Re: [boost] optional<optional<T>>

Andrei Alexandrescu wrote:

Hello,

I'm defining an "optional" type for D's standard library modeled similarly to Boost.optional. An interesting question came up - should optional<optional<T>> fold itself into optional<T>, or is "double optional" an interesting concept of its own?

I thought I'd ask here because by now there's a significant body of experience with optional<T>. I perused the online documentation and the forum and couldn't find information about that specific detail.

Why make optional<optional<T> > an exception to the normal case ? Even if you imagined no practical use for it, that's no reason to create a one-off situation.