Re: [boost] [type_traits] common_type and SFINAE

Subject: Re: [boost] [type_traits] common_type and SFINAE
From: Jeffrey Lee Hellrung, Jr. (jeffrey.hellrung_at_[hidden])
Date: 2012-10-04 09:02:14

On Thu, Oct 4, 2012 at 12:28 AM, Lorenzo Caminiti <lorcaminiti_at_[hidden]>wrote:

> Hello all,
>
> common_type<T, U>::type is defined in a way that gives a hard compiler
> error if T and U do not have a common type (this is also how
> common_type is implemented in C++11).
>
> An alternative design (I'm not sure if implementable) would have been
> to not define the type member in case T and U have no common type.
> This way I could use SFINAE to detect if common_type<T, U>::type does
> not exist and therefore if T and U have not common type -- so to
> implement N3351's concept Common<T, U>.
>
> Is there a way to implement this alternative design?
>

Do you also need this in C++03?

- Jeff