| Keyword |
Description |
| Empty |
Used to indicate an uninitialized variable value. A
variable value is uninitialized when it is first created and no value is
assigned to it, or when a variable value is explicitly set to empty.
Example:
Dim x
'the variable x is uninitialized!
x="ff" 'the variable x is NOT uninitialized anymore
x=Empty 'the variable x is uninitialized!
Note: This is not the same as Null!! |
| IsEmpty |
Used to test if a variable is uninitialized.
Example: If (IsEmpty(x)) 'is x uninitialized? |
| Nothing |
Used to indicate an uninitialized object value, or to
disassociate an object variable from an object to release system resources. Example:
Set myObject=Nothing |
| Is Nothing |
Used to test if a value is an initialized object.
Example: If (myObject Is Nothing) 'is it unset?
Note: If you compare a value to Nothing, you will not get the
right result! Example: If (myObject = Nothing) 'always false! |
| Null |
Used to indicate that a variable contains no valid data.
One way to think of Null is that someone has explicitly set the value to
"invalid", unlike Empty where the value is "not set".
Note: This is not the same as Empty or Nothing!!
Example: x=Null 'x contains no valid data |
| IsNull |
Used to test if a value contains invalid data.
Example: if (IsNull(x)) 'is x invalid? |
| True |
Used to indicate a Boolean condition that is correct (True has a value of -1) |
| False |
Used to indicate a Boolean condition that is not correct (False has a value of 0) |
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