[英]Call functor from variadic template
是否可以编写可变参数模板类
template<typename Functor, int... D>
struct Foo
{
void bar()
{
// ???
}
};
相当于
template<typename Functor, int D0>
struct Foo<Functor, D0>
{
void bar()
{
Functor f;
double d0[D0];
f(d0);
}
};
template<typename Functor, int D0, int D1>
struct Foo<Functor, D0, D1>
{
void bar()
{
Functor f;
double d0[D0];
double d1[D1];
f(d0, d1);
}
};
// And so on...
也就是说,传递给函子的参数数量等于模板参数的数量。 参数应在堆栈上分配。
通过std::tuple
在堆栈上跟随参数的版本:
// Helper class to be able to use expansion of std::get<Index>(tuple)
template <int... Is> struct index_sequence {};
// Following create index_sequence<0, 1, 2, .., sizeof...(Is) - 1>
template <int Index, int... Is>
struct make_index_sequence { // recursively build a sequence of indices
typedef typename make_index_sequence<Index - 1, Index -1, Is...>::type type;
};
template <int... Is>
struct make_index_sequence<0, Is...> { // stop the recursion when 0 is reached
typedef index_sequence<Is...> type;
};
template<typename Functor, int... Ds>
struct Foo
{
void bar()
{
bar(typename make_index_sequence<sizeof...(Ds)>::type());
}
private:
template <int... Is>
void bar(index_sequence<Is...>)
{
Functor f;
std::tuple<double[Ds]...> t; // std::tuple<doudle[D0], double[D1], ..>
f(std::get<Is>(t)...); // f(std::get<0>(t), std::get<1>(t), ..);
}
};
那是你要的吗?
template<typename Functor, int... D>
struct Foo
{
template<std::size_t N>
std::array<double, N> create()
{
return std::array<double, N>();
}
void bar()
{
Functor f;
f(create<D>()...);
}
};
也许这可行:
template <typename Functor, int i, int... others>
struct Foo
{
template <typename ...T>
void bar(T ... rest)
{
double d[i];
Foo<Functor, others...> foo;
foo.bar(rest..., d);
}
};
template <typename Functor, int i>
struct Foo<Functor, i>
{
template <typename ...T>
void bar(T ... rest)
{
double d[i];
Functor f;
f(d, rest...);
}
};
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.