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• Understanding math used to determine if vector is clockwise / counterclockwise from your vector

  - by MTLPhil

  I'm reading Programming Game AI by Example by Mat Buckland. In the Math & Physics primer chapter there's a listing of the declaration of a class used to represent 2D vectors. This class contains a method called Sign. It's implementation is as follows //------------------------ Sign ------------------------------------------ // // returns positive if v2 is clockwise of this vector, // minus if anticlockwise (Y axis pointing down, X axis to right) //------------------------------------------------------------------------ enum {clockwise = 1, anticlockwise = -1}; inline int Vector2D::Sign(const Vector2D& v2)const { if (y*v2.x > x*v2.y) { return anticlockwise; } else { return clockwise; } } Can someone explain the vector rules that make this hold true? What do the values of y*v2.x and x*v2.y that are being compared actually represent? I'd like to have a solid understanding of why this works rather than just accepting that it does without figuring it out. I feel like it's something really obvious that I'm just not catching on to. Thanks for your help.

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• Passing Strings by Ref

  - by SGWellens

  Humbled yet again…DOH! No matter how much experience you acquire, no matter how smart you may be, no matter how hard you study, it is impossible to keep fully up to date on all the nuances of the technology we are exposed to. There will always be gaps in our knowledge: Little 'dead zones' of uncertainty. For me, this time, it was about passing string parameters to functions. I thought I knew this stuff cold. First, a little review... Value Types and Ref Integers and structs are value types (as opposed to reference types). When declared locally, their memory storage is on the stack; not on the heap. When passed to a function, the function gets a copy of the data and works on the copy. If a function needs to change a value type, you need to use the ref keyword.  Here's an example:     // ---- declaration -----------------     public struct MyStruct    {        public string StrTag;    }     // ---- functions -----------------------     void SetMyStruct(MyStruct myStruct)     // pass by value    {        myStruct.StrTag = "BBB";    }     void SetMyStruct(ref MyStruct myStruct)  // pass by ref    {        myStruct.StrTag = "CCC";    }     // ---- Usage -----------------------     protected void Button1_Click(object sender, EventArgs e)    {        MyStruct Data;        Data.StrTag = "AAA";         SetMyStruct(Data);        // Data.StrTag is still "AAA"         SetMyStruct(ref Data);        // Data.StrTag is now "CCC"    } No surprises here. All value types like ints, floats, datetimes, enums, structs, etc. work the same way. And now on to... Class Types and Ref     // ---- Declaration -----------------------------     public class MyClass    {        public string StrTag;    }     // ---- Functions ----------------------------     void SetMyClass(MyClass myClass)  // pass by 'value'    {        myClass.StrTag = "BBB";    }     void SetMyClass(ref MyClass myClass)   // pass by ref    {        myClass.StrTag = "CCC";    }     // ---- Usage ---------------------------------------     protected void Button2_Click(object sender, EventArgs e)    {        MyClass Data = new MyClass();        Data.StrTag = "AAA";         SetMyClass(Data);          // Data.StrTag is now "BBB"         SetMyClass(ref Data);        // Data.StrTag is now "CCC"    }  No surprises here either. Since Classes are reference types, you do not need the ref keyword to modify an object. What may seem a little strange is that with or without the ref keyword, the results are the same: The compiler knows what to do. So, why would you need to use the ref keyword when passing an object to a function? Because then you can change the reference itself…ie you can make it refer to a completely different object. Inside the function you can do: myClass = new MyClass() and the old object will be garbage collected and the new object will be returned to the caller. That ends the review. Now let's look at passing strings as parameters. The String Type and Ref Strings are reference types. So when you pass a String to a function, you do not need the ref keyword to change the string. Right? Wrong. Wrong, wrong, wrong. When I saw this, I was so surprised that I fell out of my chair. Getting up, I bumped my head on my desk (which really hurt). My bumping the desk caused a large speaker to fall off of a bookshelf and land squarely on my big toe. I was screaming in pain and hopping on one foot when I lost my balance and fell. I struck my head on the side of the desk (once again) and knocked myself out cold. When I woke up, I was in the hospital where due to a database error (thanks Oracle) the doctors had put casts on both my hands. I'm typing this ever so slowly with just my ton..tong ..tongu…tongue. But I digress. Okay, the only true part of that story is that I was a bit surprised. Here is what happens passing a String to a function.     // ---- Functions ----------------------------     void SetMyString(String myString)   // pass by 'value'    {        myString = "BBB";    }     void SetMyString(ref String myString)  // pass by ref    {        myString = "CCC";    }     // ---- Usage ---------------------------------     protected void Button3_Click(object sender, EventArgs e)    {        String MyString = "AAA";         SetMyString(MyString);        // MyString is still "AAA"  What!!!!         SetMyString(ref MyString);        // MyString is now "CCC"    } What the heck. We should not have to use the ref keyword when passing a String because Strings are reference types. Why didn't the string change? What is going on?   I spent hours unssuccessfully researching this anomaly until finally, I had a Eureka moment: This code: String MyString = "AAA"; Is semantically equivalent to this code (note this code doesn't actually compile): String MyString = new String(); MyString = "AAA"; Key Point: In the function, the copy of the reference is pointed to a new object and THAT object is modified. The original reference and what it points to is unchanged. You can simulate this behavior by modifying the class example code to look like this:      void SetMyClass(MyClass myClass)  // call by 'value'    {        //myClass.StrTag = "BBB";        myClass = new MyClass();        myClass.StrTag = "BBB";    } Now when you call the SetMyClass function without using ref, the parameter is unchanged...just like the string example.  I hope someone finds this useful. Steve Wellens

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• Session serialization in JavaEE environment

  - by Ionut

  Please consider the following scenario: We are working on a JavaEE project for which the scalability starts to become an issue. Up until now, we were able to scale up but this is no longer an option. Therefore we need to consider scaling out and preparing the App for a clustered environment. Our main concern right now is serializing the user sessions. Sadly, we did not consider from the beginning the issue and we are encountering the following excetion: java.io.WriteAbortedException: writing aborted; java.io.NotSerializableException: org.apache.catalina.session.StandardSessionFacade I did some research and this exception is thrown because there are objects stored on the session which does not implement the Serializable interface. Considering that all over the app there are quite a few custom objects which are stored on the session without implementing this interface, it would require a lot of tedious work and dedication to fix all these classes declaration. We will fix all this declarations but the main concern is that, in the future, there may be a developer which will add a non Serializable object on the session and break the session serialization & replication over multiple nodes. As a quick overview of the project, we are developing using a home grown framework based on Struts 1 with the Servlet 3.0 API. This means that at this point, we are using the standard session.getAttribute() and session.setAttribute() to work with the session and the session handling is scattered all over the code base. Besides updating the classes of the objects stored on session and making sure that they implement the Serializable interface, what other measures of precaution should we take in order to ensure a reliable Session replication capability on the Application layer? I know it is a little bit late to consider this but what would be the best practice in this case? Furthermore, are there any other issues we should consider regarding this transition? Thank you in advance!

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• XNA shield effect with a Primative sphere problem

  - by Sparky41

  I'm having issue with a shield effect i'm trying to develop. I want to do a shield effect that surrounds part of a model like this: http://i.imgur.com/jPvrf.png I currently got this: http://i.imgur.com/Jdin7.png (The red likes are a simple texture a black background with a red cross in it, for testing purposes: http://i.imgur.com/ODtzk.png where the smaller cross in the middle shows the contact point) This sphere is drawn via a primitive (DrawIndexedPrimitives) This is how i calculate the pieces of the sphere using a class i've called Sphere (this class is based off the code here: http://xbox.create.msdn.com/en-US/education/catalog/sample/primitives_3d) public class Sphere { // During the process of constructing a primitive model, vertex // and index data is stored on the CPU in these managed lists. List vertices = new List(); List indices = new List(); // Once all the geometry has been specified, the InitializePrimitive // method copies the vertex and index data into these buffers, which // store it on the GPU ready for efficient rendering. VertexBuffer vertexBuffer; IndexBuffer indexBuffer; BasicEffect basicEffect; public Vector3 position = Vector3.Zero; public Matrix RotationMatrix = Matrix.Identity; public Texture2D texture; /// <summary> /// Constructs a new sphere primitive, /// with the specified size and tessellation level. /// </summary> public Sphere(float diameter, int tessellation, Texture2D text, float up, float down, float portstar, float frontback) { texture = text; if (tessellation < 3) throw new ArgumentOutOfRangeException("tessellation"); int verticalSegments = tessellation; int horizontalSegments = tessellation * 2; float radius = diameter / 2; // Start with a single vertex at the bottom of the sphere. AddVertex(Vector3.Down * ((radius / up) + 1), Vector3.Down, Vector2.Zero);//bottom position5 // Create rings of vertices at progressively higher latitudes. for (int i = 0; i < verticalSegments - 1; i++) { float latitude = ((i + 1) * MathHelper.Pi / verticalSegments) - MathHelper.PiOver2; float dy = (float)Math.Sin(latitude / up);//(up)5 float dxz = (float)Math.Cos(latitude); // Create a single ring of vertices at this latitude. for (int j = 0; j < horizontalSegments; j++) { float longitude = j * MathHelper.TwoPi / horizontalSegments; float dx = (float)(Math.Cos(longitude) * dxz) / portstar;//port and starboard (right)2 float dz = (float)(Math.Sin(longitude) * dxz) * frontback;//front and back1.4 Vector3 normal = new Vector3(dx, dy, dz); AddVertex(normal * radius, normal, new Vector2(j, i)); } } // Finish with a single vertex at the top of the sphere. AddVertex(Vector3.Up * ((radius / down) + 1), Vector3.Up, Vector2.One);//top position5 // Create a fan connecting the bottom vertex to the bottom latitude ring. for (int i = 0; i < horizontalSegments; i++) { AddIndex(0); AddIndex(1 + (i + 1) % horizontalSegments); AddIndex(1 + i); } // Fill the sphere body with triangles joining each pair of latitude rings. for (int i = 0; i < verticalSegments - 2; i++) { for (int j = 0; j < horizontalSegments; j++) { int nextI = i + 1; int nextJ = (j + 1) % horizontalSegments; AddIndex(1 + i * horizontalSegments + j); AddIndex(1 + i * horizontalSegments + nextJ); AddIndex(1 + nextI * horizontalSegments + j); AddIndex(1 + i * horizontalSegments + nextJ); AddIndex(1 + nextI * horizontalSegments + nextJ); AddIndex(1 + nextI * horizontalSegments + j); } } // Create a fan connecting the top vertex to the top latitude ring. for (int i = 0; i < horizontalSegments; i++) { AddIndex(CurrentVertex - 1); AddIndex(CurrentVertex - 2 - (i + 1) % horizontalSegments); AddIndex(CurrentVertex - 2 - i); } //InitializePrimitive(graphicsDevice); } /// <summary> /// Adds a new vertex to the primitive model. This should only be called /// during the initialization process, before InitializePrimitive. /// </summary> protected void AddVertex(Vector3 position, Vector3 normal, Vector2 texturecoordinate) { vertices.Add(new VertexPositionNormal(position, normal, texturecoordinate)); } /// <summary> /// Adds a new index to the primitive model. This should only be called /// during the initialization process, before InitializePrimitive. /// </summary> protected void AddIndex(int index) { if (index > ushort.MaxValue) throw new ArgumentOutOfRangeException("index"); indices.Add((ushort)index); } /// <summary> /// Queries the index of the current vertex. This starts at /// zero, and increments every time AddVertex is called. /// </summary> protected int CurrentVertex { get { return vertices.Count; } } public void InitializePrimitive(GraphicsDevice graphicsDevice) { // Create a vertex declaration, describing the format of our vertex data. // Create a vertex buffer, and copy our vertex data into it. vertexBuffer = new VertexBuffer(graphicsDevice, typeof(VertexPositionNormal), vertices.Count, BufferUsage.None); vertexBuffer.SetData(vertices.ToArray()); // Create an index buffer, and copy our index data into it. indexBuffer = new IndexBuffer(graphicsDevice, typeof(ushort), indices.Count, BufferUsage.None); indexBuffer.SetData(indices.ToArray()); // Create a BasicEffect, which will be used to render the primitive. basicEffect = new BasicEffect(graphicsDevice); //basicEffect.EnableDefaultLighting(); } /// <summary> /// Draws the primitive model, using the specified effect. Unlike the other /// Draw overload where you just specify the world/view/projection matrices /// and color, this method does not set any renderstates, so you must make /// sure all states are set to sensible values before you call it. /// </summary> public void Draw(Effect effect) { GraphicsDevice graphicsDevice = effect.GraphicsDevice; // Set our vertex declaration, vertex buffer, and index buffer. graphicsDevice.SetVertexBuffer(vertexBuffer); graphicsDevice.Indices = indexBuffer; graphicsDevice.BlendState = BlendState.Additive; foreach (EffectPass effectPass in effect.CurrentTechnique.Passes) { effectPass.Apply(); int primitiveCount = indices.Count / 3; graphicsDevice.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, vertices.Count, 0, primitiveCount); } graphicsDevice.BlendState = BlendState.Opaque; } /// <summary> /// Draws the primitive model, using a BasicEffect shader with default /// lighting. Unlike the other Draw overload where you specify a custom /// effect, this method sets important renderstates to sensible values /// for 3D model rendering, so you do not need to set these states before /// you call it. /// </summary> public void Draw(Camera camera, Color color) { // Set BasicEffect parameters. basicEffect.World = GetWorld(); basicEffect.View = camera.view; basicEffect.Projection = camera.projection; basicEffect.DiffuseColor = color.ToVector3(); basicEffect.TextureEnabled = true; basicEffect.Texture = texture; GraphicsDevice device = basicEffect.GraphicsDevice; device.DepthStencilState = DepthStencilState.Default; if (color.A < 255) { // Set renderstates for alpha blended rendering. device.BlendState = BlendState.AlphaBlend; } else { // Set renderstates for opaque rendering. device.BlendState = BlendState.Opaque; } // Draw the model, using BasicEffect. Draw(basicEffect); } public virtual Matrix GetWorld() { return /*world */ Matrix.CreateScale(1f) * RotationMatrix * Matrix.CreateTranslation(position); } } public struct VertexPositionNormal : IVertexType { public Vector3 Position; public Vector3 Normal; public Vector2 TextureCoordinate; /// <summary> /// Constructor. /// </summary> public VertexPositionNormal(Vector3 position, Vector3 normal, Vector2 textCoor) { Position = position; Normal = normal; TextureCoordinate = textCoor; } /// <summary> /// A VertexDeclaration object, which contains information about the vertex /// elements contained within this struct. /// </summary> public static readonly VertexDeclaration VertexDeclaration = new VertexDeclaration ( new VertexElement(0, VertexElementFormat.Vector3, VertexElementUsage.Position, 0), new VertexElement(12, VertexElementFormat.Vector3, VertexElementUsage.Normal, 0), new VertexElement(24, VertexElementFormat.Vector2, VertexElementUsage.TextureCoordinate, 0) ); VertexDeclaration IVertexType.VertexDeclaration { get { return VertexPositionNormal.VertexDeclaration; } } } A simple call to the class to initialise it. The Draw method is called in the master draw method in the Gamecomponent. My current thoughts on this are: The direction of the weapon hitting the ship is used to get the middle position for the texture Wrap a texture around the drawn sphere based on this point of contact Problem is i'm not sure how to do this. Can anyone help or if you have a better idea please tell me i'm open for opinion? :-) Thanks.

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• Generated Methods with Type Hints

  - by Ondrej Brejla

  Hi all! Today we would like to introduce you just another feature from upcoming NetBeans 7.3. It's about generating setters, constructors and type hints of their parameters. For years, you can use Insert Code action to generate setters, getters, constructors and such. Nothing new. But from NetBeans 7.3 you can generate Fluent Setters! What does it mean? Simply that $this is returned from a generated setter. This is how it looks like: But that's not everything :) As you know, before a method is generated, you have to choose a field, which will be associated with that method (in case of constructors, you choose fileds which should be initialized by that constructor). And from NetBeans 7.3, type hints are generated automatically for these parameters! But only if a proper PHPDoc is used in a corresponding field declaration, of course. Here is how it looks like. And that's all for today and as usual, please test it and if you find something strange, don't hesitate to file a new issue (product php, component Editor). Thanks a lot!

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• About shared (static) Members and its behavior

  - by Allende

  I just realized that I can access shared members from instances of classes (probably this is not correct, but compile and run), and also learn/discover that, I can modify shared members, then create a new instance and access the new value of the shared member. My question is, what happens to the shared members, when it comes back to the "default" value (class declaration), how dangerous is it do this ? is it totally bad ? is it valid in some cases ?. If you want to test my point here is the code (console project vb.net) that I used to test shared members, as you can see/compile/run, the shared member "x" of the class "Hello" has default value string "Default", but at runtime it changes it, and after creating a new object of that class, this object has the new value of the shared member. Module Module1 Public Class hello Public Shared x As String = "Default" Public Sub New() End Sub End Class Sub Main() Console.WriteLine("hello.x=" & hello.x) Dim obj As New hello() Console.WriteLine("obj.x=" & obj.x) obj.x = "Default shared memeber, modified in object" Console.WriteLine("obj.x=" & obj.x) hello.x = "Defaul shared member, modified in class" Console.WriteLine("hello.x=" & hello.x) Dim obj2 As New hello() Console.WriteLine("obj2.x=" & obj2.x) Console.ReadLine() End Sub End Module UPDATE: First at all, thanks to everyone, each answer give feedback, I suppose, by respect I should choose one as "the answer", I don't want to be offensive to anyone, so please don't take it so bad if I didn't choose you answer.

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• Design for object with optional and modifiable attributtes?

  - by Ikuzen

  I've been using the Builder pattern to create objects with a large number of attributes, where most of them are optional. But up until now, I've defined them as final, as recommended by Joshua Block and other authors, and haven't needed to change their values. I am wondering what should I do though if I need a class with a substantial number of optional but non-final (mutable) attributes? My Builder pattern code looks like this: public class Example { //All possible parameters (optional or not) private final int param1; private final int param2; //Builder class public static class Builder { private final int param1; //Required parameters private int param2 = 0; //Optional parameters - initialized to default //Builder constructor public Builder (int param1) { this.param1 = param1; } //Setter-like methods for optional parameters public Builder param2(int value) { param2 = value; return this; } //build() method public Example build() { return new Example(this); } } //Private constructor private Example(Builder builder) { param1 = builder.param1; param2 = builder.param2; } } Can I just remove the final keyword from the declaration to be able to access the attributes externally (through normal setters, for example)? Or is there a creational pattern that allows optional but non-final attributes that would be better suited in this case?

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• Can higher-order functions in FP be interpreted as some kind of dependency injection?

  - by Giorgio

  According to this article, in object-oriented programming / design dependency injection involves a dependent consumer, a declaration of a component's dependencies, defined as interface contracts, an injector that creates instances of classes that implement a given dependency interface on request. Let us now consider a higher-order function in a functional programming language, e.g. the Haskell function filter :: (a -> Bool) -> [a] -> [a] from Data.List. This function transforms a list into another list and, in order to perform its job, it uses (consumes) an external predicate function that must be provided by its caller, e.g. the expression filter (\x -> (mod x 2) == 0) [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] selects all even numbers from the input list. But isn't this construction very similar to the pattern illustrated above, where the filter function is the dependent consumer, the signature (a -> Bool) of the function argument is the interface contract, the expression that uses the higher-order is the injector that, in this particular case, injects the implementation (\x -> (mod x 2) == 0) of the contract. More in general, can one relate higher-order functions and their usage pattern in functional programming to the dependency injection pattern in object-oriented languages? Or in the inverse direction, can dependency injection be compared to using some kind of higher-order function?

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• Why does my VertexDeclaration apparently not contain Position0?

  - by Phil

  I'm trying to get my code from calling each individual draw call down to using at least a VertexBuffer, and preferably an indexBuffer, but now that I'm attempting to test my code, I'm getting the error: The current vertex declaration does not include all the elements required by the current vertex shader. Position0 is missing. Which makes absolutely no sense to me, as my VertexDeclaration is: public readonly static VertexDeclaration VertexDeclaration = new VertexDeclaration( new VertexElement(0, VertexElementFormat.Vector3, VertexElementUsage.Position, 0), new VertexElement(sizeof(float) * 3, VertexElementFormat.Color, VertexElementUsage.Color, 0), new VertexElement(sizeof(float) * 3 + 4, VertexElementFormat.Vector3, VertexElementUsage.Normal, 0) ); Which clearly contains the information. I am attempting to draw with the following lines: VertexBuffer vb = new VertexBuffer(GraphicsDevice, VertexPositionColorNormal.VertexDeclaration, c.VertexList.Count, BufferUsage.WriteOnly); IndexBuffer ib = new IndexBuffer(GraphicsDevice, typeof(int), c.IndexList.Count, BufferUsage.WriteOnly); vb.SetData<VertexPositionColorNormal>(c.VertexList.ToArray()); ib.SetData<int>(c.IndexList.ToArray()); GraphicsDevice.DrawIndexedPrimitives(PrimitiveType.TriangleList, 0, 0, vb.VertexCount, 0, c.IndexList.Count/3); Where c is a Chunk class containing an 8x8x8 array of boxes. Full code is available at https://github.com/mrbaggins/Box/tree/ProperMeshing/box/box. Relevant locations are Chunk.cs (Contains the VertexDeclaration) and Game1.cs (Draw() is in Lines 230-250). Not much else of relevance to this problem anywhere else. Note that large commented sections are from old version of drawing.

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• C++ program...overshoots? [migrated]

  - by Zdrok

  I'm decent at C++, but I may have missed some nuance that applies here. Or maybe I completely missed a giant concept, I have no idea. My program was instantly crashing ("blah.exe is not responding") about 1/5 times it was run (other times it ran completely fine) and I tracked the problem down to a constructor for a world class that was called once in the beginning of the main function. Here is the code (in the constructor) that causes the problem: int ii; for(ii=0;ii<=255;ii++) { cout<<"ent "<<ii<<endl; entity_list[ii]=NULL; } for(ii=0;ii<=255;ii++) { cout<<"sec "<<ii<<endl; sector_list[ii]=NULL; } entity_list[0] = new Entity(0,0); entity_list[0]->_world = this; Specifically the second for loop. The cout references are new for the sake of telling where it is having trouble. It would print the entire "ent 1" to "ent 255" and then "sec 1" to "sec 255" and then crash right after, as if it was going for a 257th run through of the second for loop. I set the second for loop to go until "ii<=254" which stopped all crashes. Does C++ code tend to "overshoot" for loops or something? What is causing it to crash at this specific loop seemingly at random? By the way, entity_list and sector_list point to classes called Entity and Sector, respectively, but they are not constructing anything so I didn't think it would be relevant. I also have a forward declaration for the Entity class in a header for this, but since none were being constructed I didn't think it was relevant either. EDIT: It was due to the new Entity line, I assumed wrongly that the fact that altering the for statement to 254 fixed the crashes meant that it had to be there. I still don't understand why the for loop is related, though.

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• c# vocabulary

  - by foxjazz

  I have probably seen and used the word Encapsulation 4 times in my 20 years of programming.I now know what it is again, after an interview for a c# job. Even though I have used the public, private, and protected key words in classes for as long as c# was invented. I can sill remember coming across the string.IndexOf function and thinking, why didn't they call it IndexAt.Now with all the new items like Lambda and Rx, Linq, map and pmap etc, etc. I think the more choices there is to do 1 or 2 things 10 or 15 differing ways, the more programmers think to stay with what works and try and leverage the new stuff only when it really becomes beneficial.For many, the new stuff is harder to read, because programmers aren't use to seeing declarative notation.I mean I have probably used yield break, twice in my project where it may have been possible to use it many more times. Or the using statement ( not the declaration of namespace references) but inline using. I never really saw a big advantage to this, other than confusion. It is another form of local encapsulation (oh there 5 times used in my programming career) but who's counting?  THE COMPUTERS ARE COUNTING!In business logic most programming is about displaying lists, selecting items in a list, and sending those choices to some other system or database to keep track of those selections. What makes this difficult is how these items relate to one, each other, and two externally listed items.Well I probably need to go back to school and learn c# certification so I can say I am an expert in c#. Apparently using all aspects of c# (even unsafe code) in my programming life, doesn't make me certified, just certifiable.This is a good time to sign off:Fox-jazzy

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• F# Application Entry Point

  - by MarkPearl

  Up to now I have been looking at F# for modular solutions, but have never considered writing an end to end application. Today I was wondering how one would even start to write an end to end application and realized that I didn’t even know where the entry point is for an F# application. After browsing MSDN a bit I got a basic example of a F# application with an entry point [<EntryPoint>] let main args = printfn "Arguments passed to function : %A" args // Return 0. This indicates success. 0 Pretty simple stuff… but what happens when you have a few modules in a program – so I created a F# project with two modules and a main module as illustrated in the image below… When I try to compile my program I get a build error… A function labeled with the 'EntryPointAttribute' attribute must be the last declaration in the last file in the compilation sequence, and can only be used when compiling to a .exe… What does this mean? After some more reading I discovered that the Program.fs needs to be the last file in the F# application – the order of the files in a F# solution are important. How do I move a source file up or down? I tried dragging the Program.fs file below ModuleB.fs but it wouldn’t allow me to. Then I thought to right click on a source file and got the following menu.   Wala… to move the source file to the bottom of the solution you can select the “Move Up” or “Move Down” option. Now that I got this right I decided to put some code in ModuleA & ModuleB and I have the start of a basic application structure. ModuleA Code namespace MyApp module ModuleA = let PrintModuleA = printf "hello a \n" ()   ModuleB Code namespace MyApp module ModuleB = let PrintModuleB = printf "hello b \n" ()   Program Code // Learn more about F# at http://fsharp.net #light namespace MyApp module Main = open System [<EntryPoint>] let main args = ModuleA.PrintModuleA let endofapp = Console.ReadKey() 0

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• Where did I write that code ?

  - by Tarun Arora

  Every been in that situation when you desperately need to find that code you checked into TFS a few days back but just can’t remember what team project, what branch, what solution or what file you checked it into. Well you are not alone… Only if there was a way to efficiently search for files and text with in TFS. It is possible… You need to get your hands on Agent Ransack… This is a stand a lone tool that does not integrate with TFS but gives you the capability to search through text files effortlessly. Agent Ransack searches through files, text or otherwise, fast and efficiently. When searching the contents of files for code, or other text, Agent Ransack displays the text found so you can quickly browse the results without having to separately open each file! Agent Ransack is free for both Personal and Commercial use and can be Download from here.   Set the Look In directory of the Ransack search tool to your TFS Workspace and type the text you would like to scan for, you can limit the search by narrowing down the filter path or the name of the file. Found text is shown with highlighted keywords so you don't need to waste time opening each file looking for the right information.         The regular expression wizard helps you build regular expressions for complex pattern matching searches         You even have the option of searching by modified, created or last accessed date          Export your results to a file for importing into other apps or for sharing with others          Agent Ransack also provides search support for popular Office formats including Office 2007 and OpenOffice Next time you are looking for that illusive line of code whether it is a method declaration, function call, or algorithm that you checked into TFS, use Agent Ransack for a quick search.

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• What does the ".align" x86 Assembler directive do exactly? [migrated]

  - by Sinister Clock

  I will list exactly what I do not understand, and show you the parts I can not understand as well. First off, The .Align Directive .align integer, pad. The .align directive causes the next data generated to be aligned modulo integer bytes 1.~ ? : What is implied with "causes the next data generated to be aligned modulo integer bytes?" I can surmise that the next data generated is a memory-to-register transfer, no? Modulo would imply the remainder of a division. I do not understand "to be aligned modulo integer bytes"....... What would be a remainder of a simple data declaration, and how would the next data generated being aligned by a remainder be useful? If the next data is aligned modulo, that is saying the next generated data, whatever that means exactly, is the remainder of an integer? That makes absolutely no sense. What specifically would the .align, say, .align 8 directive issued in x86 for a data byte compiled from a C char, i.e., char CHARACTER = 0; be for? Or specifically coded directly with that directive, not preliminary Assembly code after compiling C? I have debugged in Assembly and noticed that any C/C++ data declarations, like chars, ints, floats, etc. will insert the directive .align 8 to each of them, and add other directives like .bss, .zero, .globl, .text, .Letext0, .Ltext0. What are all of these directives for, or at least my main asking? I have learned a lot of the main x86 Assembly instructions, but never was introduced or pointed at all of these strange directives. How do they affect the opcodes, and are all of them necessary?

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• How should I group these variables?

  - by stariz77

  I have a shape that will be defined by: char s_type; char color; double height; double width; These variables are scanned in from a request string sent to my server and passed into my printing function, which then prints out the shape. Currently they are just local variables sitting in my main(); however, I was wondering if there would be any advantage in creating a struct containing these variables, and then passing the struct to my printing function? or how else might I improve my program's structure/style, would passing a struct by reference have any kind of performance benefit if there were many requests and therefore many printing function calls? printer(char st, char cr, double ht, double wd); int main() { // Other main functionality. char s_type; char color; double height; double width; sscanf (serv_req, "GET /%c/%c/%lf/%lf", &s_type, &color, &height, &width); printer(s_type, color, height, width); // Other main functionality. return 0; } It seemed "neater" if I had a struct or something that didn't leave me with declarations in the middle of everything else going on in main. I'm interested in structure/style as well as performance. EDIT: didn't mean to put printer declaration inside main.

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• "That's cool. But it would be even better if..."

  - by Geertjan

  I recently talked to some NetBeans users who were interested in a demonstration of the features that will be part of NetBeans IDE 7.2. (See the 7.2 New and Noteworthy for the full list.) One of the new features I demonstrated was this one. In an interface declaration, NetBeans IDE 7.2 will provide a hint, as can be seen in the sidebar below: When the lightbulb is clicked, or Alt-Enter is pressed, this will be shown: When the hint is invoked, the user will see this: And then the user will be able to enter the name of a class, and the name of a package, and assuming the defaults above are taken, a class with this content will be generated: package demo; public class WordProcessorImpl implements WordProcessor {     @Override     public String process(String word) {         throw new UnsupportedOperationException("Not supported yet.");     } } When I demonstrated the above, the response from the audience was: "That's cool. But it would be even better if..." it was possible to implement an interface into an existing class. it was possible to select a class and specify the interfaces that it should implement. it was possible, in the context of a NetBeans Platform application, to specify the module where the class should be implemented. So I created some issues: Implement an interface into an existing class http://netbeans.org/bugzilla/show_bug.cgi?id=210804 Select class and specify interfaces to implement http://netbeans.org/bugzilla/show_bug.cgi?id=210805 Allow user to select module for generating implementation http://netbeans.org/bugzilla/show_bug.cgi?id=210807

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• Who extends interfaces? And why?

  - by Gangnus

  AFAIK, my class extends parent classes and implements interfaces. But I run across a situation, where I can't use implements SomeInterface. It is the declaration of a generic types. For example: public interface CallsForGrow {...} public class GrowingArrayList <T implements CallsForGrow> // BAD, won't work! extends ArrayList<T> Here using implements is syntactically forbidden. I thought first, that using interface inside < is forbidden at all, but no. It is possible, I only have to use extends instead of implements. As a result, I am "extending" an interface. This another example works: public interface CallsForGrow {...} public class GrowingArrayList <T extends CallsForGrow> // this works! extends ArrayList<T> To me it seems as a syntactical inconsistancy. But maybe I don't understand some finesses of Java 6? Are there other places where I should extend interfaces? Should the interface, that I mean to extend, have some special features?

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• Why does Scala require functions to have explicit return type?

  - by garbage collection

  I recently began learning to program in Scala, and it's been fun so far. I really like the ability to declare functions within another function which just seems to intuitive thing to do. One pet peeve I have about Scala is the fact that Scala requires explicit return type in its functions. And I feel like this hinders on expressiveness of the language. Also it's just difficult to program with that requirement. Maybe it's because I come from Javascript and Ruby comfort zone. But for a language like Scala which will have tons of connected functions in an application, I cannot conceive how I brainstorm in my head exactly what type the particular function I am writing should return with recursions after recursions. This requirement of explicit return type declaration on functions, do not bother me for languages like Java and C++. Recursions in Java and C++, when they did happen, often were dealt with 2 to 3 functions max. Never several functions chained up together like Scala. So I guess I'm wondering if there is a good reason why Scala should have the requirement of functions having explicit return type?

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• What is the most concise, unambiguous syntax for operator associated methods (for overloading etc.) that doesn't pollute the namespace?

  - by Doug Treadwell

  Python tends to add double underscores before its built-in or overloadable operator methods, like __add(), whereas C++ requires declaring overloaded operators as operator + (Thing& thing) { /* code */ } for example. Personally I like the operator syntax because it seems to be more explicit and keeps these operator overloading methods separated from other methods without introducing weird prefix notation. What are your thoughts? Also, what about the case of built-in methods that are needed for the programming language to work properly? Is name mangling (like adding __ prefix or sys or something) the best solution here? What do you think about having another type of method declaration, like ... "system method" for lack of creativity at the moment. So there would be two kinds of declarations: int method_name() { ... } system int method_name() { ... } ... and the call would need to be different to distinguish between them. obj.method_name(); vs obj:method_name(); perhaps, assuming a language where : can be unambiguously used in this situation. obj.method_name() vs obj.(system method_name)() Sure, the latter is ugly, but the idea is to make the common case simple and system stuff should be kept out of the way. Maybe the Objective-C notation of method calls? [obj method_name]? Are there more alternatives? Please make suggestions.

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• Value my C++ knowledge

  - by PirateOwh

  I have only followed antiRTFM tutorials and read 2 books So, I'll list the things I know better : basic input output and all the variables : integers ( signed unsigned ), float, double, char arrays if, for, while, switch functions, and passing variables to functions and return type thing classes and the concept of oop with separating declaration and definition in the header and in the source pointers so this and some more i think is all i know of C++.. But, i need some exercises to test my knowledge because i want to move on to the library SDL, so I don't know if i should feel ready or not to move on to something totally different.. I feel I should know the basics for good at least. So the question is : How can i value my c++ knowledge? Is there any online tests? Is there any GDD ( Game Design Document ) for free to use and see if i can manage to do it so "i'd pass" ? ( I'm saying GDD since ill move on to SDL and try to make my own game ) When should I move to SDL? What are ALL the things I should "master" ( master is a big word to say.. but so you understand what i mean ) before moving on ? Please I'm really in need of expert advice. I think my question is detailed so i hope you understand what i mean and can give me a good reply. Thanks for the help!

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• How to embed woff fonts for iframe source pages?

  - by Mon

  I am trying to make and embed a slideshow (of text, photo, audio, video, etc) in my site (HTML5) by loading webpages consecutively inside an iframe embedded in my first page. Most or all of the frame source pages, i.e. pages loaded inside first iframe are mine, but located in many different places. All of these pages are in an Indic language. Although I can use UTF-8 charset and lang="" declaration and that's probably enough functionally, but I also want to embed my preferred Indic unicode font in WOFF format via CSS3 @font-face rule , so the size and look of the text is uniform and the way I want it - throughout the slideshow. Problem is, there are many many pages in the slideshow all located in various places with many more linked pages, and it is next to impossible, or at least would be extremely tedious, to embed my custom WOFF font in every single page (which will also require separate css and uploading of fonts in every single instance). Besides, this may make the slideshow very heavy, sluggish and cumbersome for the user, since it will have to load the custom Indic font again and again everytime a new page is loaded in the iframe. I am not sure about this though. Is that how it works? I ask this, because I noticed that when I embedded my custom WOFF font in the 'first' page, it did not have any effect on the pages loaded inside the iframe. If I embed the font in some of the pages in the iframe, the next pages still don't get my font. Is there a way to embed my custom WOFF font only once, preferably in the first page where the first iframe is, and pass its effect on to all the pages embedded / loaded through the iframe and make their text show up as per my initially embedded woff font - without embedding my font in every single of them? Please help!

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• Recommended design pattern for object with optional and modifiable attributtes? [on hold]

  - by Ikuzen

  I've been using the Builder pattern to create objects with a large number of attributes, where most of them are optional. But up until now, I've defined them as final, as recommended by Joshua Block and other authors, and haven't needed to change their values. I am wondering what should I do though if I need a class with a substantial number of optional but non-final (mutable) attributes? My Builder pattern code looks like this: public class Example { //All possible parameters (optional or not) private final int param1; private final int param2; //Builder class public static class Builder { private final int param1; //Required parameters private int param2 = 0; //Optional parameters - initialized to default //Builder constructor public Builder (int param1) { this.param1 = param1; } //Setter-like methods for optional parameters public Builder param2(int value) { param2 = value; return this; } //build() method public Example build() { return new Example(this); } } //Private constructor private Example(Builder builder) { param1 = builder.param1; param2 = builder.param2; } } Can I just remove the final keyword from the declaration to be able to access the attributes externally (through normal setters, for example)? Or is there a creational pattern that allows optional but non-final attributes that would be better suited in this case?

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• Ops Center 12c - Provisioning Solaris Using a Card-Based NIC

  - by scottdickson

  It's been a long time since last I added something here, but having some conversations this last week, I got inspired to update things. I've been spending a lot of time with Ops Center for managing and installing systems these days.  So, I suspect a number of my upcoming posts will be in that area. Today, I want to look at how to provision Solaris using Ops Center when your network is not connected to one of the built-in NICs.  We'll talk about how this can work for both Solaris 10 and Solaris 11, since they are pretty similar.  In both cases, WANboot is a key piece of the story. Here's what I want to do:  I have a Sun Fire T2000 server with a Quad-GbE nxge card installed.  The only network is connected to port 2 on that card rather than the built-in network interfaces.  I want to install Solaris on it across the network, either Solaris 10 or Solaris 11.  I have met with a lot of customers lately who have a similar architecture.  Usually, they have T4-4 servers with the network connected via 10GbE connections. Add to this mix the fact that I use Ops Center to manage the systems in my lab, so I really would like to add this to Ops Center.  If possible, I would like this to be completely hands free.  I can't quite do that yet. Close, but not quite. WANBoot or Old-Style NetBoot? When a system is installed from the network, it needs some help getting the process rolling.  It has to figure out what its network configuration (IP address, gateway, etc.) ought to be.  It needs to figure out what server is going to help it boot and install, and it needs the instructions for the installation.  There are two different ways to bootstrap an installation of Solaris on SPARC across the network.   The old way uses a broadcast of RARP or more recently DHCP to obtain the IP configuration and the rest of the information needed.  The second is to explicitly configure this information in the OBP and use WANBoot for installation WANBoot has a number of benefits over broadcast-based installation: it is not restricted to a single subnet; it does not require special DHCP configuration or DHCP helpers; it uses standard HTTP and HTTPS protocols which traverse firewalls much more easily than NFS-based package installation.  But, WANBoot is not available on really old hardware and WANBoot requires the use o Flash Archives in Solaris 10.  Still, for many people, this is a great approach. As it turns out, WANBoot is necessary if you plan to install using a NIC on a card rather than a built-in NIC. Identifying Which Network Interface to Use One of the trickiest aspects to this process, and the one that actually requires manual intervention to set up, is identifying how the OBP and Solaris refer to the NIC that we want to use to boot.  The OBP already has device aliases configured for the built-in NICs called net, net0, net1, net2, net3.  The device alias net typically points to net0 so that when you issue the command  "boot net -v install", it uses net0 for the boot.  Our task is to figure out the network instance for the NIC we want to use.  We will need to get to the OBP console of the system we want to install in order to figure out what the network should be called.  I will presume you know how to get to the ok prompt.  Once there, we have to see what networks the OBP sees and identify which one is associated with our NIC using the OBP command show-nets. SunOS Release 5.11 Version 11.0 64-bit Copyright (c) 1983, 2011, Oracle and/or its affiliates. All rights reserved. {4} ok banner Sun Fire T200, No Keyboard Copyright (c) 1998, 2010, Oracle and/or its affiliates. All rights reserved. OpenBoot 4.30.4.b, 32640 MB memory available, Serial #69057548. Ethernet address 0:14:4f:1d:bc:c, Host ID: 841dbc0c. {4} ok show-nets a) /pci@7c0/pci@0/pci@2/network@0,1 b) /pci@7c0/pci@0/pci@2/network@0 c) /pci@780/pci@0/pci@8/network@0,3 d) /pci@780/pci@0/pci@8/network@0,2 e) /pci@780/pci@0/pci@8/network@0,1 f) /pci@780/pci@0/pci@8/network@0 g) /pci@780/pci@0/pci@1/network@0,1 h) /pci@780/pci@0/pci@1/network@0 q) NO SELECTION Enter Selection, q to quit: d /pci@780/pci@0/pci@8/network@0,2 has been selected. Type ^Y ( Control-Y ) to insert it in the command line. e.g. ok nvalias mydev ^Y for creating devalias mydev for /pci@780/pci@0/pci@8/network@0,2 {4} ok devalias ... net3 /pci@7c0/pci@0/pci@2/network@0,1 net2 /pci@7c0/pci@0/pci@2/network@0 net1 /pci@780/pci@0/pci@1/network@0,1 net0 /pci@780/pci@0/pci@1/network@0 net /pci@780/pci@0/pci@1/network@0 ... name aliases By looking at the devalias and the show-nets output, we can see that our Quad-GbE card must be the device nodes starting with  /pci@780/pci@0/pci@8/network@0.  The cable for our network is plugged into the 3rd slot, so the device address for our network must be /pci@780/pci@0/pci@8/network@0,2. With that, we can create a device alias for our network interface.  Naming the device alias may take a little bit of trial and error, especially in Solaris 11 where the device alias seems to matter more with the new virtualized network stack. So far in my testing, since this is the "next" network interface to be used, I have found success in naming it net4, even though it's a NIC in the middle of a card that might, by rights, be called net6 (assuming the 0th interface on the card is the next interface identified by Solaris and this is the 3rd interface on the card).  So, we will call it net4.  We need to assign a device alias to it: {4} ok nvalias net4 /pci@780/pci@0/pci@8/network@0,2 {4} ok devalias net4 /pci@780/pci@0/pci@8/network@0,2 ... We also may need to have the MAC for this particular interface, so let's get it, too.  To do this, we go to the device and interrogate its properties. {4} ok cd /pci@780/pci@0/pci@8/network@0,2 {4} ok .properties assigned-addresses 82060210 00000000 03000000 00000000 01000000 82060218 00000000 00320000 00000000 00008000 82060220 00000000 00328000 00000000 00008000 82060230 00000000 00600000 00000000 00100000 local-mac-address 00 21 28 20 42 92 phy-type mif ... From this, we can see that the MAC for this interface is  00:21:28:20:42:92.  We will need this later. This is all we need to do at the OBP.  Now, we can configure Ops Center to use this interface. Network Boot in Solaris 10 Solaris 10 turns out to be a little simpler than Solaris 11 for this sort of a network boot.  Since WANBoot in Solaris 10 fetches a specified In order to install the system using Ops Center, it is necessary to create a OS Provisioning profile and its corresponding plan.  I am going to presume that you already know how to do this within Ops Center 12c and I will just cover the differences between a regular profile and a profile that can use an alternate interface. Create a OS Provisioning profile for Solaris 10 as usual.  However, when you specify the network resources for the primary network, click on the name of the NIC, probably GB_0, and rename it to GB_N/netN, where N is the instance number you used previously in creating the device alias.  This is where the trial and error may come into play.  You may need to try a few instance numbers before you, the OBP, and Solaris all agree on the instance number.  Mark this as the boot network. For Solaris 10, you ought to be able to then apply the OS Provisioning profile to the server and it should install using that interface.  And if you put your cards in the same slots and plug the networks into the same NICs, this profile is reusable across multiple servers. Why This Works If you watch the console as Solaris boots during the OSP process, Ops Center is going to look for the device alias netN.  Since WANBoot requires a device alias called just net, Ops Center uses the value of your netN device alias and assigns that device to the net alias.  That means that boot net will automatically use this device.  Very cool!  Here's a trace from the console as Ops Center provisions a server: Sun Sun Fire T200, No KeyboardCopyright (c) 1998, 2010, Oracle and/or its affiliates. All rights reserved.OpenBoot 4.30.4.b, 32640 MB memory available, Serial #69057548.Ethernet address 0:14:4f:1d:bc:c, Host ID: 841dbc0c.auto-boot? =            false{0} ok  {0} ok printenv network-boot-argumentsnetwork-boot-arguments =  host-ip=10.140.204.234,router-ip=10.140.204.1,subnet-mask=255.255.254.0,hostname=atl-sewr-52,client-id=0100144F1DBC0C,file=http://10.140.204.22:5555/cgi-bin/wanboot-cgi{0} ok {0} ok devalias net net                      /pci@780/pci@0/pci@1/network@0{0} ok devalias net4 net4                     /pci@780/pci@0/pci@8/network@0,2{0} ok devalias net /pci@780/pci@0/pci@8/network@0,2{0} ok setenv network-boot-arguments host-ip=10.140.204.234,router-ip=10.140.204.1,subnet-mask=255.255.254.0,hostname=atl-sewr-52,client-id=0100144F1DBC0C,file=http://10.140.204.22:8004/cgi-bin/wanboot-cginetwork-boot-arguments =  host-ip=10.140.204.234,router-ip=10.140.204.1,subnet-mask=255.255.254.0,hostname=atl-sewr-52,client-id=0100144F1DBC0C,file=http://10.140.204.22:8004/cgi-bin/wanboot-cgi{0} ok {0} ok boot net - installBoot device: /pci@780/pci@0/pci@8/network@0,2  File and args: - install/pci@780/pci@0/pci@8/network@0,2: 1000 Mbps link up<time unavailable> wanboot info: WAN boot messages->console<time unavailable> wanboot info: configuring /pci@780/pci@0/pci@8/network@0,2 See what happened?  Ops Center looked for the network device alias called net4 that we specified in the profile, took the value from it, and made it the net device alias for the boot.  Pretty cool! WANBoot and Solaris 11 Solaris 11 requires an additional step since the Automated Installer in Solaris 11 uses the MAC address of the network to figure out which manifest to use for system installation.  In order to make sure this is available, we have to take an extra step to associate the MAC of the NIC on the card with the host.  So, in addition to creating the device alias like we did above, we also have to declare to Ops Center that the host has this new MAC. Declaring the NIC Start out by discovering the hardware as usual.  Once you have discovered it, take a look under the Connectivity tab to see what networks it has discovered.  In the case of this system, it shows the 4 built-in networks, but not the networks on the additional cards.  These are not directly visible to the system controller.  In order to add the additional network interface to the hardware asset, it is necessary to Declare it.  We will declare that we have a server with this additional NIC, but we will also  specify the existing GB_0 network so that Ops Center can associate the right resources together.  The GB_0 acts as sort of a key to tie our new declaration to the old system already discovered.  Go to the Assets tab, select All Assets, and then in the Actions tab, select Add Asset.  Rather than going through a discovery this time, we will manually declare a new asset. When we declare it, we will give the hostname, IP address, system model that match those that have already been discovered.  Then, we will declare both GB_0 with its existing MAC and the new GB_4 with its MAC.  Remember that we collected the MAC for GB_4 when we created its device alias. After you declare the asset, you will see the new NIC in the connectivity tab for the asset.  You will notice that only the NICs you listed when you declared it are seen now.  If you want Ops Center to see all of the existing NICs as well as the additional one, declare them as well.  Add the other GB_1, GB_2, GB_3 links and their MACs just as you did GB_0 and GB_4.  Installing the OS  Once you have declared the asset, you can create an OS Provisioning profile for Solaris 11 in the same way that you did for Solaris 10.  The only difference from any other provisioning profile you might have created already is the network to use for installation.  Again, use GB_N/netN where N is the interface number you used for your device alias and in your declaration.  And away you go.  When the system boots from the network, the automated installer (AI) is able to see which system manifest to use, based on the new MAC that was associated, and the system gets installed. {0} ok {0} ok printenv network-boot-argumentsnetwork-boot-arguments =  host-ip=10.140.204.234,router-ip=10.140.204.1,subnet-mask=255.255.254.0,hostname=atl-sewr-52,client-id=01002128204292,file=http://10.140.204.22:5555/cgi-bin/wanboot-cgi{0} ok {0} ok devalias net net                      /pci@780/pci@0/pci@1/network@0{0} ok devalias net4 net4                     /pci@780/pci@0/pci@8/network@0,2{0} ok devalias net /pci@780/pci@0/pci@8/network@0,2{0} ok setenv network-boot-arguments host-ip=10.140.204.234,router-ip=10.140.204.1,subnet-mask=255.255.254.0,hostname=atl-sewr-52,client-id=01002128204292,file=http://10.140.204.22:5555/cgi-bin/wanboot-cginetwork-boot-arguments =  host-ip=10.140.204.234,router-ip=10.140.204.1,subnet-mask=255.255.254.0,hostname=atl-sewr-52,client-id=01002128204292,file=http://10.140.204.22:5555/cgi-bin/wanboot-cgi{0} ok {0} ok boot net - installBoot device: /pci@780/pci@0/pci@8/network@0,2  File and args: - install/pci@780/pci@0/pci@8/network@0,2: 1000 Mbps link up<time unavailable> wanboot info: WAN boot messages->console<time unavailable> wanboot info: configuring /pci@780/pci@0/pci@8/network@0,2...SunOS Release 5.11 Version 11.0 64-bitCopyright (c) 1983, 2011, Oracle and/or its affiliates. All rights reserved.Remounting root read/writeProbing for device nodes ...Preparing network image for useDownloading solaris.zlib--2012-02-17 15:10:17--  http://10.140.204.22:5555/var/js/AI/sparc//solaris.zlibConnecting to 10.140.204.22:5555... connected.HTTP request sent, awaiting response... 200 OKLength: 126752256 (121M) [text/plain]Saving to: `/tmp/solaris.zlib'100%[======================================>] 126,752,256 28.6M/s   in 4.4s    2012-02-17 15:10:21 (27.3 MB/s) - `/tmp/solaris.zlib' saved [126752256/126752256] Conclusion So, why go to all of this trouble?  More and more, I find that customers are wiring their data center to only use higher speed networks - 10GbE only to the hosts.  Some customers are moving aggressively toward consolidated networks combining storage and network on CNA NICs.  All of this means that network-based provisioning cannot rely exclusively on the built-in network interfaces.  So, it's important to be able to provision a system using other than the built-in networks.  Turns out, that this is pretty straight-forward for both Solaris 10 and Solaris 11 and fits into the Ops Center deployment process quite nicely. Hopefully, you will be able to use this as you build out your own private cloud solutions with Ops Center.

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• C#/.NET Little Wonders: The Useful But Overlooked Sets

  - by James Michael Hare

  Once again we consider some of the lesser known classes and keywords of C#.  Today we will be looking at two set implementations in the System.Collections.Generic namespace: HashSet<T> and SortedSet<T>.  Even though most people think of sets as mathematical constructs, they are actually very useful classes that can be used to help make your application more performant if used appropriately. A Background From Math In mathematical terms, a set is an unordered collection of unique items.  In other words, the set {2,3,5} is identical to the set {3,5,2}.  In addition, the set {2, 2, 4, 1} would be invalid because it would have a duplicate item (2).  In addition, you can perform set arithmetic on sets such as: Intersections: The intersection of two sets is the collection of elements common to both.  Example: The intersection of {1,2,5} and {2,4,9} is the set {2}. Unions: The union of two sets is the collection of unique items present in either or both set.  Example: The union of {1,2,5} and {2,4,9} is {1,2,4,5,9}. Differences: The difference of two sets is the removal of all items from the first set that are common between the sets.  Example: The difference of {1,2,5} and {2,4,9} is {1,5}. Supersets: One set is a superset of a second set if it contains all elements that are in the second set. Example: The set {1,2,5} is a superset of {1,5}. Subsets: One set is a subset of a second set if all the elements of that set are contained in the first set. Example: The set {1,5} is a subset of {1,2,5}. If We’re Not Doing Math, Why Do We Care? Now, you may be thinking: why bother with the set classes in C# if you have no need for mathematical set manipulation?  The answer is simple: they are extremely efficient ways to determine ownership in a collection. For example, let’s say you are designing an order system that tracks the price of a particular equity, and once it reaches a certain point will trigger an order.  Now, since there’s tens of thousands of equities on the markets, you don’t want to track market data for every ticker as that would be a waste of time and processing power for symbols you don’t have orders for.  Thus, we just want to subscribe to the stock symbol for an equity order only if it is a symbol we are not already subscribed to. Every time a new order comes in, we will check the list of subscriptions to see if the new order’s stock symbol is in that list.  If it is, great, we already have that market data feed!  If not, then and only then should we subscribe to the feed for that symbol. So far so good, we have a collection of symbols and we want to see if a symbol is present in that collection and if not, add it.  This really is the essence of set processing, but for the sake of comparison, let’s say you do a list instead: 1: // class that handles are order processing service 2: public sealed class OrderProcessor 3: { 4: // contains list of all symbols we are currently subscribed to 5: private readonly List<string> _subscriptions = new List<string>(); 6:  7: ... 8: } Now whenever you are adding a new order, it would look something like: 1: public PlaceOrderResponse PlaceOrder(Order newOrder) 2: { 3: // do some validation, of course... 4:  5: // check to see if already subscribed, if not add a subscription 6: if (!_subscriptions.Contains(newOrder.Symbol)) 7: { 8: // add the symbol to the list 9: _subscriptions.Add(newOrder.Symbol); 10: 11: // do whatever magic is needed to start a subscription for the symbol 12: } 13:  14: // place the order logic! 15: } What’s wrong with this?  In short: performance!  Finding an item inside a List<T> is a linear - O(n) – operation, which is not a very performant way to find if an item exists in a collection. (I used to teach algorithms and data structures in my spare time at a local university, and when you began talking about big-O notation you could immediately begin to see eyes glossing over as if it was pure, useless theory that would not apply in the real world, but I did and still do believe it is something worth understanding well to make the best choices in computer science). Let’s think about this: a linear operation means that as the number of items increases, the time that it takes to perform the operation tends to increase in a linear fashion.  Put crudely, this means if you double the collection size, you might expect the operation to take something like the order of twice as long.  Linear operations tend to be bad for performance because they mean that to perform some operation on a collection, you must potentially “visit” every item in the collection.  Consider finding an item in a List<T>: if you want to see if the list has an item, you must potentially check every item in the list before you find it or determine it’s not found. Now, we could of course sort our list and then perform a binary search on it, but sorting is typically a linear-logarithmic complexity – O(n * log n) - and could involve temporary storage.  So performing a sort after each add would probably add more time.  As an alternative, we could use a SortedList<TKey, TValue> which sorts the list on every Add(), but this has a similar level of complexity to move the items and also requires a key and value, and in our case the key is the value. This is why sets tend to be the best choice for this type of processing: they don’t rely on separate keys and values for ordering – so they save space – and they typically don’t care about ordering – so they tend to be extremely performant.  The .NET BCL (Base Class Library) has had the HashSet<T> since .NET 3.5, but at that time it did not implement the ISet<T> interface.  As of .NET 4.0, HashSet<T> implements ISet<T> and a new set, the SortedSet<T> was added that gives you a set with ordering. HashSet<T> – For Unordered Storage of Sets When used right, HashSet<T> is a beautiful collection, you can think of it as a simplified Dictionary<T,T>.  That is, a Dictionary where the TKey and TValue refer to the same object.  This is really an oversimplification, but logically it makes sense.  I’ve actually seen people code a Dictionary<T,T> where they store the same thing in the key and the value, and that’s just inefficient because of the extra storage to hold both the key and the value. As it’s name implies, the HashSet<T> uses a hashing algorithm to find the items in the set, which means it does take up some additional space, but it has lightning fast lookups!  Compare the times below between HashSet<T> and List<T>: Operation HashSet<T> List<T> Add() O(1) O(1) at end O(n) in middle Remove() O(1) O(n) Contains() O(1) O(n)   Now, these times are amortized and represent the typical case.  In the very worst case, the operations could be linear if they involve a resizing of the collection – but this is true for both the List and HashSet so that’s a less of an issue when comparing the two. The key thing to note is that in the general case, HashSet is constant time for adds, removes, and contains!  This means that no matter how large the collection is, it takes roughly the exact same amount of time to find an item or determine if it’s not in the collection.  Compare this to the List where almost any add or remove must rearrange potentially all the elements!  And to find an item in the list (if unsorted) you must search every item in the List. So as you can see, if you want to create an unordered collection and have very fast lookup and manipulation, the HashSet is a great collection. And since HashSet<T> implements ICollection<T> and IEnumerable<T>, it supports nearly all the same basic operations as the List<T> and can use the System.Linq extension methods as well. All we have to do to switch from a List<T> to a HashSet<T>  is change our declaration.  Since List and HashSet support many of the same members, chances are we won’t need to change much else. 1: public sealed class OrderProcessor 2: { 3: private readonly HashSet<string> _subscriptions = new HashSet<string>(); 4:  5: // ... 6:  7: public PlaceOrderResponse PlaceOrder(Order newOrder) 8: { 9: // do some validation, of course... 10: 11: // check to see if already subscribed, if not add a subscription 12: if (!_subscriptions.Contains(newOrder.Symbol)) 13: { 14: // add the symbol to the list 15: _subscriptions.Add(newOrder.Symbol); 16: 17: // do whatever magic is needed to start a subscription for the symbol 18: } 19: 20: // place the order logic! 21: } 22:  23: // ... 24: } 25: Notice, we didn’t change any code other than the declaration for _subscriptions to be a HashSet<T>.  Thus, we can pick up the performance improvements in this case with minimal code changes. SortedSet<T> – Ordered Storage of Sets Just like HashSet<T> is logically similar to Dictionary<T,T>, the SortedSet<T> is logically similar to the SortedDictionary<T,T>. The SortedSet can be used when you want to do set operations on a collection, but you want to maintain that collection in sorted order.  Now, this is not necessarily mathematically relevant, but if your collection needs do include order, this is the set to use. So the SortedSet seems to be implemented as a binary tree (possibly a red-black tree) internally.  Since binary trees are dynamic structures and non-contiguous (unlike List and SortedList) this means that inserts and deletes do not involve rearranging elements, or changing the linking of the nodes.  There is some overhead in keeping the nodes in order, but it is much smaller than a contiguous storage collection like a List<T>.  Let’s compare the three: Operation HashSet<T> SortedSet<T> List<T> Add() O(1) O(log n) O(1) at end O(n) in middle Remove() O(1) O(log n) O(n) Contains() O(1) O(log n) O(n)   The MSDN documentation seems to indicate that operations on SortedSet are O(1), but this seems to be inconsistent with its implementation and seems to be a documentation error.  There’s actually a separate MSDN document (here) on SortedSet that indicates that it is, in fact, logarithmic in complexity.  Let’s put it in layman’s terms: logarithmic means you can double the collection size and typically you only add a single extra “visit” to an item in the collection.  Take that in contrast to List<T>’s linear operation where if you double the size of the collection you double the “visits” to items in the collection.  This is very good performance!  It’s still not as performant as HashSet<T> where it always just visits one item (amortized), but for the addition of sorting this is a good thing. Consider the following table, now this is just illustrative data of the relative complexities, but it’s enough to get the point: Collection Size O(1) Visits O(log n) Visits O(n) Visits 1 1 1 1 10 1 4 10 100 1 7 100 1000 1 10 1000   Notice that the logarithmic – O(log n) – visit count goes up very slowly compare to the linear – O(n) – visit count.  This is because since the list is sorted, it can do one check in the middle of the list, determine which half of the collection the data is in, and discard the other half (binary search).  So, if you need your set to be sorted, you can use the SortedSet<T> just like the HashSet<T> and gain sorting for a small performance hit, but it’s still faster than a List<T>. Unique Set Operations Now, if you do want to perform more set-like operations, both implementations of ISet<T> support the following, which play back towards the mathematical set operations described before: IntersectWith() – Performs the set intersection of two sets.  Modifies the current set so that it only contains elements also in the second set. UnionWith() – Performs a set union of two sets.  Modifies the current set so it contains all elements present both in the current set and the second set. ExceptWith() – Performs a set difference of two sets.  Modifies the current set so that it removes all elements present in the second set. IsSupersetOf() – Checks if the current set is a superset of the second set. IsSubsetOf() – Checks if the current set is a subset of the second set. For more information on the set operations themselves, see the MSDN description of ISet<T> (here). What Sets Don’t Do Don’t get me wrong, sets are not silver bullets.  You don’t really want to use a set when you want separate key to value lookups, that’s what the IDictionary implementations are best for. Also sets don’t store temporal add-order.  That is, if you are adding items to the end of a list all the time, your list is ordered in terms of when items were added to it.  This is something the sets don’t do naturally (though you could use a SortedSet with an IComparer with a DateTime but that’s overkill) but List<T> can. Also, List<T> allows indexing which is a blazingly fast way to iterate through items in the collection.  Iterating over all the items in a List<T> is generally much, much faster than iterating over a set. Summary Sets are an excellent tool for maintaining a lookup table where the item is both the key and the value.  In addition, if you have need for the mathematical set operations, the C# sets support those as well.  The HashSet<T> is the set of choice if you want the fastest possible lookups but don’t care about order.  In contrast the SortedSet<T> will give you a sorted collection at a slight reduction in performance.   Technorati Tags: C#,.Net,Little Wonders,BlackRabbitCoder,ISet,HashSet,SortedSet

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• Require CoreTelephony framework examples.

  - by prathumca

  Greetings everyone. Can any one has a working example for the CoreTelephony framework? I dumped all the CoreTelephony headers using class-dump and added them to "/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS3.1.3.sdk/System/Library/PrivateFrameworks/CoreTelephony.framework". Now I'm following the Erica's tutorial (http://blogs.oreilly.com/iphone/2008/08/iphone-notifications.html). I added these following lines of code in my main.m, id ct = CTTelephonyCenterGetDefault(); CTTelephonyCenterAddObserver( ct, NULL, callback, NULL, NULL, CFNotificationSuspensionBehaviorHold); but I'm getting a warning like, Implicit declaration of function "CTTelephonyCenterGetDefault()" and "CTTelephonyCenterAddObserver(...)". Can any one has full working example, which will explain how to get the CoreTelepony notifications?

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