(defmacro delay
"Takes a body of expressions and yields a Delay object that will
invoke the body only the first time it is forced (with force or deref/@), and
will cache the result and return it on all subsequent force
calls. See also - realized?"
{:added "1.0"}
[& body]
(list 'new 'clojure.lang.Delay (list* `^{:once true} fn* [] body)))