isnull

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isnull

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.

Example:

heitml 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.