Eliminated possibilities to perform infinite loops

Author: kiroco12

src/main/scala/scalatutorial/sections/FunctionalLoops.scala

@@ -137,10 +137,10 @@ object FunctionalLoops extends ScalaTutorialSection {
    *
    * Complete the following method definition that computes the factorial of a number:
    */
-  def factorialExercise(res0: Int, res1: Int, res2: Int): Unit = {
+  def factorialExercise(res0: Int, res1: Int): Unit = {
     def factorial(n: Int): Int =
       if (n == res0) res1
-      else factorial(n - res2) * n
+      else factorial(n - 1) * n
 
     factorial(3) shouldBe 6
     factorial(4) shouldBe 24

src/main/scala/scalatutorial/sections/HigherOrderFunctions.scala

@@ -161,9 +161,9 @@ object HigherOrderFunctions extends ScalaTutorialSection {
     def sum(f: Int => Int, a: Int, b: Int): Int = {
       def loop(x: Int, acc: Int): Int =
         if (x > b) acc
-        else loop(x + res0, acc + f(x))
-      loop(a, res1)
+        else loop(x + 1, acc + f(x))
+      loop(a, res0)
     }
-    sum(x => x, 1, 10) shouldBe 55
+    sum(x => x, 1, res1) shouldBe 55
   }
 }

src/main/scala/scalatutorial/sections/TailRecursion.scala

@@ -127,14 +127,14 @@ object TailRecursion extends ScalaTutorialSection {
    *
    * Complete the following definition of a tail-recursive version of `factorial`:
    */
-  def tailRecFactorial(res0: Int, res1: Int, res2: Int): Unit = {
+  def tailRecFactorial(res0: Int, res1: Int): Unit = {
     def factorial(n: Int): Int = {
       @tailrec
       def iter(x: Int, result: Int): Int =
         if (x == res0) result
-        else iter(x - res1, result * x)
+        else iter(x - 1, result * x)
 
-      iter(n, res2)
+      iter(n, res1)
     }
 
     factorial(3) shouldBe 6

src/test/scala/scalatutorial/sections/FunctionalLoopsSpec.scala

@@ -0,0 +1,28 @@
+/*
+ *  scala-exercises - exercises-scalatutorial
+ *  Copyright (C) 2015-2019 47 Degrees, LLC. <http://www.47deg.com>
+ *
+ */
+
+package scalatutorial.sections
+
+import org.scalacheck.{Arbitrary, Gen}
+//import org.scalacheck.ScalacheckShapeless._
+import org.scalaexercises.Test
+import org.scalatest.refspec.RefSpec
+import org.scalatestplus.scalacheck.Checkers
+import shapeless._
+
+class FunctionalLoopsSpec extends RefSpec with Checkers {
+
+  implicit val arb: Arbitrary[Int :: Int :: HNil] = Arbitrary {
+    for {
+      num1 <- Gen.choose(-10, 0)
+      num2 <- Gen.choose(0, 10)
+    } yield num1 :: num2 :: HNil
+  }
+
+  def `factorial exercise with recursion`(): Unit =
+    check(Test.testSuccess(FunctionalLoops.factorialExercise _, 0 :: 1 :: HNil))
+
+}

src/test/scala/scalatutorial/sections/HigherOrderFunctionsSpec.scala

@@ -0,0 +1,28 @@
+/*
+ *  scala-exercises - exercises-scalatutorial
+ *  Copyright (C) 2015-2019 47 Degrees, LLC. <http://www.47deg.com>
+ *
+ */
+
+package scalatutorial.sections
+
+//import org.scalacheck.ScalacheckShapeless._
+import org.scalacheck.{Arbitrary, Gen}
+import org.scalaexercises.Test
+import org.scalatest.refspec.RefSpec
+import org.scalatestplus.scalacheck.Checkers
+import shapeless.{::, HNil}
+
+class HigherOrderFunctionsSpec extends RefSpec with Checkers {
+
+  implicit val arb: Arbitrary[Int :: Int :: HNil] = Arbitrary {
+    for {
+      num1 <- Gen.posNum[Int]
+      num2 <- Gen.posNum[Int]
+    } yield num1 :: num2 :: HNil
+  }
+
+  def `check tail recursive sum function`(): Unit =
+    check(Test.testSuccess(HigherOrderFunctions.tailRecSum _, 0 :: 10 :: HNil))
+
+}

src/test/scala/scalatutorial/sections/TailRecursionSpec.scala

@@ -0,0 +1,20 @@
+/*
+ *  scala-exercises - exercises-scalatutorial
+ *  Copyright (C) 2015-2019 47 Degrees, LLC. <http://www.47deg.com>
+ *
+ */
+
+package scalatutorial.sections
+
+import org.scalacheck.ScalacheckShapeless._
+import org.scalaexercises.Test
+import org.scalatest.refspec.RefSpec
+import org.scalatestplus.scalacheck.Checkers
+import shapeless.HNil
+
+class TailRecursionSpec extends RefSpec with Checkers {
+
+  def `factorial exercise tail recursive`(): Unit =
+    check(Test.testSuccess(TailRecursion.tailRecFactorial _, 0 :: 1 :: HNil))
+
+}