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Tip of the Day
Language: VB4,VB5,VB6,VBS
Expertise: beginner
Oct 16, 1999

Write concise code with Boolean expressions

When setting a Boolean value based upon the result of an expression, avoid using an unnecessary If/Then/Else structure.

'Instead of using this lengthy syntax . . .
If SomeVar > SomeOtherVar Then
   BoolVal = True
Else
   BoolVal = False
End If

'Use this one, which is easier to read and executes faster. The
'parenthesis are not necessary, but I use them to enhance 
'readability when quickly scanning code.
BoolVal = (SomeVar > SomeOtherVar)
The second method ran anywhere between 50% and 85% of the time required for the first method, depending upon which operations were performed in the expression. The parenthesis that I use make no difference in execution speed.

At times, it isn't obvious that you can use this method to write more concise code. The point is that you should keep in mind that all comparison operators are just diadic operators that can return 0 (False) or -1 (True). So, for example the two following pieces of code are absolutely equivalent, but the second runs slightly faster:


' the standard way
If SomeVar > SomeOtherVar Then
    x = x + 1
End If

' the more concise way 
' notice that we need a minus sign to actually add 1 to x
x = x - (SomeVar > SomeOtherVar)
Bryan Fazekas
 
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