lazy

produces a lazy evaluation

Like delay, but if the first forced result is a promise, it will continue to be forced until a non-promise result is capable of being returned.

An Example

(define p (lazy
            (println "hello once")
            (delay
              (println "hello twice")
              "hello")))
(force p) ;; prints "hello once / hello twice"
(force p)

The first invocation of p will print “hello once” followed by “hello twice” to the console, also returning the string “hello”. Subsequent invocations of p will only return “hello”.