P019 with some Traits to structur the problems

src/.gitignore

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+*.class
+*~

src/p019.scala

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+object p019 extends Solutions[SolutionP019]{
+
+  def doc = """
+    http://aperiodic.net/phil/scala/s-99/p19.scala
+    P19 (**) Rotate a list N places to the left.
+    Examples:
+    scala> rotate(3, List('a, 'b, 'c, 'd, 'e, 'f, 'g, 'h, 'i, 'j, 'k))
+    res0: List[Symbol] = List('d, 'e, 'f, 'g, 'h, 'i, 'j, 'k, 'a, 'b, 'c)
+
+    scala> rotate(-2, List('a, 'b, 'c, 'd, 'e, 'f, 'g, 'h, 'i, 'j, 'k))
+    res1: List[Symbol] = List('j, 'k, 'a, 'b, 'c, 'd, 'e, 'f, 'g, 'h, 'i)
+  """
+
+  def tests()={
+    for (sol <- implementations) {
+      print ("Test implementation " + sol.simpleName)
+
+
+      val expected=List('d, 'e, 'f, 'g, 'h, 'i, 'j, 'k, 'a, 'b, 'c)
+      val result=sol.rotate(3, List('a, 'b, 'c, 'd, 'e, 'f, 'g, 'h, 'i, 'j, 'k))
+      require(expected==result)
+      println (" : OK ")
+    }
+  }
+
+  def implementations ()=List(DavidBernard, AlexisAgahi, AriéBénichou )
+
+  object DavidBernard extends SolutionP019 {
+    def rotate[A](k:Int, l:List[A]) = if(l.isEmpty) Nil else {
+      val nk = k % l.length
+      val pk = if(k < 0) l.length + k else k
+      l.drop(pk) ::: l.take(pk)
+    }
+  }
+
+  object BenjaminLerman extends SolutionP019 {
+    def rotate[A](k:Int, l:List[A]) = if(l.isEmpty) Nil else {
+      val nk = k % l.length
+      val pk = if(k < 0) l.length + nk else nk
+      l.drop(pk) ::: l.take(pk)
+    }
+  }
+
+  object AlexisAgahi extends SolutionP019 {
+    def rotate[T]( n:Int, list:List[T]):List[T] = {
+      val size = list.size
+      require( size > 0 )
+      val i = if( n < 0) size + n % size else n % size
+      val (l1, l2 ) = list.splitAt( i )
+      l2 ::: l1
+    }
+  }
+
+  object AriéBénichou extends SolutionP019 {
+
+
+    def rotate[T](n: Int, ls: List[T]): List[T] = {
+      if (ls == null)
+	return Nil
+
+      val length = ls.length      
+      if (length == 0)
+	return Nil
+
+      val (l, r) = ls.splitAt(if (n < 0) length + n % length else n % length);
+      r ::: l      
+    }
+  }
+}
+

src/p020.scala

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+
+object p020 extends Solutions[SolutionP020]{
+  def doc = """
+  scala> removeAt(1, List('a, 'b, 'c, 'd))
+  res0: (List[Symbol], Symbol) = (List('a, 'c, 'd),'b)
+  """
+
+  def tests ()={
+    for (sol <- implementations) {
+      print ("Test implementation " + sol.simpleName)
+      val expected=(List('a, 'c, 'd),'b)
+	val result=sol.removeAt(1, List('a, 'b, 'c, 'd))
+      require(expected==result)
+      println (" : OK ")
+    }
+  }
+
+  def implementations ()=List(BenjaminLerman)
+
+  object BenjaminLerman extends SolutionP020 {
+    def removeAt[A](k:Int, l:List[A]) = (l.take(k):::l.drop(k+1), l(k))
+  }
+}

src/problems.scala

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+import scala.util.matching.Regex
+
+trait Solution {
+  val pattern = new Regex("""(.*)\$(.*)\$""", "problem", "solutionName");
+  def simpleName:String=pattern.findFirstMatchIn(this.getClass.getSimpleName).get.group ("solutionName")
+}
+trait Solutions[Problem] {
+  def doc():String
+  def tests ()
+  def implementations ():List[Problem]
+
+  def main(args: Array[String]) = {
+    println (doc)
+    tests
+  }
+}
+
+
+
+trait SolutionP019 extends Solution {
+  def rotate[T] (n:Int, l:List[T]):List[T]
+}
+
+trait SolutionP020 extends Solution {
+  def removeAt[T] (n:Int, l:List[T]):(List[T], T)
+}