C + + Learning Note template remove_reference (reference removal)

int Main () {  int a[] = {1,2,3};  Decltype (*a) b = a[0];  a[04;   // Output 4  return 0 ;}

The output is 4 because Decltype (*a) returns the type of *a, which is actually a int& we just want to have a way to get rid of this reference.

Try 1

 template <typename t>class   remove_ reference{ public  : typedef T type;};  int   main () { int  a[] = {1 , 2 , 3   }; Remove_reference  <decltype (*a) >::type B = A[0  ]; a[ 0 ] = 4   ; cout  << B; //   output 4,  return  0  ;}  

We introduced the class remove_reference to remove the reference, and during compilation, it was deduced that type T was int&,typedef t type, and that the type was actually a kind int&, so the result is still 4.

Try 2

Template <typename t>classremove_reference{ Public: typedef T type;}; Template<typename t>classRemove_reference<t&>{ Public: typedef T type;};intMain () {intA[] = {1,2,3}; Remove_reference<decltype (*a) >::type B = a[0]; a[0] =4; cout<< b;//Output 1  return 0;} 

We are special to the template class, as a reference, when T is int&, the actual T in the class is int, the function of reference removal is completed.

So we found a way to achieve the mutual transformation between types t,t&,t*, as shown below

Template <typename t>classgettype{ Public: typedef T type; typedef T&Type_ref; typedef T*Type_pointer;}; Template<typename t>class GetType<T&>{ Public: TypeDef typename Remove_reference<T>:: Type type; typedef typename Remove_reference<T>:: Type_ref type_ref; typedef typename Remove_reference<T>:: Type_pointer type_pointer;}; Template<typename t>class GetType<T*>{ Public: TypeDef typename Remove_reference<T>:: Type type; typedef typename Remove_reference<T>:: Type_ref type_ref; typedef typename Remove_reference<T>:: Type_pointer type_pointer;};

C + + Learning Note template remove_reference (reference removal)