我有兴趣学习一些关于模板元编程的知识.在下面的代码中,我试图找到一个足够大的无符号整数类型,用于保存在编译时指定的N位,使用一些模板递归.
template <typename T>
struct NextIntegralType
{
};
template <>
struct NextIntegralType<void>
{
typedef unsigned char type;
};
template <>
struct NextIntegralType<unsigned char>
{
typedef unsigned short type;
};
...More type 'iteration' here...
template<size_t BITS, typename T>
struct FindIntegralType2
{
typedef std::conditional<BITS <= sizeof(typename T::type)*8, T, FindIntegralType2<BITS, NextIntegralType<typename T::type>>> _type;
typedef typename _type::type type;
};
template<size_t BITS>
struct FindIntegralType
{
typedef typename FindIntegralType2<BITS, NextIntegralType<void>>::type type;
};
当我声明一个变量并为其赋值时...
FindIntegralType<15>::type test(4000);
我得到以下内容:
error: no matching function for call to ‘FindIntegralType2<15u, NextIntegralType<unsigned char> …