September 2017 Update

Task/Four-bit-adder/Clojure/four-bit-adder-3.clj

@@ -0,0 +1,33 @@
+(defn to-binary-seq [^long x]
+  (map #(- (int %) (int \0))
+       (Long/toBinaryString x)))
+
+(defn half-adder [a b]
+  [(bit-xor a b)
+   (bit-and a b)])
+
+(defn full-adder [a b carry]
+  (let [added (half-adder b carry)
+        half-sum (first added)]
+    [(first (half-adder a half-sum))
+     (bit-or (second (half-adder a half-sum)) (second added))]))
+
+(defn ripple-carry-adder [a b]
+  (loop [a (reverse a)
+         b (reverse b)
+         sum '()
+         carry 0]
+    (let [added (full-adder (first a) (first b) carry)]
+      (if (and (empty? (next a)) (empty? (next b)))
+        (conj sum (first added) (bit-or carry 1))
+        (recur (next a) (next b) (conj sum (first added)) (second added))))))
+
+(deftest adder
+  (is (= (Long/parseLong (apply str (ripple-carry-adder (to-binary-seq 10) (to-binary-seq 10))) 2)
+         (+ 10 10)))
+  (is (= (Long/parseLong (apply str (ripple-carry-adder (to-binary-seq 50) (to-binary-seq 50))) 2)
+         (+ 50 50)))
+  (is (= (Long/parseLong (apply str (ripple-carry-adder (to-binary-seq 32) (to-binary-seq 38))) 2)
+         (+ 32 38)))
+  (is (= (Long/parseLong (apply str (ripple-carry-adder (to-binary-seq 130) (to-binary-seq 250))) 2)
+         (+ 130 250))))