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GBIC >> Source Code >> Visual Basic >> Snippet

07 Boolean logic


'Boolean refers to logical relationships - True or False, and is named
'after mathematician George Boole.

'VB supports the following Boolean opertors
Or
And  
Not
Xor

'The following operators are also supported but see very little use by VB programmers
Eqv
Imp
Is

'To create a Boolean variable, use this:
Dim X As Boolean

'Mathematical values used in Boolean expresssion are converted to Boolean values as follows:
0 becomes False
all other values become True .

'Boolean values used in mathematical expressions are converted to mathematical values as follows:
False becomes 0        i.e.   False * 2 = 0
True becomes - 1        i.e.   True * 5 = - 5

'results of applying Val to Boolean
Val( True ) = 0
Val( False ) = 0
Abs( True ) =  1
Abs( False ) = 0
CInt ( True ) = - 1
CInt ( False ) = 0
Print True   --->    True
Print False --->    False

If A Then    
    '0 value is treated as False
    'non-zero value is treated as True
End If