Data commit

Task/Pi/Clojure/pi.clj

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+(ns pidigits
+  (:gen-class))
+
+(def calc-pi
+        ;  integer division rounding downwards to -infinity
+  (let [div (fn [x y] (long (Math/floor (/ x y))))
+
+          ; Computations performed after yield clause in Python code
+          update-after-yield (fn [[q r t k n l]]
+                         (let [nr (* 10 (- r (* n t)))
+                               nn (- (div (* 10 (+ (* 3 q) r)) t) (* 10 n))
+                               nq (* 10 q)]
+                           [nq nr t k nn l]))
+
+          ; Update of else clause in Python code: if (< (- (+ (* 4 q) r) t) (* n t))
+          update-else (fn [[q r t k n l]]
+                        (let [nr (* (+ (* 2 q) r) l)
+                              nn (div (+ (* q 7 k) 2 (* r l)) (* t l))
+                              nq (* k q)
+                              nt (* l t)
+                              nl (+ 2 l)
+                              nk (+ 1 k)]
+                          [nq nr nt nk nn nl]))
+
+          ; Compute the lazy sequence of pi digits translating the Python code
+          pi-from (fn pi-from [[q r t k n l]]
+                    (if (< (- (+ (* 4 q) r) t) (* n t))
+                      (lazy-seq (cons n (pi-from (update-after-yield [q r t k n l]))))
+                      (recur (update-else [q r t k n l]))))]
+
+      ; Use Clojure big numbers to perform the math (avoid integer overflow)
+      (pi-from [1N 0N 1N 1N 3N 3N])))
+
+;; Indefinitely Output digits of pi, with 40 characters per line
+(doseq [[i q] (map-indexed vector calc-pi)]
+  (when (= (mod i 40) 0)
+    (println))
+  (print q))