10.3 Isxxxxxx Intrinsic Functions
Many Intrinsic Function names begin with IS. This type of function will return a Boolean result, and can be thought of as a short form of an If/Else construct.
For example, the isnull intrinsic tests the value of the supplied value and returns a true if the value is blanks or zero.
Previously, testing for this situation would look like the following
If_Null Field(#Value)
Set Com(#Button) Enabled(True)
Else
Set Com(#Button) Enabled(False)
Endif
Using the intrinsic, we could write
If (#Value.IsNull)
Set Com(#Button) Enabled(True)
Else
Set Com(#Button) Enabled(False)
Endif
Clearly, this does not give any great benefit, unless combining with multiple conditions. However, we could write
#Button.Enabled := #Value.IsNull
In this example, as Isnull returns a Boolean state, it can be applied directly to any Boolean property.
This concept can be extended to use multiple conditions, And, Or and Not operators.