pep-material: comparison progs/lecture1.scala

equal deleted inserted replaced

-:c58105a9a329
+:1bd1e9cd8c72
 // Scala Lecture 1
 //=================
 // Value assignments
 // (their names should be lower case)
 //====================================
 val x = 42
 val y = 3 + 4
 val z = x / y
 val x = 70
 print(z)
 // (you cannot reassign values: z = 9 will give an error)
 //var z = 9
 //z = 10
 // For-Comprehensions (not For-Loops)
 //====================================
-(1 to 10).toList
+val lst = (1 to 10).toList
-for (n <- (1 to 10).toList) yield {
+for (n <- lst) yield n * n
-square(n) + 1
+for (n <- lst) yield {
+square(n) + double(n)
 }
 for (n <- (1 to 10).toList;
-m <- (1 to 10).toList) yield (m, n)
+m <- (1 to 5).toList) yield (n, m, n * m)
 // you can assign the result of a for-comprehension
 // to a value
 val mult_table =
 for (n <- (1 to 10).toList;
-m <- (1 to 10).toList) yield m * n
+m <- (1 to 10).toList) yield n * m
 println(mult_table.mkString)
 mult_table.sliding(10,10).mkString("\n")
-// the list/set/... can also be constructed in any
+// for-comprehensions also work for other
-// other way
+// collections
 for (n <- Set(10,12,4,5,7,8,10)) yield n * n
 for (n <- (1 to 10)) yield {
 n * n
 }
+// with if-predicates / filters
 if (1 == 2) "a" else "b"
-// with if-predicates / filters
 for (n <- (1 to 3).toList;
 m <- (1 to 3).toList;
 if (n + m) % 2 == 0) yield (n, m)
-for (n <- (1 to 3).toList;
-m <- (1 to 3).toList;
-if ((((n + m) % 2 == 0)))) yield (n, m)
 // with patterns
 val lst = List((1, 4), (2, 3), (3, 2), (4, 1))
 // general pattern of for-yield
 // (yield can be several lines)
-for (p <- ...) yield {
+for (pat <- ...) yield {
 // potentially complicated
 // calculation of a result
 }
+// For without yield
+//===================
+// with only a side-effect (no list is produced),
+// has no "yield"
+for (n <- (1 to 10).toList) println(n * n)
+for (n <- (1 to 10).toList) yield n * n
+// BTW: a roundabout way of printing out a list, say
+val lst = ('a' to 'm').toList
+for (i <- (0 until lst.length)) println(lst(i))
+// Why not just? Why making your life so complicated?
+for (c <- lst) println(c)
 // Functions producing multiple outputs
 //======================================
 def get_ascii(c: Char) : (Char, Int) =
 strs.maxBy(_._2)
 strs.maxBy(_._1)
-// For without yield
-//===================
-// with only a side-effect (no list is produced),
-// has no "yield"
-for (n <- (1 to 10)) println(n)
-(1 to 10).toList
-(1 until 10).toList
-// BTW: a roundabout way of printing out a list, say
-val lst = ('a' to 'm').toList
-for (i <- (0 until lst.length)) println(lst(i))
-// Why not just? Why making your life so complicated?
-for (c <- lst) println(c)
 // Aside: concurrency
 // scala -Yrepl-class-based -cp scala-parallel-collections_2.13-0.2.0.jar

changeset 360	1bd1e9cd8c72
parent 359	c58105a9a329
child 361	736a60afedbc