polymorphic_cast was suggested by Bjarne Stroustrup in "The C++ Programming Language".

polymorphic_downcast was contributed by Dave Abrahams.

polymorphic_pointer_downcast was contributed by Boris Rasin and polymorphic_pointer_cast by Antony Polukhin.

An old numeric_cast that was contributed by Kevlin Henney is now superseeded by the Boost Numeric Conversion Library