## Logical operator

### Boolean operator

```X : Boolean := A < 10 .mw-parser-output .ada-kw{background:none;border:none;padding:0;margin:0;color:DodgerBlue;font-weight:bold}.mw-parser-output .ada-kw a,.mw-parser-output .ada-kw a:visited{color:inherit}`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

### Ada Quality and Style Guide

`abort` `else` `new` `return`
`abs` `elsif` `not` `reverse`
`abstract` (Ada 95) `end` `null`
`accept` `entry` `select`
`access` `exception` `of` `separate`
`aliased` (Ada 95) `exit` `or` `some` (Ada 2012)
`all` `others` `subtype`
`and` `for` `out` `synchronized` (Ada 2005)
`array` `function` `overriding` (Ada 2005)
`at` `tagged` (Ada 95)
`generic` `package` `task`
`begin` `goto` `pragma` `terminate`
`body` `private` `then`
`if` `procedure` `type`
`case` `in` `protected` (Ada 95)
`constant` `interface` (Ada 2005) `until` (Ada 95)
`is` `raise` `use`
`declare` `range`
`delay` `limited` `record` `when`
`delta` `loop` `rem` `while`
`digits` `renames` `with`
`do` `mod` `requeue` (Ada 95) `xor`