The Sather Specification - Types and Classes Go to the first , previous , next , last section, table of contents .
Abstract types represent sets of concrete types.
External types specify interfaces to other languages. The type graph for a program is a directed acyclic graph that is constructed from the program's source text. Its nodes are types and its edges represent the subtype relationship. If there is a path in this graph from a type t1 to a type t2, we say that t2 is a subtype of t1 and that t1 is a supertype of t2. Every Sather variable has a declared type.