Operator ANDALSO (Short Circuit Conjunction)
Returns the short circuit-and (conjunction) of two numeric values
Syntax:
Usage:
result = lhs AndAlso rhs
Parameters:
lhs
The left-hand side expression.
T1
Any numeric or boolean type.
rhs
The right-hand side expression.
T2
Any numeric or boolean type.
Ret
A numeric or boolean type (varies with T1 and T2).
Return Value:
Returns the short circuit-and (conjunction) of the two operands.
Description:
This operator evaluates the left hand side expression. If the result is zero, then zero is immediately returned. If the result is nonzero then the right hand side is evaluated, and the logical result from that is returned.
(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-and operation, the '-' denotes that the operand is not evaluated.
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 non-zero (true) is the right hand side rhs also evaluated. If the left hand side evaluation lhs returns zero (false), it is known that at that point that the overall condition is false, 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.
(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-and operation, the '-' denotes that the operand is not evaluated.
| Lhs Value | Rhs Value | Result |
| 0 | - | 0 |
| nonzero | 0 | 0 |
| nonzero | nonzero | -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 non-zero (true) is the right hand side rhs also evaluated. If the left hand side evaluation lhs returns zero (false), it is known that at that point that the overall condition is false, 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.
Examples:
'' Using the ANDALSO operator to guard against array access
'' when the index is out of range
Dim As Integer isprime(1 To 10) = { _
_ ' 1 2 3 4 5 6 7 8 9 10
0, 1, 1, 0, 1, 0, 1, 0, 0, 0 _
}
Dim As Integer n
Input "Enter a number between 1 and 10: ", n
'' isprime() array will only be accessed if n is in range
If (n >= 1 And n <= 10) andalso isprime(n) Then
Print "n is prime"
Else
Print "n is not prime, or out of range"
End If
'' when the index is out of range
Dim As Integer isprime(1 To 10) = { _
_ ' 1 2 3 4 5 6 7 8 9 10
0, 1, 1, 0, 1, 0, 1, 0, 0, 0 _
}
Dim As Integer n
Input "Enter a number between 1 and 10: ", n
'' isprime() array will only be accessed if n is in range
If (n >= 1 And n <= 10) andalso isprime(n) Then
Print "n is prime"
Else
Print "n is not prime, or out of range"
End If
Differences from QB:
- This operator was not available in QB.
See also:
Back to Short Circuit Operators
Back to Operators
