Re: [boost] [optional] operator<(optional<T>, T) -- is it wrong?

On Sun, Nov 30, 2014 at 5:19 PM, Olaf van der Spek wrote:

On Mon, Dec 1, 2014 at 1:58 AM, Matt Calabrese wrote:

...

Why? What makes the string default ordering "reasonable" and complex or variant not? There are a lot of ways to order strings that might even be more sensible in more cases than the current default (I.E. having different

I think this kind of reasoning isn't very fruitful. Optional is not a string, string is not an optional. One having operator< does not imply the other should have it to.

Hmm? What isn't reasonable is arbitrarily deciding what should and should not have a default ordering (not talking about operator< since that's a much more controversial matter). The notion of default ordering is useful because many datastructures and algorithms can make use of it, particularly those in the standard. There is absolutely nothing wrong with ordering tuples or optionals or variants, or any type at all. The only thing you accomplish by not having a default ordering is that you arbitrarily make the type difficult to use with these datastructures and algorithms. The recommendation of "prefer unordered set" is already an example of the type of poor programming advice that comes from this as a side effect. -- -Matt Calabrese