I want to have a template function that is a member of a class. Is this possible? This code snippet is how I would think the syntax would go, although it doesn't compile. How would I achieve the same effect?
Code:
class myclass {
public:
int member ;
} ;
template <typename T> void myclass::func( T& arg )
[Code] .....
When I do this:
// header file:
#include <list>
using namespace std;
class myClass {
list<int> myMethod();
};
// cpp file:
list<int> myClass::myMethod() {
}
In the cpp file, 'myMethod' is underlined in red and when I hover over it, it says:
"std::list<int, std::allocator<int>> myClass::myMethod()
Error: declaration is incompatible with "<error-type> myClass::myMethod()""
But when I make it as a standalone function, outside a class, with no pre-declaration, there is no problem.
How to initialize a static member of a class with template, which type is related to a nested class?
This code works (without nested class):
#include<iostream>
using namespace std;
struct B{
B(){cout<<"here"<<endl;}
};
template<typename Z>
[Code] ,....
I just happened to find that a nested private template class can be accessed directly outside the enclosing class using a using alias:
namespace ns {
class __wrapper
{
private:
[Code].....
I was hoping to see a "__wrapper::__tklass is private" error message in the first using statement as well as during the instantiation of ns::tklass, but no error is issued. I tried this on gcc-4.9.2, clang-3.5.0 and visual_studio 2013 express.
why exactly doesn't the compiler flag tklass as an error? Is it allowed by the standard? If so, wouldn't that be a serious access violation?
This week we are learning to use templates, and I don't understand how to call my member functions with my template based class. I tried the standard convention of calling member functions, but I keep getting an error saying name following"::" must be a class or namespace name. I'm thinking my problem lies with my typename T, but I am unsure. Line 16 is where I am getting tripped up.
#include "stdafx.h"
#include <iostream>
#include <string>
using namespace std;
template<class T>
T Set
{
public:
[Code]...
I'm trying to implement a simple template array class, but when i came into the operator< i actually have to use a template :
my code is something like :
template<typename _Type, std::size_t _Size>
class array {
public :
[Code] ......
but i am having an error of shadows template param 'class _Type' is it w/ the name conflict between the array template parameter and the function template parameter ?
How can a member function in my derived class call the same function from its base class?
View 1 Replies View RelatedI am writing a program which is using SDL library. I have two different classes which one of them is Timer Class and the other is EventHandling Class.
I need to use some member functions and variables of Timer in some Eventhandling Class member functions, Although I want to define an object of Timer in int main {} and relate it to its member function that has been used in Eventhandling member function in order that it becomes easier to handle it, I mean that I want to have for example two objects of timer and two objects of Eventhandling class for two different users.
I do not know how to relate an object of a class from int main{} to its member function which is being used in another class member function.
Lets have it as a sample code:
class Timer {
private:
int x;
public:
Timer();
get_X();
start_X();
[Code] ....
i want to use a class to print data stored as vector or array with different data types. i also want the print function two take more than one vector or array or combination of both so that they can be written to file as two columns. so i wrote the following class:
right now it has only one member function for printing two vectors. later i'll add additional functions as required.
note: there has to be template functions inside the class
i also want the object to be global so that i need not pass it as an argument to other calling functions
class printdata
{
public:
template<typename T1,typename T2>
void SaveData( vector<T1> &data1,vector<T2> &data2, std::string var)
{
[Code]....
then i want to call this template function in another ordinary function written in a seperate cpp file
these function declarations are put in a header file. so i need know whether i should put the declaration of the template function in the header to use the function in different functions
i want to use a class to print data stored as vector or array with different data types.
i also want the print function two take more than one vector or array or combination of both so that they can be written to file as two columns.so i wrote the following class:
right now it has only one member function for printing two vectors. later i'll add additional functions as required.
note: there has to be template functions inside the class / i also want the object to be global so that i need not pass it as an argument to other calling functions
class printdata {
public:
template<typename T1,typename T2>
void SaveData( vector<T1> &data1,vector<T2> &data2, std::string var){
std::ofstream myfile;
std::string filename;
[code].....
then i want to call this template function in another ordinary function written in a seperate cpp file these function declarations are put in a header file. so i need know whether i should put the declaration of the template function in the header to use the function in different functions.
I have this class templates And This UML.I have to write this function +operator=(source: Array<ElemType, SIZE>): Array<ElemType, SIZE> but I do not know how to start the declaration / or start the function. I have to return a template but I do not know how to do it,
UML
Array<ElemType, SIZE>
-elements: ElemType[SIZE]
+Array()
+Array(source: Array<ElemType, SIZE>)
+operator=(source: Array<ElemType, SIZE>): Array<ElemType, SIZE>
+operator==(other: Array<ElemType, SIZE>): Boolean
+operator!=(other: Array<ElemType, SIZE>): Boolean
<<L-value>>+operator[](index: Integer): ElemType
<<R-value>>+operator[](index: Integer): ElemType
[code]....
I want to use a template function of a class.
This is my code:
#include "Comparison.h"
#include <iostream>
using namespace std;
int main(int argc, char** argv) {
Comparison c;
[Code] ....
But I get the error message:
main.cpp:10: undefined reference to `int Comparison::max<int>(int, int)'
I mount a function (parameter - numeric vector; returns a string). However, this same function is used in several classes. To avoid that I keep duplicating the same code within these classes there is a way to do that as the code below?
std::string func( const vector<int> vec ) {
//processamento
return result;
} class A {
[Code] ....
whether i can define a member function inside a class or not in C++. Is the following code is legal?
#include<iostream> using namespace std;
class adder {
private:
int a;
int b;
int c;
int answer;
public:
[code]....
Firstly, is it legal to overload a template function in a class? This is what I did
class FILE_txt
{
public:
FILE_txt(const char* );
[Code]....
I have encountered following lines in base class and I do not comprehend its meaning of "= 0" at the end of the member functions;
distance_list intersect(ray & r) = 0;
appearance get_appearance(vector & pt) = 0;
where distance_list is a list of doubles and appearance is properties.
In general, what does this "equal sign and 0 " mean for the member functions in the base class?
I keep getting an error saying ui.h:30: error: 'class BTree<Word>' has no member named 'prntInOrder'
I have no line 30 in my ui.h but if i count the lines from the .cpp as if they were attached to the .h i find the call to the BTree printInOrder()
here is my ui.h
Code:
#pragma once
#include "btree.h"
#include <fstream>
#include <iostream>
using namespace std;
[Code].....
As you can see the printInOrder() function is there so would it not see it?
Error:
Code:
ui.h: In member function 'void UI::go(std::string)':
ui.h:30: error: 'class BTree<Word>' has no member named 'printInOrder'
When we use a function template, we use a function template like a regular function, for example,
Code:
template<class T>
void foo(T t1, T t2)
{
}
foo(1,3);
Based on the arguments passed to foo, the compiler can deduct the type T. But on the other hand, when we use a class template, we always need to specify the type, for example,
Code:
template<class T>
struct sum {
static void foo(T t1, T t2)
{
}
};
sum<int>::foo(1,3);
Here we can't call sum::foo(1,3), otherwise we get compiler errors. My question is why the compiler can't deduct the type based on the arguments passed to foo? In addition, if we call function template foo like this,
Code:
foo(1, '3');
Then we get compiler errors. We need to specify the type like foo<int>(1.'3'). Since '3' can be always treated as integer, why we need to specify the type here?
I have a class I am building called date and I've built all my functions to run and done all the necessary error checking in each function. However, my last and final function I have to write is where the # of days passed in as a parameter and then I have to increment the days by that many. And if the user does not increment any days at all in the parameter and leaves it blank, then it automatically increments by one day. I am having trouble with this. So for example if the user was to do this:
Date d1(10, 31, 1998); // Oct 31, 1998
Date d2(6, 29, 1950);// June 29, 1950
d1.Increment(); // d1 is now Nov 1, 1998
d2.Increment(5);// d2 is now July 4, 1950
The function starts out looking like this
void Date::Increment(int numDays = 1) {
}
I know I have to use a for loop to accomplish this. I just don't know how to get it to where the days passed in will go to the next month and then days passed in would go to the next year.
I have the following problem: I am using NLOpt for optimization. The API provides functions to set the objective. This is done as follows:
double objective(const vector<double> &x, vector<double> &grad, void *data)
{
return x[1]*x[0];
}
int main(){
nlopt::opt opti(nlopt::LD_MMA,2);
opti.set_min_objective(objective,NULL);
vector<double> x(2);
[Code]....
Now I want to make the function objective a member of a class:
class Foo {
public:
double objective(...){..}
};
How can I give this method to opti.optimize? If I make objective static I can use
opti.optimize(Foo::objective,NULL);
but I do not want to have a static member. Is it possible to create an object of type Foo and give it to opti.optimize?
Some background: I have a class, A, with members, B and C and D; I also have an array of A objects; I want to be able to have a function which takes said array and performs a certain calculation on either the B, C, or D members of each of the A objects, depending upon certain circumstances; I want to perform the same calculation regardless of which member is to be used in said calculation, such as always assigning the value 3 or multiplying the member's value by a cofactor of some sort.
My question, therefore, is: how I might do this using only one function be it a template or not?
In C++, how do i call a method member of class A from a class B, using a pointer. By the way Class A and B are of different types.
I read that when a pointer is pointing to member function it can only point member functions within the class. But how can i point to a member function outside the class.?????
for example
class A {
public:
int add(int x) {
return x+x;
[Code] .....
Usually we use the following statements to export a class or member functions,
Code:
#ifdef DLLMICRO
#define DLLIO __declspec(dllexport)
#else
#define DLLIO __declspec(dllimport)
#endif
I understand that the files using the exported class or function need to call this class or function with dllimport and the file containing the exported class or function needs to call this class or function with dllexport. But I tried to use __declspec(dllexport) only instead of the statements above. It still works. Is there anything I am missing?Why'd we have to switch between dllexport and dllimport?
I have a simple question about inheritance. Consider the following code:
Code:
Class Base {
int type;
Base(){};
};
Class Derived1 : public Base
[Code] ....
I get the following error: Class "Base" has no member "Function1";
That makes sense - as Base has not declared Function1. But how can I loop through a vector of Bases, and then if the object is of type Derived1, call the function Function1?
I have in the past written code for templated functions where one function argument can be either a function pointer or a Functor. Works pretty straightforward.
Now I am in a situation where I am actually trying to pass a function pointer as template argument to a class. Unfortunately this does not work, I can pass the Functor class but not the function pointer. Below code illustrates the issue:
Code:
#include <string>
#include <iostream>
#include <sstream>
#include <cstdlib>
// For demonstration
const char * external_library_call() {
return "FFFF";
[Code] .....
The idea is to have the definition of the Record class simple and readable and have a maintainable way to add auto-conversion functions to the class. So the lines I commented out are the desirable way how I want my code to look. Unfortunately I could not come up with any way that was close to readable for solving this.
I'm currently programming a server which uses multiple threads- I have a class for one map in the game. Each map has a thread for timed events(tile regeneration, NPC regeneration, etc.), and a thread for handling NPCs(movement, combat, etc.). A basic structure of the class looks like this:
class Region {
public:
/* game values are here, they are public so
they can be accessed from outside of the class
inside of packet-handling functions and such */
int value;
void *Function();
[Code] ....
The program crashes when I use a member of the same class the function is located in- in the context I have shown about it would crash on "value++".