One of the most obvious perks of using the Clojure is the user community organized around it. With this clip, the fourth installment in Sean Devlin's "Full Disclojure" series of Clojure video tutorials, you'll learn how to use the new constraint system in Clojure 1.1. Constraints are certain pre and post conditions that need to be met in order for a function to execute properly. If you've used D or Eiffel you've worked with constraints before. For more information, including a detailed, step-by-step overview, watch this programmer's guide.