Array of Booleans does not set Boolean variables?

[Guest]

Dim bNcd, bNcm, bNqa, bNcur, bN0, bN1, bN2, bN3, bN4 As Boolean
Dim arrBool As Boolean() = {bNcd, bNcm, bNqa, bNcur, bN0, bN1, bN2, bN3, bN4}
Dim i As Integer

bNcd = True
bNcm = True
bNqa = True
bNcur = True
bN0 = True
bN1 = True
bN2 = True
bN3 = True
bN4 = True

For i = 0 To arrBool.Length - 1
Console.WriteLine(arrBool(i)) '--these are all False instead of True
Next

For i = 0 To arrBool.Length - 1 : arrBool(i) = False : Next

'--these are still True
Console.WriteLine("bNcd is " & bNcd)
Console.WriteLine("bNcm is " & bNcm)
Console.WriteLine("bNqa is " & bNqa)
Console.WriteLine("bNcur is " & bNcur)
Console.WriteLine("bN0 is " & bN0)
Console.WriteLine("bN1 is " & bN1)
Console.WriteLine("bN2 is " & bN2)
Console.WriteLine("bN3 is " & bN3)
Console.WriteLine("bN4 is " & bN4)

Is there a way to set boolean vars from an array?

Thanks,
Rich

 

[Herfried K. Wagner [MVP]]

Dim bNcd, bNcm, bNqa, bNcur, bN0, bN1, bN2, bN3, bN4 As Boolean
Dim arrBool As Boolean() = {bNcd, bNcm, bNqa, bNcur, bN0, bN1, bN2, bN3,
bN4}
Dim i As Integer

bNcd = True
bNcm = True
bNqa = True
bNcur = True
bN0 = True
bN1 = True
bN2 = True
bN3 = True
bN4 = True

For i = 0 To arrBool.Length - 1
Console.WriteLine(arrBool(i)) '--these are all False instead of True
Next

'Boolean' is a value type, and thus 'arrBool' doesn't store references to
the boolean variables. Instead, a copies of their values are stored in the
array.

Is there a way to set boolean vars from an array?

You could use an array variable instead of individual variables.

 

[Mythran]

Dim bNcd, bNcm, bNqa, bNcur, bN0, bN1, bN2, bN3, bN4 As Boolean
Dim arrBool As Boolean() = {bNcd, bNcm, bNqa, bNcur, bN0, bN1, bN2, bN3,
bN4}
Dim i As Integer

bNcd = True
bNcm = True
bNqa = True
bNcur = True
bN0 = True
bN1 = True
bN2 = True
bN3 = True
bN4 = True

For i = 0 To arrBool.Length - 1
Console.WriteLine(arrBool(i)) '--these are all False instead of True
Next

For i = 0 To arrBool.Length - 1 : arrBool(i) = False : Next

'--these are still True
Console.WriteLine("bNcd is " & bNcd)
Console.WriteLine("bNcm is " & bNcm)
Console.WriteLine("bNqa is " & bNqa)
Console.WriteLine("bNcur is " & bNcur)
Console.WriteLine("bN0 is " & bN0)
Console.WriteLine("bN1 is " & bN1)
Console.WriteLine("bN2 is " & bN2)
Console.WriteLine("bN3 is " & bN3)
Console.WriteLine("bN4 is " & bN4)

Is there a way to set boolean vars from an array?

Thanks,
Rich

This is because, boolean values are value-types, not reference types. When
you change the value of a value-type, only the value you changed is updated.

Dim a As Boolean = True
Dim b As Boolean = a

a = False

You set the "value" of a to True.
You then set the "value" of b to the "value" of a, which is True.
You set the "value" of a to False.

The "value" of b is still True.

Dim a As ArrayList = New ArrayList()
a.Add(True)
Dim b As ArrayList = a

a.Clear()
a.Add(False)

You set the "reference" of a to a new array list and add the value True.
You set the "reference" of b to the "reference" of b.
You clear the "reference" values.
You add the value False to the "reference" a.

The "reference" of b still points to the same ArrayList instance of a.
Therefore the ArrayList of b is the same as a and contains the "value" of
False.

Understand?

HTH,
Mythran

(Did not use technical terms as this may prevent understanding the basics of
reference types vs value types...)

 

[Armin Zingler]

Dim bNcd, bNcm, bNqa, bNcur, bN0, bN1, bN2, bN3, bN4 As Boolean
Dim arrBool As Boolean() = {bNcd, bNcm, bNqa, bNcur, bN0, bN1, bN2, bN3, bN4}
Dim i As Integer

bNcd = True
bNcm = True
bNqa = True
bNcur = True
bN0 = True
bN1 = True
bN2 = True
bN3 = True
bN4 = True

For i = 0 To arrBool.Length - 1
Console.WriteLine(arrBool(i)) '--these are all False instead of True
Next

You did not change the array content. You changed the single variables.

For i = 0 To arrBool.Length - 1 : arrBool(i) = False : Next

'--these are still True
Console.WriteLine("bNcd is " & bNcd)
Console.WriteLine("bNcm is " & bNcm)
Console.WriteLine("bNqa is " & bNqa)
Console.WriteLine("bNcur is " & bNcur)
Console.WriteLine("bN0 is " & bN0)
Console.WriteLine("bN1 is " & bN1)
Console.WriteLine("bN2 is " & bN2)
Console.WriteLine("bN3 is " & bN3)
Console.WriteLine("bN4 is " & bN4)

Is there a way to set boolean vars from an array?

You would have to copy it back to the array.

Armin

 

[Guest]

Thank you all for your replies and explanations. Yes, it makes sense.
Fundamental stuff about references and Value. Need to brush up. I was just
checking if there were a more efficient way to do what I want instead of

arrBool(0) = False
arrBool(1) = False
....

I guess I could go the way of the ArrayList. Might try that.

Thanks again.