Note: Some of the plain-text notes on this page cite books whose references are given below.

Eiffel

• Modern Guarded Commands
• Simpler tuples, nice consequences
• Modularity without Abstraction is no more than Syntactic Sugar
• Dessy: Simpler, Faster A library of data structures
• Meine Studienarbeit Die ganze Wahrheit über Covarianz: Typsysteme, Typregeln, Typtheorien und praktische Zusammenhänge, eine Aufstellung problematischer Programmiermuster und neue gute Typregeln für Eiffel. For a translation see below.
• Before I had a terrible accident with rm -r there was an article called Caring for Covariance with Complete Contract Conformance. Since then I am left with only some inconsistent drafts of the article. If anyone out there happens to have a downloaded copy, please send it to me!

Messages on Covariance

A famous language designer has put me in charge to update him on the recent developments of Covariance -- that is generally speaking: Advanced Typing in Object-Oriented languages. Since I don't have much time to spend on this work, I'm doing the instruction in portions of small electronic mail messages. And since this information is so valuable to the object-oriented language designer and user community at large, I'm making it available here. (This translates the main ideas of my Studienarbeit and already adds some new things, e.g. the algorithm in the first message.)

1. Generic Conformance (Attachments: generic_conformance.hs, SimpleMap.hs)
2. The method doesn't need it
3. Generic Programming
4. Grey Zones
5. Advances in Typing
6. Generic Routines
7. Actions

Appendices

1. Method of Inheritance
2. Disciplined exceptions
3. To appreciate Generic Conformace fully read a bit about Dessy, especially its immutable structures.

The image relates the different kinds of errors that are mentioned in the note on Disciplined Exceptions. Design by Contract (especially with tool support) effectively fights implementation errors which are all logical. Tools to prevent logical errors during analysis need languages of much higher level. Finally, approximation errors are intrinsic to the gap between the real world and its computer model and they can never be eliminated, but only be minimised.

References

• OOSC1: Bertrand Meyer, 1988: Object-Oriented Software Construction, Prentice Hall
• Bertrand Meyer, 1988: Disciplined Exceptions
• Carroll Morgan: Programming from Specifications, 2nd ed., Prentice Hall 1994.
• Eric C.R. Hehner: A practical theory of programming, 2nd ed., 2004
  The book's main ideas can be found in the papers Theories, Implementations, and Transformations and Boolean Formalism and Explanations on Hehner's homepage.