c++ - 为什么说C++不支持参数多态？

Question

根据 Parametric Polymorphism 的维基百科页面:

Some implementations of type polymorphism are superficially similar to parametric polymorphism while also introducing ad hoc aspects. One example is C++ template specialization.

问题: 为什么说 C++ 只实现表面上类似于参数化多态的东西？特别是，模板不就是完全参数化多态性的一个例子吗？

Answer 1

您链接到的文章解释了这一点。您引用的文本实际上给出了一个将 C++ 模板与纯参数多态性区分开来的示例:C++ 模板特化。

它继续这个主题:

Following Christopher Strachey,^[2] parametric polymorphism may be contrasted with ad hoc polymorphism, in which a single polymorphic function can have a number of distinct and potentially heterogeneous implementations depending on the type of argument(s) to which it is applied. Thus, ad hoc polymorphism can generally only support a limited number of such distinct types, since a separate implementation has to be provided for each type.

因此，如前所述，C++ 模板接近于——但不完全是——参数多态性。