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Extension

 

ThinBASIC offers the extends keyword to create new UDT by extending existing UDT.

 

In our case, creating Point3D would be as straightforward as:

 

TYPE Point3D EXTENDS Point2D
  z AS SINGLE
END TYPE

 

Now, the Point3D will have new z element, while the x and y will be inherited from Point2D.

 

Note: The elements of base UDT will be placed as first in the newly created UDT

 

Note: In case you would add new element to base UDT, it will get promoted to UDT which extends it.

 

Note: In case you would reorder the elements in base UDT, they will get reordered in UDT which extends it.