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Name Resolution Rules

An expression consisting of two relations connected by and then or or
else (a shortcircuit control form) shall resolve to be of some boolean
type; the expected type for both relations is that same boolean type.
Static Semantics

The following logical operators are predefined for every boolean type T,
for every modular type T, and for every onedimensional array type T
whose component type is a boolean type:

function "and"(Left, Right : T) return T
function "or" (Left, Right : T) return T
function "xor"(Left, Right : T) return T

For boolean types, the predefined logical operators and, or, and xor
perform the conventional operations of conjunction, inclusive
disjunction, and exclusive disjunction, respectively.

For modular types, the predefined logical operators are defined on a
bitbybit basis, using the binary representation of the value of the
operands to yield a binary representation for the result, where zero
represents False and one represents True. If this result is outside the
base range of the type, a final subtraction by the modulus is performed
to bring the result into the base range of the type.

The logical operators on arrays are performed on a
componentbycomponent basis on matching components (as for equality 
See section 4.5.2 Relational Operators and Membership Tests.), using the predefined logical operator for the component
type. The bounds of the resulting array are those of the left operand.
Dynamic Semantics

The shortcircuit control forms and then and or else deliver the same
result as the corresponding predefined and and or operators for boolean
types, except that the left operand is always evaluated first, and the
right operand is not evaluated if the value of the left operand
determines the result.

For the logical operators on arrays, a check is made that for each
component of the left operand there is a matching component of the right
operand, and vice versa. Also, a check is made that each component of
the result belongs to the component subtype. The exception
Constraint_Error is raised if either of the above checks fails.
NOTES

(12) The conventional meaning of the logical operators is given by the
following truth table:

A B (A and B) (A or B) (A xor B)
True True True True False
True False False True True
False True False True True
False False False False False
Examples

Examples of logical operators:

Sunny or Warm
Filter(1 .. 10) and Filter(15 .. 24)  See section 3.6.1 Index Constraints and Discrete Ranges

Examples of shortcircuit control forms:

Next_Car.Owner /= null and then Next_Car.Owner.Age > 25
 See section 3.10.1 Incomplete Type Declarations
N = 0 or else A(N) = Hit_Value
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