intro verbesserung

Author: cryptoki

src/main/worksheets/a_bridge/c_collections.sc

@@ -3,29 +3,95 @@
 // | Lists        - immutable (normally)                |
 // +----------------------------------------------------+
 
+// ====================================
+// Array
+// ====================================
 val array = Array(2,3,4,5)
 array.update(2,400)
 array
 
 
-// define an empty list
-val list1 = List()
+// ====================================
+// List
+// ====================================
+
+// TODO -1-  define a list with values 1,2,3,4
+val list1: List[Int] = List(1,2,3,4)
+
+assert(list1.sum == 10)
+
+// TODO -2-  define a list with value "b", "c"
+val list2: List[String] = List("b", "c")
+
+assert(list2(0) == "b")
+assert(list2(1) == "c")
+
 
 // append
 // ------
 // the operator '::' is defined in List
 //   - Scala use internal case class '::' which extends List
 //   - add the left operand as first element to the new list and return it
-"a" :: "b" :: list1
+// TODO -me-  append value "a" to the head of list2
+val list3:List[String] = "a" :: list2
+
+assert(list3(0) == "a")
 
 // the same to ::
-list1.::("b").::("a")
+list2.::("a")
 // => http://www.scala-lang.org/api/2.11.5/index.html#scala.collection.immutable.List
 // => Scala Basic Part I
 
 
-// ADD
-val list2 = List(1,2)
-list2 ++ List(3,4)
-list2 :+ 3
-list2.+:(3)
+// TODO -me- concat list2 and list3
+val list4:List[String] = list2 ++ list3
+
+assert(list4(2) == "a")
+
+
+// TODO -me-  addon
+// additional
+val list5 = List(1,2)
+// concat two lists
+list5 ++ List(3,4)
+// add right
+list5 :+ 3
+// add left
+list5.+:(3)
+
+
+// ====================================
+// Methods
+// ====================================
+val seq1: Seq[Int] = Seq(1,2,3,4,5,6)
+
+// TODO -1-  multiply each value by 2 and
+//           sum up every value
+val seq1Sum = seq1.map(x => x*2).sum
+assert(seq1Sum == 42)
+
+// TODO -me-  bring the synatic sugar
+seq1.map((x: Int) => x*2).sum
+seq1 map(_*2) sum
+
+// TODO -me-  what is (x: Int) => x*2?
+val f = (x: Int) => x*2
+seq1.map(f).sum
+seq1 map f sum
+
+
+// +---------------------------------------------
+// | TODO -me-  addon => only as reference
+// | additional - reference
+// +---------------------------------------------
+// head / tail
+seq1.head
+seq1.tail
+// some methods
+seq1.filter(_ % 2 == 0)
+seq1.groupBy(x => x%2)
+seq1.reduce((x,y) => x+y)
+seq1.partition(_ % 2 == 0)
+// zip and map
+val seq2: Seq[Int] = seq1.reverse
+seq1.zip(seq2).map(x => x._1+x._2)

src/main/worksheets/a_bridge/c_collections_array.sc

@@ -1,9 +1,9 @@
-// a )
-// -1- define an array of Integer with initial values 2,3,4,5
-// -2- overwrite the value 4 with 400
-
+// TODO -1-  define an array of Integer with
+//           initial values 2,3,4,5
 val array:Array[Int] = ???
 assert(array(3) == 4)
 
+// TODO -2-  overwrite the value 4 with 400
 
 assert(array(3) == 400)
+

src/main/worksheets/a_bridge/c_collections_list.sc

@@ -1,23 +1,33 @@
-// a )
-// -1- define a list with values 1,2,3,4
-val list1: List[Int] = List()
+// TODO -1-  define a list with values 1,2,3,4
+val list1: List[Int] = ???
 
 assert(list1.sum == 10)
 
-// -2- define a list with value "b", "c"
+// TODO -2-  define a list with value "b", "c"
 val list2: List[String] = List()
 
 assert(list2(0) == "b")
 assert(list2(1) == "c")
 
 
-// -3- append value "a" to the head of list2
-val list3 = list2
+// TODO -me-  append value "a" to the head of list2
+val list3:List[String] = ???
 
 assert(list3(0) == "a")
 
 
-// -4- append list2 and list3
-val list4 = list2
+// TODO -me- concat list2 and list3
+val list4:List[String] = ???
 
 assert(list4(2) == "a")
+
+
+// TODO -me-  addon
+// additional
+val list5 = List(1,2)
+// concat two lists
+list5 ++ List(3,4)
+// add right
+list5 :+ 3
+// add left
+list5.+:(3)

src/main/worksheets/a_bridge/c_collections_methods.sc

@@ -0,0 +1,32 @@
+val seq1: Seq[Int] = Seq(1,2,3,4,5,6)
+
+// TODO -1-  multiply each value by 2 and
+//           sum up every value
+val seq1Sum = seq1.map(x => x*2).sum
+assert(seq1Sum == 42)
+
+// TODO -me-  bring the synatic sugar
+seq1.map((x: Int) => x*2).sum
+seq1 map(_*2) sum
+
+// TODO -me-  what is (x: Int) => x*2?
+val f = (x: Int) => x*2
+seq1.map(f).sum
+seq1 map f sum
+
+// +---------------------------------------------
+// | TODO -me-  addon => only as reference
+// | additional - reference
+// +---------------------------------------------
+// head / tail
+seq1.head
+seq1.tail
+// some methods
+seq1.filter(_ % 2 == 0)
+seq1.groupBy(x => x%2)
+seq1.reduce((x,y) => x+y)
+seq1.partition(_ % 2 == 0)
+// zip and map
+val seq2: Seq[Int] = seq1.reverse
+seq1.zip(seq2).map(x => x._1+x._2)
+