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• Boost tuple + transform

  - by JH

  Is it possible to do the following. Say my boost tuple has <String, int> I would like to use std::transform + mem_fun to insert only the String element in a corresponding vector. Is it possible or are we required to use a loop and push_back(get<0) Ie the following doesn't like to compile... (unknown types...) result.resize(storage.size()) std::transform(storage.begin(), storage.end(), result.begin(), std::mem_fun(&boost::get<0>)); Here is an example (trying one of the comments): #include <boost/tuple/tuple.hpp> #include <vector> #include <string> #include <algorithm> int main(int argc, char**argv) { std::vector< boost::tuple<std::string, int> > storage; std::vector< std::string> result; result.resize(storage.size()); std::transform(storage.begin(), storage.end(), result.begin(), &boost::get<0, boost::tuple<std::string, int> >); return 0; } Output: g++ test.cpp /usr/include/boost/tuple/detail/tuple_basic.hpp: In instantiation of `boost::tuples::cons<boost::tuples::tuple<std::string, int, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>, TT>': /usr/include/boost/tuple/detail/tuple_basic.hpp:151: instantiated from `boost::tuples::element<0, boost::tuples::cons<boost::tuples::tuple<std::string, int, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>, TT> >' test.cpp:14: instantiated from here /usr/include/boost/tuple/detail/tuple_basic.hpp:329: error: `boost::tuples::cons<HT, TT>::tail' has incomplete type /usr/include/boost/tuple/detail/tuple_basic.hpp:329: error: invalid use of template type parameter test.cpp: In function `int main(int, char**)': test.cpp:14: error: no matching function for call to `transform(__gnu_cxx::__normal_iterator<boost::tuples::tuple<std::string, int, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>*, std::vector<boost::tuples::tuple<std::string, int, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>, std::allocator<boost::tuples::tuple<std::string, int, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type> > > >, __gnu_cxx::__normal_iterator<boost::tuples::tuple<std::string, int, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>*, std::vector<boost::tuples::tuple<std::string, int, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type>, std::allocator<boost::tuples::tuple<std::string, int, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type, boost::tuples::null_type> > > >, __gnu_cxx::__normal_iterator<std::string*, std::vector<std::string, std::allocator<std::string> > >, <unresolved overloaded function type>)'

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• Join 3 tables in 1 LINQ-EF

  - by user100161

  I have to fill warehouse table cOrders with program using Ado.NET EF. I have SQL command but i don't know how to do this with LINQ. static void Main(string[] args) { var SPcontex = new PI_NorthwindSPEntities(); var contex = new NorthwindEntities(); dCustomers dimenzijaCustomers = new dCustomers(); dDatum dimenzijaDatum = new dDatum(); ... CREATE TABLE PoslovnaInteligencija.dbo.cOrders( cOrdersID int PRIMARY KEY IDENTITY(1,1), OrderID int NOT NULL, dCustomersID int FOREIGN KEY REFERENCES PoslovnaInteligencija.dbo.dCustomers(dCustomersID), dEmployeesID int FOREIGN KEY REFERENCES PoslovnaInteligencija.dbo.dEmployees(dEmployeesID), OrderDateID int FOREIGN KEY REFERENCES PoslovnaInteligencija.dbo.dDatum(sifDatum), RequiredDateID int FOREIGN KEY REFERENCES PoslovnaInteligencija.dbo.dDatum(sifDatum), ShippedDateID int FOREIGN KEY REFERENCES PoslovnaInteligencija.dbo.dDatum(sifDatum), dShippersID int FOREIGN KEY REFERENCES PoslovnaInteligencija.dbo.dShippers(dShippersID), dShipID int FOREIGN KEY REFERENCES PoslovnaInteligencija.dbo.dShip(dShipID), Freight money, WaitingDay int ) INSERT INTO PoslovnaInteligencija.dbo.cOrders (OrderID, dCustomersID, dEmployeesID, OrderDateID, RequiredDateID, dShippersID, dShipID, Freight, ShippedDateID, WaitingDay) SELECT OrderID, dc.dCustomersID, de.dEmployeesID, orderD.sifDatum, requiredD.sifDatum, dShippersID, ds.dShipID, Freight, ShippedDateID=CASE WHEN (ShippedDate IS NULL) THEN -1 ELSE shippedD.sifDatum END, WaitingDay=CASE WHEN (shippedD.sifDatum - orderD.sifDatum) IS NULL THEN -1 ELSE shippedD.sifDatum - orderD.sifDatum END FROM PoslovnaInteligencija.dbo.dShippers AS s, PoslovnaInteligencija.dbo.dCustomers AS dc, PoslovnaInteligencija.dbo.dEmployees AS de, PoslovnaInteligencija.dbo.dShip AS ds,PoslovnaInteligencija.dbo.dDatum AS orderD, PoslovnaInteligencija.dbo.dDatum AS requiredD, PoslovnaInteligencija.dbo.Orders AS o LEFT OUTER JOIN PoslovnaInteligencija.dbo.dDatum AS shippedD ON shippedD.datum=DATEADD(dd, 0, DATEDIFF(dd, 0, o.ShippedDate)) WHERE o.ShipVia=s.ShipperID AND dc.CustomerID=o.CustomerID AND de.EmployeeID=o.EmployeeID AND ds.ShipName=o.ShipName AND orderD.datum=DATEADD(dd, 0, DATEDIFF(dd, 0, o.OrderDate)) AND requiredD.datum=DATEADD(dd, 0, DATEDIFF(dd, 0, o.RequiredDate));

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• Rotate two dimensional array 90 degrees clockwise

  - by user69514

  I have a two dimensional array that I need to rotate 90 degrees clockwise, however I keep getting arrayindexoutofbounds... public int[][] rorateArray(int[][] arr){ //first change the dimensions vertical length for horizontal length //and viceversa int[][] newArray = new int[arr[0].length][arr.length]; //invert values 90 degrees clockwise by starting from button of //array to top and from left to right int ii = 0; int jj = 0; for(int i=0; i<arr[0].length; i++){ for(int j=arr.length-1; j>=0; j--){ newArray[ii][jj] = arr[i][j]; jj++; } ii++; } return newArray; }

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• Problem with JOGL and Framebuffer Render-to-texture: Invalid Framebuffer Operation Error

  - by quadelirus

  Okay, so I am trying to render a scene to a small 32x32 texture and ran into problems. I get an "invalid framebuffer operation" error when I try to actually draw anything to the texture. I have simplified the code below so that it simply tries to render a quad to a texture and then bind that quad as a texture for another quad that is rendered to the screen. So my question is this... where is the error? This is using JOGL 1.1.1. The error occurs at Checkpoint2 in the code. import java.awt.event.*; import javax.media.opengl.*; import javax.media.opengl.glu.*; import javax.swing.JFrame; import java.nio.*; public class Main extends JFrame implements GLEventListener, KeyListener, MouseListener, MouseMotionListener, ActionListener{ /* GL related variables */ private final GLCanvas canvas; private GL gl; private GLU glu; private int winW = 600, winH = 600; private int texRender_FBO; private int texRender_RB; private int texRender_32x32; public static void main(String args[]) { new Main(); } /* creates OpenGL window */ public Main() { super("Problem Child"); canvas = new GLCanvas(); canvas.addGLEventListener(this); canvas.addKeyListener(this); canvas.addMouseListener(this); canvas.addMouseMotionListener(this); getContentPane().add(canvas); setSize(winW, winH); setLocationRelativeTo(null); setDefaultCloseOperation(EXIT_ON_CLOSE); setVisible(true); canvas.requestFocus(); } /* gl display function */ public void display(GLAutoDrawable drawable) { gl.glBindFramebufferEXT(GL.GL_FRAMEBUFFER_EXT, this.texRender_FBO); gl.glPushAttrib(GL.GL_VIEWPORT_BIT); gl.glViewport(0, 0, 32, 32); gl.glClearColor(1.f, 0.f, 0.f, 1.f); System.out.print("Checkpoint1: "); outputError(); gl.glBegin(GL.GL_QUADS); { //gl.glTexCoord2f(0.0f, 0.0f); gl.glColor3f(1.f, 0.f, 0.f); gl.glVertex3f(0.0f, 1.0f, 1.0f); //gl.glTexCoord2f(1.0f, 0.0f); gl.glColor3f(1.f, 1.f, 0.f); gl.glVertex3f(1.0f, 1.0f, 1.0f); //gl.glTexCoord2f(1.0f, 1.0f); gl.glColor3f(1.f, 1.f, 1.f); gl.glVertex3f(1.0f, 0.0f, 1.0f); //gl.glTexCoord2f(0.0f, 1.0f); gl.glColor3f(1.f, 0.f, 1.f); gl.glVertex3f(0.0f, 0.0f, 1.0f); } gl.glEnd(); System.out.print("Checkpoint2: "); outputError(); //Here I get an invalid framebuffer operation gl.glPopAttrib(); gl.glBindFramebufferEXT(GL.GL_FRAMEBUFFER_EXT, 0); gl.glClearColor(0.f, 0.f, 0.f, 1.f); gl.glClear(GL.GL_COLOR_BUFFER_BIT); gl.glColor3f(1.f, 1.f, 1.f); gl.glBindTexture(GL.GL_TEXTURE_1D, this.texRender_32x32); gl.glBegin(GL.GL_QUADS); { gl.glTexCoord2f(0.0f, 0.0f); //gl.glColor3f(1.f, 0.f, 0.f); gl.glVertex3f(0.0f, 1.0f, 1.0f); gl.glTexCoord2f(1.0f, 0.0f); //gl.glColor3f(1.f, 1.f, 0.f); gl.glVertex3f(1.0f, 1.0f, 1.0f); gl.glTexCoord2f(1.0f, 1.0f); //gl.glColor3f(1.f, 1.f, 1.f); gl.glVertex3f(1.0f, 0.0f, 1.0f); gl.glTexCoord2f(0.0f, 1.0f); //gl.glColor3f(1.f, 0.f, 1.f); gl.glVertex3f(0.0f, 0.0f, 1.0f); } gl.glEnd(); } /* initialize GL */ public void init(GLAutoDrawable drawable) { gl = drawable.getGL(); glu = new GLU(); gl.glClearColor(.3f, .3f, .3f, 1f); gl.glClearDepth(1.0f); gl.glMatrixMode(GL.GL_PROJECTION); gl.glLoadIdentity(); gl.glOrtho(0, 1, 0, 1, -10, 10); gl.glMatrixMode(GL.GL_MODELVIEW); //Set up the 32x32 texture this.texRender_FBO = genFBO(gl); gl.glBindFramebufferEXT(GL.GL_FRAMEBUFFER_EXT, this.texRender_FBO); this.texRender_32x32 = genTexture(gl); gl.glBindTexture(GL.GL_TEXTURE_2D, this.texRender_32x32); gl.glTexImage2D(GL.GL_TEXTURE_2D, 0, GL.GL_RGB_FLOAT32_ATI, 32, 32, 0, GL.GL_RGB, GL.GL_FLOAT, null); gl.glFramebufferTexture2DEXT(GL.GL_FRAMEBUFFER_EXT, GL.GL_COLOR_ATTACHMENT0_EXT, GL.GL_TEXTURE_2D, this.texRender_32x32, 0); //gl.glDrawBuffer(GL.GL_COLOR_ATTACHMENT0_EXT); this.texRender_RB = genRB(gl); gl.glBindRenderbufferEXT(GL.GL_RENDERBUFFER_EXT, this.texRender_RB); gl.glRenderbufferStorageEXT(GL.GL_RENDERBUFFER_EXT, GL.GL_DEPTH_COMPONENT24, 32, 32); gl.glFramebufferRenderbufferEXT(GL.GL_FRAMEBUFFER_EXT, GL.GL_DEPTH_ATTACHMENT_EXT, GL.GL_RENDERBUFFER_EXT, this.texRender_RB); gl.glBindFramebufferEXT(GL.GL_FRAMEBUFFER_EXT, 0); gl.glBindRenderbufferEXT(GL.GL_RENDERBUFFER_EXT, 0); outputError(); } private void outputError() { int c; if ((c = gl.glGetError()) != GL.GL_NO_ERROR) System.out.println(glu.gluErrorString(c)); } private int genRB(GL gl) { int[] array = new int[1]; IntBuffer ib = IntBuffer.wrap(array); gl.glGenRenderbuffersEXT(1, ib); return ib.get(0); } private int genFBO(GL gl) { int[] array = new int[1]; IntBuffer ib = IntBuffer.wrap(array); gl.glGenFramebuffersEXT(1, ib); return ib.get(0); } private int genTexture(GL gl) { final int[] tmp = new int[1]; gl.glGenTextures(1, tmp, 0); return tmp[0]; } /* mouse and keyboard callback functions */ public void reshape(GLAutoDrawable drawable, int x, int y, int width, int height) { winW = width; winH = height; gl.glViewport(0, 0, width, height); } //Sorry about these, I just had to delete massive amounts of code to boil this thing down and these are hangers-on public void mousePressed(MouseEvent e) {} public void mouseDragged(MouseEvent e) {} public void mouseReleased(MouseEvent e) {} public void keyPressed(KeyEvent e) {} public void displayChanged(GLAutoDrawable drawable, boolean modeChanged, boolean deviceChanged) { } public void keyTyped(KeyEvent e) { } public void keyReleased(KeyEvent e) { } public void mouseMoved(MouseEvent e) { } public void actionPerformed(ActionEvent e) { } public void mouseClicked(MouseEvent e) { } public void mouseEntered(MouseEvent e) { } public void mouseExited(MouseEvent e) { } }

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• Multidimensional array with unequal second dimension size using malloc()

  - by user288422

  Hello, I am playing around with multidimensional array of unequal second dimension size. Lets assume that I need the following data structure: [&ptr0]-[0][1][2][3][4][5][6][7][8][9] [&ptr1]-[0][1][2] [&ptr2]-[0][1][2][3][4] int main() { int *a[3]; int *b; int i; a[0] = (int *)malloc(10 * sizeof(int)); a[1] = (int *)malloc(2 * sizeof(int)); a[2] = (int *)malloc(4 * sizeof(int)); for(i=0; i<10; i++) a[0][i]=i; for(i=0; i<2; i++) a[1][i]=i; for(i=0; i<4; i++) a[2][i]=i; } I did some tests and it seems like I can store a value at a[1][3]. Does it mean that rows in my array are of equal size 10?

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• for my project I have problem in report

  - by pink rose

  public stack(int size) { this.size=size; Array = new int[size]; } public void push(int j) { if (top < size) { Array[++top] = j; } } public int pop() { return Array[top--]; } public int top() { return Array[top]; } public boolean isEmpty() { return (top == -1); } } import javax.swing.JOptionPane; public class menu { private static stack s; private static int numbers[]; public static void main(String args[]) { start(); } public static void start() { int i = Integer.parseInt(JOptionPane.showInputDialog("1. size of array\n2. data entry\n3. display content\n4. exit")); switch (i) { case 1: setSize(); break; case 2: addElement(); break; case 3: showElements(); break; case 4: exit(); } } public static void setSize() { int size = Integer.parseInt(JOptionPane.showInputDialog("Please Enter The Size")); s = new stack(size); numbers = new int[10]; start(); } public static void addElement() { for(int x=0;x<s.size;x++) { int e = Integer.parseInt(JOptionPane.showInputDialog("Please Enter The Element")); numbers[e]++; s.push(e); } start(); } public static void showElements() { String result = ""; int temp; while (!s.isEmpty()) { temp = s.pop(); if (numbers[temp] == 1) { result = temp+result; } } JOptionPane.showMessageDialog(null, result); start(); } public static void exit() { System.exit(0); } } This my project I was finished but I have problem in question in my report Conclusion. It should summarize the state of your project and indicate which part of your project is working and which part is not working or with limitations. You may also provide your suggestions and comments to this project what I can answer I didn't have any idea

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• a non recursive approach to the problem of generating combinations at fault

  - by mark

  Hi, I wanted a non recursive approach to the problem of generating combination of certain set of characters or numbers. So, given a subset k of numbers n, generate all the possible combination n!/k!(n-k)! The recursive method would give a combination, given the previous one combination. A non recursive method would generate a combination of a given value of loop index i. I approached the problem with this code: Tested with n = 4 and k = 3, and it works, but if I change k to a number 3 it does not work. Is it due to the fact that (n-k)! in case of n = 4 and k = 3 is 1. and if k 3 it will be more than 1? Thanks. int facto(int x); int len,fact,rem=0,pos=0; int str[7]; int avail[7]; str[0] = 1; str[1] = 2; str[2] = 3; str[3] = 4; str[4] = 5; str[5] = 6; str[6] = 7; int tot=facto(n) / facto(n-k) / facto(k); for (int i=0;i<tot;i++) { avail[0]=1; avail[1]=2; avail[2]=3; avail[3]=4; avail[4]=5; avail[5]=6; avail[6]=7; rem = facto(i+1)-1; cout<<rem+1<<". "; for(int j=len;j>0;j--) { int div = facto(j); pos = rem / div; rem = rem % div; cout<<avail[pos]<<" "; avail[pos]=avail[j]; } cout<<endl; } int facto(int x) { int fact=1; while(x0) fact*=x--; return fact; }

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• can I access a struct inside of a struct without using the dot operator?

  - by yan bellavance

  I have 2 structures that have 90% of their fields the same. I want to group those fields in a structure but I do not want to use the dot operator to access them. The reason is I already coded with the first structure and have just created the second one. before: struct{ int a; int b; int c; object1 name; } str1; struct{ int a; int b; int c; object2 name; } str2; now I would create a third struct: struct{ int a; int b; int c; } str3; and would change the str1 and atr2 to this: struct{ str3 str; object1 name; } str1; struct { str3 str; object2 name; } str2; Finally I would like to be able to access a,b and c by doing: str1 myStruct; myStruct.a; myStruct.b; myStruct.c; and not: myStruct.str.a; myStruct.str.b; myStruct.str.c; Is there a way to do such a thing. The reason for doing this is I want keep the integrety of the data if chnges to the struct were to occur and to not repeat myself and not have to change my existing code and not have fields nested too deeply. RESOLVED: thx for all your answers. The final way of doing it so that I could use auto-completion also was the following: struct str11 { int a; int b; int c; }; typedef struct str22 : public str11 { QString name; }hi;

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• How do I eliminate Error 3002?

  - by Andrew

  Say I have the following table definitions in SQL Server 2008: CREATE TABLE Person (PersonId INT IDENTITY NOT NULL PRIMARY KEY, Name VARCHAR(50) NOT NULL, ManyMoreIrrelevantColumns VARCHAR(MAX) NOT NULL) CREATE TABLE Model (ModelId INT IDENTITY NOT NULL PRIMARY KEY, ModelName VARCHAR(50) NOT NULL, Description VARCHAR(200) NULL) CREATE TABLE ModelScore (ModelId INT NOT NULL REFERENCES Model (ModelId), Score INT NOT NULL, Definition VARCHAR(100) NULL, PRIMARY KEY (ModelId, Score)) CREATE TABLE PersonModelScore (PersonId INT NOT NULL REFERENCES Person (PersonId), ModelId INT NOT NULL, Score INT NOT NULL, PRIMARY KEY (PersonId, ModelId), FOREIGN KEY (ModelId, Score) REFERENCES ModelScore (ModelId, Score)) The idea here is that each Person may have only one ModelScore per Model, but each Person may have a score for any number of defined Models. As far as I can tell, this SQL should enforce these constraints naturally. The ModelScore has a particular "meaning," which is contained in the Definition. Nothing earth-shattering there. Now, I try translating this into Entity Framework using the designer. After updating the model from the database and doing some editing, I have a Person object, a Model object, and a ModelScore object. PersonModelScore, being a join table, is not an object but rather is included as an association with some other name (let's say ModelScorePersonAssociation). The mapping details for the association are as follows: - Association - Maps to PersonModelScore - ModelScore ModelId : Int32 <=> ModelId : int Score : Int32 <=> Score : int - Person PersonId : Int32 <=> PersonId : int On the right-hand side, the ModelId and PersonId values have primary key symbols, but the Score value does not. Upon compilation, I get: Error 3002: Problem in Mapping Fragment starting at line 5190: Potential runtime violation of table PersonModelScore's keys (PersonModelScore.ModelId, PersonModelScore.PersonId): Columns (PersonModelScore.PersonId, PersonModelScore.ModelId) are mapped to EntitySet ModelScorePersonAssociation's properties (ModelScorePersonAssociation.Person.PersonId, ModelScorePersonAssociation.ModelScore.ModelId) on the conceptual side but they do not form the EntitySet's key properties (ModelScorePersonAssociation.ModelScore.ModelId, ModelScorePersonAssociation.ModelScore.Score, ModelScorePersonAssociation.Person.PersonId). What have I done wrong in the designer or otherwise, and how can I fix the error? Many thanks!

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• Assembly Language bug with space character

  - by Bobby

  Having a bit of difficulty getting my input to print once a white space character is inputted. So far, i have it to display the uppercase/lowercase of the input but once i enter a string it doesnt read whats after the white space character. any suggestions? EDIT: intel x86 processor and im using EMU8086 org 100h include 'emu8086.inc' printn "Enter string to convert" mov dx,20 call get_string printn mov bx,di mov ah,0eh mov al,[ds+bx] cmp al, 41h cmp al, 5Ah jle ToLower1 cmp al, 61h cmp al, 7ah jle ToUpper1 ToLower1: add al, 20h int 10h jmp stop1 ToUpper1: sub al, 20h int 10h stop1: inc bx mov al,[ds+bx] cmp al, 41h cmp al, 5Ah jle ToLower2 cmp al, 61h cmp al, 7ah jle ToUpper2 ToLower2: add al, 20h int 10h jmp stop2 ToUpper2: sub al, 20h int 10h stop2: inc bx mov al,[ds+bx] cmp al, 41h cmp al, 5Ah jle ToLower3 cmp al, 61h cmp al, 7ah jle ToUpper3 ToLower3: add al, 20h int 10h jmp stop3 ToUpper3: sub al, 20h int 10h stop3: inc bx mov al,[ds+bx] cmp al, 41h cmp al, 5Ah jle ToLower4 cmp al, 61h cmp al, 7ah jle ToUpper4 ToLower4: add al, 20h int 10h jmp stop4 ToUpper4: sub al, 20h int 10h stop4: inc bx mov al,[ds+bx] cmp al, 41h cmp al, 5Ah jle ToLower5 cmp al, 61h cmp al, 7ah jle ToUpper5 ToLower5: add al, 20h int 10h jmp stop5 ToUpper5: sub al, 20h int 10h stop5: printn hlt define_get_string define_print_string end

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• How to befriend a templated class's constructor?

  - by Kyle

  Why does class A; template<typename T> class B { private: A* a; public: B(); }; class A : public B<int> { private: friend B<int>::B<int>(); int x; }; template<typename T> B<T>::B() { a = new A; a->x = 5; } int main() { return 0; } result in ../src/main.cpp:15: error: invalid use of constructor as a template ../src/main.cpp:15: note: use ‘B::B’ instead of ‘B::class B’ to name the constructor in a qualified name yet changing friend B<int>::B<int>() to friend B<int>::B() results in ../src/main.cpp:15: error: no ‘void B::B()’ member function declared in class ‘B’ while removing the template completely class A; class B { private: A* a; public: B(); }; class A : public B { private: friend B::B(); int x; }; B::B() { a = new A; a->x = 5; } int main() { return 0; } compiles and executes just fine -- despite my IDE saying friend B::B() is invalid syntax?

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• C# Random Number Generator getting stuck in a cycle

  - by Jean Azzopardi

  Hi, I am using .NET to create an artificial life program and I am using C#'s pseudo random class defined in a Singleton. The idea is that if I use the same random number generator throughout the application, I could merely save the seed and then reload from the seed to recompute a certain interesting run. public sealed class RandomNumberGenerator : Random { private static readonly RandomNumberGenerator instance = new RandomNumberGenerator(); RandomNumberGenerator() { } public static RandomNumberGenerator Instance { get { return instance; } } } I also wanted a method that could give me two different random numbers. public static Tuple<int, int> TwoDifferentRandomNumbers(this Random rnd, int minValue, int maxValue) { if (minValue >= maxValue) throw new ArgumentOutOfRangeException("maxValue", "maxValue must be greater than minValue"); if (minValue + 1 == maxValue) return Tuple.Create<int, int>(minValue, maxValue); int rnd1 = rnd.Next(minValue, maxValue); int rnd2 = rnd.Next(minValue, maxValue); while (rnd1 == rnd2) { rnd2 = rnd.Next(minValue, maxValue); } return Tuple.Create<int, int>(rnd1, rnd2); } The problem is that sometimes rnd.Next(minValue,maxValuealways returns minValue. If I breakpoint at this point and try creating a double and setting it to rnd.NextDouble(), it returns 0.0. Anyone know why this is happening? I know that it is a pseudo random number generator, but frankly, I hadn't expected it to lock at 0. The random number generator is being accessed from multiple threads... could this be the source of the problem?

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• Trouble move-capturing std::unique_ptr in a lambda using std::bind

  - by user2478832

  I'd like to capture a variable of type std::vector<std::unique_ptr<MyClass>> in a lambda expression (in other words, "capture by move"). I found a solution which uses std::bind to capture unique_ptr (http://stackoverflow.com/a/12744730/2478832) and decided to use it as a starting point. However, the most simplified version of the proposed code I could get doesn't compile (lots of template mistakes, it seems to try to call unique_ptr's copy constructor). #include <functional> #include <memory> std::function<void ()> a(std::unique_ptr<int>&& param) { return std::bind( [] (int* p) {}, std::move(param)); } int main() { a(std::unique_ptr<int>(new int())); } Can anybody point out what is wrong with this code? EDIT: tried changing the lambda to take a reference to unique_ptr, it still doesn't compile. #include <functional> #include <memory> std::function<void ()> a(std::unique_ptr<int>&& param) { return std::bind( [] (std::unique_ptr<int>& p) {}, // also as a const reference std::move(param)); } int main() { a(std::unique_ptr<int>(new int())); }

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• LINQ and Aggregate function

  - by vik20000in

  LINQ also provides with itself important aggregate function. Aggregate function are function that are applied over a sequence like and return only one value like Average, count, sum, Maximum etc…Below are some of the Aggregate functions provided with LINQ and example of their implementation. Count     int[] primeFactorsOf300 = { 2, 2, 3, 5, 5 };     int uniqueFactors = primeFactorsOf300.Distinct().Count();The below example provided count for only odd number.     int[] primeFactorsOf300 = { 2, 2, 3, 5, 5 };     int uniqueFactors = primeFactorsOf300.Distinct().Count(n => n%2 = 1);  Sum     int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };        double numSum = numbers.Sum();  Minimum      int minNum = numbers.Min(); Maximum      int maxNum = numbers.Max();Average      double averageNum = numbers.Average();  Aggregate      double[] doubles = { 1.7, 2.3, 1.9, 4.1, 2.9 };     double product = doubles.Aggregate((runningProduct, nextFactor) => runningProduct * nextFactor);  Vikram

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• Macro access to members of object where macro is defined

  - by Marc Grue

  Say I have a trait Foo that I instantiate with an initial value val foo = new Foo(6) // class Foo(i: Int) and I later call a second method that in turn calls myMacro foo.secondMethod(7) // def secondMethod(j: Int) = macro myMacro then, how can myMacro find out what my initial value of i (6) is? I didn't succeed with normal compilation reflection using c.prefix, c.eval(...) etc but instead found a 2-project solution: Project B: object CompilationB { def resultB(x: Int, y: Int) = macro resultB_impl def resultB_impl(c: Context)(x: c.Expr[Int], y: c.Expr[Int]) = c.universe.reify(x.splice * y.splice) } Project A (depends on project B): trait Foo { val i: Int // Pass through `i` to compilation B: def apply(y: Int) = CompilationB.resultB(i, y) } object CompilationA { def makeFoo(x: Int): Foo = macro makeFoo_impl def makeFoo_impl(c: Context)(x: c.Expr[Int]): c.Expr[Foo] = c.universe.reify(new Foo {val i = x.splice}) } We can create a Foo and set the i value either with normal instantiation or with a macro like makeFoo. The second approach allows us to customize a Foo at compile time in the first compilation and then in the second compilation further customize its response to input (i in this case)! In some way we get "meta-meta" capabilities (or "pataphysic"-capabilities ;-) Normally we would need to have foo in scope to introspect i (with for instance c.eval(...)). But by saving the i value inside the Foo object we can access it anytime and we could instantiate Foo anywhere: object Test extends App { import CompilationA._ // Normal instantiation val foo1 = new Foo {val i = 7} val r1 = foo1(6) // Macro instantiation val foo2 = makeFoo(7) val r2 = foo2(6) // "Curried" invocation val r3 = makeFoo(6)(7) println(s"Result 1 2 3: $r1 $r2 $r3") assert((r1, r2, r3) ==(42, 42, 42)) } My question Can I find i inside my example macros without this double compilation hackery?

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• question about joGL (glTexImage2D)

  - by Nour

  Hi everybody I was trying to load a texture using joGL library but it seems that something is missing when using this method glTexImage2D at : IOStream wdis = new IOStream(fileName); wdis.skipBytes(18); int width = wdis.readIntW(); // dis.skipBytes(2); int height = wdis.readIntW(); // dis.skipBytes(2); wdis.skipBytes(28); byte buf[] = new byte[wdis.available()]; wdis.read(buf); wdis.close(); gl.glBindTexture(GL.GL_TEXTURE_2D, BMPtextures[index]); gl.glTexImage2D(GL.GL_TEXTURE_2D, 0, 3, width, height, 0, GL.GL_BGR, GL.GL_UNSIGNED_BYTE, buf); gl.glTexParameteri(GL.GL_TEXTURE_2D, GL.GL_TEXTURE_MAG_FILTER, GL.GL_LINEAR); gl.glTexParameteri(GL.GL_TEXTURE_2D, GL.GL_TEXTURE_MIN_FILTER, GL.GL_LINEAR); as IOStream is a class that extends DataInputStream it shows a message that glTexImage2D(int,int,int,int,int,int,int,int,byte[]) is not found at javax.media.opengl.GL I couldn't figure the problem her because it's an open source code and it seems to work perfectly with my friends but unfortunately not with me even though we are using the same library and the same JDK version what shall I do ??

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• custom type face class by dinesh?

  - by dineshpeiris

  package typeface{ import flash.display.*; import flash.events.Event; import flash.filters.BitmapFilter; import flash.filters.BitmapFilterQuality; import flash.filters.BlurFilter; public class Main extends Sprite { private var typeSet:String="SEE > THINK > CREATE"; private var collectionSet:MovieClip; private var w:int = 1; public function Main():void { trace("start typeface application"); collectionSet = new MovieClip(); for (var n:int = 0; n < typeSet.length; n++) { var _x:int = 0 + (40 * n); var _y:int = 0; var Type:TypeCollector = new TypeCollector(_x, _y, stringToCharacter(typeSet, n), collectionSet); Type.addEventListener("action", actionHandler); } collectionSet.x = 100; collectionSet.y = (stage.stageHeight / 2) - 80; addChild(collectionSet); } private function actionHandler(event:Event):void { if (w == 16) { collectionSet.filters = [new BlurFilter(30, 30, BitmapFilterQuality.HIGH)]; removeChild(collectionSet); } w++; } public function stringToCharacter(str:String, n:int):String { if (str.length == 1) { return str; } return str.slice(n, n+1); } } } package typeface { import flash.display.*; import flash.events.Event; import flash.utils.Timer; import flash.events.TimerEvent; import flash.filters.BitmapFilter; import flash.filters.BitmapFilterQuality; import flash.filters.BlurFilter; import flash.events.EventDispatcher; public class TypeCollector extends EventDispatcher { private var TYPE_MC:typeMC; private var typeArray:Array = new Array("A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z", "1", "2", "3", "4", "5", "6", "7", "8", "9", "0", "<", ">"); private var character:String; private var num:int = 0; private var TypeTimer:Timer; private var _xNum:int; private var _yNum:int; private var movieClip:MovieClip; public function TypeCollector(_x:int, _y:int, char:String, movie:MovieClip) { var totalNum:int = typeArray.length; _xNum = _x; _yNum = _y; movieClip = movie; character = char; TypeTimer = new Timer(100, totalNum); TypeTimer.addEventListener("timer", TypeRoutTimer); TypeTimer.start(); } public function TypeRoutTimer(event:TimerEvent):void { CreateTypeFace(num, _xNum, _yNum, character); num++; } public function CreateTypeFace(num:int, _x:int, _y:int, character:String) { if (character == " ") { } else { if (TYPE_MC != null) { TYPE_MC.filters = [new BlurFilter(30, 30, BitmapFilterQuality.HIGH)]; movieClip.removeChild(TYPE_MC); } if (typeArray[num] == character) { TYPE_MC = new typeMC(); TYPE_MC.x = _x; TYPE_MC.y = _y; TYPE_MC.typeTF.text = typeArray[num]; TYPE_MC.filters = [new BlurFilter(5, 5, BitmapFilterQuality.HIGH)]; movieClip.addChild(TYPE_MC); dispatchEvent(new Event("action")); TypeTimer.stop(); } else { TYPE_MC = new typeMC(); TYPE_MC.x = _x; TYPE_MC.y = _y; TYPE_MC.typeTF.text = typeArray[num]; TYPE_MC.filters = [new BlurFilter(10, 10, BitmapFilterQuality.HIGH)]; movieClip.addChild(TYPE_MC); } } } } }

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• IBasic Accumulator

  - by Tara

  I am trying to do an accumulator in IBasic for a college assignment and I have the general stuff down but I cannot get it to accumulate. The code is below. My question is how do I get it to accumulate and pass to the different module. I'm trying to calculate how many right answers the user gets. Also, i need to calculate the percentage of right answers. so if the user gets 9 out of 10 right theyed answer 90% right. 'October 15, 2009 ' 'Lab 7.5 Programming Challenge 1 - Average Test Scores ' 'This is a dice game ' declare main() declare inputName(name:string) declare getAnswer(num1:int, num2:int) declare getResult(num1:int, num2:int, answer:int) declare avgRight(getRight:int) declare printInfo(name:string, getRight:int, averege:float) openconsole main() do:until inkey$<>"" closeconsole end sub main() def name:string def num1, num2, answer, total, getRight:int def averege:float inputName (name) getRight = 0 For counter = 1 to 10 getRight = getAnswer(num1, num2) getRight = getRight + 1 next counter average = avgRight (getRight) printInfo(Name, getRight, average) end sub inputName (name) Input "Please enter your name: " ,name return sub getAnswer(num1, num2) def answer, getRight:int num1 = rnd (10) + 1 num2 = rnd (10) + 1 Print num1, "+ " ,num2 Input "What is the answer to the equation? " ,answer getRight = getResult(num1, num2, answer) return getRight sub getResult(num1, num2, answer) def getRight:int if answer = num1 + num2 getRight = 1 else getRight = 0 endif return getRight sub avgRight(getRight) def average:float average = getRight / 10 return average sub printInfo(name, getRight, averege) Print "The students name is: " ,name Print "The number right is: " ,getRight Print Using ("&##.#&", "The average right is " ,averege * 100, "%") return

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• abstract data type list. . .

  - by aldrin

  A LIST is an ordered collection of items where items may be inserted anywhere in the list. Implement a LIST using an array as follows: struct list { int *items; // pointer to the array int size; // actual size of the array int count; // number of items in the array }; typedef struct list *List; // pointer to the structure Implement the following functions: a) List newList(int size); - will create a new List and return its pointer. Allocate space for the structure, allocate space for the array, then initialize size and count, return the pointer. b) void isEmpty(List list); c) void display(List list); d) int contains(List list, int item); e) void remove(List list, int i) ; f) void insertAfter(List list,int item, int i); g) void addEnd(List list,int item) - add item at the end of the list – simply store the data at position count, then increment count. If the array is full, allocate an array twice as big as the original. count = 5 size = 10 0 1 2 3 4 5 6 7 8 9 5 10 15 20 30 addEnd(list,40) will result to count = 6 size = 10 0 1 2 3 4 5 6 7 8 9 5 10 15 20 30 40 h) void addFront(List list,int item) - shift all elements to the right so that the item can be placed at position 0, then increment count. Bonus: if the array is full, allocate an array twice as big as the original. count = 5 size = 10 0 1 2 3 4 5 6 7 8 9 5 10 15 20 30 addFront(list,40) will result to count = 6 size = 10 0 1 2 3 4 5 6 7 8 9 40 5 10 15 20 30 i) void removeFront(List list) - shift all elements to the left and decrement count; count = 6 size = 10 0 1 2 3 4 5 6 7 8 9 40 5 10 15 20 30 removeFront(list) will result to count = 5 size = 10 0 1 2 3 4 5 6 7 8 9 5 10 15 20 30 j) void remove(List list,int item) - get the index of the item in the list and then shift all elements to the count = 6 size = 10 0 1 2 3 4 5 6 7 8 9 40 5 10 15 20 30 remove(list,10) will result to count = 5 size = 10 0 1 2 3 4 5 6 7 8 9 40 5 15 20 30

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• Pointer to 2D array. Why does this example work?

  - by Louise

  I have this code example, but I don't understand why changing the values in the array inside outputUsingArray() are changing the original array. I would have expected changing the values of the array in outputUsingArray() would only be for a local copy of the array. Why isn't that so? However, this is the behaviour I would like, but I don't understand why it work. #include <stdlib.h> #include <stdio.h> void outputUsingArray(int array[][4], int n_rows, int n_cols) { int i, j; printf("Output Using array\n"); for (i = 0; i < n_rows; i++) { for (j = 0; j < n_cols; j++) { // Either can be used. //printf("%2d ", array[i][j] ); printf("%2d ", *(*(array+i)+j)); } printf("\n"); } printf("\n"); array[0][0] = 100; array[2][3] = 200; } void outputUsingPointer(int (*array)[4], int n_rows, int n_cols) { int i, j; printf("Output Using Pointer to Array i.e. int (*array)[4]\n"); for (i = 0; i < n_rows; i++) { for (j = 0; j < n_cols; j++) { printf("%2d ", *(*(array+i) + j )); } printf("\n"); } printf("\n"); } int main() { int array[3][4] = { { 0, 1, 2, 3 }, { 4, 5, 6, 7 }, { 8, 9, 10, 11 } }; outputUsingPointer((int (*)[4])array, 3, 4); outputUsingArray(array, 3, 4); printf("0,0: %i\n", array[0][0]); printf("2,3: %i\n", array[2][3]); return 0; }

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• object_getInstanceVariable works for float, int, bool, but not for double?

  - by Russel West

  I've got object_getInstanceVariable to work as here however it seems to only work for floats, bools and ints not doubles. I do suspect I'm doing something wrong but I've been going in circles with this. float myFloatValue; float someFloat = 2.123f; object_getInstanceVariable(self, "someFloat", (void*)&myFloatValue); works, and myFloatValue = 2.123 but when I try double myDoubleValue; double someDouble = 2.123f; object_getInstanceVariable(self, "someDouble", (void*)&myDoubleValue); i get myDoubleValue = 0. If I try to set myDoubleValue before the function eg. double myDoubleValue = 1.2f, the value is unchanged when I read it after the object_getInstanceVariable call. setting myIntValue to some other value before the getinstancevar function above returns 2 as it should, ie. it has been changed. then I tried Ivar tmpIvar = object_getInstanceVariable(self, "someDouble", (void*)&myDoubleValue); if i do ivar_getName(tmpIvar) i get "someDouble", but myDoubuleValue = 0 still! then i try ivar_getTypeEncoding(tmpIvar) and i get "d" as it should be. So to summarize, if typeEncoding = float, it works, if it is a double, the result is not set but it correctly reads the variable and the return value (Ivar) is also correct. I must be doing something basic wrong that I cant see so I'd appreciate if someone could point it out.

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• unsigned char* buffer (FreeType2 Bitmap) to System::Drawing::Bitmap.

  - by Dennis Roche

  Hi, I'm trying to convert a FreeType2 bitmap to a System::Drawing::Bitmap in C++/CLI. FT_Bitmap has a unsigned char* buffer that contains the data to write. I have got somewhat working save it disk as a *.tga, but when saving as *.bmp it renders incorrectly. I believe that the size of byte[] is incorrect and that my data is truncated. Any hints/tips/ideas on what is going on here would be greatly appreciated. Links to articles explaining byte layout and pixel formats etc. would be helpful. Thanks!! C++/CLI code. FT_Bitmap *bitmap = &face->glyph->bitmap; int width = (face->bitmap->metrics.width / 64); int height = (face->bitmap->metrics.height / 64); // must be aligned on a 32 bit boundary or 4 bytes int depth = 8; int stride = ((width * depth + 31) & ~31) >> 3; int bytes = (int)(stride * height); // as *.tga void *buffer = bytes ? malloc(bytes) : NULL; if (buffer) { memset(buffer, 0, bytes); for (int i = 0; i < glyph->rows; ++i) memcpy((char *)buffer + (i * width), glyph->buffer + (i * glyph->pitch), glyph->pitch); WriteTGA("Test.tga", buffer, width, height); } // as *.bmp array<Byte>^ values = gcnew array<Byte>(bytes); Marshal::Copy((IntPtr)glyph->buffer, values, 0, bytes); Bitmap^ systemBitmap = gcnew Bitmap(width, height, PixelFormat::Format24bppRgb); // create bitmap data, lock pixels to be written. BitmapData^ bitmapData = systemBitmap->LockBits(Rectangle(0, 0, width, height), ImageLockMode::WriteOnly, bitmap->PixelFormat); Marshal::Copy(values, 0, bitmapData->Scan0, bytes); systemBitmap->UnlockBits(bitmapData); systemBitmap->Save("Test.bmp"); Reference, FT_Bitmap typedef struct FT_Bitmap_ { int rows; int width; int pitch; unsigned char* buffer; short num_grays; char pixel_mode; char palette_mode; void* palette; } FT_Bitmap; Reference, WriteTGA bool WriteTGA(const char *filename, void *pxl, uint16 width, uint16 height) { FILE *fp = NULL; fopen_s(&fp, filename, "wb"); if (fp) { TGAHeader header; memset(&header, 0, sizeof(TGAHeader)); header.imageType = 3; header.width = width; header.height = height; header.depth = 8; header.descriptor = 0x20; fwrite(&header, sizeof(header), 1, fp); fwrite(pxl, sizeof(uint8) * width * height, 1, fp); fclose(fp); return true; } return false; } Update FT_Bitmap *bitmap = &face->glyph->bitmap; // stride must be aligned on a 32 bit boundary or 4 bytes int depth = 8; int stride = ((width * depth + 31) & ~31) >> 3; int bytes = (int)(stride * height); target = gcnew Bitmap(width, height, PixelFormat::Format8bppIndexed); // create bitmap data, lock pixels to be written. BitmapData^ bitmapData = target->LockBits(Rectangle(0, 0, width, height), ImageLockMode::WriteOnly, target->PixelFormat); array<Byte>^ values = gcnew array<Byte>(bytes); Marshal::Copy((IntPtr)bitmap->buffer, values, 0, bytes); Marshal::Copy(values, 0, bitmapData->Scan0, bytes); target->UnlockBits(bitmapData);

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• collect2: ld returned 1 exit status error in Xcode

  - by user573949

  Hello, Im getting the error Command /Developer/usr/bin/gcc-4.2 failed with exit code 1 and when the full log is opened, the error is more accurately listed as: collect2: ld returned 1 exit status from this simple Cocoa script: #import "Controller.h" @implementation Controller int skillcheck (int level, int modifer, int difficulty) { if (level + modifer >= difficulty) { return 1; } if (level + modifer <= difficulty) { return 0; } } int main () { skillcheck(10, 2, 10); } @end the .h file is this: // // Controller.h // // Created by Duo Oratar on 15/01/2011. // Copyright 2011 __MyCompanyName__. All rights reserved. // #import <Cocoa/Cocoa.h> @interface Controller : NSObject { int skillcheck; int contestcheck; } @end and no line was specified that the error came from, does anyone know what the source of this error is, and more importantly, how to fix it? EDIT: I removed the class so now I have this: // // Controller.m // // Created by Duo Oratar on 15/01/2011. // Copyright 2011 __MyCompanyName__. All rights reserved. // #import "Controller.h" int skillcheck (int level, int modifer, int difficulty) { if (level + modifer >= difficulty) { return 1; } if (level + modifer <= difficulty) { return 0; } } int main () { skillcheck(10, 2, 10); } and for the .h file: // // Controller.h // // Created by Duo Oratar on 15/01/2011. // Copyright 2011 __MyCompanyName__. All rights reserved. // #import <Cocoa/Cocoa.h> and the log says: (thanks to the guy who said how to open it) Ld build/Debug/Calculator.app/Contents/MacOS/Calculator normal x86_64 cd /Users/kids/Desktop/Calculator setenv MACOSX_DEPLOYMENT_TARGET 10.6 /Developer/usr/bin/gcc-4.2 -arch x86_64 -isysroot /Developer/SDKs/MacOSX10.6.sdk -L/Users/kids/Desktop/Calculator/build/Debug -F/Users/kids/Desktop/Calculator/build/Debug -filelist /Users/kids/Desktop/Calculator/build/Calculator.build/Debug/Calculator.build/Objects-normal/x86_64/Calculator.LinkFileList -mmacosx-version-min=10.6 -framework Cocoa -o /Users/kids/Desktop/Calculator/build/Debug/Calculator.app/Contents/MacOS/Calculator ld: duplicate symbol _main in /Users/kids/Desktop/Calculator/build/Calculator.build/Debug/Calculator.build/Objects-normal/x86_64/Controller.o and /Users/kids/Desktop/Calculator/build/Calculator.build/Debug/Calculator.build/Objects-normal/x86_64/main.o collect2: ld returned 1 exit status Command /Developer/usr/bin/gcc-4.2 failed with exit code 1 ld: duplicate symbol _main in /Users/kids/Desktop/Calculator/build/Calculator.build/Debug/Calculator.build/Objects-normal/x86_64/Controller.o and /Users/kids/Desktop/Calculator/build/Calculator.build/Debug/Calculator.build/Objects-normal/x86_64/main.o Command /Developer/usr/bin/gcc-4.2 failed with exit code 1

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• Multiple constructors in C

  - by meepz

  Hello, I am making a string class in C as a homework and I was wondering how I can make multiple constructors with the same name given the parameter. The commented out area is what I tried to do with results from a few searches but that gives me errors. Pretty much I have some cases where I want to create my new string without any parameter then in other cases create a string with a pointer to character. Here is mystring.h #include <stdio.h> #include <stdlib.h> typedef struct mystring { char * c; int length; int (*sLength)(void * s); char (*charAt)(void * s, int i); int (*compareTo)(void * s1, void * s2); struct mystring * (*concat)(void * s1, void * s2); struct mystring * (*subString)(void * s, int begin, int end); void (*printS)(void * s); } string_t; typedef string_t * String; String newString(char * c); String newString2(); int slength(void * s); char charat(void * S, int i); int compareto(void * s1, void * s2); String concat(void * s1, void * s2); String substring(void * S, int begin, int end); void printstring(void * s); And here is mystring.c #include "mystring.h" String newString(){ } String newString(char * input){ //String newString::newString(char * input) { String s; s = (string_t *) malloc(sizeof(string_t)); s->c = (char *) malloc(sizeof(char) * 20); int i = 0; if (input == NULL){ s->c[0] = '\0'; return s; } while (input[i] != '\0') { s->c[i] = input[i]; i++; } //functions s->sLength = slength; s->charAt = charat; s->compareTo = compareto; s->concat = concat; s->subString = substring; s->printS = printstring; return s; }

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• Query on simple C++ threadpool implementation

  - by ticketman

  Stackoverflow has been a tremendous help to me and I'd to give something back to the community. I have been implementing a simple threadpool using the tinythread C++ portable thread library, using what I have learnt from Stackoverflow. I am new to thread programming, so not that comfortable with mutexes, etc. I have a question best asked after presenting the code (which runs quite well under Linux): // ThreadPool.h class ThreadPool { public: ThreadPool(); ~ThreadPool(); // Creates a pool of threads and gets them ready to be used void CreateThreads(int numOfThreads); // Assigns a job to a thread in the pool, but doesn't start the job // Each SubmitJob call will use up one thread of the pool. // This operation can only be undone by calling StartJobs and // then waiting for the jobs to complete. On completion, // new jobs may be submitted. void SubmitJob( void (*workFunc)(void *), void *workData ); // Begins execution of all the jobs in the pool. void StartJobs(); // Waits until all jobs have completed. // The wait will block the caller. // On completion, new jobs may be submitted. void WaitForJobsToComplete(); private: enum typeOfWorkEnum { e_work, e_quit }; class ThreadData { public: bool ready; // thread has been created and is ready for work bool haveWorkToDo; typeOfWorkEnum typeOfWork; // Pointer to the work function each thread has to call. void (*workFunc)(void *); // Pointer to work data void *workData; ThreadData() : ready(false), haveWorkToDo(false) { }; }; struct ThreadArgStruct { ThreadPool *threadPoolInstance; int threadId; }; // Data for each thread ThreadData *m_ThreadData; ThreadPool(ThreadPool const&); // copy ctor hidden ThreadPool& operator=(ThreadPool const&); // assign op. hidden // Static function that provides the function pointer that a thread can call // By including the ThreadPool instance in the void * parameter, // we can use it to access other data and methods in the ThreadPool instance. static void ThreadFuncWrapper(void *arg) { ThreadArgStruct *threadArg = static_cast<ThreadArgStruct *>(arg); threadArg->threadPoolInstance->ThreadFunc(threadArg->threadId); } // The function each thread calls void ThreadFunc( int threadId ); // Called by the thread pool destructor void DestroyThreadPool(); // Total number of threads available // (fixed on creation of thread pool) int m_numOfThreads; int m_NumOfThreadsDoingWork; int m_NumOfThreadsGivenJobs; // List of threads std::vector<tthread::thread *> m_ThreadList; // Condition variable to signal each thread has been created and executing tthread::mutex m_ThreadReady_mutex; tthread::condition_variable m_ThreadReady_condvar; // Condition variable to signal each thread to start work tthread::mutex m_WorkToDo_mutex; tthread::condition_variable m_WorkToDo_condvar; // Condition variable to signal the main thread that // all threads in the pool have completed their work tthread::mutex m_WorkCompleted_mutex; tthread::condition_variable m_WorkCompleted_condvar; }; cpp file: // // ThreadPool.cpp // #include "ThreadPool.h" // This is the thread function for each thread. // All threads remain in this function until // they are asked to quit, which only happens // when terminating the thread pool. void ThreadPool::ThreadFunc( int threadId ) { ThreadData *myThreadData = &m_ThreadData[threadId]; std::cout << "Hello world: Thread " << threadId << std::endl; // Signal that this thread is ready m_ThreadReady_mutex.lock(); myThreadData->ready = true; m_ThreadReady_condvar.notify_one(); // notify the main thread m_ThreadReady_mutex.unlock(); while(true) { //tthread::lock_guard<tthread::mutex> guard(m); m_WorkToDo_mutex.lock(); while(!myThreadData->haveWorkToDo) // check for work to do m_WorkToDo_condvar.wait(m_WorkToDo_mutex); // if no work, wait here myThreadData->haveWorkToDo = false; // need to do this before unlocking the mutex m_WorkToDo_mutex.unlock(); // Do the work switch(myThreadData->typeOfWork) { case e_work: std::cout << "Thread " << threadId << ": Woken with work to do\n"; // Do work myThreadData->workFunc(myThreadData->workData); std::cout << "#Thread " << threadId << ": Work is completed\n"; break; case e_quit: std::cout << "Thread " << threadId << ": Asked to quit\n"; return; // ends the thread } // Now to signal the main thread that my work is completed m_WorkCompleted_mutex.lock(); m_NumOfThreadsDoingWork--; // Unsure if this 'if' would make the program more efficient // if(NumOfThreadsDoingWork == 0) m_WorkCompleted_condvar.notify_one(); // notify the main thread m_WorkCompleted_mutex.unlock(); } } ThreadPool::ThreadPool() { m_numOfThreads = 0; m_NumOfThreadsDoingWork = 0; m_NumOfThreadsGivenJobs = 0; } ThreadPool::~ThreadPool() { if(m_numOfThreads) { DestroyThreadPool(); delete [] m_ThreadData; } } void ThreadPool::CreateThreads(int numOfThreads) { // Check a thread pool has already been created if(m_numOfThreads > 0) return; m_NumOfThreadsGivenJobs = 0; m_NumOfThreadsDoingWork = 0; m_numOfThreads = numOfThreads; m_ThreadData = new ThreadData[m_numOfThreads]; ThreadArgStruct threadArg; for(int i=0; i<m_numOfThreads; ++i) { threadArg.threadId = i; threadArg.threadPoolInstance = this; // Creates the thread and save in a list so we can destroy it later m_ThreadList.push_back( new tthread::thread( ThreadFuncWrapper, (void *)&threadArg ) ); // It takes a little time for a thread to get established. // Best wait until it gets established before creating the next thread. m_ThreadReady_mutex.lock(); while(!m_ThreadData[i].ready) // Check if thread is ready m_ThreadReady_condvar.wait(m_ThreadReady_mutex); // If not, wait here m_ThreadReady_mutex.unlock(); } } // Adds a job to the batch, but doesn't start the job void ThreadPool::SubmitJob(void (*workFunc)(void *), void *workData) { // Check that the thread pool has been created if(!m_numOfThreads) return; if(m_NumOfThreadsGivenJobs >= m_numOfThreads) return; m_ThreadData[m_NumOfThreadsGivenJobs].workFunc = workFunc; m_ThreadData[m_NumOfThreadsGivenJobs].workData = workData; std::cout << "Submitted job " << m_NumOfThreadsGivenJobs << std::endl; m_NumOfThreadsGivenJobs++; } void ThreadPool::StartJobs() { // Check that the thread pool has been created // and some jobs have been assigned if(!m_numOfThreads || !m_NumOfThreadsGivenJobs) return; // Set 'haveworkToDo' flag for all threads m_WorkToDo_mutex.lock(); for(int i=0; i<m_NumOfThreadsGivenJobs; ++i) m_ThreadData[i].haveWorkToDo = true; m_NumOfThreadsDoingWork = m_NumOfThreadsGivenJobs; // Reset this counter so we can resubmit jobs later m_NumOfThreadsGivenJobs = 0; // Notify all threads they have work to do m_WorkToDo_condvar.notify_all(); m_WorkToDo_mutex.unlock(); } void ThreadPool::WaitForJobsToComplete() { // Check that a thread pool has been created if(!m_numOfThreads) return; m_WorkCompleted_mutex.lock(); while(m_NumOfThreadsDoingWork > 0) // Check if all threads have completed their work m_WorkCompleted_condvar.wait(m_WorkCompleted_mutex); // If not, wait here m_WorkCompleted_mutex.unlock(); } void ThreadPool::DestroyThreadPool() { std::cout << "Ask threads to quit\n"; m_WorkToDo_mutex.lock(); for(int i=0; i<m_numOfThreads; ++i) { m_ThreadData[i].haveWorkToDo = true; m_ThreadData[i].typeOfWork = e_quit; } m_WorkToDo_condvar.notify_all(); m_WorkToDo_mutex.unlock(); // As each thread terminates, catch them here for(int i=0; i<m_numOfThreads; ++i) { tthread::thread *t = m_ThreadList[i]; // Wait for thread to complete t->join(); } m_numOfThreads = 0; } Example of usage: (this calculates pi-squared/6) struct CalculationDataStruct { int inputVal; double outputVal; }; void LongCalculation( void *theSums ) { CalculationDataStruct *sums = (CalculationDataStruct *)theSums; int terms = sums->inputVal; double sum; for(int i=1; i<terms; i++) sum += 1.0/( double(i)*double(i) ); sums->outputVal = sum; } int main(int argc, char** argv) { int numThreads = 10; // Create pool ThreadPool threadPool; threadPool.CreateThreads(numThreads); // Create thread workspace CalculationDataStruct sums[numThreads]; // Set up jobs for(int i=0; i<numThreads; i++) { sums[i].inputVal = 3000*(i+1); threadPool.SubmitJob(LongCalculation, &sums[i]); } // Run the jobs threadPool.StartJobs(); threadPool.WaitForJobsToComplete(); // Print results for(int i=0; i<numThreads; i++) std::cout << "Sum of " << sums[i].inputVal << " terms is " << sums[i].outputVal << std::endl; return 0; } Question: In the ThreadPool::ThreadFunc method, would better performance be obtained if the following if statement if(NumOfThreadsDoingWork == 0) was included? Also, I'd be grateful of criticisms and ways to improve the code. At the same time, I hope the code is of use to others.

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