C++的template模板中class与typename关键字的区别分析

template class Simple;
template class Simple;

template


void add(const T &acontainer, T &sum)
{
  T::const_iterator iter = container.begin();
  for (; iter != container.end(); ++iter) {
    sum += *iter;
  }
}

template


void add(const T &container)
{
  T::const_iterator *x;
  ...
}

template
void add(const T &container, T &sum)
{
  typename T::const_iterator iter = container.begin();
  for (; iter != container.end(); ++iter) {
    sum += *iter;
  }
}

template
class Drived: public Base::Nested { // 基类列表，不要使用typename
public:
  explicit Derived(int x): Base::Nested(x) { // 成员初始化列表，不要使用typename
    typename Base::Nested temp;
    ...
  }
  ...
};

templaet <typename T>void myPrint(const T& t){
  t::const_iterator iter(t.begin());
}

template <typename T>void myPrint(const T& t){
  t::const_iterator * x;
}

template <typename T>void myPrint(const T& t){
  typename t::const_iterator * x;   //这样便不会造成困惑了}

template <typename T>void f(const T& t, typename T::const_iterator cit){
   //T不是嵌套从属名称，而T::const_iterator是，所以要在T::const_iterator前面加上typename    //....}

template <typename T>class Derived: public Base<T>::Nested {         //基类列表中不允许使用typenamepublic:
  explicit Derived(int x): Base<T>::Nested(int x){  //初始化列表中不允许使用typename    typename Base<T>::Nested temp;         //嵌套从属名称(既不在基类列表中又不在初始化列表中)前面必须要加typename  }
}