Re: [Boost-users] C++ guru required!

Subject: Re: [Boost-users] C++ guru required!
From: Robert Ramey (ramey_at_[hidden])
Date: 2012-02-27 09:45:22

Nathan Ridge wrote:
>>   > Sorry it took me a bit longer, but here are my ideas....
>>  > Code from Slide 12 of Andrei's presentation at Going Native 2012:
>>  >
>>  >
>>  > template<class T>
>>  > struct container
>>  > {
>>  >   ...
>>  >   static if(debug_mode<T>::value)
>>  >   {
>>  >     class const_iterator { ... };
>>  >     static if(std::is_const<T>::value)
>>  >     {
>>  >       typedef const_iterator iterator;
>>  >     }
>>  >     else
>>  >     {
>>  >       class iterator { ... };
>>  >     }
>>  >   }
>>  >   else
>>  >   {
>>  >     class const_iterator { ... };
>>  >     clas iterator { ... };
>>  >   }
>>  > };
>>  >
>> and my view would be that removing the "static" wouldn't change
>> anything in the program - so why is it necessary.
>>
>>  > template<class PointerWrapper>
>>  > struct grab_pointer_type
>>  > {
>>  >   static if(has_element_type<PointerWrapper>::value)
>>  >   {
>>  >     typedef typename PointerWrapper::element_type pointer_type;
>>  >   }
>>  >   else
>>  >   {
>>  >     typedef typename PointerWrapper::value_type pointer_type;
>>  >   }
>>  > };
>>
>> also in this example, removing the static wouldn't change the
>> program in any way.
>
> But the static_if is being used at class scope here - regular
> if statements cannot be used at class scope!

lol - I completely overlooked the fact this isn't a function - which
was my original question.

As I remember, andrei's other example could have been better
handled with a static_assert - but I may be mis-remembering.

the above case would be handled adequetly today with TMP which
admitadly is an unwieldy syntax.

Robert Ramey

>
> Regards,
> Nate