没有<>的模板方法实现

Question

我在class中有一个模板方法：

template<class T>
    A& doSomething(T value)

那我有一个实现

template<class T>
    A& A::doSomething(T value){
        // do something with value
        return *this;
    }

然后我有一个专业化让我们说 bool

template<>
    A& A::doSomething(bool value){
        // do something special with value of type bool
        return *this
    }

这是我的理解，现在在代码中有这样的东西，我不知道是什么意思：

template A& A::doSomething(char const*);
template A& A::doSomething(char);
template A& A::doSomething(int);
template A& A::doSomething(int*);
template A& A::doSomething(double);
...

模板最后 5 行的确切含义是什么？

谢谢

Answer 1

这几行不是实现。对于类型 char const*、char、int、int * 和 double

template A& A::doSomething(char const*);
template A& A::doSomething(char);
template A& A::doSomething(int);
template A& A::doSomething(int*);
template A& A::doSomething(double);

Answer 2

它是Explicit instantiation，它强制使用指定的模板参数实例化模板，并阻止它们的隐式实例化。

An explicit instantiation definition forces instantiation of the function or member function they refer to. It may appear in the program anywhere after the template definition, and for a given argument-list, is only allowed to appear once in the program.

An explicit instantiation declaration (an extern template) prevents implicit instantiations: the code that would otherwise cause an implicit instantiation has to use the explicit instantiation definition provided somewhere else in the program.

并查看 Explicit instantiation - when is it used?

^{因为你标记了c++03，请注意链接页面中提到的extern template是从c++11引入的。}

没有<>的模板方法实现

Template method implementation without <>

c++

templates

gcc

c++03