From: Kim Barrett (kab_at_[hidden])
Date: 2006-03-16 17:31:56
The archive concepts include an is_saving and is_loading typedef.
For concrete polymorphic archive types, such as
polymorphic_binary_iarchive, attempting to access these values
results in a compilation error due to ambiguity - there are two
accessible definitions, from different base classes, specifically
detail::interface_iarchive<binary_iarchive>
detail::interface_iarchive<polymorphic_iarchive>