The expression may refer to self and to the routine's arguments. The expression may refer to self and to the routine's arguments. Iters are similar to routines but encapsulate iteration abstractions. The description of routine arguments and pre and post constructs also applies to iter definitions. The pre clause must be true each time the iter is called and the post clause must be true each time it yields.
Implementation inheritance is defined by include clauses .
External classes may not have include clauses. The include clause may begin with the keyword private , in which case any unmodified included feature is made private. We say that there is an include path from one type to another if there is a sequence of types between them such that each includes the next in the sequence. There must be no cycle of classes such that each class includes the next, ignoring the values of any type parameters but not their number. In this case, the listed features are included as part of the public interface unless they are specified as private or readonly .