Ada Programming/Keywords/or

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Logical operator

Boolean operator

X : Boolean := A < 10 or A > 20;

Boolean shortcut operator

In the below example the function G is only called when F(X) returns the value False.

if F(X) or else G(Y) then

    Walk_The_Dog;
 
end if;

This shortcut operator is sometimes used to speed up the evaluation of boolean expressions, but the Ada Style Guide recommends to compare the performance of both forms before switching one to the other. In general, it is good idea to use or else in sake of performance only when the second expression involves a function call.

The or else form is also used when the second expression is known to raise an exception unless the first expression is False.

Unlike C/C++, Ada short-cut operators are not the standard way to evaluate boolean expressions. This is because Ada is designed to do by default what is generally safer, but lets the programmer request a different behaviour.

Boolean operator on arrays

The or 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 or Y;

Bitwise operator

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

Select statement

alternative

See Ada Programming/Tasking#Selective waiting.

delay

See Ada Programming/Tasking#Timeout.

See also

Wikibook

• Ada Programming
• Ada Programming/Keywords
• Ada Programming/Operators

Ada 95 Reference Manual

• 2.9 Reserved Words (Annotated)
• 4.4 Expressions (Annotated)
• 4.5.1 Logical Operators and Short-circuit Control Forms (Annotated)
• Annex P (informative) Syntax Summary (Annotated)

Ada 2005 Reference Manual

• 2.9 Reserved Words (Annotated)
• 4.4 Expressions (Annotated)
• 4.5.1 Logical Operators and Short-circuit Control Forms (Annotated)
• Annex P (informative) Syntax Summary (Annotated)

Ada Quality and Style Guide

• 3.1.3 Capitalization

• 5.5.5 Short Circuit Forms of the Logical Operators
• 10.5.2 Short-Circuit Operators
• 10.6.3 Bit Operations on Modular Types