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Introduction and Obligatory Hype ¶

This book has two intended audiences. The larger one is Common Lisp programmers, or people who at least have been learning the language, who want to explore the benefits of modern functional collections.

There’s a second audience, however, I also hope to reach, consisting not of people who expect to use Common Lisp or FSet, but rather designers of other languages and/or libraries for those languages. I refer such readers to the chapters Conceptual Background and Recommendations for Language Designers; the other chapters will still be worth reading, I think, but of less importance.

For those who may want to actually use FSet, though, this book does assume some basic proficiency in Common Lisp; I don’t recommend it as a first text for those learning the language. You will need to know, at the very least:

• how to run your chosen CL implementation and interact with its REPL
• what to do when an error brings up the debugger
• how to write simple Lisp functions that operate on lists
• the difference between a function and a macro (“Functions compute; macros translate.” — David A. Moon)

For a fuller understanding, these topics will also be helpful:

• how to define classes with defclass or deftype
• how CLOS generic functions work, including how to define methods with defmethod

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• Why I Wrote FSet
• Benefits of Functional Collections