C++ :: Template Method Based On The Type Passed Should Return A Value
Mar 8, 2014
I have a class where a method based on the type passed I should return a value.
prototype declared in the header file:
template <typename T>int getNum() const;
Code of the cpp file:
template <typename T> int class::getNum() const{
int c = 0;
for(int i=0;i<v.size();i++)
if(typeid(*(Pro*)v.at(i)) == typeid(T)) c++;
return c;
}
To invoke the method as I do:
ostream & operator << (ostream & os, Pro & obj) {
return os << obj.getNum();
}
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Apr 29, 2014
I am new to c++ and trying to learn. for instance. i have a struct and method.I am trying to learn what i can do with the method if i define the return type as struct type.
struct S {
int age;
string name;
};
S method() {
//what i can do in here. with the Struct. I mean can i reach members of the struct. etc
}
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Oct 3, 2012
I sew lot of sample for ASP WEB API. In althose link the post method is using
HttpResponseMessage as return tyope
Is it possible to use return type bool in WEB API post method?
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Jul 27, 2012
Is this really the preferred way to get the return type, for use in a derived class, of a function defined in the template parameter?
template<class PARAMETER> class C {
protected:
typedef typeof (reinterpret_cast<PARAMETER*>(0))->function() returntype;
};
This works just fine for me, but seems inelegant.
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Dec 9, 2013
I have this code:
#include <iostream>
#include <vector>
#include <map>
#include <string>
using namespace std;
[Code]...
and it does not compile.
The error is:
test.cpp: In function ‘int main()’:
test.cpp:20:30: error: no matching function for call to ‘func1(std::vector<int>&)’
test.cpp:20:30: note: candidate is:
test.cpp:8:45: note: template<class T, class U> std::map<T, T> func1(U)
test.cpp:8:45: note: template argument deduction/substitution failed:
test.cpp:20:30: note: couldn't deduce template parameter ‘T’
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Mar 29, 2013
I'm writing some functions pertaining to binary trees. I've used recursion once before while learning quicksort but am still quite new and unfamiliar with it. And this is my first time touching a binary tree. So my question: In my addnode function, will the return root statement at the end ever return a value other than the value passed to the function?
Code:
#include <stdlib.h>
struct tnode
{
int data;
struct tnode * left;
struct tnode * right;
}
[code]....
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Oct 12, 2013
Let me put it into the code snippet:
/**
This class build the singleton design pattern.
Here you have full control over construction and deconstruction of the object.
*/
template<class T>
class Singleton
[Code]....
I am getting error at the assertion points when i call to the class as follows:
osgOpenCL::Context *cxt = osgOpenCL::Singleton<osgOpenCL::Context>::getPtr();
I tried commenting assertion statements and then the debugger just exits at the point where getPtr() is called.
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Mar 15, 2015
We're assigned a project working with classes and fractions. My goal is to display a fraction in proper from based on 2 arguments passed to a class member function proper();
My strategy was to utilize the greatest common factor between the 2 arguements, then divide both the numerator and denominator by that number and then it would display.
The program actually runs, but only seems to divide the numerator and not the denominator. This in return makes my other class member functions have incorrect comparisons and sums.
Code:
#include<iostream>
#include<conio.h>
class Fraction {
friend void compare(Fraction a, Fraction b);
friend void sum(Fraction a, Fraction b);
[Code] ....
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Sep 13, 2014
I am supposed to update the value temp without using a return statement, or a global variable. I have never ran across a problem like this before and I am totally stuck. I think I'm missing something really simple and need a hint. Here is the code that was provided for "fixing".
#include "stdafx.h"
#include <iostream>
#include <cstdlib>
using namespace std;
[Code]....
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Feb 24, 2015
How to check the type of argument passed to each function, checktype, in below?.
void checktype(void *p)
{
}
or
template <typename Type>
Type checktype(Type t) {
}
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Jul 8, 2014
Code:
class A {
public:
template<class T>
ObjectsBase* createObject(T* objType, Ogre::String name, Ogre::Vector3 position);
};
template<class T>
ObjectBase* A::createObject(T* objType, Ogre::String name, Ogre::Vector3 position);
My goal is to create any ObjectBase* derived object and return it to class A....
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Aug 1, 2014
Code:
bool CObject<class T>::Create(LPDIRECT3DDEVICE9 pDevice, T *pMesh, float fAnimSpeed) {
if(pMesh == NULL)
return false;
m_pDevice = pDevice;
m_pMesh = pMesh;
if(m_pMesh->GetAnimController() != NULL) {
DWORD dwNumAnimSet = m_pMesh->GetAnimController()->GetMaxNumAnimationSets();
In here, T can be from the class CMesh * or CSkinnedMesh *, both have signature of GetAnimController
This maybe a flaw in my design... But I want Create to accept any kinds of meshes.
Should I create an interface or abstract class above all of those?
I have added an IMesh class that every derived classes has to have the needed interface.
But since then, I have another question, I feel that it is very cumbersome to include a template argument in every class/prototype that is associated with CObject
Say
bool CreatePlanesFromObject(CObject *pObject, D3DXPLANE *pPlanes);
Requires me to do this
template<class T> bool CreatePlanesFromObject(CObject<T>* pObject, D3DXPLANE* pPlanes);
Any ways I can omit the template argument, because it doesn't make sense to know the Mesh type in other classes...
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Jan 22, 2015
PHP Code:
class B {
public:
template<class T>
T foo(){}
};
class D1:public B {
[Code] ....
I have that code piece and would want it to work but it doesn't.
Error "Error2error C2993: 'double' : illegal type for non-type template parameter '__formal' ....
I have no choice and have to use double and float for template typename when specializing. I tried to wrap it up like this
PHP Code:
typedef struct DOUBLE {
DOUBLE(double d){ val = d; }
double val;
};
but it's of no use.
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Nov 28, 2013
I try to make dll and install it under "Component Services". I tried to make method that return string but when i test it i don't get any result :
Code:
STDMETHODIMP CSimpleChat::CellMe(BSTR name, BSTR** helloMessage) {
CString temp = _T("Hi ");
temp += name;
temp += ", welcome to the simple chat server!";
BSTR str = temp.AllocSysString();
*helloMessage = &str;
return S_OK;
}
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Jan 21, 2013
I want to specialize a particular function for Integer datatype inside a class template. My XX.h will be
namespace ZZ {
template <class T>
class XX {
void doSomething(T x);
};
}
provide me XX.cpp which has template specialization for the function doSomething on Integer datatype.
I tried the following in XX.cpp
#include "XX.h"
using namespace ZZ;
template <class T>
void XX<T>::doSomething(T x) {
[Code] ...
But this code is not working.
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Oct 24, 2013
I have been experimenting with variadic templates with the aim of caching a call to a class method by storing away the object pointer, method pointer and parameters. I've actually had some reasonable success but have now hit a stumbling block. I now wish to wrap my parameters in a simple template class when I cache them. My success is as follows:
Using variadic template functions to store these pointers and paremeters;
I'm able to pass a method pointer and unwrapped parametersI'm able to pass wrapped parameters on their own.I'm NOT able to pass a method pointer and wrapped parameters I set up a little prototype project to demonstrate the issue and added comments above the function calls to indicate the compilation results. Here is the code:
Code:
#include "stdafx.h"
//////////////////////////////////////////////////
// Basic class with a simple method
//////////////////////////////////////////////////
class MyClass {
public:
char Method( int i, float f ) {
return 'A';
[code]....
But I'm convinced it should take three arguments, the method pointer and two wrapped parameters. Visual studio even suggested it should as shown below:
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Feb 10, 2013
class IFoo {
virtual void Bar() = 0;
};
class FooAbstract {
virtual void Bar() {}
[Code] .....
How to call the Bar() method from FooTemplate in FooDerived::Bar()?
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Dec 4, 2014
Say I have a GetSomething(char type) function which returns two different variables based on what you pass it, like so:
float Flashlight::GetSomething(char type){
if(type == 'x'){
return velocityX;
} else if(type == 'y'){
return velocityY;
} else {
std::cout << "Debug: Programming error getting flashlight velocity
"; } }
On a scale of null pointers to (insert something notably good), how good or bad is this practice? Just asking out of pure curiosity.
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Sep 27, 2014
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]...
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May 26, 2013
I want my method of the class to take as an input an array of data type derived from class. How can I do this?
Code:
class Planet {
public:
// typedef class Planet PlanetType;
void GetForce(int, PlanetType []);
};
Or when should I define my new data type PlanetType?
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Sep 18, 2014
I got base class called Statistic and inherited classes from it : lsp, cpu, memory. Those methods inheriting some of methods from Statistic and implement also theirself methods. I prepared some new class called ExecuteRequest which is taking Statistic object in the constructor. What i want to achieve is after i put e.g LSP to this class i would like to determinate what specific object it is in this case LSP right? Then having that i would like to put this object to RunRequest method. How can i achieve that? See my code below:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace SOAP_testing {
public class ExecuteRequest
[Code] .....
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Jul 10, 2012
Another fun question... Is it possible to make a type, based on a value ?
What I'm looking for is way to return the smallest (sizeof) unsigned integral type that will hold a certain value.
smallest_type<14>::type // unsigned char
smallest_type<127>::type // unsigned char
smallest_type<255>::type // unsigned char
smallest_type<256>::type // unsigned short
smallest_type<64000>::type // unsigned short
smallest_type<128000>::type // unsigned long
smallest_type<5000000000>::type // unsigned long long
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Apr 10, 2014
Is there a way to use preprocessing to conditionally return different types in a template. More specifically, is there a way to use preprocessing to block out conditional parts of code for one type verse another?
Example of what I can't get to compile for anything but POD types:
template <class T>returnTypeMatching(string inputName,string typeName) {
if(typeName="string") {
cerr<<"string types matched so returning string '"<< inputName <<"'"<<endl;
return inputName;
[Code] .....
If I switch string to long, the implied conversions let it work. I'm imagining there might be some preprocessing way to hide irrelevant conditions. I mean, this code would cause an error to return a string when T=double, so I get why there is a compiler error. However, is there a way to make that part of the code get hidden in that case when the template is processed when T=double?
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Dec 2, 2014
is it possible to define as template the following get functions.
class Config {
public:
enum { NO_ID = 999 };
struct ValueType {
bool a;
size_t b;
std::time_t c;
[code]....
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Mar 22, 2013
I am posting this simplified piece of code that is a bit confusing for me. There are two functions that I call. One shows the expected results but the result of the other one rather puzzles me.
//#define defineVecTyp Vec3f
#define defineVecTyp float
template <typename vecTyp>
vecTyp buildLaplacianPyramid(cv::Mat inputmat) {
vecTyp lapPyr;
[Code].....
Calling the function sum1 does not change the values stored in the variables val1 and val2. The output of the program is as follows:
val1= 1 ## val2= 10 // before the call of function sum1
val1= 1 ## val2= 10 // after the call of function sum1
sumOfVals= 22
This is quite obvious and as expected and I just pasted this piece of code as an example for better clarification.
However, if I call the function buildLaplacianPyramid and apply a function for Gaussian Blurring, this also effects the cv::Mat passed to the function. The line imshow("M1, after buildLaplacianPyramid",M1); therefore shows an image that is blurred. Since I am not passing a pointer to the cv::Mat I do not understand why this should be happening. I was assuming that there would be a copy of the cv::Mat M1 to be used within the function. Therefore I was expecting the cv::Mat M1 to retain its original value. I was expecting that all changes applied to cv::Mat inputmat within the function would not have any influence on the cv::Mat M1. Just like in my other example with the sum.
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Dec 12, 2013
unknownType func( void );
std::vector< /* type of unknownType */ > objects
The source of my question is trying to make a templated button:
template <typename T>
class Button
{
T m_func;
[Code]....
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