2016 Update

Task/Arithmetic-geometric-mean/JavaScript/arithmetic-geometric-mean-2.js

@@ -0,0 +1,43 @@
+(() => {
+    'use strict';
+
+    // ARITHMETIC-GEOMETRIC MEAN
+
+    // agm :: Num a => a -> a -> a
+    let agm = (a, g) => {
+            let abs = Math.abs,
+                sqrt = Math.sqrt;
+
+            return until(
+                    m => abs(m.an - m.gn) < tolerance,
+                    m => {
+                        return {
+                            an: (m.an + m.gn) / 2,
+                            gn: sqrt(m.an * m.gn)
+                        };
+                    }, {
+                        an: (a + g) / 2,
+                        gn: sqrt(a * g)
+                    }
+                )
+                .an;
+        },
+
+        // GENERIC
+
+        // until :: (a -> Bool) -> (a -> a) -> a -> a
+        until = (p, f, x) => {
+            let v = x;
+            while (!p(v)) v = f(v);
+            return v;
+        };
+
+
+    // TEST
+
+    let tolerance = 0.000001;
+
+
+    return agm(1, 1 / Math.sqrt(2));
+
+})();