{Boolean} There
is a predefined enumeration type named Boolean, [declared in the visible
part of package Standard]. {False} {True}
It has the two enumeration literals False and True
ordered with the relation False < True. {boolean
type} Any descendant of the predefined
type Boolean is called a boolean type.
1.a
Implementation Note: An
implementation is not required to support enumeration representation
clauses on boolean types that impose an unacceptable implementation burden.
See 13.4, ``Enumeration
Representation Clauses''. However, it is generally straightforward
to support representations where False is zero and True is 2**n - 1 for
some n.