Ada Programming/Keywords/and

Keywords and __TOC__ Logical operator Boolean operator X : Boolean := A > 10 and 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. if Dog /= null and then G (Dog) then Walk (Dog); end if; 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. type Day_Of_Month is range 1 .. 31; type Month_Array is array (Day_Of_Month) of Boolean; X : Month_Array := Function_1; Y : Month_Array := Function_2; Z : Month_Array := X and Y; Bitwise operator The operator and could be used with modular types to perform bitwise operations. Adding interfaces to tagged types And type Programmer is new Person and Printable with record Skilled_In : Language_List; end record; See also Wikibook Ada Programming Ada Programming/Keywords Ada Programming/Operators Ada Programming/Keywords/interface Ada 95 Reference Manual 2 9 Reserved Words 4 4 Expressions P (informative) Syntax Summary Ada 2005 Reference Manual 2 9 Reserved Words 3 9 4 Interface Types 4 4 Expressions P (informative) Syntax Summary Ada Quality and Style Guide 3 1 3 Capitalization And