Specialization and overload

本文对C++的两种static polymorphism方式:

1、specialization

2、overload

进行探讨。

Full specialization and partial specialization

参见 Template-specialization 章节。

Function specialization and function overload

在 Function-template 章节对此进行了深入讨论。

准确表达overload and specialization

C++的语法是比较冗杂的，有时候稍微的差异，表达的含义却是天差地别，这一点在template + overload的时候尤其明显，下面结合如下两篇文章中的内容进行说明：

1、stackoverflow Template Specialization VS Function Overloading

2、accu An introduction to C++ Traits

stackoverflow Template Specialization VS Function Overloading

NOTE: 其中给出了如下例子:

#include <iostream>
template <typename T> void foo(T)
{
    std::cout<<"foo(T)"<<std::endl;
}
template <typename T> void foo(T*) // overload of foo(T)
{
    std::cout<<"foo(T*)"<<std::endl;
}
template <> void foo<int>(int*) // specialisation of foo(T*)
{
    std::cout<<"foo(int*)"<<std::endl;
}

int main()
{
foo(new int); // calls foo<int>(int*);
}

#include <iostream>
template <typename T> void foo(T)
{
    std::cout<<"foo(T)"<<std::endl;
}
template<> void foo<int*>(int*) // specialisation of foo(T)
{
    std::cout<<"foo<int*>(int*)"<<std::endl;
}
template<typename T> void foo(T*) // overload of foo(T*)
{
    std::cout<<"foo(T*)"<<std::endl;
}

int main()
{
foo(new int); // calls foo<int>(int*);
}

accu An introduction to C++ Traits

NOTE: 其中给出的例子

is_pointer

Now, while fully specialized templates are useful and in my experience, the most common sort of trait class specialization, I think that it is worth quickly looking at partial specialization, in this case, boost::is_pointer [boost]. Again, a default template class is defined:

template< typename T > 
struct is_pointer{ 
  static const bool value = false; 
};

And a partial specialization for all pointer types is added:

template< typename T > 
struct is_pointer< T* >{ 
  static const bool value = true; 
};

简而言之：

1、template< typename T > struct is_pointer

2、template< typename T > struct is_pointer< T* >//partial specialization