Merge pull request #62 from andreas-roehler/master

solution2.2.6.5 provided

chapter02/worksheets/solution2.2.6.5.scala

@@ -0,0 +1,41 @@
+/** 
+  Exercise 2.2.6.5
+  Split a sequence into subsequences (“batches”) of length at most
+  𝑛.
+  The required type signature and a sample test:
+
+  def byLength[A](xs: Seq[A], maxLength: Int): Seq[Seq[A]] = ???
+
+  scala> byLength(Seq("a", "b", "c", "d"), 2)
+  res0: Seq[Seq[String]] = List(List(a, b), List(c, d))
+
+  scala> byLength(Seq(1, 2, 3, 4, 5, 6, 7), 3)
+  res1: Seq[Seq[Int]] = List(List(1, 2, 3), List(4, 5, 6), List(7))
+ */
+
+def byLength[A](xs: Seq[A], maxLength: Int): Seq[Seq[A]] = {
+  if (xs.length <= maxLength)
+    Seq(xs)
+  else
+    Seq(xs.take(maxLength)) ++ byLength(xs.drop(maxLength), maxLength)
+}
+
+val expected = Seq(Seq("a", "b"), List("c", "d"))
+val result = byLength(Seq("a", "b", "c", "d"), 2)
+assert(result == expected) 
+val a =  Seq(Seq(1, 2, 3), List(4, 5, 6), List(7))
+val b =  byLength(Seq(1, 2, 3, 4, 5, 6, 7), 3)
+assert(a == b)
+val c =  Seq(Seq(1, 2))
+val d =  byLength(Seq(1, 2), 3)
+assert(c == d)
+
+
+// scala> :load solution2.2.6.5.scala
+// :load solution2.2.6.5.scala
+// def byLength[A](xs: Seq[A], maxLength: Int): Seq[Seq[A]]
+// val expected: Seq[Seq[String]] = List(List(a, b), List(c, d))
+// val result: Seq[Seq[String]] = List(List(a, b), List(c, d))
+// val a: Seq[Seq[Int]] = List(List(1, 2, 3), List(4, 5, 6), List(7))
+// val b: Seq[Seq[Int]] = List(List(1, 2, 3), List(4, 5, 6), List(7))
+