Editing Lithe (section)

==Overview==
The standard [[class-based programming]] model does not specify a mechanism by which to manipulate objects: where [[Smalltalk]] uses message passing, Lithe uses [[syntax-directed translation]] (SDT). SDT is a method of translating a string into a sequence of ''actions'' by attaching one such action to each rule of a grammar. Thus, parsing a string of the grammar produces a sequence of rule applications. Lithe merges SDT with the class model by using classes as the non-terminal alphabet of the grammar. Since the grammar class used by Lithe properly contains all context-free grammars, a wide variety of syntax can be described, and SDT provides a simple way to attach semantics to any such syntax.

The ''package'' is the unit of [[modularity (programming)|program modularity]] in Lithe. A package is divided into two parts: one that defines classes and another that defines rules. [[Information hiding]] is achieved by requiring both ''export'' keywords on those rules and classes that are to be seen outside a package ''and'' that the source package names be included in the ''with'' clause of the consumer package.