On 1/24/2012 1:54 AM, TONGARI wrote:
2012/1/24 Andrey Semashev <andrey.semashev@gmail.com>
2. I would like the keyword have additional methods, in particular, for default attribute value provision. Extending my initial syntax, this would be:
BOOST_LOG_REGISTER_ATTRIBUTE("Severity", severity, my_severity)
attribute_values_view attrs;
severity(attrs); // returns optional<my_severity> severity.or_default(info)(attrs); // returns my_severity, which is info by default
As I understand, the only way I can do that, except for reimplementing phoenix::actor, is to derive my actor from phoenix::actor. This makes the attribute keyword non-POD in C++03 but is it still safe to be constructed in the namespace scope, provided that the keyword does not have its own data members?
I'm not sure as well, that's what I always want to ask Eric: http://www.boost.org/doc/libs/1_48_0/doc/html/proto/appendices.html#boost_pr...
Proto doesn't force you to use inheritance to extend and expression with additional member (see BOOST_PROTO_EXTENDS). But Phoenix may, I don't know. Thomas?
Anyway, I played a trick while not knowing if it's available. The idea is:
struct Pod {...you could have some data...}; struct Derived : Pod {}; // non-POD in C++03 Pod p_base = {...some data...}; // statically initialized Derived& p = static_cast<Derived&>(p_base); // statically initialized, not?
Aside from the fact that this is non-standard, not all compilers statically initialize references, though they should. -- Eric Niebler BoostPro Computing http://www.boostpro.com