) T.User.find('ded', function(user) { user.timeline(function(statuses) { statuses.first(20).filter(filterer).each(function(status) { $('div#tweets').append('<p>' + status.text + '</p>'); }); }); }); It finds the user, gets their tweet timeline, filters only the first 20 tweets, applies a custom filter, and ultimately uses the callback function to process each tweet. I am guessing that a well designed API like this should work like a query builder (think ORMs) where each function call builds the query (HTTP URL in this case), until it hits a looping function such as each/map/etc., the HTTP call is made and the passed in function becomes the callback. An easy development route would be to make each AJAX call synchronous, but that's probably not the best solution. I am interested in figuring out a way to make it asynchronous, and still hide the asynchronous nature of AJAX.

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  • Designing a fluent Javascript interface to abstract away the asynchronous nature of AJAX

    - by Anurag
    How would I design an API to hide the asynchronous nature of AJAX and HTTP requests, or basically delay it to provide a fluid interface. To show an example from Twitter's new Anywhere API: // get @ded's first 20 statuses, filter only the tweets that // mention photography, and render each into an HTML element T.User.find('ded').timeline().first(20).filter(filterer).each(function(status) { $('div#tweets').append('<p>' + status.text + '</p>'); }); function filterer(status) { return status.text.match(/photography/); } vs this (asynchronous nature of each call is clearly visible) T.User.find('ded', function(user) { user.timeline(function(statuses) { statuses.first(20).filter(filterer).each(function(status) { $('div#tweets').append('<p>' + status.text + '</p>'); }); }); }); It finds the user, gets their tweet timeline, filters only the first 20 tweets, applies a custom filter, and ultimately uses the callback function to process each tweet. I am guessing that a well designed API like this should work like a query builder (think ORMs) where each function call builds the query (HTTP URL in this case), until it hits a looping function such as each/map/etc., the HTTP call is made and the passed in function becomes the callback. An easy development route would be to make each AJAX call synchronous, but that's probably not the best solution. I am interested in figuring out a way to make it asynchronous, and still hide the asynchronous nature of AJAX.

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  • Abstract out repeated code

    - by CookieMonster
    The code in this event is repeated exactly in two other event handlers. How do I put the repeated code into a method and call that method from the event handlers so I only have to maintain it in one place? I'm not sure how to pass the event args to the calling method. protected void gvDocAssoc_RowDataBound(object sender, GridViewRowEventArgs e) { if (e.Row.RowType == DataControlRowType.DataRow) { if ((Convert.ToString(DataBinder.Eval(e.Row.DataItem, "DETAIL_TYPE_DESC")) == "Transcript") && (Convert.ToString(DataBinder.Eval(e.Row.DataItem, "INSTITUTION_CODE")) == "")) { e.Row.BackColor = System.Drawing.Color.Red; } if ((Convert.ToString(DataBinder.Eval(e.Row.DataItem, "DETAIL_TYPE_DESC")) == "Certified Diploma") && (Convert.ToString(DataBinder.Eval(e.Row.DataItem, "INSTITUTION_CODE")) == "")) { e.Row.BackColor = System.Drawing.Color.Red; } if ((Convert.ToString(DataBinder.Eval(e.Row.DataItem, "DOC_TYPE_DESC")) == "Post Graduate conditions") && (Convert.ToString(DataBinder.Eval(e.Row.DataItem, "INSTITUTION_CODE")) == "")) { e.Row.BackColor = System.Drawing.Color.Red; } } }

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