Re: Problem with partial specialized member functions

From:
 bjeremy <bjeremy@sbcglobal.net>
Newsgroups:
comp.lang.c++
Date:
Mon, 23 Jul 2007 09:00:57 -0700
Message-ID:
<1185206457.639466.42360@57g2000hsv.googlegroups.com>
Olaf wrote:

int19h@gmail.com schrieb:

On Jul 22, 11:13 pm, Olaf <o...@mdcc.de> wrote:

    class EasyCurl : boost::noncopyable {
    public:
        template<typename T, long ID>
        void setopt(const CurlOption<T, ID>& opt); //L351

    };

and partially specialize the member function

    template<long ID>
    inline
    void EasyCurl::setopt(const CurlOption<bool, ID>& opt) { //L389
        curl_easy_setopt(m_curl, opt.option(), opt.value() ? 1 : 0);
    }

The try to compile results in the error:


The problem is that C++ simply does not allow partial specialization
of functions, but only of classes. The common workaround is to move
the code from the function into a helper template class (so that the
function just delegates any calls to that class), and then specialize
the class.


Do you have an examples of this?

Thanks
Olaf


Usually I like to look at my references since my long term memory is
swiss cheese.. but

//Helper Template class
template <typename T>
struct Type2Type
{
   typedef T OrigType;
};

//Generic Implementation
template <class U, class T>
T* Foo(const U& arg, Type2Type<T>)
{
   return new T(arg);
}

//Partial Specialization
template <class U>
Bar* Foo(const U& arg, Type2Type<Bar>)
{
   return new Bar(arg);
}

// Usage
String* pStr = Foo("Hello", Type2Type<String>());
Bar* pBar = Foo(1, Type2Type<Bar>());

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