[v3] ext/type_traits.h

[Howard Hinnant]

On Sep 15, 2006, at 10:19 AM, Peter Doerfler wrote:

>> Index: include/tr1/random.tcc
>> ===================================================================
>> --- include/tr1/random.tcc	(revision 116965)
>> +++ include/tr1/random.tcc	(working copy)
>> @@ -88,34 +88,26 @@
>>        };
>>
>>      template<typename _ValueT>
>> -      struct _To_Unsigned_Type
>> +      struct _To_unsigned_type
>>        { typedef _ValueT _Type; };
>>
>>      template<>
>> -      struct _To_Unsigned_Type<short>
>> +      struct _To_unsigned_type<short>
>>        { typedef unsigned short _Type; };
>>
>>      template<>
>> -      struct _To_Unsigned_Type<int>
>> +      struct _To_unsigned_type<int>
>>        { typedef unsigned int _Type; };
>>
>>      template<>
>> -      struct _To_Unsigned_Type<long>
>> +      struct _To_unsigned_type<long>
>>        { typedef unsigned long _Type; };
>>
>>  #ifdef _GLIBCXX_USE_LONG_LONG
>>      template<>
>> -      struct _To_Unsigned_Type<long long>
>> +      struct _To_unsigned_type<long long>
>>        { typedef unsigned long long _Type; };
>>  #endif
>
>
>
> I think it makes sense to move these out as well. Even if they are  
> only
> used in random ATM that seems to be a general concept that could be
> useful elsewhere. Following the lead of tr1::type_traits the name
> "add_unsigned" might be better, and the corresponding  
> "remove_unsigned"
> could be added as well.
>
> Maybe this is even another candidate for Howard's list?

I too have needed these utilities.  Fwiw I called them:

to_unsigned<T>::type;
and
to_signed<T>::type;

I note that specializations don't exist for signed/unsigned char.  It  
seems like that would be useful as well.  But when you do that, then  
remove_unsigned<unsigned char>::type -> signed char, doesn't seem to  
fit as well.

-Howard