3.5.3 Boolean Types
There is a predefined enumeration
type named Boolean, [declared in the visible part of package Standard].
It has the two enumeration literals
False and True ordered with the relation False < True.
descendant of the predefined type Boolean is called a boolean
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.
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