Object-oriented Software in Ada 95

Containers 261
A deep copy of this structure:
List original, copy;
copy := original;
-- Deep copy
would give the memory layout as illustrated in Figure 17.6.
Original
Red
Green
Blue
Copy
Red
Green
Blue
Figure 17.6 Effect of the deep Copy := Original;.
A shallow copy :
List original, copy;
copy := original;
-- Shallow copy
would produce the memory layout as illustrated in Figure 17.7.
Original
Red
Green
Blue
Copy
Figure 17.7 Effect of the shallow copy copy := original;
The major problem with the shallow copy is that serious errors will occur in a program if a change to the original
data structure is made. This is because the copy will change as well. Worse, if the storage for the Original
object is released, then the
object Copy will be unsafe as it now points to storage that is no longer considered active by the Ada run-time
system.
© M A Smith - May not be reproduced without permission