Chapter 11
Type abstraction

Aims

• To introduce the notion of type abstraction, and its realisation through the Miranda abstype mechanism.
• To illustrate multiple implementations of abstype signatures.
• To compare the effect of modifying the implementation of a type when it is concretely or abstractly presented.
• To present standard data types: stacks, queues, search trees, sets, relations and graphs, together with their abstract interfaces.
• To discuss principles of abstract data type design, and to illustrate their use in the simulation case study.

Issues

Modification

I have tried to give an illustration of the value of type abstraction using the abstype of search trees. The implementation has a size field added, and we can then examine the effect on the functions using the search trees. It would be interesting to illustrate this using abstypes from other case studies.

Design

There is plenty of scope for class exercises to design abstract data types, particularly examples which have been presented earlier in the course.

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