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CRTP pattern doesn't trigger full template instantiation


By : Guillaume Aubert
Date : September 14 2020, 10:00 PM
seems to work fine I've created a template class which triggers a runtime text output whenever an instantiation of it occurs: , Your CRTP usage falls under implicit instantiation:
code :
template<typename T>
struct base
{
    inline static verbose<T> v;
    base() { (void)&v; }
};


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C++ CRTP(template pattern) question


By : user2000850
Date : March 29 2020, 07:55 AM
Any of those help In CRTP the base class template take advantage of the fact that member function bodies (definitions) are not instantiated until long after their declarations. In your code the base class depends on incomplete type.

What is the curiously recurring template pattern (CRTP)?


By : Saul Gutierrez
Date : March 29 2020, 07:55 AM
hop of those help? In short, CRTP is when a class A has a base class which is a template specialization for the class A itself. E.g.
code :
template <class T> 
class X{...};
class A : public X<A> {...};
template <class ActualClass> 
class Singleton
{
   public:
     static ActualClass& GetInstance()
     {
       if(p == nullptr)
         p = new ActualClass;
       return *p; 
     }

   protected:
     static ActualClass* p;
   private:
     Singleton(){}
     Singleton(Singleton const &);
     Singleton& operator = (Singleton const &); 
};
template <class T>
T* Singleton<T>::p = nullptr;
class A: public Singleton<A>
{
   //Rest of functionality for class A
};
template<class Derived>
class Equality
{
};

template <class Derived>
bool operator == (Equality<Derived> const& op1, Equality<Derived> const & op2)
{
    Derived const& d1 = static_cast<Derived const&>(op1);//you assume this works     
    //because you know that the dynamic type will actually be your template parameter.
    //wonderful, isn't it?
    Derived const& d2 = static_cast<Derived const&>(op2); 
    return !(d1 < d2) && !(d2 < d1);//assuming derived has operator <
}
struct Apple:public Equality<Apple> 
{
    int size;
};

bool operator < (Apple const & a1, Apple const& a2)
{
    return a1.size < a2.size;
}
int main()
{
    Apple a1;
    Apple a2; 

    a1.size = 10;
    a2.size = 10;
    if(a1 == a2) //the compiler won't complain! 
    {
    }
}

multiple curiously recurring template pattern (CRTP) in c#?


By : Evan Farmer
Date : March 29 2020, 07:55 AM
will be helpful for those in need Im trying to implement CRTP interface to my code, but the constraint make me stuck. how to implement the constraints if i have code structure look like this? Is this legal? Thank you.
code :
 public abstract class MyBase
{
    /// <summary>
    /// The my test method. divyang
    /// </summary>
    public virtual void MyVirtualMethodWhichIsOverridedInChild()
    {
        Console.Write("Method1 Call from MyBase");
    }

    /// <summary>
    /// The my another test method.
    /// </summary>
    public abstract void MyAnotherTestMethod();

    /// <summary>
    /// The my best method.
    /// </summary>
    public virtual void MyVirualMethodButNotOverridedInChild()
    {
        Console.Write("Method2 Call from MyBase");
    }
}
public abstract class CrtpBaseWrapper<T> : MyBase
    where T : CrtpBaseWrapper<T>
{
}
public class CrtpChild : CrtpBaseWrapper<CrtpChild>
{
    /// <summary>
    /// The my test method. divyang
    /// </summary>
    public override void MyVirtualMethodWhichIsOverridedInChild()
    {
        Console.Write("Method1 Call from CrtpChild");
    }

    /// <summary>
    /// The my another test method.
    /// </summary>
    public override void MyAnotherTestMethod()
    {
        Console.Write("MyAnotherTestMethod Call from CrtpChild");
    }
}

Force explicit template instantiation with CRTP


By : sherry
Date : March 29 2020, 07:55 AM
should help you out You could pass the variable as a reference template argument. Then the object is needed which causes an instantiation
code :
template <typename T, T /*unnamed*/>
struct NonTypeParameter { };

template <typename T>
class InitCRTP
{
public:
     static InitHelper init;
     typedef NonTypeParameter<InitHelper&, init> object_user_dummy;
};

Is the Curiously Recurring Template Pattern (CRTP) the right solution here?


By : user2276382
Date : March 29 2020, 07:55 AM
this one helps. Scenario , How about the other way:
code :
template <typename ...Ts>
class Logger : private Ts...
{
public:
    using Ts::write...;

    void write(int x) { /*...*/ }
    void write(double x) { /*...*/ }
    // ...

    template <typename T>
    void writeLine(T x) { write(x); /*...*/ }
    // ...
};

class FooWriter
{
public:
    void write(FooType1 x) { /*...*/ }
    void write(FooType2 x) { /*...*/ }
};
using FooLogger = Logger<FooWriter>;
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