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  • XNA calculate normals for linesegment

    - by Gerhman
    I am quite new to 3D graphical programming and thus far only understand that normal somehow define the direction in which a vertex faces and therefore the direction in which light is reflected. I have now idea how they are calculated though, only that they are defined by a Vector3. For a visualizer that I am creating I am importing a bunch of coordinate which represent layer upon layer of line segments. At the moment I am only using a vertex buffer and adding the start and end point of each line and then rendering a linelist. The thing is now that I need to calculate the normal for the vertices of these line segments so that I can get some realistic lighting. I have no idea how to calculate these normal but I know they all face sideways and not up or down. To calculate them all I have are the start and end positions of each line segment. The below image is a representation of what I think I need to do in the case of an example layer: The red arrows represent the normal that should be calculates, the blue text represent the coordinates of the vertices and the green numbers represent their indices. I would greatly appreciate it if someone could please explain to me how I should calculate these normal.

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  • why is glVertexAttribDivisor crashing?

    - by 2am
    I am trying to render some trees with instancing. This is rather weird, but before sleeping yesterday night, I checked the code, and it was in a running state, when I got up this morning, it is crashing when I am calling glVertexAttribDivisor I haven't changed any code since yesterday. Here is how I am sending data to GPU for instancing. glGenBuffers(1, &iVBO); glBindBuffer(GL_ARRAY_BUFFER, iVBO); glBufferData(GL_ARRAY_BUFFER, (ml_instance->i_positions.size()*sizeof(glm::vec4)) , NULL, GL_STATIC_DRAW); glBufferSubData(GL_ARRAY_BUFFER, 0, (ml_instance->i_positions.size()*sizeof(glm::vec4)), &ml_instance->i_positions[0]); And then in vertex specification-- glBindBuffer(GL_ARRAY_BUFFER, iVBO); glVertexAttribPointer(i_positions, 4, GL_FLOAT, GL_FALSE, 0, 0); glEnableVertexAttribArray(i_positions); glVertexAttribDivisor(i_positions,1); // **THIS IS WHERE THE PROGRAM CRASHES** glDrawElementsInstanced(GL_TRIANGLES, indices.size(), GL_UNSIGNED_INT, 0,TREES_INSTANCE_COUNT); I have checked ml_instance->i_positions, it has all the data that needs to render. I have checked the value of i_positions in vertex shader, it is the same as whatever I have defined there. I am little out of ideas here, everything looks pretty much fine. What am I missing?

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  • Does pdksh (public domain korn shell) support associative arrays?

    - by George Jempty
    I recently ran up against a wall doing some bash shell programming where an associative array would have solved my problems. I googled about features of the Korn shell and learned that it supports associative arrays, so I installed Cygwin's pdksh (public domain korn shell). However, when trying to create an associative array in the prescribed manner (typeset -A varName), I received the following errors, so I'm beginning to suspect pdksh does not support associative arrays. ./find_actions.ksh: line 2: typeset: -A: invalid option typeset: usage: typeset [-afFirtx] [-p] name[=value] ... Guess I'll be considering Perl instead, but I really wanted a good excuse to learn a dialect/language new to me

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  • in java, which is better - three arrays of booleans or 1 array of bytes?

    - by joe_shmoe
    I know the question sounds silly, but consider this: I have an array of items and a labelling algorithm. at any point the item is in one of three states. The current version holds these states in a byte array, where 0, 1 and 2 represent the three states. alternatively, I could have three arrays of boolean - one for each state. which is better (consumes less memory) depends on how jvm (sun's version) stores the arrays - is a boolean represented by 1 bit? (p.s. don't start with all that "this is not the way OO/Java works" - I know, but here performance comes in front. plus the algorithm is simple and perfectly readable even in such form). Thanks a lot

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  • "Single NSMutableArray" vs. "Multiple C-arrays" --Which is more Efficient/Practical?

    - by RexOnRoids
    Situation: I have a DAY structure. The DAY structure has three variables or attributes: a Date (NSString*), a Temperature (float), and a Rainfall (float). Problem: I will be iterating through an array of about 5000 DAY structures and graphing a portion of these onto the screen using OpenGL. Question: As far as drawing performance, which is better? I could simply create an NSMutableArray of DAY structures (NSObjects) and iterate on the array on each draw call -- which I think would be hard on the CPU. Or, I could instead manually manage three different C-Arrays -- One for the Date String (2-Dimensional), One for the temperature (1-Dimensional) and One for the Rainfall (1-Dimensional). I could keep track of the current Day by referencing the current index of the iterated C-Arrays.

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  • How to combine two arrays of same length to one array with two fields (not append/merge)

    - by Raj
    Say, I have an array with months $months = array('Jan', 'Feb', 'Mar'...'Dec'); And another, with days (say, for year 2010) $mdays = array(31, 28, 31...31); I want to merge/combine these two arrays, into an array like this: $monthdetails[0] = ('month' => 'Jan', 'days' => 31) $monthdetails[1] = ('month' => 'Feb', 'days' => 28) ... $monthdetails[11] = ('month' => 'Dec', 'days' => 31) I can loop through both the arrays and fill the $monthdetails. I want to know whether there are any functions/easier way for achieving the same result. Thanks! Raj

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  • How to find kth minimal element in the union of two sorted arrays?

    - by Michael
    This is a homework question. They say it takes O(logN + logM) where N and M are the arrays lengths. Let's name the arrays a and b. Obviously we can ignore all a[i] and b[i] where i k. First let's compare a[k/2] and b[k/2]. Let b[k/2] a[k/2]. Therefore we can discard also all b[i], where i k/2. Now we have all a[i], where i < k and all b[i], where i < k/2 to find the answer. What is the next step?

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  • In Perl, is there a built in way to compare two arrays for equality?

    - by Bill
    I have two arrays of strings that I would like to compare for equality: my @array1 = ("part1", "part2", "part3", "part4"); my @array2 = ("part1", "PART2", "part3", "part4"); Is there a built-in way to compare arrays like there is for scalars? I tried: if (@array1 == @array2) {...} but it just evaluated each array in scalar context, and so compared the length of each array. I can roll my own function to do it, but it seems like such a low-level operation that there should be a built-in way to do it. Is there? Edit: sadly, I don't have access to 5.10+ or optional components.

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  • Pixel Shader Giving Black output

    - by Yashwinder
    I am coding in C# using Windows Forms and the SlimDX API to show the effect of a pixel shader. When I am setting the pixel shader, I am getting a black output screen but if I am not using the pixel shader then I am getting my image rendered on the screen. I have the following C# code using System; using System.Collections.Generic; using System.Linq; using System.Windows.Forms; using System.Runtime.InteropServices; using SlimDX.Direct3D9; using SlimDX; using SlimDX.Windows; using System.Drawing; using System.Threading; namespace WindowsFormsApplication1 { // Vertex structure. [StructLayout(LayoutKind.Sequential)] struct Vertex { public Vector3 Position; public float Tu; public float Tv; public static int SizeBytes { get { return Marshal.SizeOf(typeof(Vertex)); } } public static VertexFormat Format { get { return VertexFormat.Position | VertexFormat.Texture1; } } } static class Program { public static Device D3DDevice; // Direct3D device. public static VertexBuffer Vertices; // Vertex buffer object used to hold vertices. public static Texture Image; // Texture object to hold the image loaded from a file. public static int time; // Used for rotation caculations. public static float angle; // Angle of rottaion. public static Form1 Window =new Form1(); public static string filepath; static VertexShader vertexShader = null; static ConstantTable constantTable = null; static ImageInformation info; [STAThread] static void Main() { filepath = "C:\\Users\\Public\\Pictures\\Sample Pictures\\Garden.jpg"; info = new ImageInformation(); info = ImageInformation.FromFile(filepath); PresentParameters presentParams = new PresentParameters(); // Below are the required bare mininum, needed to initialize the D3D device. presentParams.BackBufferHeight = info.Height; // BackBufferHeight, set to the Window's height. presentParams.BackBufferWidth = info.Width+200; // BackBufferWidth, set to the Window's width. presentParams.Windowed =true; presentParams.DeviceWindowHandle = Window.panel2 .Handle; // DeviceWindowHandle, set to the Window's handle. // Create the device. D3DDevice = new Device(new Direct3D (), 0, DeviceType.Hardware, Window.Handle, CreateFlags.HardwareVertexProcessing, presentParams); // Create the vertex buffer and fill with the triangle vertices. (Non-indexed) // Remember 3 vetices for a triangle, 2 tris per quad = 6. Vertices = new VertexBuffer(D3DDevice, 6 * Vertex.SizeBytes, Usage.WriteOnly, VertexFormat.None, Pool.Managed); DataStream stream = Vertices.Lock(0, 0, LockFlags.None); stream.WriteRange(BuildVertexData()); Vertices.Unlock(); // Create the texture. Image = Texture.FromFile(D3DDevice,filepath ); // Turn off culling, so we see the front and back of the triangle D3DDevice.SetRenderState(RenderState.CullMode, Cull.None); // Turn off lighting D3DDevice.SetRenderState(RenderState.Lighting, false); ShaderBytecode sbcv = ShaderBytecode.CompileFromFile("C:\\Users\\yashwinder singh\\Desktop\\vertexShader.vs", "vs_main", "vs_1_1", ShaderFlags.None); constantTable = sbcv.ConstantTable; vertexShader = new VertexShader(D3DDevice, sbcv); ShaderBytecode sbc = ShaderBytecode.CompileFromFile("C:\\Users\\yashwinder singh\\Desktop\\pixelShader.txt", "ps_main", "ps_3_0", ShaderFlags.None); PixelShader ps = new PixelShader(D3DDevice, sbc); VertexDeclaration vertexDecl = new VertexDeclaration(D3DDevice, new[] { new VertexElement(0, 0, DeclarationType.Float3, DeclarationMethod.Default, DeclarationUsage.PositionTransformed, 0), new VertexElement(0, 12, DeclarationType.Float2 , DeclarationMethod.Default, DeclarationUsage.TextureCoordinate , 0), VertexElement.VertexDeclarationEnd }); Application.EnableVisualStyles(); MessagePump.Run(Window, () => { // Clear the backbuffer to a black color. D3DDevice.Clear(ClearFlags.Target | ClearFlags.ZBuffer, Color.Black, 1.0f, 0); // Begin the scene. D3DDevice.BeginScene(); // Setup the world, view and projection matrices. //D3DDevice.VertexShader = vertexShader; //D3DDevice.PixelShader = ps; // Render the vertex buffer. D3DDevice.SetStreamSource(0, Vertices, 0, Vertex.SizeBytes); D3DDevice.VertexFormat = Vertex.Format; // Setup our texture. Using Textures introduces the texture stage states, // which govern how Textures get blended together (in the case of multiple // Textures) and lighting information. D3DDevice.SetTexture(0, Image); // Now drawing 2 triangles, for a quad. D3DDevice.DrawPrimitives(PrimitiveType.TriangleList , 0, 2); // End the scene. D3DDevice.EndScene(); // Present the backbuffer contents to the screen. D3DDevice.Present(); }); if (Image != null) Image.Dispose(); if (Vertices != null) Vertices.Dispose(); if (D3DDevice != null) D3DDevice.Dispose(); } private static Vertex[] BuildVertexData() { Vertex[] vertexData = new Vertex[6]; vertexData[0].Position = new Vector3(-1.0f, 1.0f, 0.0f); vertexData[0].Tu = 0.0f; vertexData[0].Tv = 0.0f; vertexData[1].Position = new Vector3(-1.0f, -1.0f, 0.0f); vertexData[1].Tu = 0.0f; vertexData[1].Tv = 1.0f; vertexData[2].Position = new Vector3(1.0f, 1.0f, 0.0f); vertexData[2].Tu = 1.0f; vertexData[2].Tv = 0.0f; vertexData[3].Position = new Vector3(-1.0f, -1.0f, 0.0f); vertexData[3].Tu = 0.0f; vertexData[3].Tv = 1.0f; vertexData[4].Position = new Vector3(1.0f, -1.0f, 0.0f); vertexData[4].Tu = 1.0f; vertexData[4].Tv = 1.0f; vertexData[5].Position = new Vector3(1.0f, 1.0f, 0.0f); vertexData[5].Tu = 1.0f; vertexData[5].Tv = 0.0f; return vertexData; } } } And my pixel shader and vertex shader code are as following // Pixel shader input structure struct PS_INPUT { float4 Position : POSITION; float2 Texture : TEXCOORD0; }; // Pixel shader output structure struct PS_OUTPUT { float4 Color : COLOR0; }; // Global variables sampler2D Tex0; // Name: Simple Pixel Shader // Type: Pixel shader // Desc: Fetch texture and blend with constant color // PS_OUTPUT ps_main( in PS_INPUT In ) { PS_OUTPUT Out; //create an output pixel Out.Color = tex2D(Tex0, In.Texture); //do a texture lookup Out.Color *= float4(0.9f, 0.8f, 0.0f, 1); //do a simple effect return Out; //return output pixel } // Vertex shader input structure struct VS_INPUT { float4 Position : POSITION; float2 Texture : TEXCOORD0; }; // Vertex shader output structure struct VS_OUTPUT { float4 Position : POSITION; float2 Texture : TEXCOORD0; }; // Global variables float4x4 WorldViewProj; // Name: Simple Vertex Shader // Type: Vertex shader // Desc: Vertex transformation and texture coord pass-through // VS_OUTPUT vs_main( in VS_INPUT In ) { VS_OUTPUT Out; //create an output vertex Out.Position = mul(In.Position, WorldViewProj); //apply vertex transformation Out.Texture = In.Texture; //copy original texcoords return Out; //return output vertex }

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  • Refactoring an immediate drawing function into VBO, access violation error

    - by Alex
    I have a MD2 model loader, I am trying to substitute its immediate drawing function with a Vertex Buffer Object one.... I am getting a really annoying access violation reading error and I can't figure out why, but mostly I'd like an opinion as to whether this looks correct (never used VBOs before). This is the original function (that compiles ok) which calculates the keyframe and draws at the same time: glBegin(GL_TRIANGLES); for(int i = 0; i < numTriangles; i++) { MD2Triangle* triangle = triangles + i; for(int j = 0; j < 3; j++) { MD2Vertex* v1 = frame1->vertices + triangle->vertices[j]; MD2Vertex* v2 = frame2->vertices + triangle->vertices[j]; Vec3f pos = v1->pos * (1 - frac) + v2->pos * frac; Vec3f normal = v1->normal * (1 - frac) + v2->normal * frac; if (normal[0] == 0 && normal[1] == 0 && normal[2] == 0) { normal = Vec3f(0, 0, 1); } glNormal3f(normal[0], normal[1], normal[2]); MD2TexCoord* texCoord = texCoords + triangle->texCoords[j]; glTexCoord2f(texCoord->texCoordX, texCoord->texCoordY); glVertex3f(pos[0], pos[1], pos[2]); } } glEnd(); What I'd like to do is to calculate all positions before hand, store them in a Vertex array and then draw them. This is what I am trying to replace it with (in the exact same part of the program) int vCount = 0; for(int i = 0; i < numTriangles; i++) { MD2Triangle* triangle = triangles + i; for(int j = 0; j < 3; j++) { MD2Vertex* v1 = frame1->vertices + triangle->vertices[j]; MD2Vertex* v2 = frame2->vertices + triangle->vertices[j]; Vec3f pos = v1->pos * (1 - frac) + v2->pos * frac; Vec3f normal = v1->normal * (1 - frac) + v2->normal * frac; if (normal[0] == 0 && normal[1] == 0 && normal[2] == 0) { normal = Vec3f(0, 0, 1); } indices[vCount] = normal[0]; vCount++; indices[vCount] = normal[1]; vCount++; indices[vCount] = normal[2]; vCount++; MD2TexCoord* texCoord = texCoords + triangle->texCoords[j]; indices[vCount] = texCoord->texCoordX; vCount++; indices[vCount] = texCoord->texCoordY; vCount++; indices[vCount] = pos[0]; vCount++; indices[vCount] = pos[1]; vCount++; indices[vCount] = pos[2]; vCount++; } } totalVertices = vCount; glEnableClientState(GL_NORMAL_ARRAY); glEnableClientState(GL_TEXTURE_COORD_ARRAY); glEnableClientState(GL_VERTEX_ARRAY); glNormalPointer(GL_FLOAT, 0, indices); glTexCoordPointer(2, GL_FLOAT, sizeof(float)*3, indices); glVertexPointer(3, GL_FLOAT, sizeof(float)*5, indices); glDrawElements(GL_TRIANGLES, totalVertices, GL_UNSIGNED_BYTE, indices); glDisableClientState(GL_VERTEX_ARRAY); // disable vertex arrays glEnableClientState(GL_TEXTURE_COORD_ARRAY); glDisableClientState(GL_NORMAL_ARRAY); First of all, does it look right? Second, I get access violation error "Unhandled exception at 0x01455626 in Graphics_template_1.exe: 0xC0000005: Access violation reading location 0xed5243c0" pointing at line 7 Vec3f pos = v1->pos * (1 - frac) + v2->pos * frac; where the two Vs seems to have no value in the debugger.... Till this point the function behaves in exactly the same way as the one above, I don't understand why this happens? Thanks for any help you may be able to provide!

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  • SSD for Visual studio : Intel X25-m G2 or OCZ Vertex

    - by meska
    hi, looking for laptop upgrade, and thinking about SSD drive. Laptop would be Dell Studio XPS with T9400 as i can get one for a very good price. So i was thinking about replacing the built in 500 GB hdd with some kind of SDD Currently two choices: OCZ Vertex Series 60 GB vs. Intel X25-M G2 MLC 80 GB Price is almost the same. From anandtech Intel performs badly in sequential write, but scores very high numbers in random write and random read (good for visual studio?) and i get more space. What do you think? OCZ Vertex or Intel X25-M G2 ? Purely from Visual Studio 2008 and upcoming 2010 perspective?

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  • How do I combine two arrays in PHP based on a common key?

    - by Eoghan O'Brien
    Hi, I'm trying to join two associative arrays together based on an entry_id key. Both arrays come from individual database resources, the first stores entry titles, the second stores entry authors, the key=value pairs are as follows: array ( 'entry_id' => 1, 'title' => 'Test Entry' ) array ( 'entry_id' => 1, 'author_id' => 2 I'm trying to achieve an array structure like: array ( 'entry_id' => 1, 'author_id' => 2, 'title' => 'Test Entry' ) Currently, I've solved the problem by looping through each array and formatting the array the way I want, but I think this is a bit of a memory hog. $entriesArray = array(); foreach ($entryNames as $names) { foreach ($entryAuthors as $authors) { if ($names['entry_id'] === $authors['entry_id']) { $entriesArray[] = array( 'id' => $names['entry_id'], 'title' => $names['title'], 'author_id' => $authors['author_id'] ); } } } I'd like to know is there an easier, less memory intensive method of doing this?

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  • Accessing appropriate array of double arrays in order of last created.

    - by Zach
    I have an array of double arrays, they are within a specified time window (8am-5pm), and are in order of last created over a period of several days. They are all timestamped and as such I have access to all C# DateTime methods. I then have a different iterative function that goes in the same order of the array of double arrays, however it isn't within a specified time window, it's 24/7. I want to access from this iterative function, the appropriate double array from the one within the window. Let's say that it's 4:30PM on DayOfYear 52, I'd like to access the last double array less than or equal to 4:30PM on DayOfYear 52. I'd expect the same double array if the time were 12:30AM on DayOfYear 53. However, if it were 9:00 AM of DayOfYear 53, well then I'd expect it to return something from the DayOfYear 53, less than or equal to 9:00AM. I think you get the idea. So I'm a having a bit of trouble grokking how to do this. Is anyone willing to offer a starting point or how they'd approach it? Edit: It is not a literal double[][], it is exactly as Anthony Pegram says: Dictionary<DateTime, double[]>

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  • How do I pass three arrays from on method to another?

    - by user2966716
    I have a method studentSummary, that scans the input and creates three arrays examMark,courseworkMark and courseworkWeight. I need these arrays passing over to a different method, so I can use them to calculate moduleResult. heres my code: public static int[] studentSummary(int[] courseworkWeight2, int [] examMark2 , int [] courseworkMark2){ int examMark[] = { 0, 0, 0, 0, 0, 0 }; int courseworkMark[] = { 0, 0, 0, 0, 0, 0 }; Scanner resultInput = new Scanner(System.in); int courseworkWeight[] = { 0, 0, 0, 0, 0, 0 }; for (int k = 1; k < 7; k++) { System.out.print("Please enter exam marks for module " + k + ":"); examMark[k - 1] = resultInput.nextInt(); System.out.print("Please enter Coursework marks for module " + k + ":"); courseworkMark[k - 1] = resultInput.nextInt(); System.out.print("Please enter Coursework weighting for module " + k + ":"); courseworkWeight[k - 1] = resultInput.nextInt(); } Calculator method: public static int[] markCalculator() { int[] courseworkWeight = new int [6]; int[] courseworkMark = new int [6]; int[] examMark = new int [6]; for (int i = 0; i < 6; i++) { computedModuleMark = ((courseworkMark[i] * courseworkWeight[i]) + (examMark[i] * (100 - courseworkWeight[i]))) / 100; if ((computedModuleMark) < 35) { if (examMark[i]<35){ } } moduleMark[i] = computedModuleMark; } computeResult(moduleMark); StudentChart.draw(moduleMark); StudentChart.printSummary(moduleMark); return moduleMark; }

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  • Using NumPy arrays as 2D mathematical vectors?

    - by CorundumGames
    Right now I'm using lists as position, velocity, and acceleration vectors in my game. Is that a better option than using NumPy's arrays (not the standard library's) as vectors (with float data types)? I'm frequently adding vectors and changing their values directly, then placing the values in these vectors into a Pygame Rect. The vector is used for position (because Rects can't hold floats, so we can't go "between" pixels), and the Rect is used for rendering (because Pygame will only take in Rects for rendering positions).

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  • Fastest way to check if two square 2D arrays are rotationally and reflectively distinct

    - by kustrle
    The best idea I have so far is to rotate first array by {0, 90, 180, 270} degrees and reflect it horizontally or/and vertically. We basically get 16 variations [1] of first array and compare them with second array. if none of them matches the two arrays are rotationally and reflectively distinct. I am wondering if there is more optimal solution than this brute-force approach? [1] 0deg, no reflection 0deg, reflect over x 0deg, reflect over y 0deg, reflect over x and y 90deg, no reflection ...

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  • PHP Arrays: A good way to check if an array is associative or sequential?

    - by Wilco
    PHP treats all arrays as associative, so there aren't any built in functions. Can anyone recommend a fairly efficient way to check if an array contains only numeric keys? Basically, I want to be able to differentiate between this: $sequentialArray = array('apple', 'orange', 'tomato', 'carrot'); and this: $assocArray = array('fruit1' => 'apple', 'fruit2' => 'orange', 'veg1' => 'tomato', 'veg2' => 'carrot');

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  • How do i merge the arrays in a particular format?

    - by Pankaj Khurana
    Hi, I have following arrays: 1) for total placed Array ( [0] => Array ( [centers] => Array ( [name] => delhi [id] => 1 ) [0] => Array ( [totalplaced] => 8 ) ) [1] => Array ( [centers] => Array ( [name] => mumbai [id] => 2 ) [0] => Array ( [totalplaced] => 1 ) ) ) 2) for total working Array ( [0] => Array ( [centers] => Array ( [name] => delhi [id] => 1 ) [0] => Array ( [totalworking] => 4 ) ) [1] => Array ( [centers] => Array ( [name] => mumbai [id] => 2 ) [0] => Array ( [totalworking] => 1 ) ) ) 3) for total trained Array ( [0] => Array ( [centers] => Array ( [name] => delhi [id] => 1 ) [0] => Array ( [totaltrained] => 8 ) ) [1] => Array ( [centers] => Array ( [name] => mumbai [id] => 2 ) [0] => Array ( [totaltrained] => 1 ) ) ) I wanted to merge these arrays so that the resultant array should look like this [newarray] => Array( [0] => Array ( [centers] => Array ( [name] => delhi [id] => 1 [totalplaced] => 8 [totalworking] => 4 [totaltrained] => 8 ) ) [1]=> Array( [centers] => Array ( [name] => mumbai [id] => 2 [totalplaced] => 1 [totalworking] => 1 [totaltrained] => 1 ) ) ) This is the tabular representation of the above data which i want to display centername totalplaced totalworking totaltrained delhi 8 4 8 mumbai 1 1 1 Please help me on this. Thanks Pankaj Khurana

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  • Arrays of Objects: For each element in array 1, does an object value exist as a value in any of the objects in array 2

    - by DevOtts
    I have two arrays which contain objects in each element of the array. var array1 = [{firstName: "John", lastName: "McDonald"}, {firstName: "Sandy", lastName: "Johnson"},....,] var array2 = [{userName: "Donald"}, {userName: "John"},....,] In psuedo-code, I want to do the following: for each element in array1, is array1[i].firstName == to any of the userName's in array2. In plain english I want to look at each firstname in array1 and see if it exists at all in array2 as the value associated with the userName property.

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  • How to tell if 2 arrays share the same element.

    - by Ommit
    So this is a simpler form of my problem. Lets say I have 2 arrays. A= {1,2} and B={2,4,6}. If A and B share an element then delete that element from B. I know you can loop through and compare each element in A to each element in B, but there's got to be a better way!

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  • What's the purpose of arrays starting with nonzero index?

    - by helios35
    I tried to find answers, but all I got was answers on how to realize arrays starting with nonzero indexes. Some languages, such as pascal, provide this by default, e.g., you can create an array such as var foobar: array[1..10] of string; I've always been wondering: Why would you want to have the array index not to start with 0? I guess it may be more familiar for beginners to have arrays starting with 1 and the last index being the size of the array, but on a long-term basis, programmers should get used to values starting with 0. Another purpose I could think of: In some cases, the index could actually represent something thats contained in the respective array-entry. e.g., you want to get all capital letters in an array, it may be handy to have an index being the ASCII-Code of the respective letter. But its pretty easy just to subtract a constant value. In this example, you could (in C) simply do something like this do get all capital letters and access the letter with ascii-code 67: #define ASCII_SHIFT 65 main() { int capital_letters[26]; int i; for (i=0; i<26; i++){ capital_letters[i] = i+ASCII_SHIFT; } printf("%c\n", capital_letters[67-ASCII_SHIFT]); } Also, I think you should use hash tables if you want to access entries by some sort of key. Someone might retort: Why should the index always start with 0? Well, it's a hell of a lot simpler this way. You'll be faster when you just have to type one index when declaring an array. Also, you can always be sure that the first entry is array[0] and the last one is array[length_of_array-1]. It is also common that other data structures start with 0. e.g., if you read a binary file, you start with the 0th byte, not the first. Now, why do some programming languages have this "feature" and why do some people ask how to achieve this in languages such as C/C++?, is there any situation where an array starting with a nonzero index is way more useful, or even, something simply cannot be done with an array starting at 0?

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  • How to create multiple arrays from 2? (actionscript, flash)

    - by Ole Jak
    so I have array like ParamsArray {a,b,a,a,...b} (so i have 2 kinds of parameters in this array - a and b) (here I have N strings) and another array - DataArray {data1,data2,...dataN} (different strings) (here I have N strings) Now I created 2 new arrays ArrayA and ArrayB and I wanta want to feel arra ArrayA with all data (strings) from DataArray which correspond (by index in array) to a param in ParamsArray. and so strings that correspond to param B should appear in ArrayB. How to do such thing in actionscript? (Please - I need a code example)

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  • Given an XML which contains a representation of a graph, how to apply it DFS algorithm? [on hold]

    - by winston smith
    Given the followin XML which is a directed graph: <?xml version="1.0" encoding="iso-8859-1" ?> <!DOCTYPE graph PUBLIC "-//FC//DTD red//EN" "../dtd/graph.dtd"> <graph direct="1"> <vertex label="V0"/> <vertex label="V1"/> <vertex label="V2"/> <vertex label="V3"/> <vertex label="V4"/> <vertex label="V5"/> <edge source="V0" target="V1" weight="1"/> <edge source="V0" target="V4" weight="1"/> <edge source="V5" target="V2" weight="1"/> <edge source="V5" target="V4" weight="1"/> <edge source="V1" target="V2" weight="1"/> <edge source="V1" target="V3" weight="1"/> <edge source="V1" target="V4" weight="1"/> <edge source="V2" target="V3" weight="1"/> </graph> With this classes i parsed the graph and give it an adjacency list representation: import java.io.IOException; import java.util.HashSet; import java.util.LinkedList; import java.util.Collection; import java.util.Iterator; import java.util.logging.Level; import java.util.logging.Logger; import practica3.util.Disc; public class ParsingXML { public static void main(String[] args) { try { // TODO code application logic here Collection<Vertex> sources = new HashSet<Vertex>(); LinkedList<String> lines = Disc.readFile("xml/directed.xml"); for (String lin : lines) { int i = Disc.find(lin, "source=\""); String data = ""; if (i > 0 && i < lin.length()) { while (lin.charAt(i + 1) != '"') { data += lin.charAt(i + 1); i++; } Vertex v = new Vertex(); v.setName(data); v.setAdy(new HashSet<Vertex>()); sources.add(v); } } Iterator it = sources.iterator(); while (it.hasNext()) { Vertex ver = (Vertex) it.next(); Collection<Vertex> adyacencias = ver.getAdy(); LinkedList<String> ls = Disc.readFile("xml/graphs.xml"); for (String lin : ls) { int i = Disc.find(lin, "target=\""); String data = ""; if (lin.contains("source=\""+ver.getName())) { Vertex v = new Vertex(); if (i > 0 && i < lin.length()) { while (lin.charAt(i + 1) != '"') { data += lin.charAt(i + 1); i++; } v.setName(data); } i = Disc.find(lin, "weight=\""); data = ""; if (i > 0 && i < lin.length()) { while (lin.charAt(i + 1) != '"') { data += lin.charAt(i + 1); i++; } v.setWeight(Integer.parseInt(data)); } if (v.getName() != null) { adyacencias.add(v); } } } } for (Vertex vert : sources) { System.out.println(vert); System.out.println("adyacencias: " + vert.getAdy()); } } catch (IOException ex) { Logger.getLogger(ParsingXML.class.getName()).log(Level.SEVERE, null, ex); } } } This is another class: import java.util.Collection; import java.util.Objects; public class Vertex { private String name; private int weight; private Collection ady; public Collection getAdy() { return ady; } public void setAdy(Collection adyacencias) { this.ady = adyacencias; } public String getName() { return name; } public void setName(String nombre) { this.name = nombre; } public int getWeight() { return weight; } public void setWeight(int weight) { this.weight = weight; } @Override public int hashCode() { int hash = 7; hash = 43 * hash + Objects.hashCode(this.name); hash = 43 * hash + this.weight; return hash; } @Override public boolean equals(Object obj) { if (obj == null) { return false; } if (getClass() != obj.getClass()) { return false; } final Vertex other = (Vertex) obj; if (!Objects.equals(this.name, other.name)) { return false; } if (this.weight != other.weight) { return false; } return true; } @Override public String toString() { return "Vertice{" + "name=" + name + ", weight=" + weight + '}'; } } And finally: /** * * @author user */ /* -*-jde-*- */ /* <Disc.java> Contains the main argument*/ import java.io.*; import java.util.LinkedList; /** * Lectura y escritura de archivos en listas de cadenas * Ideal para el uso de las clases para gráficas. * * @author Peralta Santa Anna Victor Miguel * @since Julio 2011 */ public class Disc { /** * Metodo para lectura de un archivo * * @param fileName archivo que se va a leer * @return El archivo en representacion de lista de cadenas */ public static LinkedList<String> readFile(String fileName) throws IOException { BufferedReader file = new BufferedReader(new FileReader(fileName)); LinkedList<String> textlist = new LinkedList<String>(); while (file.ready()) { textlist.add(file.readLine().trim()); } file.close(); /* for(String linea:textlist){ if(linea.contains("source")){ //String generado = linea.replaceAll("<\\w+\\s+\"", ""); //System.out.println(generado); } }*/ return textlist; }//readFile public static int find(String linea,String palabra){ int i,j; boolean found = false; for(i=0,j=0;i<linea.length();i++){ if(linea.charAt(i)==palabra.charAt(j)){ j++; if(j==palabra.length()){ found = true; return i; } }else{ continue; } } if(!found){ i= -1; } return i; } /** * Metodo para la escritura de un archivo * * @param fileName archivo que se va a escribir * @param tofile la lista de cadenas que quedaran en el archivo * @param append el bit que dira si se anexa el contenido o se empieza de cero */ public static void writeFile(String fileName, LinkedList<String> tofile, boolean append) throws IOException { FileWriter file = new FileWriter(fileName, append); for (int i = 0; i < tofile.size(); i++) { file.write(tofile.get(i) + "\n"); } file.close(); }//writeFile /** * Metodo para escritura de un archivo * @param msg archivo que se va a escribir * @param tofile la cadena que quedaran en el archivo * @param append el bit que dira si se anexa el contenido o se empieza de cero */ public static void writeFile(String msg, String tofile, boolean append) throws IOException { FileWriter file = new FileWriter(msg, append); file.write(tofile); file.close(); }//writeFile }// I'm stuck on what can be the best way to given an adjacency list representation of the graph how to apply it Depth-first search algorithm. Any idea of how to aproach to complete the task?

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