Scala : move sqrt into sandbox and Scala : add recursion.scala

3 files changed, 64 insertions, 0 deletions

diff --git a/Scala/sandbox/main.scala b/Scala/sandbox/main.scala
new file mode 100644
index 0000000..e770ece
--- /dev/null
+++ b/Scala/sandbox/main.scala
@@ -0,0 +1,7 @@
+
+object Main extends App {
+
+  Sqrt.run
+  Recursion.run
+
+}
diff --git a/Scala/sandbox/recursion.scala b/Scala/sandbox/recursion.scala
new file mode 100644
index 0000000..e7c29a5
--- /dev/null
+++ b/Scala/sandbox/recursion.scala
@@ -0,0 +1,29 @@
+
+object Recursion {
+
+  // Tail recursion - tail calls
+  // the function calls itself (or another one) as last action
+  // -> the function's stack frame can be reused!
+  // -> this is as efficient as a loop
+  def gcd(a: Int, b: Int): Int =
+    if (b == 0) a else gcd(b, a % b)
+
+  println(gcd(21, 56))
+
+  // there is still the multiplication to be performed
+  // -> the stack frame can't be reused
+  def fact(n: Int): Int =
+    if (n == 0) 1 else n * fact(n - 1)
+
+  println(fact(4))
+
+  // tail recursive version of factorial
+  def factr(n: Int): Int = {
+    def factIter(acc: Int, n: Int): Int =
+      if (n == 0) acc else factIter(acc * n, n - 1)
+    factIter(1, n)
+  }
+
+  def run = println(factr(4))
+
+}
diff --git a/Scala/sandbox/sqrt.scala b/Scala/sandbox/sqrt.scala
new file mode 100644
index 0000000..2544425
--- /dev/null
+++ b/Scala/sandbox/sqrt.scala
@@ -0,0 +1,28 @@
+
+object Sqrt {
+
+  def abs(x:Double) = if (x < 0) -x else x
+
+  def sqrt(x: Double) = {
+
+    def sqrtIter(guess: Double): Double =
+      if (isGoodEnough(guess)) guess
+      else sqrtIter(improve(guess))
+
+    def isGoodEnough(guess: Double) =
+      abs(guess * guess - x ) /x < 0.001
+
+    def improve(guess: Double) =
+      (guess + x / guess) / 2
+
+    sqrtIter(1.0)
+  }
+
+  def run =
+    println(sqrt(2))
+    println(sqrt(0.001))
+    println(sqrt(0.1e-20))
+    println(sqrt(1.0e20))
+    println(sqrt(1.0e50))
+
+}