clojure (with-timeout ... macro)

Question

I'm looking for a macro that will throw an exception if an expression takes longer than X seconds to complete.

Answer 1

This question has better answers here: Executing a function with a timeout

Futures to the rescue!

user=> (let [f (future (reduce * (range 1 1001)))]
  (.get f 1 java.util.concurrent.TimeUnit/MILLISECONDS))
java.util.concurrent.TimeoutException (NO_SOURCE_FILE:0)

And to make a macro of it:

(defmacro time-limited [ms & body]
  `(let [f# (future ~@body)]
     (.get f# ~ms java.util.concurrent.TimeUnit/MILLISECONDS)))

So you can do this:

user=> (time-limited 1 (reduce * (range 1 1001)))
java.util.concurrent.TimeoutException (NO_SOURCE_FILE:0)
user=> (time-limited 1 (reduce * (range 1 101)))
93326215443944152681699238856266700490715968264381621468592963895217599993229915
608941463976156518286253697920827223758251185210916864000000000000000000000000