Re: [boost] [optional_io] InputStreamable refinement

Subject: Re: [boost] [optional_io] InputStreamable refinement
From: Alexander Nasonov (alnsn_at_[hidden])
Date: 2009-03-03 09:55:45

Fernando Cacciola <fernando.cacciola <at> gmail.com> writes:
> [skip]
> Or are you saying that, since supporting such a requirement is not 
> entirely possible since in the end is up to T, it isn't worth doing the 
> best optional<T> itself can?

Yes, that's what I'm saying except that I tend to disagree with the word
"best" in this part of your sentence "doing the best optional<T> itself can" :)
I believe, based on my reading of documentation, that my proposal is more
correct.

> > I don't care about lexical_cast here
> 
> OK, but you two clearly care for extracting an optional<T> from a stream 
> that was insterted a bare T instead of an optional<T>.

You're right. Current version of boost doesn't support this

lexical_cast< optional<int> >(0)

but I'm going to make a special case when TargetType is optional<T>
to return a default value rather than throwing an exception:

lexical_cast< optional<int> >("not a number").get_value_or(0);

Since it's a special case, I can easily avoid using optional_io.hpp.

Alex