3. Jess Language Basics 11 3. Jess Language Basics Most of the time, you'll write Jess rules in the Jess rule language . If you've never used Lisp, the Jess rule language may look a bit odd at first, but it doesn't take long to learn. The payoff is that it's very expressive, and can implement complex logical relationships with very little code. In this chapter, we'll look at the basic syntax of the Jess language. In subsequent chapters, we'll learn how to define high-level concepts like facts and rules, but here, we'll just be looking at the nuts and bolts. In this language guide, I'll use an extremely informal notation to describe syntax. Basically strings in <angle-brackets> are some kind of data that must be supplied; things in [square brackets] are optional, things ending with + can appear one or more times, and things ending with * can appear zero or more times. In general, input to Jess is free-format. Newlines are generally not significant and are treated as whitespace; exceptions will be noted. 3.1. Symbols
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