+(define-condition defconstant-uneql (error)
+ ((name :initarg :name :reader defconstant-uneql-name)
+ (old-value :initarg :old-value :reader defconstant-uneql-old-value)
+ (new-value :initarg :new-value :reader defconstant-uneql-new-value))
+ (:report
+ (lambda (condition stream)
+ (format stream
+ "~@<The constant ~S is being redefined (from ~S to ~S)~@:>"
+ (defconstant-uneql-name condition)
+ (defconstant-uneql-old-value condition)
+ (defconstant-uneql-new-value condition)))))