[英]C++ variadic template to replace typelist
I would like to utilize variadic templates to replace this below standard typelist code. 我想利用可变参数模板来替换下面的标准类型列表代码。 Also, note, this uses int as the type.
另外,请注意,这使用int作为类型。 I am trying to incorperate strongly typed enums as defined by C++11 so i want to replace the int HEAD with a template parameter type.
我试图加入C ++ 11定义的强类型枚举,所以我想用模板参数类型替换int HEAD。
template <int HEAD, class TAIL>
struct IntList {
enum { head = HEAD };
typedef TAIL tail;
};
struct IntListEnd {};
#define LIST1(a) IntList<a,IntListEnd>
#define LIST2(a,b) IntList<a,LIST1(b) >
#define LIST3(a,b,c) IntList<a,LIST2(b,c) >
#define LIST4(a,b,c,d) IntList<a,LIST3(b,c,d) >
Here is what the road I was trying to go down: 这就是我试图走下去的道路:
template <class T, T... Args>
struct vlist;
template <class T, T value, T... Args>
struct vlist {
T head = value;
bool hasNext() {
if (...sizeof(Args) >=0 )
return true;
}
vlist<T,Args> vlist;
vlist getNext () {
return vlist;
}
};
template <class T>
struct vlist { };
And an example of initializing this I should be similar to the below: 初始化这个的例子我应该类似于下面的:
enum class FishEnum { jellyfish, trout, catfish };
vlist <FishEnum, FishEnum::jellyfish, FishEnum::trout, FishEnum::catfish> myvlist;
I have searched the forums of a good example of a template struct that can accept the type and the type values without luck. 我在论坛上搜索了一个模板结构的好例子,它可以接受类型和类型值而没有运气。 Any suggestions on where to go from here?
关于从哪里去的任何建议? I have pasted my compilation errors below from the above code,
我在上面的代码中粘贴了下面的编译错误,
note: previous declaration 'template<class T, T ...Args> struct vlist' used 2 template parameters
template <class T, T... Args> struct vlist;
^
error: redeclared with 1 template parameter
struct vlist { };
^
note: previous declaration 'template<class T, T ...Args> struct vlist' used 2 template parameters
template <class T, T... Args> struct vlist;
You're missing a number of parameter expansions and specializations for the base template. 您缺少基本模板的许多参数扩展和特化。 One thing to keep in mind: once you have declared the base template, all other templates must be specializations of that base:
有一点要记住:一旦你声明的基础模板,所有其他模板必须是基础的专业 :
// Base template
template <class T, T... Args>
struct vlist;
// Specialization for one value
template <typename T, T Head>
struct vlist<T, Head>
{
T head = Head;
constexpr bool has_next() const { return false; }
};
// Variadic specialization
template <class T, T Value, T... Args>
struct vlist<T, Value, Args...>
{
T head = Value;
constexpr bool has_next() const { return true; }
constexpr vlist<T, Args...> next() const
{
return vlist<T, Args...>();
}
};
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