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c++templatesparameter-passingtypename
Sandlord
Sandlord

Reputation: 89

C++ Passing a tempate typename class as function parameter

I need to pass a template class as parameter to a function but i can retrieve the typename inside the function for initialize a temporal variable

the class is declared as follows:

template <typename Type> class ListIndex_Linked

here is the inicialization of the class in the main and the call of the function

ListIndex_Linked<std::string> L;
insertion(L);

and what i'm trying to do

template <class list <typename Type>>
void insertion( list<Type>& L ) 
{
    Type& temp = L.get(0); 
    {
        int max = L.numElem();
        for ( int i = 1, ; i < max; i++ )
        {

        }
    }
}

but i get this error:

error: 'list' is not a template
void insertion( list<Type>& L )
             ^

thanks in advance for the help

Upvotes: 5

Views: 4865

Answers (3)

Jarod42
Jarod42

Reputation: 218323

An other way is to use auto to not mandate Type:

template <typename Container>
void insertion(Container& L ) 
{
    auto& temp = L.get(0); 
    {
        int max = L.numElem();
        for ( int i = 1, ; i < max; i++ )
        {

        }
    }
}

There is also the typedef inside Container which may help, something like

typename Container::reference temp = L.get(0); // or Container::value_type&

which requires something like:

template <typename Type>
class ListIndex_Linked
{
public:
    using value_type = Type;
    using reference = Type&;
    // ...
    // Your code
};

Upvotes: 1

songyuanyao
songyuanyao

Reputation: 173044

You're not declaring list as a template template parameter correctly.

template <template <typename> class list, typename Type>
void insertion( list<Type>& L ) 
{
  ...
}

Reference: http://en.cppreference.com/w/cpp/language/template_parameters

Upvotes: 6

juanchopanza
juanchopanza

Reputation: 227608

If insertion is only supposed to work with ListIndex_Linked, then you can write it as a template in terms if the list's template parameter:

template <typename Type>
void insertion(ListIndex_Linked<Type>& L) 
{
  ...
}

Otherwise, you can use template template parameters:

template<template<class> class List, class Type>
void insertion(const List<Type>& L)
{
  ...
}

Upvotes: 3

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