c – 专门化模板别名的最佳方式(或解决方法)

如果为运算符定义了一个基类,那么它有一个结果typedef(我已经决定使用整数包装器,如std :: integral_constant作为值而不是原始整数值,以便在库中提供统一的接口),以及n-ary运算符基类,检查运算符是否至少有一个操作数：

template<typename RESULT>
struct operator
{
    using result = RESULT;
};

template<typename RESULT,typename... OPERANDS>
struct nary_operator : public operator<RESULT>
{
    static_assert( sizeof... OPERANDS > 0,"An operator must take at least one operand" );
};

所以我为一元和二元运算符定义了别名：

template<typename OP,typename RESULT>
using unary_operator = nary_operator<RESULT,OP>;

template<typename LHS,typename RHS,typename RESULT>
using binary_operator = nary_operator<RESULT,LHS,RHS>;

该操作符接口用于将自定义运算符定义为别名,如下面的比较运算符：

template<typename LHS,typename RHS>
using equal = binary_operator<LHS,RHS,bool_wrapper<LHS::value == RHS::value>>;

template<typename LHS,typename RHS>
using not_equal = logical_not<equal<LHS,RHS>>;

template<typename LHS,typename RHS>
using less_than = binary_operator<LHS,bool_wrapper<LHS::value < RHS::value>>;

template<typename LHS,typename RHS>
using bigger_than = less_than<RHS,LHS>;

template<typename LHS,typename RHS>
using less_or_equal = logical_not<bigger_than<LHS,typename RHS>
using bigger_or_equal = logical_not<less_than<LHS,RHS>>;

现在假设我们想为我们自己的类实现我们的自定义相等运算符.例如：

template<typename X,typename Y,typename Z>
struct vec3
{
    using x = X;
    using y = Y;
    using z = Z;
};

如果相等运算符是继承的,而不是别名,则可以通过模板专门轻松完成：

//Equaity comparator implemented through inheritance:
template<typename LHS,typename RHS>
struct equal : public binary_operator<LHS,bool_wrapper<LHS::value == RHS::value>> {};

//Specialitation of the operator for vec3:

template<typename X1,typename Y1,typename Z1,typename X2,typename Y2,typename Z2>
struct equal<vec3<X1,Y1,Z1>,vec3<X2,Y2,Z2>> : public binary_operator<vec3<X1,Z2>,bool_wrapper<X1 == X2 && Y1 == Y2 && Z1 == Z2>> {};

我知道template alias cannot be specialized.
我的问题是：是否有一种方法,即不使用继承dessign而不是模板别名来专门化这种模板别名？