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 this:

     If_

...

Null Field(#Value)

...

     Set Com(#Button)

...

 Enabled(True)
     Else

...

     Set Com(#Button)

...

 Enabled(False)
     Endif

Using the intrinsic, you 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, you 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.