Variants and Constants

If I declare a constant like this:

Code:

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Const NUM_EMPLOYEES As Integer = 4

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then Visual Basic uses a 2-byte integer to store my constant.

If I instead declare the constant this way:

Code:

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Const NUM_EMPLOYEES = 4

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will Visual Basic use a 16-byte Variant to store the constant????

constants aren't actually stored, The compiler simply replaces any references to that constant in your code to the value of that constant.


so this

Code:

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Const MYVAL = 46

Public Sub Command1_Click

Msgbox MYVAL

Msgbox MYVAL + 4

End Sub

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will compile exactly the same as

Code:

---

Public Sub Command1_Click

Msgbox 46

Msgbox 46 + 4

End Sub

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The value is stored each time you use the constant as the same type as the function you are using the constant in expects.


The reason you can set types for constants is to avoid overflows, for example

Code:

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Const MYVAL = 250

Public Sub Command1_Click

Msgbox MYVAL * MYVAL

End Sub

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will cause an overflow because the compiler interprets 250 as an integer (If you had typed Msgbox 250 * 250 you would still get an overflow)

Code:

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Const MYVAL As Long = 250

Public Sub Command1_Click

Msgbox MYVAL * MYVAL

End Sub

---

will avoid this, it's the equivilant of

Code:

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Public Sub Command1_Click

Msgbox CLng(MYVAL) * CLng(MYVAL)

End Sub

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but it desn't loose speed converting because it calculates CLng(250) at compile time.