9. Appendix: Programming Language Design Principles

This is the list of programming language design principles from Bruce MacLennan’s excellent Principles of Programming Languages (2nd edition, 1986, ISBN 0-03-005163-0, found on Oliver Wyman’s blog.

  • Abstraction: Avoid requiring something to be stated more than once; factor out the recurring pattern.

  • Automation: Automate mechanical, tedious, or error-prone activities.

  • Defense in Depth: Have a series of defences so that if an error isn’t caught by one, it will probably be caught by another.

  • Information Hiding: The language should permit modules designed so that (1) the user has all of the information needed to use the module correctly, and nothing more; and (2) the implementor has all of the information needed to implement the module correctly, and nothing more.

  • Labeling: Avoid arbitrary sequences more than a few items long. Do not require the user to know the absolute position of an item in a list. Instead, associate a meaningful label with each item and allow the items to occur in any order.

  • Localized Cost: Users should only pay for what they use; avoid distributed costs.

  • Manifest Interface: All interfaces should be apparent (manifest) in the syntax.

  • Orthogonality: Independent functions should be controlled by independent mechanisms.

  • Portability: Avoid features or facilities that are dependent on a particular machine or a small class of machines.

  • Preservation of Information: The language should allow the representation of information that the user might know and that the compiler might need.

  • Regularity: Regular rules, without exceptions, are easier to learn, use, describe, and implement.

  • Security: No program that violates the definition of the language, or its own intended structure, should escape detection.

  • Simplicity: A language should be as simple as possible. There should be a minimum number of concepts, with simple rules for their combination.

  • Structure: The static structure of the program should correspond in a simple way to the dynamic structure of the corresponding computations.

  • Syntactic Consistency: Similar things should look similar; different things different.

  • Zero-One-Infinity: The only reasonable numbers are zero, one, and infinity.