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Format: isnull ( value )

Purpose: Checks whether the given value is null or not declared.

Return Values: A value is null if:

  • it is a variable or object (field) and is not declared
  • it is the null value.
If one of the conditions is fulfilled, isnull() returns true, otherwise false.


input:resulting output:
<? isnull(null)>true
<? isnull(U)>true
<? isdecl(U)>false
<? isempty(U)>true
<let D=null; ? isnull(D)>true
<let D=null; ? isdecl(D)>true
<let D=null; ? isempty(D)>true
<? isnull(" ")>false
<? isempty(" ")>true

Tip: If it's not obvious how to use this function, imagine that you have a variable named D that has been declared, but has been assigned a null value and another variable U that has not been declared. In contrast to the isdecl() function, isnull() would return true for both variables.

See Also: isdecl(), isempty().

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