Ada Programming/Keywords/and

Boolean operator
X : Boolean := A > 10 A < 20;

Boolean shortcut operator
Shortcut operators are used to make the evaluation of parts of boolean expressions conditional: and then, or else. This should never be done to speed up the evaluation (with modern optimizing compilers, it will possibly not have that effect). The correct use is to prevent the evaluation of expressions known to raise an exception.

Dog /=   G (Dog) Walk (Dog); ;

In the example above, G (Dog) is only called when the pointer Dog is not null, i.e. it actually points to something.

Actually and then and or else are not operators in the sense of the reference manual, they are called 'Short-circuit Control Forms'. The difference is that (true) operators can be redefined (i.e. overloaded), whereas these cannot. They are however defined for any boolean type.

Since Ada allows parallel evaluation of the arguments for an expression, shortcut operators are not the standard way of evaluating boolean expressions. In any case where the final result of the evaluation is guaranteed to be the same, the compiler is allowed to use a shortcut evaluation.

Boolean operator on arrays
The and operator is applied to each pair of boolean elements from the left and right arrays. The result has the same bounds as the left operand.

Day_Of_Month  1 .. 31;             Month_Array   (Day_Of_Month)  Boolean; X : Month_Array := Function_1; Y : Month_Array := Function_2; Z : Month_Array := X Y;

Bitwise operator
The operator and could be used with modular types to perform bitwise operations.

Adding interfaces to tagged types
Programmer  Person Printable Skilled_In : Language_List; ;

Wikibook

 * Ada Programming
 * Ada Programming/Keywords
 * Ada Programming/Operators
 * Ada Programming/Keywords/interface

Ada Quality and Style Guide


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