added assignment 7 ex 4

src/Assignment7/Ex4.sc

@@ -0,0 +1,19 @@
+
+def THRESHOLD: Double = 0.0001
+
+def sqr(x: Double): Double = x * x
+
+def sqrt_stream(value: Double): LazyList[Double] = {
+  def helper(target: Double, approx: Double): LazyList[Double] = {
+    approx #:: helper(target, approx - (sqr(approx) - target) / (2 * approx))
+  }
+  helper(value, value)
+}
+
+sqrt_stream(2).take(10).toList
+
+def threshold(list: LazyList[Double], thresh: Double) = {
+  list.zip(list.drop(1)).filter(p => math.abs(p._2 - p._1) < thresh).head._2
+}
+
+threshold(sqrt_stream(2), 1e-15)