The Fortress Language Specification - CiteSeerX

False: BooleanInterval
Uncertain: BooleanInterval
Impossible:BooleanInterval
test testData[ ] = { True, False, Uncertain, Impossible }
24.2.1 coercion (x: Boolean)
A boolean value can always serve as a BooleanInterval value. The value true is coerced to True; the value false is
coerced to False.
24.2.2 opr ∧(self,other: BooleanInterval): BooleanInterval
The logical AND operator ∧ ( AND ) returns Impossible if either argument is Impossible; otherwise it returns False
if either argument is False; otherwise it returns Uncertain if either argument is Uncertain; otherwise it returns True.
It obeys the interval containment rule. The ∧ operator may be described by this table:
∧ Uncertain True False Impossible
Uncertain Uncertain Uncertain False Impossible
True Uncertain True False Impossible
False False False False Impossible
Impossible Impossible Impossible Impossible Impossible
24.2.3 opr ∨(self,other: BooleanInterval): BooleanInterval
The logical OR operator ∨ ( OR ) returns Impossible if either argument is Impossible; otherwise it returns True if
either argument is True; otherwise it returns Uncertain if either argument is Uncertain; otherwise it returns False.
It obeys the interval containment rule. The ∧ operator may be described by this table:
∧ Uncertain True False Impossible
Uncertain Uncertain True Uncertain Impossible
True True True True Impossible
False Uncertain True False Impossible
Impossible Impossible Impossible Impossible Impossible
24.2.4 opr ¬(self): BooleanInterval
The logical NOT operator ¬ ( NOT ) returns Impossible if its argument is Impossible, Uncertain if its argument is
Uncertain, False if its argument is True, and True if its argument is False. It obeys the interval containment rule.
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