Operator Orelse (Short Circuit Inclusive Disjunction)
Returns the short circuit-or (Inclusive Disjunction) of two numeric values
result = lhs OrElse rhs
lhs
Returns the short circuit-or (inclusive disjunction) of the two operands.
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.
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.
Syntax
Usage
result = lhs OrElse rhs
Parameters
lhs
The left-hand side expression.
T1Any numeric or boolean type.
rhsThe right-hand side expression.
T2Any numeric or boolean type.
RetA numeric or boolean type (varies with T1 and T2).
Return Value
Returns the short circuit-or (inclusive disjunction) of the two operands.
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.
Example
'' 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
'' 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
Differences from QB
- This operator was not available in QB.
See also