具有非类型参数的成员函数的部分专业化 [英] Partial specialisation of member function with non-type parameter

问题描述

我有一个同时具有类型和非类型模板参数的模板类.我想对成员函数进行专业化处理，我发现，如下面的示例所示，我可以进行完全的专业化处理.

I have a template class with both a type and a non-type template parameter. I want to specialize a member function, what I finding is, as in the example below, I can do a full specialization fine.

template<typename T, int R>
struct foo
{
    foo(const T& v) :
        value_(v)
    {}

    void bar()
    {
        std::cout << "Generic" << std::endl;
        for (int i = 0; i < R; ++i)
            std::cout << value_ << std::endl;
    }

    T value_;
};

template<>
void foo<float, 3>::bar()
{
    std::cout << "Float" << std::endl;
    for (int i = 0; i < 3; ++i)
        std::cout << value_ << std::endl;
}

但是这种部分专业化不会编译.

However this partial specialization won't compile.

template<int R>
void foo<double, R>::bar()
{
    std::cout << "Double" << std::endl;
    for (int i = 0; i < R; ++i)
        std::cout << value_ << std::endl;
}

有没有一种方法可以实现我正在尝试的任何人都知道的?我在MSVC 2010中尝试过.

Is there a way to achieve what I'm attempting would anyone know? I tried this in MSVC 2010.

推荐答案

您可以将函数包装在类中.

You can wrap the function inside a class.

仅类(而不是函数)可能是部分专用的.

Only classes, not functions, may be partially specialized.

template<typename T, int R>
struct foo
{
    foo(const T& v) :
        value_(v)
    {}

    void bar()
    {
        return bar_impl< T, R >::bar( * this );
    }

    friend struct bar_impl< T, R >;

    T value_;
};

template< typename T, int R >
struct bar_impl {
    static void bar( foo< T, R > &t ) {
        std::cout << "Generic" << std::endl;
        for (int i = 0; i < R; ++i)
            std::cout << t.value_ << std::endl;
    }
};

template<>
struct bar_impl<float, 3> {
static void bar( foo< float, 3 > &t ) {
    std::cout << "Float" << std::endl;
    for (int i = 0; i < 3; ++i)
        std::cout << t.value_ << std::endl;
}
};

template<int R>
struct bar_impl<double, R> {
static void bar( foo< double, R > &t ) {
    std::cout << "Double" << std::endl;
    for (int i = 0; i < R; ++i)
        std::cout << t.value_ << std::endl;
}
};

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