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Subject: Re: [boost] optional<optional<T>>
From: Joel de Guzman (joel_at_[hidden])
Date: 2009-09-02 22:52:30

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.

We use boost.optional extensively in Boost.Spirit. IIRC, we collapse
such things. Usually they occur in generic code. I see no real need
for optional<optional<T>>. If there's a use for it, I too would like
to hear it.


Joel de Guzman

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