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  • Multiple generic types in one container

    - by Lirik
    I was looking at the answer of this question regarding multiple generic types in one container and I can't really get it to work: the properties of the Metadata class are not visible, since the abstract class doesn't have them. Here is a slightly modified version of the code in the original question: public abstract class Metadata { } public class Metadata<T> : Metadata { // ... some other meta data public T Function{ get; set; } } List<Metadata> metadataObjects; metadataObjects.Add(new Metadata<Func<double,double>>()); metadataObjects.Add(new Metadata<Func<int,double>>()); metadataObjects.Add(new Metadata<Func<double,int>>()); foreach( Metadata md in metadataObjects) { var tmp = md.Function; // <-- Error: does not contain a definition for Function } The exact error is: error CS1061: 'Metadata' does not contain a definition for 'Function' and no extension method 'Function' accepting a first argument of type 'Metadata' could be found (are you missing a using directive or an assembly reference?) I believe it's because the abstract class does not define the property Function, thus the whole effort is completely useless. Is there a way that we can get the properties?

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  • Building a survey to put in a WordPress website using Python/Django

    - by chiurox
    So I've been given a task to build a survey to get data regarding time slot preferences of prospective students for a particular course. I know there are really quick solutions to this like Google Forms, SurveyMonkey, but since it's not unusually hard, I want to implement the survey myself in a totally new language as an opportunity to get started with it and also be able to customize and provide dynamic info to the users who are voting. Although I have done some stuff in PHP, C++, javascript, etc, I'm pretty new to Python+Django framework but it's something I've been meaning to get into since a long time ago. Initially, what I want is to make a grid with the days of the week as columns and time-durations as rows. In each cell I want to provide users a way to choose how strong (high/medium/low) their preference for this particular day+time is. I also want to show how many "votes" have already been cast for this particular preference because this will influence a lot in their decisions and as a result make this process easier when we are going to define the classes. I'll probably store the data in MySQL. Could anyone point me to some really good Python+Django tutorials for my particular purpose? Does anyone think I'm wasting my time with this trivial task by choosing new tools and that I should just use something I already know (like PHP) or a free service or plugin for Wordpress? Thanks!

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  • Generic Constraints And Type Parameters Mess

    - by Dummy01
    Hi everyone, I have the following base abstract class defined as: public abstract class BaseObject<T> : IComparable, IComparable<T>, IEquatable<T> {} I also have an interface defined as: public interface ICode<T> where T : struct { T Code { get; } } Now I want to derive a class that is inherited from BaseObject<T> and includes interface ICode<T>. I tried to define it like that: public class DerivedObject<T, U> : BaseObject<T>, ICode<U> where T : DerivedObject<T, U> where U : struct { public DerivedObject(U code) { Code = code; } // From BaseObject protected override int InstanceCompareTo(T obj) { return Code.CompareTo(obj.Code); } // From BaseObject protected override bool InstanceEquals(T obj) { return Code.Equals(obj.Code); } // From ICode U _Code; public U Code { get { return _Code; } protected set { _Code = value; } } } The only error that comes from the compiler is for Code.CompareTo(obj.Code) with the message: 'U' does not contain a definition for 'CompareTo' and no extension method 'CompareTo' accepting a first argument of type 'U' could be found. But U is a value type and should know CompareTo. Have you any idea what I am doing wrong, or if I do all wrong? My final aim is to derive classes such these: public class Account : DerivedObject<Account, int> public class ItemGroup : DerivedObject<ItemGroup, string> Big Thanks In Advance!

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  • SSE (SIMD extensions) support in gcc

    - by goldenmean
    Hi, I see a code as below: include "stdio.h" #define VECTOR_SIZE 4 typedef float v4sf __attribute__ ((vector_size(sizeof(float)*VECTOR_SIZE))); // vector of four single floats typedef union f4vector { v4sf v; float f[VECTOR_SIZE]; } f4vector; void print_vector (f4vector *v) { printf("%f,%f,%f,%f\n", v->f[0], v->f[1], v->f[2], v->f[3]); } int main() { union f4vector a, b, c; a.v = (v4sf){1.2, 2.3, 3.4, 4.5}; b.v = (v4sf){5., 6., 7., 8.}; c.v = a.v + b.v; print_vector(&a); print_vector(&b); print_vector(&c); } This code builds fine and works expectedly using gcc (it's inbuild SSE / MMX extensions and vector data types. this code is doing a SIMD vector addition using 4 single floats. I want to understand in detail what does each keyword/function call on this typedef line means and does: typedef float v4sf __attribute__ ((vector_size(sizeof(float)*VECTOR_SIZE))); What is the vector_size() function return; What is the __attribute__ keyword for Here is the float data type being type defined to vfsf type? I understand the rest part. thanks, -AD

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  • Creating a C++ DLL and then using it in C#

    - by Major
    Ok I'm trying to make a C++ DLL that I can then call and reference in a c# App. I've already made a simple dll using the numberous guides out there, however when I try to reference it in the C# app I get the error Unable to load DLL 'SDES.dll': The specified module could not be found. The code for the program is as follows (bear with me I'm going to include all the files) //These are the DLL Files. ifndef TestDLL_H define TestDLL_H extern "C" { // Returns a + b __declspec(dllexport) double Add(double a, double b); // Returns a - b __declspec(dllexport) double Subtract(double a, double b); // Returns a * b __declspec(dllexport) double Multiply(double a, double b); // Returns a / b // Throws DivideByZeroException if b is 0 __declspec(dllexport) double Divide(double a, double b); } endif //.cpp include "test.h" include using namespace std; extern double __cdecl Add(double a, double b) { return a + b; } extern double __cdecl Subtract(double a, double b) { return a - b; } extern double __cdecl Multiply(double a, double b) { return a * b; } extern double __cdecl Divide(double a, double b) { if (b == 0) { throw new invalid_argument("b cannot be zero!"); } return a / b; } //C# Program using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Runtime.InteropServices; namespace ConsoleApplication1 { class Program { [DllImport("SDES.dll")] public static extern void SimulateGameDLL(int a, int b); static void Main(string[] args) { SimulateGameDLL(1, 2); //Error here... } } } Anyone have any idea's what I may be missing in my program? Let me know if I missed some code or if you have any questions.

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  • How do C++ compilers actually pass reference parameters?

    - by T.E.D.
    This question came about as a result of some mixed-langauge programming. I had a Fortran routine I wanted to call from C++ code. Fortran passes all its parameters by reference (unless you tell it otherwise). So I thought I'd be clever (bad start right there) in my C++ code and define the Fortran routine something like this: extern "C" void FORTRAN_ROUTINE (unsigned & flag); This code worked for a while but (of course right when I needed to leave) suddenly started blowing up on a return call. Clear indication of a munged call stack. Another engineer came behind me and fixed the problem, declaring that the routine had to be deinfed in C++ as extern "C" void FORTRAN_ROUTINE (unsigned * flag); I'd accept that except for two things. One is that it seems rather counter-intuitive for the compiler to not pass reference parameters by reference, and I can find no documentation anywhere that says that. The other is that he changed a whole raft of other code in there at the same time, so it theoretically could have been another change that fixed whatever the issue was. So the question is, how does C++ actually pass reference parameters? Is it perhaps free to do copy-in, copy-out for small values or something? In other words, are reference parameters utterly useless in mixed-language programming? I'd like to know so I don't make this same code-killing mistake ever again.

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  • Help with this compile error

    - by Scott
    I just picked up an old project and I'm not sure what the following error could mean. g++ -o BufferedReader.o -c -g -Wall -std=c++0x -I/usr/include/xmms2 -Ijsoncpp/include/json/ -fopenmp -I/usr/include/ImageMagick -I/usr/include/xmms2 -I/usr/include/libvisual-0.4 -D_GNU_SOURCE=1 -D_REENTRANT -I/usr/include/SDL -DQT_CORE_LIB -DQT_GUI_LIB -DQT_SCRIPT_LIB -DQT_SHARED -I/usr/include/QtCore -I/usr/include/QtGui -I/usr/include/QtScript BufferedReader.cpp In file included from BufferedReader.cpp:23: /usr/include/string.h:36:42: error: missing binary operator before token "(" In file included from /usr/lib/gcc/i686-redhat-linux/4.4.3/../../../../include/c++/4.4.3/cwchar:47, from /usr/lib/gcc/i686-redhat-linux/4.4.3/../../../../include/c++/4.4.3/bits/postypes.h:42, from /usr/lib/gcc/i686-redhat-linux/4.4.3/../../../../include/c++/4.4.3/iosfwd:42, from /usr/lib/gcc/i686-redhat-linux/4.4.3/../../../../include/c++/4.4.3/ios:39, from /usr/lib/gcc/i686-redhat-linux/4.4.3/../../../../include/c++/4.4.3/istream:40, from /usr/lib/gcc/i686-redhat-linux/4.4.3/../../../../include/c++/4.4.3/sstream:39, from BufferedReader.cpp:24: At line 24 of BufferedReader.cpp is #include <string.h>. I've tried it with just <string> but get the same thing. Any clue? Here's the snippet of code from string.h /* Tell the caller that we provide correct C++ prototypes. */ #if defined __cplusplus && __GNUC_PREREQ (4, 4) //line 36 # define __CORRECT_ISO_CPP_STRING_H_PROTO #endif Does that mean __GNUC_PREREQ isn't defined?

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  • Segmentation Fault when trying to push a string to the back of a list.

    - by user308012
    I am trying to write a logger class for my C++ calculator, but I'm experiencing a problem while trying to push a string into a list. I have tried researching this issue and have found some information on this, but nothing that seems to help with my problem. I am using a rather basic C++ compiler, with little debugging utilities and I've not used C++ in quite some time (even then it was only a small amount). My code: #ifndef _LOGGER_H_ #define _LOGGER_H_ #include <iostream> #include <list> #include <string> using std::cout; using std::cin; using std::endl; using std::list; using std::string; class Logger { private: list<string> *mEntries; public: Logger() { // Initialize the entries list mEntries = new list<string>(); } ~Logger() { // Release the list mEntries->clear(); delete mEntries; } // Public Methods void WriteEntry(string entry) { // *** BELOW LINE IS MARKED WITH THE ERROR *** mEntries->push_back(string(entryData)); } void DisplayEntries() { cout << endl << "**********************" << endl << "* Logger Entries *" << endl << "**********************" << endl << endl; for(list<string>::iterator it = mEntries->begin(); it != mEntries->end(); it++) { cout << *it << endl; } } }; #endif I am calling the WriteEntry method by simply passing in a string, like so: mLogger->WriteEntry("Testing"); Any advice on this would be greatly appreciated.

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  • Types in Haskell

    - by Linda Cohen
    I'm kind of new in Haskell and I have difficulty understanding how inferred types and such works. map :: (a -> b) -> [a] -> [b] (.) :: (a -> b) -> (c -> a) -> c -> b What EXACTLY does that mean? foldr :: (a -> b -> b) -> b -> [a] -> b foldl :: (a -> b -> a) -> a -> [b] -> a foldl1 :: (a -> a -> a) -> [a] -> a What are the differences between these? And how would I define the inferred type of something like foldr map THANKS!

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  • Using variables before include()ing them

    - by phenry
    I'm using a file, page.php, as an HTML container for several content files; i.e., page.php defines most of the common structure of the page, and the content files just contain the text that's unique to every page. What I would like to do is include some PHP code with each content file that defines metadata for the page such as its title, a banner graphic to use, etc. For example, a content file might look like this (simplified): <?php $page_title="My Title"; ?> <h1>Hello world!</h1> The name of the file would be passed as a URL parameter to page.php, which would look like this: <html> <head> <title><?php echo $page_title; ?></title> </head> <body> <?php include($_GET['page']); ?> </body> </html> The problem with this approach is that the variable gets defined after it is used, which of course won't work. Output buffering also doesn't seem to help. Is there an alternate approach I can use? I'd prefer not to define the text in the content file as a PHP heredoc block, because that smashes the HTML syntax highlighting in my text editor. I also don't want to use JavaScript to rewrite page elements after the fact, because many of these pages don't otherwise use JavaScript and I'd rather not introduce it as a dependency if I don't have to.

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  • Error using 'send_file' for ruby/rails - help appreciated

    - by user1653279
    I am trying to create a link to download a file from the file system. For this, I define the following in the "license_helper.rb" file: def license_download_link(license, link_text = nil) if link_text.blank? link_text = image_tag("download_icon.png", :border => 0, :width => 32, :height =>32, :alt => 'Download License', :title => 'Download License') end tempLicenseFile = "tempLicense.xml" File.open("#{tempLicenseFile}", 'w') do |tf| tf.puts license.data end command = "./runLicenseEncoder.bat #{tempLicenseFile}" generateEncryptedLicenseFile = `#{command}` theLicenseFile = "license.xml" link_to link_text, "license/download" end My "view" just calls this helper class: <td><%= license_download_link(license, ' ') %></td> In the 'routes.rb' file, I have defined the following: map.licensedownload "license.xml", :controller = 'licenses', :action = 'download' map.download "/licenses/download", :controller = 'licenses', :action = 'download' In the 'controller', I have 'licenses_controller.rb' which includes the following: def download theLicense = @license licenseFileName = "license.xml" send_file "#{licenseFileName}" , :type => "application/xml", :filename => "#{licenseFileName}" end However, I am unable to obtain the '@license' attribute from the database in the controller. Could someone please let me know what I am doing wrong here and why I am unable to get the value for "@license". Thanks for your time, Regards, --- AJ

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  • Using proxy models

    - by smallB
    I've created Proxy model by subclassing QAbstractProxyModel and connected it as a model to my view. I also set up source model for this proxy model. Unfortunately something is wrong because I'm not getting anything displayed on my listView (it works perfectly when I have my model supplied as a model to view but when I supply this proxy model it just doesn't work). Here are some snippets from my code: #ifndef FILES_PROXY_MODEL_H #define FILES_PROXY_MODEL_H #include <QAbstractProxyModel> #include "File_List_Model.h" class File_Proxy_Model: public QAbstractProxyModel { public: explicit File_Proxy_Model(File_List_Model* source_model) { setSourceModel(source_model); } virtual QModelIndex mapFromSource(const QModelIndex & sourceIndex) const { return index(sourceIndex.row(),sourceIndex.column()); } virtual QModelIndex mapToSource(const QModelIndex & proxyIndex) const { return index(proxyIndex.row(),proxyIndex.column()); } virtual int columnCount(const QModelIndex & parent = QModelIndex()) const { return sourceModel()->columnCount(); } virtual int rowCount(const QModelIndex & parent = QModelIndex()) const { return sourceModel()->rowCount(); } virtual QModelIndex index(int row, int column, const QModelIndex & parent = QModelIndex()) const { return createIndex(row,column); } virtual QModelIndex parent(const QModelIndex & index) const { return QModelIndex(); } }; #endif // FILES_PROXY_MODEL_H //and this is a dialog class: Line_Counter::Line_Counter(QWidget *parent) : QDialog(parent), model_(new File_List_Model(this)), proxy_model_(new File_Proxy_Model(model_)), sel_model_(new QItemSelectionModel(proxy_model_,this)) { setupUi(this); setup_mvc_(); } void Line_Counter::setup_mvc_() { listView->setModel(proxy_model_); listView->setSelectionModel(sel_model_); }

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  • Using C struct without including header file

    - by shams
    My basic problem is that I want to use some structs and functions defined in a header file by not including that header file in my code. The header file is generated by a tool. Since I don't have access to the header file, I can't include it in my program. Here's a simple example of my scenario: first.h #ifndef FIRST_H_GUARD #define FIRST_H_GUARD typedef struct ComplexS { float real; float imag; } Complex; Complex add(Complex a, Complex b); // Other structs and functions #endif first.c #include "first.h" Complex add(Complex a, Complex b) { Complex res; res.real = a.real + b.real; res.imag = a.imag + b.imag; return res; } my_program.c // I cannot/do not want to include the first.h header file here // but I want to use the structs and functions from the first.h #include <stdio.h> int main() { Complex a; a.real = 3; a.imag = 4; Complex b; b.real = 6; b.imag = 2; Complex c = add(a, b); printf("Result (%4.2f, %4.2f)\n", c.real, c.imag); return 0; } My intention is to build an executable for my_program and then use the linker to link up the executables. Is what I want to achieve possible in C?

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  • How to force my method to accept objects from external software?

    - by Roman
    I have a method which needs to take a callback object as an argument and then (at the moment when it's needed) my method will call a specific method of the callback object. I wrote a class called Manager which has a method called addListener. As the argument for this method I need to use a callback object which is defined by the external software. So, I define the addListener in the following way: public void addListener(Listener listener). Of course Eclipse complains because it does not know what Listener is (because the Listener is defined by the external software). The only think that I know (should know) about the Listener is that it has a method called doSomething. So, to pleasure Eclipse I add an interface before my Manager class: interface Listener { void doSomething(); } public class CTManager { ... The problem seems to be solved but then I try to test my software. So, I create a class called test. In this class I create an instance of the Manager class and try to use addListener method of this instance. I also create a class Listener, instantiate it and give the instance to the addListener. And it's the place where the problem appears. Eclipse writes that addListener is not applicable to the given argument. I think it's because it expect something from my Listenr interface but gets something from the Listener class. How can I solve this problem?

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  • Best practice on structuring asynchronous mailers (using Sidekiq)

    - by gbdev
    Just wondering what's the best way to go about structuring asynchronous mailers in my Rails app (using Sidekiq)? I have one ActionMailer class with multiple methods/emails... notifier.rb: class Notifier < ActionMailer::Base default from: "\"Company Name\" <[email protected]>" default_url_options[:host] = Rails.env.production? ? 'domain.com' : 'localhost:5000' def welcome_email(user) @user = user mail to: @user.email, subject: "Thanks for signing up!" end ... def password_reset(user) @user = user @edit_password_reset_url = edit_password_reset_url(user.perishable_token) mail to: @user.email, subject: "Password Reset" end end Then for example, the password_reset mail is sent in my User model by doing... user.rb: def deliver_password_reset_instructions! reset_perishable_token! NotifierWorker.perform_async(self) end notifier_worker.rb: class NotifierWorker include Sidekiq::Worker sidekiq_options queue: "mail" def perform(user) Notifier.password_reset(user).deliver end end So I guess I'm wondering a couple things here... Is it possible to define many "perform" actions in one single worker? By doing so I could keep things simple (one notifier/mail worker) as I have it and send many different emails through it. Or should I create many workers? One for each mailer (e.g. WelcomeEmailWorker, PasswordResetWorker, etc) and just assign them all to use the same "mail" queue with Sidekiq. I know it works as it is, but should I break out each of those mail methods (welcome_email, password_reset, etc) into individually mailer classes or is it ok to have them all under one class like Notifier? Really appreciate any advice here. Thanks!

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  • [c++] - Help about class and error: C3861

    - by Chelsea_cole
    Can someone help me in this error? in "cDef.h" : #pragma once class cDef { public: static int STATE_LOGO; static int STATE_MENU; static int MESSAGE_ENTER; static int MESSAGE_UPDATE; static int MESSAGE_PAINT; static int MESSAGE_EXIT; }; in "GameState.h": #pragma once #ifndef _GameState_ #define _GameState_ #include "cDef.h" class MainGame; class GameState; class GameState { public: MainGame *mg; int GAME_STATE_DEF; virtual void MessengeEnter(int message) = 0; virtual void MessengeUpdate(int message,int keys) = 0; virtual void MessengePaint(int message,CDC *pDc) = 0; void StateHandler(int message,CDC *pDc,int keys); public: GameState(void); public: ~GameState(void); }; #endif in "GameState.cpp": #include "StdAfx.h" #include "GameState.h" GameState::GameState(void) { GAME_STATE_DEF = -1; } GameState::~GameState(void) { } void GameState::StateHandler(int message,CDC *pDc,int keys) { if(message == cDef.MESSAGE_ENTER) { MessageEnter(message); } if(message == cDef.MESSAGE_UPDATE) { MessageUpdate(message,keys); } if(message == cDef.MESSAGE_PAINT) { MessagePaint(message,pDC); } } error: warning C4832: token '.' is illegal after UDT 'cDef' see declaration of 'cDef' error C3861: 'MessageUpdate': identifier not found error C3861: 'MessageEnter': identifier not found error C3861: 'MessagePaint': identifier not found ..... Thanks in advance!

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  • Design by contracts and constructors

    - by devoured elysium
    I am implementing my own ArrayList for school purposes, but to spice up things a bit I'm trying to use C# 4.0 Code Contracts. All was fine until I needed to add Contracts to the constructors. Should I add Contract.Ensures() in the empty parameter constructor? public ArrayList(int capacity) { Contract.Requires(capacity > 0); Contract.Ensures(Size == capacity); _array = new T[capacity]; } public ArrayList() : this(32) { Contract.Ensures(Size == 32); } I'd say yes, each method should have a well defined contract. On the other hand, why put it if it's just delegating work to the "main" constructor? Logicwise, I wouldn't need to. The only point I see where it'd be useful to explicitly define the contract in both constructors is if in the future we have Intelisense support for contracts. Would that happen, it'd be useful to be explicit about which contracts each method has, as that'd appear in Intelisense. Also, are there any books around that go a bit deeper on the principles and usage of Design by Contracts? One thing is having knowledge of the syntax of how to use Contracts in a language (C#, in this case), other is knowing how and when to use it. I read several tutorials and Jon Skeet's C# in Depth article about it, but I'd like to go a bit deeper if possible. Thanks

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  • What does "Select Distinct Null As xxxxx" mean?

    - by Soylent Green
    Background: I am mapping Sybase stored procedure return values to java objects using Spring. For example I map a Sybase datatype of varchar as a String type in Java, and a Sybase datatype of int as an int type in Java, etc. I have come across the following code in one of the stored procedures: SELECT DISTINCT A.Col1 AS val1, A.Col2 AS val2, NULL AS someVal, A.col3 AS val3, ... A.col9 AS val9 FROM #SomeTable A ORDER BY Col2, Col3 I have 2 related questions: What does Null mean in this scenario? I am confused as to what is happening here. I am able to determine the data type of Col1, Col2, etc. of course by looking at the table definition of Table A defined earlier in the stored procedure. Thus I know what datatype I can define in my Java object for val1, val2, etc.. But what about "someVal"? What datatype mapping am I supposed to perform for this Null value? I am fairly inexperienced in SQL. Perhaps the answer is much simpler than I realize.

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  • Friends, templates, overloading <<

    - by Crystal
    I'm trying to use friend functions to overload << and templates to get familiar with templates. I do not know what these compile errors are: Point.cpp:11: error: shadows template parm 'class T' Point.cpp:12: error: declaration of 'const Point<T>& T' for this file #include "Point.h" template <class T> Point<T>::Point() : xCoordinate(0), yCoordinate(0) {} template <class T> Point<T>::Point(T xCoordinate, T yCoordinate) : xCoordinate(xCoordinate), yCoordinate(yCoordinate) {} template <class T> std::ostream &operator<<(std::ostream &out, const Point<T> &T) { std::cout << "(" << T.xCoordinate << ", " << T.yCoordinate << ")"; return out; } My header looks like: #ifndef POINT_H #define POINT_H #include <iostream> template <class T> class Point { public: Point(); Point(T xCoordinate, T yCoordinate); friend std::ostream &operator<<(std::ostream &out, const Point<T> &T); private: T xCoordinate; T yCoordinate; }; #endif My header also gives the warning: Point.h:12: warning: friend declaration 'std::ostream& operator<<(std::ostream&, const Point<T>&)' declares a non-template function Which I was also unsure why. Any thoughts? Thanks.

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  • Is this mingw bug ?

    - by Debanjan
    Hi, I have been trying to execute this program on my migw ,through code::blocks, #include <string.h> #include <math.h> #include <stdio.h> #define N 100 int p[N / 64]; int pr[N]; int cnt; void sieve() { int i,j; for(i=0;i<N;i++) pr[i]=1; pr[0]=pr[1]=0; for(i=2;i<N;i++) if(pr[i]) { p[cnt]=i; cnt++; for(j=i+i;j<=N;j+=i) pr[j]=0; } } int main(){ sieve(); int i; for(i=0;i<cnt;i++) printf("%d ",p[i]); puts(""); printf("Total number of prime numbers : %d",cnt); return 0; } In My system the output is : 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97 Total number of prime numbers : 22 Which is completely insane,since I am completely sure about the implementation of my algorithm. So I decided to try it in Ideone where it gives correct output.Can anybody point out the reason ?

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  • how to achieve functionality of #def of c in PHP

    - by Sabya
    Well, I don't know if thats what I want. But here is my problem: In case of some error I am logging the FILE, CLASS, FUNCTION and LINE in a file. For that I am doing something like: myLog('['. __FILE__ . ']' . '[' . __CLASS__ . ']' . '[' . __FUNCTION__ . ']' . '[' . __LINE__ . ']'); The problem is everywhere I've to repeat that code in the parameter. and If I want to change the format, I've to change everywhere. How can I have something like: myLog(LOG_MSG_FORMAT); With PHP define it is not possible since it will give my the LINE number of the place where that definition is, not where the definition is getting used. Any solution to this is welcome. I am not bitchy about having C like functionality of #def.

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  • C++ Eclipse error class mynamespace::mynamespace

    - by user2969329
    I'm new to C++, coming from a Java and web programming background. I specified a header file, with class definition. The class and the namespace have the same name. I do not know if that causes this issue, eclipse is very unspecific. Here is the World.h file: `/* * World.h * * Created on: 5 nov. 2013 * Author: Mo */ #ifndef WORLD_H_ #define WORLD_H_ #include "../../lib/tinyxml/tinyxml.h" #include "Layer.h" namespace World { class World { private: Layer layers[]; public: World(); virtual ~World(); TiXmlElement toXML(); }; } /* namespace World */ #endif /* WORLD_H_ */` The error occurs in the class definition. The only thing eclipse shows is: class World::World I have been googling for the last day and a half, and haven't found anything similar. In other classes, World is not seen as a type: "World" does not name a type. What have I done wrong? Help would be greatly appreciated.

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  • Why do I have to specify pure virtual functions in the declaration of a derived class in Visual C++?

    - by neuviemeporte
    Given the base class A and the derived class B: class A { public: virtual void f() = 0; }; class B : public A { public: void g(); }; void B::g() { cout << "Yay!"; } void B::f() { cout << "Argh!"; } I get errors saying that f() is not declared in B while trying do define void B::f(). Do I have to declare f() explicitly in B? I think that if the interface changes I shouldn't have to correct the declarations in every single class deriving from it. Is there no way for B to get all the virtual functions' declarations from A automatically? EDIT: I found an article that says the inheritance of pure virtual functions is dependent on the compiler: http://www.objectmentor.com/resources/articles/abcpvf.pdf I'm using VC++2008, wonder if there's an option for this.

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  • C -- Basic Struct questions

    - by Ryan Yu
    So I'm trying to learn C right now, and I have some basic struct questions I'd like to clear up: Basically, everything centers around this snippet of code: #include <stdio.h> #include <stdlib.h> #define MAX_NAME_LEN 127 typedef struct { char name[MAX_NAME_LEN + 1]; unsigned long sid; } Student; /* return the name of student s */ const char* getName (const Student* s) { // the parameter 's' is a pointer to a Student struct return s->name; // returns the 'name' member of a Student struct } /* set the name of student s If name is too long, cut off characters after the maximum number of characters allowed. */ void setName(Student* s, const char* name) { // 's' is a pointer to a Student struct | 'name' is a pointer to the first element of a char array (repres. a string) s->name = name; } /* return the SID of student s */ unsigned long getStudentID(const Student* s) { // 's' is a pointer to a Student struct return s->sid; } /* set the SID of student s */ void setStudentID(Student* s, unsigned long sid) { // 's' is a pointer to a Student struct | 'sid' is a 'long' representing the desired SID s->sid = sid; } I've commented up the code in an attempt to solidify my understanding of pointers; I hope they're all accurate. So anyway, I have a feeling that setName and setStudentID aren't correct, but I'm not exactly sure why. Can someone explain? Thanks!

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  • Is this feasbile with GIS?

    - by Gnu Engineer
    I'm just getting myself to familiarize with GIS but i like to know before hand if the following is feasible with current GIS apps/tools... I get the point for an address by geocoding. Easy part. Now if the point falls within a boundary (may be a city/county/state) then i need to get the data (any id/flag) associated with the boundary. Based on the id/flag i then apply some business logic. My question is... How do i define the boundary? What tools should i use for it? How can i store the boundary definition in database in order to check if the point falls within it? This has to be done in the back end and not in visual maps as we don't intend to show/use maps. How do i associate my custom data (id/flag) with the above boundary definition? Hope i'm having right assumption on capabilities of GIS. Most of examples what i see is around people trying to show maps with data which is exactly not what i'm looking for. Also please suggest me some tools/books on this.

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