On Thu, Oct 4, 2012 at 9:15 AM, Vicente J. Botet Escriba < vicente.botet@wanadoo.fr> wrote:
Le 04/10/12 15:02, Jeffrey Lee Hellrung, Jr. a écrit :
On Thu, Oct 4, 2012 at 12:28 AM, Lorenzo Caminiti <lorcaminiti@gmail.com
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?
Even if Lorenzo doesn't needs it, it will be great to have it in Boost. Jeffrey, do you have something that is working already?
I don't yet, but this should be fairly straightforward based on the present C++03 implementation. I guess I can try to get this in this weekend? - Jeff