Re: [boost] Re: Formal Review: Variant Library

From: Beman Dawes (bdawes_at_[hidden])
Date: 2003-02-18 20:03:00

At 02:49 PM 2/18/2003, Itay Maman wrote:

 >"Rodolfo Lima" <rodolfo_at_[hidden]> wrote in message
 >news:b2tm6v$9o7$1_at_main.gmane.org...
 >> How different is boost::any from this new variant library? Don't they
 >> address the same issue?
 >>
 >
 >In short:
 >
 >(1) boost::any can accept a value of any possible type. boost::variant
 >accepts only values of a finite set of types, which are passed as 
template
 >parameters
 >(2) boost::any offers a query-based mechanism for accessing its held 
value:
 >any_cast<T>(a); This operation may fail (at runtime). The equivalent
 >facility of boost::variant is: apply_visitor(a_visitor, a_variant). This
 >operation will fail at *compile-time* if a_visitor is not a valid visitor
 >for a_variant. More details can about visitation can be found in 
variant's
 >docs.

Note that the need to document the difference between boost::any and 
boost::variant is common to both libraries.

Thus (assuming boost::variant is accepted) it would make sense to document 
the difference in one place (presumably boost::variant) but then also add a 
sentence with a link to the boost::any docs. Perhaps add that to your do 
list:-)

--Beman