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c++classtemplates
mchen
mchen

Reputation: 10156

Templated class: unable to match function definition to an existing declaration

Using MSVC++ 2010, defining a templated class member outside its declaration block:

template <typename T> class cls {
public:
    template <typename T> void bar(T x);
};
template <typename T> void cls<T>::bar(T x) {}

yields:

unable to match function definition to an existing declaration
1>          definition
1>          'void cls<T>::bar(T)'
1>          existing declarations
1>          'void cls<T>::bar(T)'

why?

Upvotes: 3

Views: 6905

Answers (2)

jrok
jrok

Reputation: 55395

If you're intention is for bar to be a member template, then you need this: 

template <typename T> class cls {
public:
    template <typename U> void bar(U x);
};

template<typename T>
template<typename U>
void cls<T>::bar(U x) { }

Note that, the template parameter of the member must not shadow the class template parameter, hence I changed it to U.

Upvotes: 0

David G
David G

Reputation: 96810

You need two template declarations because each construct works on a different template argument:

template <typename P>
template <typename T>
void cls<P>::bar(T x) {}

But it seems to me that bar does not need to be templated at all. Use this instead:

template <typename T>
class cls
{
    public:
        void bar(T x);
};

template <typename T> void cls<T>::bar(T x) {}

Upvotes: 6

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