hi

There is a correction in my snippet  that i attached for enable_if.
The correct snippet is

//primary class
template <std::size_t size ,
       template<std::size_t size,typename E = void >  class USER_TYPE = select_type
         >
class my_class {          
         public:
          //Primary class
          //Note that the select_type is default for USER_TYPE

};

//Specialized  class
template <std::size_t size ,
         template<std::size_t size,typename E = void > class USER_TYPE
         >
class my_class< size,SER_TYPE>  {

public:
       
       //The commented code line below does not work  for VC7.1
       // typedef typename USER_TYPE<size>::type  data_type;     //THIS DOES NOT WORK  with vc7.1      
       typedef typename USER_TYPE<size,void>::type  data_type;   //THIS WORKS                
};

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Rgds


----- Forwarded by Suresh T/BTC/SC/PHILIPS on 08/08/2005 02:03 PM -----


hi

I am using the boost::enable_if for selection of types. Something similar to below

template<std::size_t Size,class Enable = void>
struct type_select{
};

template<std::size_t Size>
struct type_select< Size,
                        typename boost::enable_if < bool_ < (size <= 8) >  >
                    >::type
                    >{  
  typedef typename char  type;    
};

template<std::size_t Size>
struct type_select< Size,
                        typename boost::enable_if < bool_ < (size > 8) >  >
                    >::type
                    >{    
  typedef typename int  type;    
};


The conditions are based on the first parameter size. The normal usage would be something like      type_select<10>::type;

My question is : If i explicitly use the second parameter ( by passing void) will the correct specialization be still used
i.e, if i use say   type_select<6,void>::type,       will it resolve to "char" in the above case.

Please note:  I was using the normal way  (without the void) for my code on linux+gcc without any problems
My problem came up when i tried to move my  code to windows + vc7.1.
The vc7.1 compiler needs the second argument  (in my usage shown below ) else it gives an error. The results are as desired, but i would like
to know whether this usage is correct.

Below is a snippet where the vc7.1 compiler gives a problem with the usage.
Note type_select is not directly used but is used as a  default type for USER_TYPE parameter

template <std::size_t size ,
         template<std::size_t size,typename E = void > class USER_TYPE
         >
class my_class
          < size,          
           USER_TYPE = select_type   //select_type is a default parameter
          >  {

public:
       //The commented code line below does not work  for VC7.1
       // typedef typename USER_TYPE<size>::type  data_type;     //THIS DOES NOT WORK  with vc7.1      

       typedef typename USER_TYPE<size,void>::type  data_type;   //THIS WORKS                

};
 
Thanks for clarification in advance..

---------------------------------------------------------------------------------------------------------
Rgds,
Suresh