//! This module contains special values used by various modules, e.g. //! a null value used both by @[Sql] and @[Standards.JSON]. //! //! In many ways these values should be considered constant, but it is //! possible for a program to replace them with extended versions, //! provided they don't break the behavior of the base classes defined //! here. Since there is no good mechanism to handle such extending in //! several steps, pike libraries should preferably ensure that the //! base classes defined here provide required functionality directly.