::type* = 0 // disable if value has type `any&` , typename boost::disable_if<boost::is_const<ValueType> >::type* =
Hi, boost::any has a perfect forward constructor declared as: template<typename ValueType> any(ValueType&& value , typename boost::disable_if<boost::is_same<any&, ValueType> 0) // disable if value has type `const ValueType&&` : content(new holder< typename decay<ValueType>::type
(static_cast<ValueType&&>(value))) {}
The is_const SFINAE exclusion forces const types to the regular copy constructor: template<typename ValueType> any(const ValueType & value) : content(new holder< BOOST_DEDUCED_TYPENAME remove_cv<BOOST_DEDUCED_TYPENAME decay<const ValueType>::type>::type >(value)) {} What is different about how the regular copy constructor treats a constant value than what the perfect forward construct would do if the is_const exclusion were removed? Thanks, David