progs/lecture2.scala
author Christian Urban <urbanc@in.tum.de>
Thu, 01 Aug 2019 09:48:34 +0100
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// Scala Lecture 2
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//=================
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// UNFINISHED BUSINESS from Lecture 1
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//====================================
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// for measuring time
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def time_needed[T](n: Int, code: => T) = {
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  val start = System.nanoTime()
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  for (i <- (0 to n)) code
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  val end = System.nanoTime()
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  (end - start) / 1.0e9
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}
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val list = (1 to 1000000).toList
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time_needed(10, for (n <- list) yield n + 42)
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time_needed(10, for (n <- list.par) yield n + 42)
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// (needs a library and 'magic' option -Yrepl-class-based)
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// Just for Fun: Mutable vs Immutable
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//====================================
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//
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// - no vars, no ++i, no +=
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// - no mutable data-structures (no Arrays, no ListBuffers)
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// Q: Count how many elements are in the intersections of 
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//    two sets?
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def count_intersection(A: Set[Int], B: Set[Int]) : Int = {
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  var count = 0
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  for (x <- A; if B contains x) count += 1 
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  count
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}
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val A = (1 to 1000).toSet
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val B = (1 to 1000 by 4).toSet
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count_intersection(A, B)
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// but do not try to add .par to the for-loop above
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//propper parallel version
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def count_intersection2(A: Set[Int], B: Set[Int]) : Int = 
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  A.par.count(x => B contains x)
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count_intersection2(A, B)
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val A = (1 to 1000000).toSet
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val B = (1 to 1000000 by 4).toSet
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time_needed(100, count_intersection(A, B))
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time_needed(100, count_intersection2(A, B))
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// For-Comprehensions Again
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//==========================
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// the first produces a result, while the second does not
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for (n <- List(1, 2, 3, 4, 5)) yield n * n
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for (n <- List(1, 2, 3, 4, 5)) println(n)
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// Higher-Order Functions
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//========================
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// functions can take functions as arguments
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def even(x: Int) : Boolean = x % 2 == 0
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def odd(x: Int) : Boolean = x % 2 == 1
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val lst = (1 to 10).toList
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lst.filter(x => even(x))
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lst.filter(even(_))
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lst.filter(even)
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lst.count(even)
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lst.find(even)
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val ps = List((3, 0), (3, 2), (4, 2), (2, 2), (2, 0), (1, 1), (1, 0))
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lst.sortWith(_ > _)
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lst.sortWith(_ < _)
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def lex(x: (Int, Int), y: (Int, Int)) : Boolean = 
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  if (x._1 == y._1) x._2 < y._2 else x._1 < y._1
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ps.sortWith(lex)
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ps.sortBy(_._1)
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ps.sortBy(_._2)
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ps.maxBy(_._1)
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ps.maxBy(_._2)
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// maps (lower-case)
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//===================
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def double(x: Int): Int = x + x
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def square(x: Int): Int = x * x
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val lst = (1 to 10).toList
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lst.map(x => (double(x), square(x)))
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lst.map(square)
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// this is actually how for-comprehensions 
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// defined as in Scala
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lst.map(n => square(n))
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for (n <- lst) yield square(n)
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// this can be iterated
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lst.map(square).filter(_ > 4)
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lst.map(square).filter(_ > 4).map(square)
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// lets define our own functions
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// type of functions, for example f: Int => Int
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lst.tail
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def my_map_int(lst: List[Int], f: Int => Int) : List[Int] = {
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  if (lst == Nil) Nil
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  else f(lst.head) :: my_map_int(lst.tail, f)
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}
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my_map_int(lst, square)
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// same function using pattern matching: a kind
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// of switch statement on steroids (see more later on)
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def my_map_int(lst: List[Int], f: Int => Int) : List[Int] = lst match {
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  case Nil => Nil
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  case x::xs => f(x)::my_map_int(xs, f)
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}
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// other function types
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//
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// f1: (Int, Int) => Int
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// f2: List[String] => Option[Int]
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// ... 
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val lst = (1 to 10).toList
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def sumOf(f: Int => Int, lst: List[Int]): Int = lst match {
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  case Nil => 0
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  case x::xs => f(x) + sumOf(f, xs)
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}
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def sum_squares(lst: List[Int]) = sumOf(square, lst)
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def sum_cubes(lst: List[Int])   = sumOf(x => x * x * x, lst)
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sum_squares(lst)
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sum_cubes(lst)
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// lets try it factorial
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def fact(n: Int) : Int = 
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  if (n == 0) 1 else n * fact(n - 1)
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def sum_fact(lst: List[Int]) = sumOf(fact, lst)
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sum_fact(lst)
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// Map type (upper-case)
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//=======================
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// Note the difference between map and Map
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def factors(n: Int) : List[Int] =
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  ((1 until n).filter { divisor =>
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      n % divisor == 0
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    }).toList
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var ls = (1 to 10).toList
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val facs = ls.map(n => (n, factors(n)))
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facs.find(_._1 == 4)
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// works for lists of pairs
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facs.toMap
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facs.toMap.get(4)
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facs.toMap.getOrElse(42, Nil)
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val facsMap = facs.toMap
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val facsMap0 = facsMap + (0 -> List(1,2,3,4,5))
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facsMap0.get(1)
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val facsMap4 = facsMap + (1 -> List(1,2,3,4,5))
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facsMap.get(1)
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facsMap4.get(1)
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val ls = List("one", "two", "three", "four", "five")
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ls.groupBy(_.length)
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ls.groupBy(_.length).get(2)
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// Option type (again)
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//=====================
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// remember, in Java if something unusually happens, 
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// you return null;
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//
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// in Scala you use Option
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//   - if the value is present, you use Some(value)
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//   - if no value is present, you use None
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List(7,2,3,4,5,6).find(_ < 4)
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List(5,6,7,8,9).find(_ < 4)
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// operations on options
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val lst = List(None, Some(1), Some(2), None, Some(3))
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lst.flatten
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Some(1).get
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None.get
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Some(1).isDefined
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None.isDefined
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None.isDefined
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val ps = List((3, 0), (3, 2), (4, 2), (2, 0), (1, 0), (1, 1))
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for ((x, y) <- ps) yield {
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  if (y == 0) None else Some(x / y)
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}
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// getOrElse is for setting a default value
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val lst = List(None, Some(1), Some(2), None, Some(3))
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for (x <- lst) yield x.getOrElse(0)
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// error handling with Option (no exceptions)
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//
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//  Try(something).getOrElse(what_to_do_in_an_exception)
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//
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import scala.util._
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import io.Source
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Source.fromURL("""http://www.inf.ucl.ac.uk/staff/urbanc/""").mkString
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Try(Source.fromURL("""http://www.inf.kcl.ac.uk/staff/urbanc/""").mkString).getOrElse("")
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Try(Some(Source.fromURL("""http://www.inf.kcl.ac.uk/staff/urbanc/""").mkString)).getOrElse(None)
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// a function that turns strings into numbers (similar to .toInt)
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Integer.parseInt("12u34")
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def get_me_an_int(s: String) : Option[Int] = 
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 Try(Some(Integer.parseInt(s))).getOrElse(None)
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val lst = List("12345", "foo", "5432", "bar", "x21", "456")
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for (x <- lst) yield get_me_an_int(x)
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// summing up all the numbers
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lst.map(get_me_an_int).flatten.sum
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lst.map(get_me_an_int).flatten.sum
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lst.flatMap(get_me_an_int).map(_.toString)
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// This may not look any better than working with null in Java, but to
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// see the value, you have to put yourself in the shoes of the
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// consumer of the get_me_an_int function, and imagine you didn't
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// write that function.
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//
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// In Java, if you didn't write this function, you'd have to depend on
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// the Javadoc of the get_me_an_int. If you didn't look at the Javadoc, 
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// you might not know that get_me_an_int could return a null, and your 
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// code could potentially throw a NullPointerException.
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// even Scala is not immune to problems like this:
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List(5,6,7,8,9).indexOf(7)
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List(5,6,7,8,9).indexOf(10)
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List(5,6,7,8,9)(-1)
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// Pattern Matching
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//==================
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// A powerful tool which is supposed to come to Java in a few years
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// time (https://www.youtube.com/watch?v=oGll155-vuQ)...Scala already
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// has it for many years ;o)
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// The general schema:
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//
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//    expression match {
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//       case pattern1 => expression1
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//       case pattern2 => expression2
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//       ...
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//       case patternN => expressionN
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//    }
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// remember?
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val lst = List(None, Some(1), Some(2), None, Some(3)).flatten
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   348
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   349
212
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   350
def my_flatten(xs: List[Option[Int]]): List[Int] = xs match {
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   351
  case Nil => Nil 
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   352
  case None::rest => my_flatten(rest)
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   353
  case Some(v)::foo => {
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   354
      v :: my_flatten(foo)
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   355
  } 
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   356
}
58
93a2b6e4b84c updated
Christian Urban <urbanc@in.tum.de>
parents: 57
diff changeset
   357
93a2b6e4b84c updated
Christian Urban <urbanc@in.tum.de>
parents: 57
diff changeset
   358
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   359
// another example
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   360
def get_me_a_string(n: Int): String = n match {
212
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   361
  case 0 | 1 | 2 => "small"
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   362
  case _ => "big"
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   363
}
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   364
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   365
get_me_a_string(0)
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   366
212
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   367
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   368
// you can also have cases combined
266
ca48ac1d3c3e updated to 2.13
Christian Urban <urbanc@in.tum.de>
parents: 212
diff changeset
   369
def season(month: String) : String = month match {
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   370
  case "March" | "April" | "May" => "It's spring"
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   371
  case "June" | "July" | "August" => "It's summer"
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   372
  case "September" | "October" | "November" => "It's autumn"
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   373
  case "December" => "It's winter"
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   374
  case "January" | "February" => "It's unfortunately winter"
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   375
}
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   376
 
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   377
println(season("November"))
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   378
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   379
// What happens if no case matches?
212
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   380
println(season("foobar"))
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   381
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   382
266
ca48ac1d3c3e updated to 2.13
Christian Urban <urbanc@in.tum.de>
parents: 212
diff changeset
   383
// Days of the months
ca48ac1d3c3e updated to 2.13
Christian Urban <urbanc@in.tum.de>
parents: 212
diff changeset
   384
def days(month: String) : Int = month match {
ca48ac1d3c3e updated to 2.13
Christian Urban <urbanc@in.tum.de>
parents: 212
diff changeset
   385
  case "March" | "April" | "May" => 31
ca48ac1d3c3e updated to 2.13
Christian Urban <urbanc@in.tum.de>
parents: 212
diff changeset
   386
  case "June" | "July" | "August" => 30
ca48ac1d3c3e updated to 2.13
Christian Urban <urbanc@in.tum.de>
parents: 212
diff changeset
   387
}
ca48ac1d3c3e updated to 2.13
Christian Urban <urbanc@in.tum.de>
parents: 212
diff changeset
   388
ca48ac1d3c3e updated to 2.13
Christian Urban <urbanc@in.tum.de>
parents: 212
diff changeset
   389
ca48ac1d3c3e updated to 2.13
Christian Urban <urbanc@in.tum.de>
parents: 212
diff changeset
   390
ca48ac1d3c3e updated to 2.13
Christian Urban <urbanc@in.tum.de>
parents: 212
diff changeset
   391
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   392
// Silly: fizz buzz
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   393
def fizz_buzz(n: Int) : String = (n % 3, n % 5) match {
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   394
  case (0, 0) => "fizz buzz"
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   395
  case (0, _) => "fizz"
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   396
  case (_, 0) => "buzz"
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   397
  case _ => n.toString  
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   398
}
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   399
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   400
for (n <- 0 to 20) 
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   401
 println(fizz_buzz(n))
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   402
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   403
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   404
// User-defined Datatypes
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   405
//========================
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   406
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   407
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   408
abstract class Colour
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   409
case object Red extends Colour 
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   410
case object Green extends Colour 
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   411
case object Blue extends Colour
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   412
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   413
def fav_colour(c: Colour) : Boolean = c match {
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   414
  case Red   => false
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   415
  case Green => true
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   416
  case Blue  => false 
173
2de1f79dedf0 updated
Christian Urban <urbanc@in.tum.de>
parents: 167
diff changeset
   417
}
2de1f79dedf0 updated
Christian Urban <urbanc@in.tum.de>
parents: 167
diff changeset
   418
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   419
fav_colour(Green)
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   420
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   421
268
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   422
// ... a tiny bit more useful: Roman Numerals
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   423
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   424
abstract class RomanDigit 
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   425
case object I extends RomanDigit 
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   426
case object V extends RomanDigit 
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   427
case object X extends RomanDigit 
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   428
case object L extends RomanDigit 
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   429
case object C extends RomanDigit 
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   430
case object D extends RomanDigit 
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   431
case object M extends RomanDigit 
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   432
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   433
type RomanNumeral = List[RomanDigit] 
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   434
212
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   435
List(X,I)
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   436
268
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   437
/*
212
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   438
I -> 1
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   439
II -> 2
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   440
III  -> 3
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   441
IV -> 4
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   442
V -> 5
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   443
VI -> 6
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   444
VII -> 7
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   445
VIII -> 8
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   446
IX -> 9
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   447
X -> X
268
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   448
*/
212
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   449
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   450
def RomanNumeral2Int(rs: RomanNumeral): Int = rs match { 
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   451
  case Nil => 0
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   452
  case M::r    => 1000 + RomanNumeral2Int(r)  
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   453
  case C::M::r => 900 + RomanNumeral2Int(r)
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   454
  case D::r    => 500 + RomanNumeral2Int(r)
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   455
  case C::D::r => 400 + RomanNumeral2Int(r)
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   456
  case C::r    => 100 + RomanNumeral2Int(r)
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   457
  case X::C::r => 90 + RomanNumeral2Int(r)
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   458
  case L::r    => 50 + RomanNumeral2Int(r)
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   459
  case X::L::r => 40 + RomanNumeral2Int(r)
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   460
  case X::r    => 10 + RomanNumeral2Int(r)
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   461
  case I::X::r => 9 + RomanNumeral2Int(r)
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   462
  case V::r    => 5 + RomanNumeral2Int(r)
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   463
  case I::V::r => 4 + RomanNumeral2Int(r)
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   464
  case I::r    => 1 + RomanNumeral2Int(r)
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   465
}
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   466
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   467
RomanNumeral2Int(List(I,V))             // 4
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   468
RomanNumeral2Int(List(I,I,I,I))         // 4 (invalid Roman number)
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   469
RomanNumeral2Int(List(V,I))             // 6
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   470
RomanNumeral2Int(List(I,X))             // 9
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   471
RomanNumeral2Int(List(M,C,M,L,X,X,I,X)) // 1979
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   472
RomanNumeral2Int(List(M,M,X,V,I,I))     // 2017
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   473
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   474
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   475
// another example
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   476
//=================
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   477
212
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   478
// Once upon a time, in a complete fictional 
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   479
// country there were Persons...
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   480
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   481
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   482
abstract class Person
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   483
case object King extends Person
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   484
case class Peer(deg: String, terr: String, succ: Int) extends Person
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   485
case class Knight(name: String) extends Person
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   486
case class Peasant(name: String) extends Person
212
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   487
173
2de1f79dedf0 updated
Christian Urban <urbanc@in.tum.de>
parents: 167
diff changeset
   488
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   489
def title(p: Person): String = p match {
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   490
  case King => "His Majesty the King"
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   491
  case Peer(deg, terr, _) => s"The ${deg} of ${terr}"
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   492
  case Knight(name) => s"Sir ${name}"
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   493
  case Peasant(name) => name
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   494
}
173
2de1f79dedf0 updated
Christian Urban <urbanc@in.tum.de>
parents: 167
diff changeset
   495
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   496
def superior(p1: Person, p2: Person): Boolean = (p1, p2) match {
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   497
  case (King, _) => true
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   498
  case (Peer(_,_,_), Knight(_)) => true
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   499
  case (Peer(_,_,_), Peasant(_)) => true
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   500
  case (Peer(_,_,_), Clown) => true
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   501
  case (Knight(_), Peasant(_)) => true
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   502
  case (Knight(_), Clown) => true
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   503
  case (Clown, Peasant(_)) => true
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   504
  case _ => false
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   505
}
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   506
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   507
val people = List(Knight("David"), 
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   508
                  Peer("Duke", "Norfolk", 84), 
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   509
                  Peasant("Christian"), 
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   510
                  King, 
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   511
                  Clown)
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   512
212
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   513
println(people.sortWith(superior).mkString("\n"))
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   514
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   515
268
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   516
// Tail Recursion
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   517
//================
147
72f7dd1a3754 updated
Christian Urban <urbanc@in.tum.de>
parents: 95
diff changeset
   518
72f7dd1a3754 updated
Christian Urban <urbanc@in.tum.de>
parents: 95
diff changeset
   519
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   520
def fact(n: Long): Long = 
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   521
  if (n == 0) 1 else n * fact(n - 1)
147
72f7dd1a3754 updated
Christian Urban <urbanc@in.tum.de>
parents: 95
diff changeset
   522
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   523
fact(10)              //ok
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   524
fact(10000)           // produces a stackoverflow
147
72f7dd1a3754 updated
Christian Urban <urbanc@in.tum.de>
parents: 95
diff changeset
   525
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   526
def factT(n: BigInt, acc: BigInt): BigInt =
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   527
  if (n == 0) acc else factT(n - 1, n * acc)
147
72f7dd1a3754 updated
Christian Urban <urbanc@in.tum.de>
parents: 95
diff changeset
   528
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   529
factT(10, 1)
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   530
factT(100000, 1)
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   531
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   532
// there is a flag for ensuring a function is tail recursive
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   533
import scala.annotation.tailrec
167
349d706586ef updated
Christian Urban <urbanc@in.tum.de>
parents: 155
diff changeset
   534
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   535
@tailrec
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   536
def factT(n: BigInt, acc: BigInt): BigInt =
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   537
  if (n == 0) acc else factT(n - 1, n * acc)
167
349d706586ef updated
Christian Urban <urbanc@in.tum.de>
parents: 155
diff changeset
   538
349d706586ef updated
Christian Urban <urbanc@in.tum.de>
parents: 155
diff changeset
   539
349d706586ef updated
Christian Urban <urbanc@in.tum.de>
parents: 155
diff changeset
   540
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   541
// for tail-recursive functions the Scala compiler
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   542
// generates loop-like code, which does not need
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   543
// to allocate stack-space in each recursive
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   544
// call; Scala can do this only for tail-recursive
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   545
// functions
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   546
147
72f7dd1a3754 updated
Christian Urban <urbanc@in.tum.de>
parents: 95
diff changeset
   547
212
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   548
// A Web Crawler / Email Harvester
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   549
//=================================
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   550
//
212
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   551
// the idea is to look for links using the
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   552
// regular expression "https?://[^"]*" and for
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   553
// email addresses using another regex.
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   554
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   555
import io.Source
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   556
import scala.util._
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   557
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   558
// gets the first 10K of a web-page
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   559
def get_page(url: String) : String = {
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   560
  Try(Source.fromURL(url)("ISO-8859-1").take(10000).mkString).
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   561
    getOrElse { println(s"  Problem with: $url"); ""}
147
72f7dd1a3754 updated
Christian Urban <urbanc@in.tum.de>
parents: 95
diff changeset
   562
}
72f7dd1a3754 updated
Christian Urban <urbanc@in.tum.de>
parents: 95
diff changeset
   563
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   564
// regex for URLs and emails
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   565
val http_pattern = """"https?://[^"]*"""".r
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   566
val email_pattern = """([a-z0-9_\.-]+)@([\da-z\.-]+)\.([a-z\.]{2,6})""".r
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   567
268
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   568
//test case:
212
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   569
//email_pattern.findAllIn
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   570
//  ("foo bla christian@kcl.ac.uk 1234567").toList
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   571
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   572
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   573
// drops the first and last character from a string
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   574
def unquote(s: String) = s.drop(1).dropRight(1)
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   575
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   576
def get_all_URLs(page: String): Set[String] = 
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   577
  http_pattern.findAllIn(page).map(unquote).toSet
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   578
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   579
// naive version of crawl - searches until a given depth,
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   580
// visits pages potentially more than once
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   581
def crawl(url: String, n: Int) : Set[String] = {
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   582
  if (n == 0) Set()
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   583
  else {
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   584
    println(s"  Visiting: $n $url")
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   585
    val page = get_page(url)
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   586
    val new_emails = email_pattern.findAllIn(page).toSet
212
4bda49ec24da updated
Christian Urban <urbanc@in.tum.de>
parents: 204
diff changeset
   587
    new_emails ++ (for (u <- get_all_URLs(page)) yield crawl(u, n - 1)).flatten
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   588
  }
147
72f7dd1a3754 updated
Christian Urban <urbanc@in.tum.de>
parents: 95
diff changeset
   589
}
72f7dd1a3754 updated
Christian Urban <urbanc@in.tum.de>
parents: 95
diff changeset
   590
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   591
// some starting URLs for the crawler
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   592
val startURL = """https://nms.kcl.ac.uk/christian.urban/"""
147
72f7dd1a3754 updated
Christian Urban <urbanc@in.tum.de>
parents: 95
diff changeset
   593
204
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   594
crawl(startURL, 2)
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   595
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   596
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   597
9b45dd24271b updated
Christian Urban <urbanc@in.tum.de>
parents: 192
diff changeset
   598
150
9a2f2a1de42b updated
Christian Urban <urbanc@in.tum.de>
parents: 148
diff changeset
   599
9a2f2a1de42b updated
Christian Urban <urbanc@in.tum.de>
parents: 148
diff changeset
   600
9a2f2a1de42b updated
Christian Urban <urbanc@in.tum.de>
parents: 148
diff changeset
   601
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   602
// Sudoku
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   603
//========
53
9f8751912560 updated
Christian Urban <urbanc@in.tum.de>
parents: 51
diff changeset
   604
57
9b88f9e04344 updated
Christian Urban <urbanc@in.tum.de>
parents: 56
diff changeset
   605
// THE POINT OF THIS CODE IS NOT TO BE SUPER
9b88f9e04344 updated
Christian Urban <urbanc@in.tum.de>
parents: 56
diff changeset
   606
// EFFICIENT AND FAST, just explaining exhaustive
9b88f9e04344 updated
Christian Urban <urbanc@in.tum.de>
parents: 56
diff changeset
   607
// depth-first search
9b88f9e04344 updated
Christian Urban <urbanc@in.tum.de>
parents: 56
diff changeset
   608
9b88f9e04344 updated
Christian Urban <urbanc@in.tum.de>
parents: 56
diff changeset
   609
55
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   610
val game0 = """.14.6.3..
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   611
              |62...4..9
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   612
              |.8..5.6..
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   613
              |.6.2....3
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   614
              |.7..1..5.
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   615
              |5....9.6.
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   616
              |..6.2..3.
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   617
              |1..5...92
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   618
              |..7.9.41.""".stripMargin.replaceAll("\\n", "")
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   619
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   620
type Pos = (Int, Int)
268
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   621
val emptyValue = '.'
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   622
val maxValue = 9
55
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   623
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   624
val allValues = "123456789".toList
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   625
val indexes = (0 to 8).toList
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   626
57
9b88f9e04344 updated
Christian Urban <urbanc@in.tum.de>
parents: 56
diff changeset
   627
268
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   628
def empty(game: String) = game.indexOf(emptyValue)
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   629
def isDone(game: String) = empty(game) == -1 
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   630
def emptyPosition(game: String) : Pos = 
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   631
  (empty(game) % maxValue, empty(game) / maxValue)
57
9b88f9e04344 updated
Christian Urban <urbanc@in.tum.de>
parents: 56
diff changeset
   632
55
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   633
268
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   634
def get_row(game: String, y: Int) = indexes.map(col => game(y * maxValue + col))
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   635
def get_col(game: String, x: Int) = indexes.map(row => game(x + row * maxValue))
147
72f7dd1a3754 updated
Christian Urban <urbanc@in.tum.de>
parents: 95
diff changeset
   636
57
9b88f9e04344 updated
Christian Urban <urbanc@in.tum.de>
parents: 56
diff changeset
   637
def get_box(game: String, pos: Pos): List[Char] = {
55
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   638
    def base(p: Int): Int = (p / 3) * 3
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   639
    val x0 = base(pos._1)
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   640
    val y0 = base(pos._2)
268
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   641
    for (x <- (x0 until x0 + 3).toList;
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   642
         y <- (y0 until y0 + 3).toList) yield game(x + y * maxValue)
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   643
}         
55
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   644
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   645
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   646
//get_row(game0, 0)
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   647
//get_row(game0, 1)
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   648
//get_box(game0, (3,1))
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   649
268
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   650
def update(game: String, pos: Int, value: Char): String = 
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   651
  game.updated(pos, value)
55
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   652
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   653
def toAvoid(game: String, pos: Pos): List[Char] = 
57
9b88f9e04344 updated
Christian Urban <urbanc@in.tum.de>
parents: 56
diff changeset
   654
  (get_col(game, pos._1) ++ get_row(game, pos._2) ++ get_box(game, pos))
55
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   655
268
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   656
def candidates(game: String, pos: Pos): List[Char] = 
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   657
  allValues.diff(toAvoid(game, pos))
55
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   658
268
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   659
//candidates(game0, (0, 0))
55
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   660
268
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   661
def pretty(game: String): String = 
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   662
  "\n" ++ (game.sliding(maxValue, maxValue).mkString("\n"))
55
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   663
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   664
def search(game: String): List[String] = {
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   665
  if (isDone(game)) List(game)
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   666
  else 
268
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   667
    candidates(game, emptyPosition(game)).
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   668
      map(c => search(update(game, empty(game), c))).flatten
55
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   669
}
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   670
268
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   671
// an easy game
55
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   672
val game1 = """23.915...
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   673
              |...2..54.
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   674
              |6.7......
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   675
              |..1.....9
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   676
              |89.5.3.17
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   677
              |5.....6..
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   678
              |......9.5
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   679
              |.16..7...
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   680
              |...329..1""".stripMargin.replaceAll("\\n", "")
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   681
57
9b88f9e04344 updated
Christian Urban <urbanc@in.tum.de>
parents: 56
diff changeset
   682
268
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   683
// a game that is in the sligtly harder category
55
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   684
val game2 = """8........
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   685
              |..36.....
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   686
              |.7..9.2..
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   687
              |.5...7...
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   688
              |....457..
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   689
              |...1...3.
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   690
              |..1....68
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   691
              |..85...1.
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   692
              |.9....4..""".stripMargin.replaceAll("\\n", "")
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   693
268
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   694
// a game with multiple solutions
55
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   695
val game3 = """.8...9743
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   696
              |.5...8.1.
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   697
              |.1.......
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   698
              |8....5...
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   699
              |...8.4...
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   700
              |...3....6
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   701
              |.......7.
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   702
              |.3.5...8.
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   703
              |9724...5.""".stripMargin.replaceAll("\\n", "")
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   704
57
9b88f9e04344 updated
Christian Urban <urbanc@in.tum.de>
parents: 56
diff changeset
   705
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   706
search(game0).map(pretty)
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   707
search(game1).map(pretty)
55
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   708
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   709
// for measuring time
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   710
def time_needed[T](i: Int, code: => T) = {
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   711
  val start = System.nanoTime()
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   712
  for (j <- 1 to i) code
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   713
  val end = System.nanoTime()
268
e43f7e92ba26 updated
Christian Urban <urbanc@in.tum.de>
parents: 266
diff changeset
   714
  s"${(end - start) / i / 1.0e9} secs"
55
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   715
}
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   716
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   717
search(game2).map(pretty)
57
9b88f9e04344 updated
Christian Urban <urbanc@in.tum.de>
parents: 56
diff changeset
   718
search(game3).distinct.length
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   719
time_needed(3, search(game2))
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   720
time_needed(3, search(game3))
55
6610c1dfa8a9 updated
Christian Urban <urbanc@in.tum.de>
parents: 53
diff changeset
   721
53
9f8751912560 updated
Christian Urban <urbanc@in.tum.de>
parents: 51
diff changeset
   722
9f8751912560 updated
Christian Urban <urbanc@in.tum.de>
parents: 51
diff changeset
   723
9f8751912560 updated
Christian Urban <urbanc@in.tum.de>
parents: 51
diff changeset
   724
192
a112e0e2325c updated
Christian Urban <urbanc@in.tum.de>
parents: 174
diff changeset
   725