CODEWITHSUNDEEP
c++templates
Kevin217
Kevin217

Reputation: 752

C++ - Definition of A Member of A Class Template

I have a template class listmap with a member called iterator. 

template <typename Key, typename Value, class Less = xless<Key>>
class listmap {
public:
   class iterator;
   //...
}

The definition for iterator is out of list map as follows,

template <typename Key, typename Value, class Less = xless<Key>>
class listmap<Key, Value, Less>::iterator {
//...
}

less is a template class for comparison,

template <typename Type>
struct xless {
   bool operator() (const Type& left, const Type& right) const {
      return left < right;
   }
};

I'm just running a simple test to see whether it works, but it gives me this error

cannot add a default template argument to the definition of a member of a class template

My understanding of template is very low. Why can't I use xless in definition of iterator here?

Upvotes: 0

Views: 70

Answers (1)

James Adkison
James Adkison

Reputation: 9602

In your class declaration for listmap you provide a default for the last template type (i.e., class Less = xless<Key>).

In your definition of the iterator you specify the default again, remove it.

template <typename Key, typename Value, class Less>
//                                      ^^^^^^^^^^
class listmap<Key, Value, Less>::iterator
{
    //...
}

Upvotes: 2

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