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I have a VB.Net assignment statement with an or clause. What does it mean?

VB.Net

dim a as Boolean = false
dim b as Boolean = true
dim c as Boolean

This line of code confuses me:
c = a or b

I've never seen a line of code like that. What does it mean?

My best guess is that it means if a is null then set c to equal b, but that's truly a wild guess. Is this even a valid line of code?

SOLUTION

Éric Moreau

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g_johnson

ASKER

So, I think you are saying that if either a or b is true, c will be true. Is that correct?

The only way c is false is if both a and b are false. Still correct?

Thanks!

SOLUTION

Fernando Soto

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Éric Moreau

>>So, I think you are saying that if either a or b is true, c will be true. Is that correct?

correct

>>The only way c is false is if both a and b are false. Still correct?

False. If a OR b is false, c is set to false.

ASKER CERTIFIED SOLUTION

it_saige

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it_saige

This all stems from a bitwise operation whereas 0 = False and 1 = True. So changing our program we can prove at the bit level that the boolean operation is correct:

Module Module1
	Sub Main()
		Console.WriteLine("Let's test Or")
		OrTest(1, 1)
		OrTest(0, 1)
		OrTest(1, 0)
		OrTest(0, 0)
		Console.WriteLine()
		Console.WriteLine("Now let's test And")
		AndTest(1, 1)
		AndTest(0, 1)
		AndTest(1, 0)
		AndTest(0, 0)
		Console.ReadLine()
	End Sub

	Sub OrTest(ByVal lhs As Short, ByVal rhs As Short)
		Console.WriteLine("{0} OR {1} = {2}", lhs, rhs, lhs Or rhs)
	End Sub

	Sub AndTest(ByVal lhs As Short, ByVal rhs As Short)
		Console.WriteLine("{0} AND {1} = {2}", lhs, rhs, lhs And rhs)
	End Sub
End Module

Open in new window

Which now produces the following output -

-saige-

g_johnson

ASKER

Thanks, all!