Re: [boost] [utility/value_init] boost::value_initialized<T> direct-initialized?

Subject: Re: [boost] [utility/value_init] boost::value_initialized<T> direct-initialized?
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2010-04-08 12:38:02

Jeffrey Lee Hellrung, Jr. wrote:
> Stewart, Robert wrote:
> > Fernando Cacciola wrote:
> >
> >> I can imagine myself explaining that "initialize<T> m(v)"  does
> >> direct-initialization, then that, OTOH, "initialized<T> m;" does
> >> value-initialization, since there is no explicit
> >> initialization in this case.
> >
> > Why does initialized<T> need to have a default constructor?
>
> Because if it wasn't default-constructible, why would you use
> it (when a
> T object would suffice)?
>
> The motivating example (I believe) is when you have a class member of
> type initialized<T>, and you want the default constructor of
> the class
> to value initialize the data member.  (You also want a (const T&)
> constructor that direct intializes the data member; otherwise,
> value_initialized<T> would suffice.)

Given that, I have to agree with Fernando that initialize is merely a superset of value_initialize and can be harder to explain unless it derives from value_initialize (even if it shares nothing from the base and only makes clear that it is a superset).

_____
Rob Stewart                           robert.stewart_at_[hidden]
Software Engineer, Core Software      using std::disclaimer;
Susquehanna International Group, LLP  http://www.sig.com

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