7.2.2.3 Subclass of ERROR

When using the condition system for error handling, you should define your conditions as subclasses of ‘ERROR’, a subclass of ‘CONDITION’. Thus, you might define ‘malformed-log-entry-error’, with a slot to hold the argument that was passed to parse-log-entry, like this:

(define-condition malformed-log-entry-error (error)
  ((text :initarg :text :reader text)))