Introduction

Compile time restricted templates are a powerful tool for creating efficient and reusable code. They allow developers to create templates that can be used in multiple contexts, while still ensuring that the code is optimized for the specific context in which it is used. This article will discuss how to create compile time restricted templates without the use of the Boost library. We will look at the advantages of using compile time restricted templates, and how to implement them without the use of Boost. Finally, we will discuss some of the potential pitfalls of using compile time restricted templates.

Solution

// Solution

#include

template
class CompileTimeRestrictedTemplate
{
private:
T data[N];

public:
CompileTimeRestrictedTemplate()
{
for (int i = 0; i < N; i++) data[i] = 0; } T& operator[](int index) { if (index < 0 || index >= N)
throw std::out_of_range(“Index out of range”);
return data[index];
}
};

int main()
{
CompileTimeRestrictedTemplate arr;
arr[0] = 10;
arr[9] = 20;
std::cout << arr[0] << " " << arr[9] << std::endl; return 0; }

#include <iostream>
#include <type_traits>

using namespace std;

template <typename T> class remove_all_pointers{
public:
    typedef T type;
};

template <typename T> class remove_all_pointers<T*>{
public:
    typedef typename remove_all_pointers<T>::type type;
};

template <typename T> class remove_all_pointers<T* const>{
public:
    typedef typename remove_all_pointers<T>::type type;
};

template <typename T> class remove_all_pointers<T* volatile>{
public:
    typedef typename remove_all_pointers<T>::type type;
};

template <typename T> class remove_all_pointers<T* const volatile >{
public:
    typedef typename remove_all_pointers<T>::type type;
};


class OverVoid{
public:

    static bool isOverVoid (){
    return true;
    }
    virtual ~OverVoid(){
    }
};

class Meta: public OverVoid{

};

class Physical{
public:

};

template<typename T, typename = typename std::enable_if<std::is_base_of<OverVoid, typename remove_all_pointers<T>::type>::value>::type>
class Move{
public:
    Move()
    {
        cout<<"### "<<remove_all_pointers<T>::type::isOverVoid()<<endl;
    }
};

/*
template<typename T,typename = typename std::enable_if<std::is_base_of<OverVoid, typename remove_all_pointers<T>::type>::value>::type>
class Move{
public:
    Move()
    {
        cout<<"### "<<remove_all_pointers<T>::type::isOverVoid()<<endl;
    }
};

template<typename T, typename = typename std::enable_if<std::is_base_of<OverVoid, typename remove_all_pointers<T>::type>::value>::type>
class Move{
public:
    Move()
    {
        cout<<"### "<<remove_all_pointers<T>::type::isOverVoid()<<endl;
    }
};
*/

int main(){
    Move<Meta***> z;
    Move<Meta**> w;
    Move<Meta*> x;
    Move<Meta> y;
}

Compile Time Restricted Templates Without Boost

Templates are a powerful tool in C++, allowing for code reuse and flexibility. However, they can also be difficult to manage, especially when dealing with compile-time restrictions. Fortunately, there are ways to restrict templates without using the Boost library.

Using Static Assertions

The most straightforward way to restrict templates is to use static assertions. These are assertions that are checked at compile-time, and can be used to ensure that a template is only used with certain types. For example, if you wanted to restrict a template to only accept integral types, you could use a static assertion like this:

template <typename T>
void foo(T t)
{
    static_assert(std::is_integral<T>::value, "T must be an integral type");
    // ...
}

This will cause a compile-time error if the template is used with a non-integral type. This is a simple and effective way to restrict templates.

Using SFINAE

Another way to restrict templates is to use SFINAE (Substitution Failure Is Not An Error). This is a technique that allows you to selectively enable or disable certain template specializations based on certain criteria. For example, if you wanted to restrict a template to only accept integral types, you could use a SFINAE expression like this:

template <typename T>
typename std::enable_if<std::is_integral<T>::value, void>::type
foo(T t)
{
    // ...
}

This will cause the template to be disabled if the type is not an integral type. This is a more advanced technique, but it can be useful in certain situations.

Conclusion

Templates can be difficult to manage, especially when dealing with compile-time restrictions. Fortunately, there are ways to restrict templates without using the Boost library. Static assertions and SFINAE are two techniques that can be used to restrict templates in a safe and effective manner.