Re: [boost] [variant] Maintainer

On 07/14/2015 11:16 AM, Nevin Liber wrote:

On 14 July 2015 at 08:01, Larry Evans wrote:

...

What about variant<>, or is that disallowed? If it is disallowed, then tuple<> should, I guess, also be disallowed.

Why?

Because of the duality between category products and coproducts: https://en.wikipedia.org/wiki/Dual_%28category_theory%29 in particular, the following: https://en.wikiversity.org/wiki/Introduction_to_Category_Theory/Products_and... says: This is called duality principle. For every construction in category theory, there's an opposite construction with arrows reversed. Also, the following: https://en.wikipedia.org/wiki/Initial_and_terminal_objects specifically mention empty products and empty coproducts: a terminal object can be thought of as an empty product... Dually, an initial object is a colimit of the empty diagram ∅ → C and can be thought of as an empty coproduct or categorical sum. I know it that, at first glance, an empty product or empty coproduct doesn't make much sense, but, then again, adding 0 to a numerical sum doesn't make any difference; hence, why is there any need for 0? Apparently the category people think there's sufficient reason to define an empty coproduct and empty product; hence, I'd guess there's some good reason. Category experts (e.g. Louis Dionne), can you supply some better explanation? -regards Larry