An interface has the form:
INTERFACE id; Imports; Decls END id.where
id
is an identifier that names the interface, Imports
is a
sequence of import statements, and Decls
is a sequence of declarations
that contains no procedure bodies or non-constant variable initializations.
The names declared in Decls
and the visible imported names must be
distinct. It is a static error for two or more interfaces to form an import
cycle.