tasks a-s

Task/Reverse-a-string/Scala/reverse-a-string-1.scala

@@ -0,0 +1 @@
+"asdf".reverse

Task/Reverse-a-string/Scala/reverse-a-string-2.scala

@@ -0,0 +1 @@
+"asdf".foldRight(""){ (a,b)=> b+a }

Task/Reverse-a-string/Scala/reverse-a-string-3.scala

@@ -0,0 +1,30 @@
+def reverseString(s: String) = {
+  import java.lang.Character._
+
+  val combiningTypes = List(NON_SPACING_MARK, ENCLOSING_MARK, COMBINING_SPACING_MARK)
+  def isCombiningCharacter(c: Char) = combiningTypes contains c.getType
+  def isCombiningSurrogate(high: Char, low: Char) = combiningTypes contains getType(toCodePoint(high, low))
+  def isCombining(l: List[Char]) = l match {
+    case List(a, b) => isCombiningSurrogate(a, b)
+    case List(a) => isCombiningCharacter(a)
+    case Nil => true
+    case _ => throw new IllegalArgumentException("isCombining expects a list of up to two characters")
+  }
+
+  def cleanSurrogate(l: List[Char]) = l match {
+    case List(a, b) if a.isHighSurrogate && b.isLowSurrogate => l
+    case List(a, b) if a.isLowSurrogate => Nil
+    case List(a, b) => List(a)
+    case _ => throw new IllegalArgumentException("cleanSurrogate expects lists of two characters, exactly")
+  }
+
+  def splitString(string: String) = (string+" ").iterator sliding 2 map (_.toList) map cleanSurrogate toList
+
+  def recurse(fwd: List[List[Char]], rev: List[Char]): String = fwd match {
+    case Nil => rev.mkString
+    case c :: rest =>
+      val (combining, remaining) = rest span isCombining
+      recurse(remaining, c ::: combining.foldLeft(List[Char]())(_ ::: _) ::: rev)
+  }
+  recurse(splitString(s), Nil)
+}