C++ :: Static And Template Sanity Check?
Sep 6, 2013
Can people just do a quick sanity check of this concept?
I'm playing around with a technique to parameterise a template with the largest 'sizeof' result for a set of classes.
A, B, C & D are classes with 1, 2, 3 & 4 members respectively.
e is an instance of E, who's array member is sized according to the largest size of A, B, C or D.
Code:
// MaxSizeOf for four parameters.
template <const size_t S1,
const size_t S2,
const size_t S3 = 0,
const size_t S4 = 0>
struct MaxSizeOf
[code].....
View 11 Replies
ADVERTISEMENT
Mar 1, 2013
I would like to avoid throwing things in constructors as much as possible.
Is this good design to have a static class method that checks arguments the caller will give to the constructor. The documentation of the class will say, thou shall call this method to validate thine arguments before calling the constructor, or else segfault may befall thoust.
View 14 Replies
View Related
Jul 18, 2012
I try to create small project in order to better understand how key word static works with templates . However some compiles errors crush my plan.
1>------ Build started: Project: 4.2b - Ex 1. Static Variable for Array Def Size. Templates, Configuration: Release Win32 ------
1> main.cpp
1>c:all myс++ha level 6solution level 6solution level 64.2b - ex1. static variable for array def size. templatesarray.cpp(40): error C2724: 'Array<Type>:efaultSize' : 'static' should not be used on member functions defined at file scope
[Code] .....
View 7 Replies
View Related
Aug 26, 2014
I need a static hash table to keep track of all objects of a particular type that are instantiated in a Qt application but I have never used a template class as a static member object before and I can't seem to figure out how to initialize it. QHash is the hash table class that follows the template convetion:
template<class key, class data>
QString is probably self explanatory.
Example Header:
class MyClass {
...
private:
static QHash<QString, MyClass*> instanceTable;
}
Here is my source that doesn't compile.
Example Source
#include header.h
// using default constructor for table...
QHash<QString key, MyClass* instance> MyClass::instanceTable(); // gives Error below.
// Error in above line is "Declaration is incompatible with QHash<QString, Myclass*>"
I have tried doing it a number of different ways and none of them work. How do you initialize a static template object?
View 2 Replies
View Related
Apr 18, 2013
class Tracker {
public:
static const int type;
typedef cv_types::CvType<type>::type_t type_t;
};
const int Tracker::type = 1;
gives me the error:
'I' : invalid template argument for 'cv_types::CvType', expected compile-time constant expression
Shouldn't the static const int be a compile time constant?
How would I specify it, so that it works?
PS.: The code works with #define type 1 at the top of the file and without the static const int.
View 3 Replies
View Related
Jan 17, 2013
I have a little problem with template classes and their specialization. Here is a short example:
template <typename T>
struct A{
// some typedefs
[Code]....
The above example is not compiling, because of the assignment of the const static double. Double needs a constructor, but that doesn't work (or seems not to work) with static.
I'm not sure, if it works at all in C++ that way. All I want is a template struct with some typedefs and a constant which is different for different specializations. Don't think it has to be static, but that would be better style, wouldn't it?
View 3 Replies
View Related
Nov 29, 2012
The below code compiles without error using VS 2012 but with g++ 4.1.2 I get this error:
Code:
main.cpp: In function 'int main(int, char**)':
main.cpp:37: error: no matching function for call to 'StringHelper::stringToNumeric(std::basic_string<char, std::char_traits<char>, std::allocator<char> >)'
Here is the code:
#include <string>
#include "boost/lexical_cast.hpp"
using boost::lexical_cast;
using boost::bad_lexical_cast;
class StringHelper {
[Code] ....
This is part of a larger program so in reality StringHelper has more static functions but this example does produce the error the same as the code when in the larger program.
To get it to compile under g++ I had to assign the return value from substr() to a string and pass that string to stringToNumeric. Why do I have to do this for g++ and not VS? Do I have something wrong with my template function that g++ is calling out and VS is not?
View 4 Replies
View Related
Oct 7, 2014
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] ,....
View 1 Replies
View Related
Apr 17, 2013
From my book:
"A static function might have this prototype:
static void Afunction(int n);
A static function can be called in relation to a particular object by a statement such as the following:
aBox.Afunction(10);
The function has no access to the non-static members of aBox. The same function could also be called without reference to an object. In this case, the statement would be:
CBox::Afunction(10);
where CBox is the class name. Using the class name and the scope resolution operator tells the compiler to which class Afunction() belongs."
Why exactly cant Afunction access non-static members?
View 7 Replies
View Related
Sep 11, 2013
What are the workarounds for accessing the non-static member variables of some class(Say A) inside static member functions of another class(Say B)? I am coding in c++. Class A is derived with public properties of class B. Any pointers?
View 7 Replies
View Related
Aug 22, 2014
Have following code:
class Program
{
static void Main(string[] args)
{
[Code]....
My question according to what i just wrote:
1. Is that mean that Do() is only available for use by Dog itself because Dog is 'oryginal' Dog, and if i create new dogs - instances of oryginal Dog (dog1, dog2 ...) they cant access because Do is only available fo 'oryginal' one? Is that correct thinking?
2. If i would want to have something common (e.g value) for all dogs is that good way to create static field/method for Dog instead of non-static once then all instances of Dog would access Dog static member to get/change it? Just stupid example: static method GetAmountOfLegs() which return 4 Then all instances can take/call that value from Dog. Is that correct thinking?
View 2 Replies
View Related
Dec 5, 2013
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 ?
View 6 Replies
View Related
Nov 6, 2013
Error1error C2955: 'DoubleLinkedListInterface' : use of class template requires template argument listdoublelinkedlist.h10
Error2error C2244: 'DoubleLinkedList<T>::DoubleLinkedList' : unable to match function definition to an existing declaration doublelinkedlist.cpp7
Error3 .cpperror C2244: 'DoubleLinkedList<T>::~DoubleLinkedList' : unable to match function definition to an existing declaration 12
.h
#pragma once
#include "DoubleLinkedListInterface.h"
#include "Node.h"
#include <iostream>
[Code]....
View 4 Replies
View Related
Aug 5, 2013
Here is the code,
Code:
class A {
};
A& CreateObject() {
static A a;
return a;
} static A aa;
int main() {
return 0;
}
So is there any difference between a defined in CreateObject and aa?
View 6 Replies
View Related
May 27, 2013
I have a generic template class with another template in one of its types. Now I want to specialize one of its methods for a particular (template) class, which leads to a compile error, however.
Here is the example:
#include <stdio.h>
template<typename Type>
class Obj1 {
public:
void ID() { printf("Object 1, size = %zu
[Code] .....
GCC ends with:
:35:27: error: type/value mismatch at argument 2 in template parameter list for ‘template<class Type, template<class> class O> class Foo’
:35:27: error: expected a class template, got ‘Obj2<Type>’
What is wrong with the specialization? Can it even be achieved and how (if so)?
View 1 Replies
View Related
Nov 2, 2014
how I want the code to look. Only problem is it doesn't work (Line 11). I have some experience with templates but I'm not a pro.
Basically I want the "Channels<3>" to be a type that I can use to specify a Cable with similar to vector<float/int> it would be Cable<Channels<2 or 3>>.
What have I messed up with the syntax?
#include <iostream>
#include <vector>
using namespace std;
[Code].....
View 4 Replies
View Related
Mar 14, 2014
I have a function:
template<class Iterator, class T>
void a(Iterator, Iterator, const T&);
and I want to be able to simplify calls to 'a' with calls like
a(someIteratableContainer);
instead of having to call:
a(someIteratableContainer.begin(), someIteratableContainer.end(), valueOfTheContainersElementType);
I also want to be able to generalize the function to handle any of the standard iteratable contains: array, vector, deque, whatever.
I was under the impression I could write:
template<template<class T> class U> a(U<T>& container) {
a(container.begin(), container.end(), g(T()));
}
where 'g()' returns an object of the element type. However, the compiler is claiming, no matter how I write a call to the overload, the original template is selected and/or the overload is invalid, depending on the various ways I attempt to write said overload.
View 7 Replies
View Related
Nov 17, 2013
[URL]
#include <iostream>
struct Outer {
template<typename T>
void go() {
std::cout << Test<T>::f() << std::endl;
[Code] .....
I have tried several variants on this code to no avail. Outer is in a header, along with the extern template statements, and the specializations after main are in their own cpp file. Main is in a different cpp file.
What do have to do to make this work? I cannot bring the definitions of f() into the header, and they will be different for different template parameters. Ideally, I want Test to remain a private member of Outer, though this can change if it's the only option.
View 1 Replies
View Related
Dec 11, 2014
I have been trying to get a hang on templates. I have the two following functions that that could be consolidated in a single template function:
void Attractor::updateFamilies(FamiliesController *_tmp, int _counter){
center.x = ofGetWidth()/2;
center.y = ofGetHeight()/3;
attractorCounter = _counter;
if(attractorCounter == 1){
[Code] .....
NotesController and FamiliesController have the same parent. The thing that I'm trying to grasp with templates is that is could something like:
template<class TYPE>
void Attractor::updateData(TYPE* *_tmp, int _counter){
center.x = ofGetWidth()/2;
center.y = ofGetHeight()/3;
attractorCounter = _counter;
[Code] ....
And then have another template function declaration for all the attractor functions where I pass the same template value as in the first one.
As you can see, I'm calling another functions inside called attractors(_tmp). I know that one way around it could be to get rid of that function and just do all the logic inside of each if statement. Is there any way to pass the same template function parameter within a template function parameter?
View 2 Replies
View Related
Feb 9, 2015
I have a class like this
PHP Code:
template<class X>
class A {
X m_x;
public:
X* foo();
X* bar();
//others are not related to X
};
I would like to get rid of
PHP Code: template<class X>
For class level but still use it for members. Like this
PHP Code:
class A {
X m_x;
public:
template<class X>
X* foo();
template<class X>
X* bar();
//others are not related to X
};
However, I am still stuck at
PHP Code: X m_x;
View 6 Replies
View Related
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.
View 7 Replies
View Related
Aug 29, 2014
Given:
#include <string>
template <class T>
class basic_container{
[Code] .....
is this possible:
#include "../basic_container/basic_container.hpp"
template <class T>
class container_vector{
[Code] .....
If not, what do I need to do to achieve my goal?
View 1 Replies
View Related
Oct 14, 2013
So, even though the virtual pointer is constant across objects of class why cant it be made as static. Why each derived instance is having the pointer to vtable.
View 4 Replies
View Related
Jun 19, 2014
I have a class where I'm trying to create two static maps. I know I haven't separated the implementation from the declaration. This is how I'm required to program at the moment.
My example class that I'm trying to compile looks like this:
#include <map>
#include <string>
class Foo {
[Code]....
I keep getting compiler errors, though, saying:
invalid use of qualified-name Foo::map1
and
invalid use of qualified-name Foo::map2
I can't initialize these maps explicitly; in my real program they're created by reading in a few different files' data on startup. I need to be able to access the maps throughout my entire application, and I don't want to be required to read in the same data file over and over again.
how static maps can be created properly, or failing that explain another methodology I could use to make them available to my entire application?
View 3 Replies
View Related
Jul 1, 2014
I have the following scenario: I plan to have an xml configuration file.I have a trader that lunch few strategies, each have different configurations. I plan to have all configuration reside in the same file as different nodes.
Now I want that each strategy will hard code the name of node it will loop up for its parameters. Since those paramters are requered for the init and I use DI (configuration are passed in the constructor) I want to make it static.
So this would be something like.
public class Strategy: Base_strategy{
public const string _conf_name = "XXX";
public static string get_conf_name(){
[Code]....
Since other people will code strategies, I want each strategy to implement this static function. I wanted to do this in an interface so that anyone coding new strategy,implementing the base strategy will have to code this static function as part of the contract.
View 5 Replies
View Related
May 2, 2013
I am just wondering what the best practice is for when to use static classes (by static class, I mean a class which has only static attributes and functions).
If you are creating more than one independent object of a particular class, then obviously this should not be static because each object will be the same. But what about the case when you know that you will only ever need one instance of a class? On its own, does this mean that you should create it as a static class?
Personally, I use static class when I want its member attributes and functions to be available globally, which I think is fine. However, I am not sure about the case when I know that only one object will be created - should this be a static class or not?
View 1 Replies
View Related
