Those techniques are equally useful for anyone designing classes. Core language C-compatible subset Classes, members, virtual, etc. Language is perhaps the first specifically designed to support Library Design. Any style of programming. Interfaces remain compatible with higher- level structures.
Basic structures suffice for interlibrary communication.
Innovative interface design using the full power of the language. Requirements Convenience for simple uses. Latin-1, EUC, Unicode, etc. The iostreams library has years of history Must generalize and internationalize without breaking existing programs. This is almost the same problem as ensuring convenience for the common case.