c++ template(7-1)模板参数声明

 

一.联合体可以使用模板

template <typename T> 
union AllocChunk { 
    T object; 
    unsigned char bytes[sizeof(T)]; 
}; 

二.函数默认缺省调用实参

template <typename T> 
void report_top (Stack<T> const&, int number = 10); 

template <typename T> 
void fill (Array<T>*, T const& = T());  // T() is zero for built-in types 

缺省调用实参要保证有默认构造函数

class Value { 
public: 
    Value(int);          // no default constructor 
}; 

void init (Array<Value>* array) 
{ 
    Value zero(0); 

    fill(array, zero);  // OK: = T() is not used 
    fill(array);        // ERROR: = T() is used, but not valid for T = Value 
} 

三.函数模板不可以声明为虚方法

template <typename T> 
class Dynamic { 
public: 
    virtual ~Dynamic();  // OK: one destructor per instance of Dynamic<T> 

    virtual void copy (){} //OK

    template <typename T2> 
    virtual void copy (T2 const&); 
    // ERROR: unknown number of instances of copy() 
    //        given an instance of Dynamic<T> 
}; 

四.类模板的声明

后面不带尖括号

template<typename T> class Box;             // OK: primary template 

template<typename T> class Box<T>;          // ERROR 

template<typename T> void translate(T*);    // OK: primary template 

template<typename T> void translate<T>(T*); // ERROR 

参考:http://www.cnblogs.com/stephen-liu74/archive/2012/08/27/2614249.html