[boost] Re: Proposal for 'is_dereferenceable' and other template metafunctions

From: David Abrahams (dave_at_[hidden])
Date: 2004-09-10 06:50:42

"Alex Chovanec" <achovane_at_[hidden]> writes:

> Hello,
>
> A while back, I proposed a template metafunction called 'is_iterator', but
> the consensus seemed to be that it was not feasible from an implementation
> standpoint. At Jonathan Turkanis' suggestion, I went ahead and implemented
> the less ambitions 'is_dereferenceable', along with two other metafunctions:
>
>     Requirements:
>
>         Given t of type T &, if the expression *t is not well-formed, then
> it must
>         neither be ambiguous nor violate access.
>
>     Description:
>
>         is_lvalue_dereferenceable<T> - true if *t is well-formed and an
> lvalue
>         is_value_dereferenceable<T> - true if *t is well-formed and non-void
>         is_dereferenceable<T> - true if *t is well-formed
>
> I would like to offer these up for inclusion in boost, whether in namespace
> boost or in boost::detail. (presumably the latter, since that's where the
> similar 'is_incrementable' is found).
>
> I have posted the source for these metafunctions along with a unit test in
> the YahooGroups Files section in a folder called 'is_dereferenceable'.
>
> Please let me know if these are of interest to anyone.

Don't you think it's time we generalized the hack into a nice macro
that generates the right code?

-- 
Dave Abrahams
Boost Consulting
http://www.boost-consulting.com