Clojure is a dialect of Lisp that runs in the JVM. It shares with Lisp the code-as-data philosophy and a powerful macro system. Clojure is predominantly a functional programming language, and features a rich set of immutable, persistent data structures. It has strong support for reliable multithreading and concurrency.

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; lazy infinite sequence with recursive definition
(def fib-seq-lazy 
  ((fn rfib [a b] 
     (lazy-seq (cons a (rfib b (+ a b)))))
   0 1))
(take 20 fib-seq-lazy)
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; 'unless' cannot be defined with a function because
; it does not always evaluate both its arguments.
(defmacro unless [pred a b]
  `(if (not ~pred) ~a ~b))
(unless false (println "Will print") (println "Will not print"))
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(defn run [nvecs nitems nthreads niters]
  (let [vec-refs (vec (map (comp ref vec)
                           (partition nitems (range (* nvecs nitems)))))
        swap #(let [v1 (rand-int nvecs)
                    v2 (rand-int nvecs)
                    i1 (rand-int nitems)
                    i2 (rand-int nitems)]
                 (let [temp (nth @(vec-refs v1) i1)]
                   (alter (vec-refs v1) assoc i1 (nth @(vec-refs v2) i2))
                   (alter (vec-refs v2) assoc i2 temp))))
        report #(do
                 (prn (map deref vec-refs))
                 (println "Distinct:"
                          (count (distinct (apply concat (map deref vec-refs))))))]
    (dorun (apply pcalls (repeat nthreads #(dotimes [_ niters] (swap)))))
; When run, we see no values get lost or duplicated in the shuffle.
; There are 36 distinct numbers before and after. 
(run 6 6 6 100000)

Using the classpath to load a jar

This first cell shows that you get an error if you try to import a class not built-in to BeakerX:

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(import com.beaker.BeakerXClasspathTest)
(def classpathTest (new BeakerXClasspathTest))

The magic %classpath allows you to add jars to your kernel.

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%classpath add jar ../resources/jar/BeakerXClasspathTest.jar
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(import com.beaker.BeakerXClasspathTest)
(def classpathTest (new BeakerXClasspathTest))
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(. classpathTest getObjectTest)
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[{:foo 1}{:foo 2}]
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(import '[com.twosigma.beakerx.chart.xychart Plot]
        '[com.twosigma.beakerx.chart.xychart.plotitem Line])
(doto (Plot.)
            (.setTitle "We Will Control the Title")
            (.setXLabel "Horizontal")
            (.setYLabel "Vertical")
            (.add (doto (Line.)
                        (.setX [0, 1, 2, 3, 4, 5])
                        (.setY [0, 1, 6, 5, 2, 8]))))

Import/Unimport magic command

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%import com.twosigma.beakerx.widget.IntSlider
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(new IntSlider)
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%unimport com.twosigma.beakerx.widget.IntSlider
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(new IntSlider)
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