Re: [boost] traits classes vs. metafunctions

On 31 March 2013 18:31, Stefan Strasser wrote:

I don't understand why they didn't get rid of the "metafunction" concept as we use it today entirely, but introduce it into the official standard via type traits. E.g. via a "constexpr" that can return types, or some other native syntax for metafunctions.

And I don't understand why people expect the standard to emerge perfectly formed from some magic source of an ideal language. This stuff doesn't just happen by magic, someone has to propose it and the people involved have limited time and resources. There are good reasons for the committee to standardise existing practice instead of trying to invent entirely new tools that noone has any experience with. The header we have today is largely based on ideas that got proposed because they were known to work and were useful in the real world. When was added to TR1 constexpr didn't exist. When constexpr was added there were no working implementations to experiment with. Noone suggested replacing the established metafunctions with constexpr functions in time for the idea to be understood, implemented and reviewed, and noone made any formal proposal to make such a change. If you think there should be something else then get involved and propose it.