Object Comparison

When comparing two DBO variables only references are compared to see if they refer to the same object. So only an equality or non-equality comparison is supported.

Syntax

object1 [ = ‖ EQ ‖ # ‖ NE ‖ <> ‖ >< ] object2

Applicability

Language and internal objects.

Comments

Comparison

Result

Object = Non-Object

Returns FALSE.

Object = Object

Returns TRUE if they both reference the same object.
Returns FALSE if they reference different objects.

Object # Non-Object

Returns TRUE

Object # Object

Returns TRUE if they reference different objects.
Returns FALSE if they both reference the same object.

All other object comparisons such as < and > generate the following fatal run time error: [B14] "Bad stack descriptor".

To compare the contents of two objects, an object-specific comparison method must be used where available.

Examples

Equality test on two objects:

IF Horse = Equine THEN ...

Inequality test on two objects:

IF Insect # Mammal THEN ...

Tests if the method Horse.SiredBy() returns a valid (non null) object. Note the use of the (object) cast.

Progenitor = Horse->SiredBy()
IF Progenitor # (object)0 THEN ...