Delayed evaluation in Clojure
- by StackedCrooked
I'm having some trouble understanding how the delay macro works in Clojure. It doesn't seem to do what expect it to do (that is: delaying evaluation). As you can see in this code sample:
; returns the current time
(defn get-timestamp [] (.getTime (java.util.Date.)))
; var should contain the current timestamp after calling "force"
(def current-time (delay (get-timestamp)))
However, calling current-time in the REPL appears to immediately evaluate the expression, even without having used the force macro:
user=> current-time
#<Delay@19b5217: 1276376485859>
user=> (force current-time)
1276376485859
Why was the evaluation of get-timestamp not delayed until the first force call?
