傳遞非特模板作爲模板參數

Question

我可以這樣做

template<class Key, class Data, class Compare = less<Key>, template<typename T> class Allocator<T> = allocator<T> > 
    class mymap { 
     typedef map<Key,Data,Compare,Allocator<pair<const Key, Data> > > storageMap; 
     typedef vector<Data,Allocator<Data> > storageVector; 
} 

所以模板傳遞給類unspecialiazed後來實例化。

Answer 1

是的，這裏有一個最小的可編譯例子：

#include <map> 
#include <vector> 
using namespace std; 

template < 
    class Key, 
    class Data, 
    class Compare = less<Key>, 
    template <typename T> class Allocator = allocator 
> 
class mymap 
{ 
public: 
    typedef map<Key,Data,Compare,Allocator<pair<const Key, Data> > > storageMap; 
    typedef vector<Data,Allocator<Data> > storageVector; 
}; 

int main() 
{ 
    mymap<int,long>::storageMap m; 
    mymap<int,long>::storageVector v; 
    return 0; 
} 

Answer 2

是的，這就是所謂的 「模板，模板參數」，並且語法

template <class Key, class Data, class Compare = less<Key>, 
      template <typename T> class Allocator = allocator > 
class mymap { 
    typedef map<Key,Data,Compare,Allocator<pair<const Key, Data> > > storageMap; 
    typedef vector<Data,Allocator<Data> > storageVector; 
}