Operator Orelse Short Circuit Inclusive Disjunction

Home › Operators › Operator Orelse (Short Circuit Inclusive Disjunction)

Operator Orelse (Short Circuit Inclusive Disjunction)

Returns the short circuit-or (Inclusive Disjunction) of two numeric values

Syntax

Declare Operator OrElse ( ByRef lhs As T1, ByRef rhs As T2 ) As Ret

Parameters

• lhs
• T1
• rhs
• T2
• Ret
• T1
• T2

Description

This operator evaluates the left hand side expression. If the result is nonzero, then -1 (true) is immediately returned. If the result is zero then the right hand side is evaluated, and the logical result from that is returned, returning -1 (true) for a nonzero value or 0 (false) for zero.
(for conversion of a boolean to an integer, false or true boolean value becomes 0 or -1 integer value)

The truth table below demonstrates all combinations of a short circuit-or operation, the '-' denotes that the operand is not evaluated.

Lhs Value	Rhs Value	Result
0	0	0
0	nonzero	-1
nonzero	(not evaluated)	-1

OrElse equivalent to: Iif( Lhs = 0, Rhs <> 0 , -1 )

Short-circuiting is performed - only expressions needed to calculate the result are evaluated. The left hand side lhs is evaluated first, and only if it evaluates to zero (false) is the right hand side rhs also evaluated. If the left hand side evaluation lhs returns non-zero (true), it is known that at that point that the overall condition is true, so the right hand side rhs is not evaluated (skipped).

The return type is almost always an Integer, of the value 0 or -1, denoting false and true respectively. Except if the left and right-hand side types are both Boolean, then the return type is also Boolean.

This operator cannot be overloaded for user-defined types.

Return Value

Returns the short circuit-or (inclusive disjunction) of the two operands.

Remarks

Usage

result = lhs OrElse rhs

Differences from QB

• This operator was not available in QB.

See also

• AndAlso
• Or
• Operator Truth Tables

Examples

'' Using the ORELSE operator to test

'' if a value is out of range

Dim As Integer n

Input "Enter a number between 1 and 10: ", n

Function test(ByVal n As Integer) As Integer

    Print "expression evaluated"

    Return n

End Function

'' print value only if n is in range [1, 10]

If test(n) < 1 OrElse test(n) > 10 Then  '' if n < 1, second expression is not evaluated

    Print "   => out of range"

Else

    Print "   => n ="; n

End If

Sleep

---

Category: Operators
Kind: operator

---

Reproduced from the FreeBASIC Wiki Manual under the GNU Free Documentation License 1.3 — with no Invariant Sections, no Front-Cover Texts and no Back-Cover Texts. Copyright © the FreeBASIC project and wiki contributors. See License.