Software Design for Flexibility How to Avoid Programming Yourself into a Corner

<b>Strategies for building large systems that can be easily adapted for new situations with only minor programming modifications.</b><br><br>Time pressures encourage programmers to write code that works well for a narrow purpose, with no room to grow. But the best systems are evolvable; they can be adapted for new situations by adding code, rather than changing the existing code. The authors describe techniques they have found effective--over their combined 100-plus years of programming experience--that will help programmers avoid programming themselves into corners.<br><br>The authors explore ways to enhance flexibility by:<br><li>Organizing systems using combinators to compose mix-and-match parts, ranging from small functions to whole arithmetics, with standardized interfaces</li><li> Augmenting data with independent annotation layers, such as units of measurement or provenance</li><li> Combining independent pieces of partial information using unification or propagation</li><li> Separating control structure from problem domain with domain models, rule systems and pattern matching, propagation, and dependency-directed backtracking</li><li> Extending the programming language, using dynamically extensible evaluators</li>