--- a/progs/lecture2.scala Mon Nov 11 14:04:22 2019 +0000
+++ b/progs/lecture2.scala Tue Nov 12 00:41:00 2019 +0000
@@ -14,11 +14,16 @@
// String Interpolations
//=======================
+def cube(n: Int) : Int = n * n * n
+
val n = 3
-println("The square of " + n + " is " + square(n) + ".")
+println("The cube of " + n + " is " + cube(n) + ".")
-println(s"The square of ${n} is ${square(n)}.")
+println(s"The cube of ${n} is ${cube(n)}.")
+// or even
+
+println(s"The cube of ${n} is ${n * n * n}.")
// helpful for debugging purposes
//
@@ -50,7 +55,6 @@
List(5,6,7,8,9).find(_ < 4)
-
// better error handling with Options (no exceptions)
//
// Try(something).getOrElse(what_to_do_in_case_of_an_exception)
@@ -92,7 +96,6 @@
get_contents("test.txt")
-
// operations on options
val lst = List(None, Some(1), Some(2), None, Some(3))
@@ -106,7 +109,7 @@
None.isDefined
-val ps = List((3, 0), (3, 2), (4, 2), (2, 0), (1, 0), (1, 1))
+val ps = List((3, 0), (4, 2), (6, 2), (2, 0), (1, 0), (1, 1))
// division where possible
@@ -121,6 +124,12 @@
for (x <- lst) yield x.getOrElse(0)
+// a function that turns strings into numbers (similar to .toInt)
+Integer.parseInt("1234")
+
+
+def get_me_an_int(s: String) : Option[Int] =
+ Try(Some(Integer.parseInt(s))).getOrElse(None)
// This may not look any better than working with null in Java, but to
@@ -130,11 +139,10 @@
//
// In Java, if you didn't write this function, you'd have to depend on
// the Javadoc of the get_me_an_int. If you didn't look at the Javadoc,
-// you might not know that get_me_an_int could return a null, and your
+// you might not know that get_me_an_int could return null, and your
// code could potentially throw a NullPointerException.
-
// even Scala is not immune to problems like this:
List(5,6,7,8,9).indexOf(7)
@@ -154,20 +162,23 @@
val lst = (1 to 10).toList
-lst.filter(x => even(x))
-lst.filter(even(_))
lst.filter(even)
-
lst.count(even)
-
-
lst.find(even)
-val ps = List((3, 0), (3, 2), (4, 2), (2, 2), (2, 0), (1, 1), (1, 0))
+lst.filter(x => x % 2 == 0)
+lst.filter(_ % 2 == 0)
lst.sortWith(_ > _)
lst.sortWith(_ < _)
+// but this only works when the arguments are clear, but
+// not with multiple occurences
+lst.find(n => odd(n) && n > 2)
+
+
+val ps = List((3, 0), (3, 2), (4, 2), (2, 2), (2, 0), (1, 1), (1, 0))
+
def lex(x: (Int, Int), y: (Int, Int)) : Boolean =
if (x._1 == y._1) x._2 < y._2 else x._1 < y._1
@@ -180,7 +191,6 @@
ps.maxBy(_._2)
-
// maps (lower-case)
//===================
@@ -207,10 +217,9 @@
lst.map(square).filter(_ > 4).map(square)
-// lets define our own functions
-// type of functions, for example f: Int => Int
+// lets define our own higher-order functions
+// type of functions is for example Int => Int
-lst.tail
def my_map_int(lst: List[Int], f: Int => Int) : List[Int] = {
if (lst == Nil) Nil
@@ -247,7 +256,7 @@
sum_squares(lst)
sum_cubes(lst)
-// lets try it factorial
+// lets try a factorial
def fact(n: Int) : Int =
if (n == 0) 1 else n * fact(n - 1)
@@ -256,30 +265,25 @@
-// if you like verbosity, you can full-specify the literal.
-// Don't go telling that to people, though
+// sometimes it is needed that you specify the type.
(1 to 100).filter((x: Int) => x % 2 == 0).sum
-// As x is known to be an Int anyway, you can omit that part
+// in this case it is clear that x mist be an Int
(1 to 100).filter(x => x % 2 == 0).sum
// As each parameter (only x in this case) is passed only once
// you can use the wizardy placeholder syntax
(1 to 100).filter(_ % 2 == 0).sum
-// But if you want to re-use your literal, you can also put it in a value
-// In this case, explicit types are required because there's nothing to infer from
-val isEven = (x: Int) => x % 2 == 0
-(1 to 100).filter(isEven).sum
-
-// Option Type again
-//===================
+// Option Type and maps
+//======================
// a function that turns strings into numbers (similar to .toInt)
Integer.parseInt("12u34")
+import scala.util._
def get_me_an_int(s: String) : Option[Int] =
Try(Some(Integer.parseInt(s))).getOrElse(None)
@@ -294,6 +298,10 @@
lst.flatMap(get_me_an_int).sum
+// maps on Options
+
+get_me_an_int("1234").map(even)
+get_me_an_int("12u34").map(even)
@@ -303,13 +311,9 @@
// Note the difference between map and Map
def factors(n: Int) : List[Int] =
- ((1 until n).filter { divisor =>
- n % divisor == 0
- }).toList
-
+ (2 until n).toList.filter(n % _ == 0)
var ls = (1 to 10).toList
-
val facs = ls.map(n => (n, factors(n)))
facs.find(_._1 == 4)
@@ -324,16 +328,18 @@
val facsMap = facs.toMap
val facsMap0 = facsMap + (0 -> List(1,2,3,4,5))
-facsMap0.get(1)
+facsMap0.get(0)
-val facsMap4 = facsMap + (1 -> List(1,2,3,4,5))
+val facsMap2 = facsMap + (1 -> List(1,2,3,4,5))
facsMap.get(1)
-facsMap4.get(1)
+facsMap2.get(1)
+
+// groupBy function on maps
val ls = List("one", "two", "three", "four", "five")
ls.groupBy(_.length)
-ls.groupBy(_.length).get(2)
+ls.groupBy(_.length).get(3)
@@ -364,13 +370,11 @@
def my_flatten(xs: List[Option[Int]]): List[Int] = xs match {
case Nil => Nil
case None::rest => my_flatten(rest)
- case Some(v)::foo => {
- v :: my_flatten(foo)
- }
+ case Some(v)::rest => v :: my_flatten(rest)
}
-// another example
+// another example with a default case
def get_me_a_string(n: Int): String = n match {
case 0 | 1 | 2 => "small"
case _ => "big"
@@ -394,15 +398,13 @@
println(season("foobar"))
-// Days of the months
+// days of some months
def days(month: String) : Int = month match {
case "March" | "April" | "May" => 31
case "June" | "July" | "August" => 30
}
-
-
// Silly: fizz buzz
def fizz_buzz(n: Int) : String = (n % 3, n % 5) match {
case (0, 0) => "fizz buzz"
@@ -415,153 +417,40 @@
println(fizz_buzz(n))
-// User-defined Datatypes
-//========================
-
-
-abstract class Colour
-case object Red extends Colour
-case object Green extends Colour
-case object Blue extends Colour
-
-def fav_colour(c: Colour) : Boolean = c match {
- case Red => false
- case Green => true
- case Blue => false
-}
-
-fav_colour(Green)
-
-
-// ... a tiny bit more useful: Roman Numerals
-
-abstract class RomanDigit
-case object I extends RomanDigit
-case object V extends RomanDigit
-case object X extends RomanDigit
-case object L extends RomanDigit
-case object C extends RomanDigit
-case object D extends RomanDigit
-case object M extends RomanDigit
-
-type RomanNumeral = List[RomanDigit]
-
-List(X,I)
-
-/*
-I -> 1
-II -> 2
-III -> 3
-IV -> 4
-V -> 5
-VI -> 6
-VII -> 7
-VIII -> 8
-IX -> 9
-X -> X
-*/
-
-def RomanNumeral2Int(rs: RomanNumeral): Int = rs match {
- case Nil => 0
- case M::r => 1000 + RomanNumeral2Int(r)
- case C::M::r => 900 + RomanNumeral2Int(r)
- case D::r => 500 + RomanNumeral2Int(r)
- case C::D::r => 400 + RomanNumeral2Int(r)
- case C::r => 100 + RomanNumeral2Int(r)
- case X::C::r => 90 + RomanNumeral2Int(r)
- case L::r => 50 + RomanNumeral2Int(r)
- case X::L::r => 40 + RomanNumeral2Int(r)
- case X::r => 10 + RomanNumeral2Int(r)
- case I::X::r => 9 + RomanNumeral2Int(r)
- case V::r => 5 + RomanNumeral2Int(r)
- case I::V::r => 4 + RomanNumeral2Int(r)
- case I::r => 1 + RomanNumeral2Int(r)
-}
-
-RomanNumeral2Int(List(I,V)) // 4
-RomanNumeral2Int(List(I,I,I,I)) // 4 (invalid Roman number)
-RomanNumeral2Int(List(V,I)) // 6
-RomanNumeral2Int(List(I,X)) // 9
-RomanNumeral2Int(List(M,C,M,L,X,X,I,X)) // 1979
-RomanNumeral2Int(List(M,M,X,V,I,I)) // 2017
-
-
-// another example
-//=================
-
-// Once upon a time, in a complete fictional
-// country there were Persons...
-
-
-abstract class Person
-case object King extends Person
-case class Peer(deg: String, terr: String, succ: Int) extends Person
-case class Knight(name: String) extends Person
-case class Peasant(name: String) extends Person
-
-
-def title(p: Person): String = p match {
- case King => "His Majesty the King"
- case Peer(deg, terr, _) => s"The ${deg} of ${terr}"
- case Knight(name) => s"Sir ${name}"
- case Peasant(name) => name
-}
-
-def superior(p1: Person, p2: Person): Boolean = (p1, p2) match {
- case (King, _) => true
- case (Peer(_,_,_), Knight(_)) => true
- case (Peer(_,_,_), Peasant(_)) => true
- case (Peer(_,_,_), Clown) => true
- case (Knight(_), Peasant(_)) => true
- case (Knight(_), Clown) => true
- case (Clown, Peasant(_)) => true
- case _ => false
-}
-
-val people = List(Knight("David"),
- Peer("Duke", "Norfolk", 84),
- Peasant("Christian"),
- King,
- Clown)
-
-println(people.sortWith(superior).mkString("\n"))
-
-
-// String interpolations as patterns
-
-val date = "2000-01-01"
-val s"$year-$month-$day" = date
-
-def parse_date(date: String) = date match {
- case s"$year-$month-$day" => Some((year.toInt, month.toInt, day.toInt))
- case s"$day/$month/$year" => Some((year.toInt, month.toInt, day.toInt))
- case _ => None
-}
// Recursion
//===========
-/* a, b, c
+// well-known example
+
+def fib(n: Int) : Int = {
+ if (n == 0 || n == 1) 1
+ else fib(n - 1) + fib(n - 2)
+}
+
-aa aaa
-ab baa
-ac caa
-ba => ......
-bb
-bc
-ca
-cb
-cc
+/* Say you have characters a, b, c.
+ What are all the combinations of a certain length?
+ All combinations of length 2:
+
+ aa, ab, ac, ba, bb, bc, ca, cb, cc
+
+ Combinations of length 3:
+
+ aaa, baa, caa, and so on......
*/
-def perms(cs: List[Char], l: Int) : List[String] = {
+def combs(cs: List[Char], l: Int) : List[String] = {
if (l == 0) List("")
- else for (c <- cs; s <- perms(cs, l - 1)) yield s"$c$s"
+ else for (c <- cs; s <- combs(cs, l - 1)) yield s"$c$s"
}
-perms("abc".toList, 2)
+combs("abc".toList, 2)
+
+
+// another well-known example
def move(from: Char, to: Char) =
println(s"Move disc from $from to $to!")
@@ -575,43 +464,11 @@
}
}
-hanoi(40, 'A', 'B', 'C')
-
-
-// Tail Recursion
-//================
+hanoi(4, 'A', 'B', 'C')
-def fact(n: Long): Long =
- if (n == 0) 1 else n * fact(n - 1)
-
-fact(10) //ok
-fact(10000) // produces a stackoverflow
-
-def factT(n: BigInt, acc: BigInt): BigInt =
- if (n == 0) acc else factT(n - 1, n * acc)
-
-factT(10, 1)
-factT(100000, 1)
-
-// there is a flag for ensuring a function is tail recursive
-import scala.annotation.tailrec
-
-@tailrec
-def factT(n: BigInt, acc: BigInt): BigInt =
- if (n == 0) acc else factT(n - 1, n * acc)
-
-
-
-// for tail-recursive functions the Scala compiler
-// generates loop-like code, which does not need
-// to allocate stack-space in each recursive
-// call; Scala can do this only for tail-recursive
-// functions
-
-
-// A Web Crawler / Email Harvester
-//=================================
+// A Recursive Web Crawler / Email Harvester
+//===========================================
//
// the idea is to look for links using the
// regular expression "https?://[^"]*" and for
@@ -643,13 +500,11 @@
// naive version of crawl - searches until a given depth,
// visits pages potentially more than once
-def crawl(url: String, n: Int) : Set[String] = {
- if (n == 0) Set()
+def crawl(url: String, n: Int) : Unit = {
+ if (n == 0) ()
else {
println(s" Visiting: $n $url")
- val page = get_page(url)
- val new_emails = email_pattern.findAllIn(page).toSet
- new_emails ++ (for (u <- get_all_URLs(page)) yield crawl(u, n - 1)).flatten
+ for (u <- get_all_URLs(get_page(url))) crawl(u, n - 1)
}
}
@@ -659,130 +514,25 @@
crawl(startURL, 2)
-
-
-
-
-
-// Sudoku
-//========
-
-// THE POINT OF THIS CODE IS NOT TO BE SUPER
-// EFFICIENT AND FAST, just explaining exhaustive
-// depth-first search
-
-
-val game0 = """.14.6.3..
- |62...4..9
- |.8..5.6..
- |.6.2....3
- |.7..1..5.
- |5....9.6.
- |..6.2..3.
- |1..5...92
- |..7.9.41.""".stripMargin.replaceAll("\\n", "")
+// a primitive email harvester
+def emails(url: String, n: Int) : Set[String] = {
+ if (n == 0) Set()
+ else {
+ println(s" Visiting: $n $url")
+ val page = get_page(url)
+ val new_emails = email_pattern.findAllIn(page).toSet
+ new_emails ++ (for (u <- get_all_URLs(page)) yield emails(u, n - 1)).flatten
+ }
+}
-type Pos = (Int, Int)
-val emptyValue = '.'
-val maxValue = 9
-
-val allValues = "123456789".toList
-val indexes = (0 to 8).toList
-
-
-def empty(game: String) = game.indexOf(emptyValue)
-def isDone(game: String) = empty(game) == -1
-def emptyPosition(game: String) : Pos =
- (empty(game) % maxValue, empty(game) / maxValue)
-
-
-def get_row(game: String, y: Int) = indexes.map(col => game(y * maxValue + col))
-def get_col(game: String, x: Int) = indexes.map(row => game(x + row * maxValue))
-
-def get_box(game: String, pos: Pos): List[Char] = {
- def base(p: Int): Int = (p / 3) * 3
- val x0 = base(pos._1)
- val y0 = base(pos._2)
- for (x <- (x0 until x0 + 3).toList;
- y <- (y0 until y0 + 3).toList) yield game(x + y * maxValue)
-}
+emails(startURL, 3)
-//get_row(game0, 0)
-//get_row(game0, 1)
-//get_box(game0, (3,1))
-
-def update(game: String, pos: Int, value: Char): String =
- game.updated(pos, value)
-
-def toAvoid(game: String, pos: Pos): List[Char] =
- (get_col(game, pos._1) ++ get_row(game, pos._2) ++ get_box(game, pos))
-
-def candidates(game: String, pos: Pos): List[Char] =
- allValues.diff(toAvoid(game, pos))
-
-//candidates(game0, (0, 0))
-
-def pretty(game: String): String =
- "\n" ++ (game.sliding(maxValue, maxValue).mkString("\n"))
-
-def search(game: String): List[String] = {
- if (isDone(game)) List(game)
- else
- candidates(game, emptyPosition(game)).
- map(c => search(update(game, empty(game), c))).flatten
-}
-
-// an easy game
-val game1 = """23.915...
- |...2..54.
- |6.7......
- |..1.....9
- |89.5.3.17
- |5.....6..
- |......9.5
- |.16..7...
- |...329..1""".stripMargin.replaceAll("\\n", "")
-
-
-// a game that is in the sligtly harder category
-val game2 = """8........
- |..36.....
- |.7..9.2..
- |.5...7...
- |....457..
- |...1...3.
- |..1....68
- |..85...1.
- |.9....4..""".stripMargin.replaceAll("\\n", "")
-
-// a game with multiple solutions
-val game3 = """.8...9743
- |.5...8.1.
- |.1.......
- |8....5...
- |...8.4...
- |...3....6
- |.......7.
- |.3.5...8.
- |9724...5.""".stripMargin.replaceAll("\\n", "")
-
-
-search(game0).map(pretty)
-search(game1).map(pretty)
-
-// for measuring time
-def time_needed[T](i: Int, code: => T) = {
- val start = System.nanoTime()
- for (j <- 1 to i) code
- val end = System.nanoTime()
- s"${(end - start) / i / 1.0e9} secs"
-}
-
-search(game2).map(pretty)
-search(game3).distinct.length
-time_needed(3, search(game2))
-time_needed(3, search(game3))
+// if we want to explore the internet "deeper", then we
+// first have to parallelise the request of webpages:
+//
+// scala -cp scala-parallel-collections_2.13-0.2.0.jar
+// import scala.collection.parallel.CollectionConverters._
--- a/progs/lecture3.scala Mon Nov 11 14:04:22 2019 +0000
+++ b/progs/lecture3.scala Tue Nov 12 00:41:00 2019 +0000
@@ -50,10 +50,137 @@
crawl(startURL, 2)
+// User-defined Datatypes
+//========================
+
+
+abstract class Colour
+case object Red extends Colour
+case object Green extends Colour
+case object Blue extends Colour
+
+def fav_colour(c: Colour) : Boolean = c match {
+ case Red => false
+ case Green => true
+ case Blue => false
+}
+
+fav_colour(Green)
+
+
+// ... a tiny bit more useful: Roman Numerals
+
+abstract class RomanDigit
+case object I extends RomanDigit
+case object V extends RomanDigit
+case object X extends RomanDigit
+case object L extends RomanDigit
+case object C extends RomanDigit
+case object D extends RomanDigit
+case object M extends RomanDigit
+
+type RomanNumeral = List[RomanDigit]
+
+List(X,I)
+
+/*
+I -> 1
+II -> 2
+III -> 3
+IV -> 4
+V -> 5
+VI -> 6
+VII -> 7
+VIII -> 8
+IX -> 9
+X -> X
+*/
+
+def RomanNumeral2Int(rs: RomanNumeral): Int = rs match {
+ case Nil => 0
+ case M::r => 1000 + RomanNumeral2Int(r)
+ case C::M::r => 900 + RomanNumeral2Int(r)
+ case D::r => 500 + RomanNumeral2Int(r)
+ case C::D::r => 400 + RomanNumeral2Int(r)
+ case C::r => 100 + RomanNumeral2Int(r)
+ case X::C::r => 90 + RomanNumeral2Int(r)
+ case L::r => 50 + RomanNumeral2Int(r)
+ case X::L::r => 40 + RomanNumeral2Int(r)
+ case X::r => 10 + RomanNumeral2Int(r)
+ case I::X::r => 9 + RomanNumeral2Int(r)
+ case V::r => 5 + RomanNumeral2Int(r)
+ case I::V::r => 4 + RomanNumeral2Int(r)
+ case I::r => 1 + RomanNumeral2Int(r)
+}
+
+RomanNumeral2Int(List(I,V)) // 4
+RomanNumeral2Int(List(I,I,I,I)) // 4 (invalid Roman number)
+RomanNumeral2Int(List(V,I)) // 6
+RomanNumeral2Int(List(I,X)) // 9
+RomanNumeral2Int(List(M,C,M,L,X,X,I,X)) // 1979
+RomanNumeral2Int(List(M,M,X,V,I,I)) // 2017
+
+
+// another example
+//=================
+
+// Once upon a time, in a complete fictional
+// country there were Persons...
+
+
+abstract class Person
+case object King extends Person
+case class Peer(deg: String, terr: String, succ: Int) extends Person
+case class Knight(name: String) extends Person
+case class Peasant(name: String) extends Person
+
+
+def title(p: Person): String = p match {
+ case King => "His Majesty the King"
+ case Peer(deg, terr, _) => s"The ${deg} of ${terr}"
+ case Knight(name) => s"Sir ${name}"
+ case Peasant(name) => name
+}
+
+def superior(p1: Person, p2: Person): Boolean = (p1, p2) match {
+ case (King, _) => true
+ case (Peer(_,_,_), Knight(_)) => true
+ case (Peer(_,_,_), Peasant(_)) => true
+ case (Peer(_,_,_), Clown) => true
+ case (Knight(_), Peasant(_)) => true
+ case (Knight(_), Clown) => true
+ case (Clown, Peasant(_)) => true
+ case _ => false
+}
+
+val people = List(Knight("David"),
+ Peer("Duke", "Norfolk", 84),
+ Peasant("Christian"),
+ King,
+ Clown)
+
+println(people.sortWith(superior).mkString("\n"))
+
+
+// String interpolations as patterns
+
+val date = "2000-01-01"
+val s"$year-$month-$day" = date
+
+def parse_date(date: String) = date match {
+ case s"$year-$month-$day" => Some((year.toInt, month.toInt, day.toInt))
+ case s"$day/$month/$year" => Some((year.toInt, month.toInt, day.toInt))
+ case _ => None
+}
+
+
+
// User-defined Datatypes and Pattern Matching
//=============================================
+
+
abstract class Exp
case class N(n: Int) extends Exp // for numbers
case class Plus(e1: Exp, e2: Exp) extends Exp
@@ -322,8 +449,37 @@
+// Tail Recursion
+//================
+def fact(n: Long): Long =
+ if (n == 0) 1 else n * fact(n - 1)
+
+fact(10) //ok
+fact(10000) // produces a stackoverflow
+
+def factT(n: BigInt, acc: BigInt): BigInt =
+ if (n == 0) acc else factT(n - 1, n * acc)
+
+factT(10, 1)
+factT(100000, 1)
+
+// there is a flag for ensuring a function is tail recursive
+import scala.annotation.tailrec
+
+@tailrec
+def factT(n: BigInt, acc: BigInt): BigInt =
+ if (n == 0) acc else factT(n - 1, n * acc)
+
+
+
+// for tail-recursive functions the Scala compiler
+// generates loop-like code, which does not need
+// to allocate stack-space in each recursive
+// call; Scala can do this only for tail-recursive
+// functions
+
Binary file slides/slides02.pdf has changed
--- a/slides/slides02.tex Mon Nov 11 14:04:22 2019 +0000
+++ b/slides/slides02.tex Tue Nov 12 00:41:00 2019 +0000
@@ -1,11 +1,11 @@
% !TEX program = xelatex
\documentclass[dvipsnames,14pt,t,xelatex]{beamer}
-\usepackage{chessboard}
-\usepackage[LSBC4,T1]{fontenc}
+%\usepackage{chessboard}
+%\usepackage[LSBC4,T1]{fontenc}
\usepackage{../slides}
\usepackage{../graphics}
\usepackage{../langs}
-
+\usetikzlibrary{shapes}
% \usepackage{../data}
\hfuzz=220pt
@@ -24,6 +24,13 @@
% beamer stuff
\renewcommand{\slidecaption}{PEP (Scala) 02, King's College London}
+\newcommand{\UParrow}[3]{%
+\begin{textblock}{0}(#2,#3)%
+\onslide<#1>{%
+\begin{tikzpicture}%
+\node at (0,0) [single arrow, shape border rotate=90, fill=red,text=red]{a};%
+\end{tikzpicture}}%
+\end{textblock}}
\begin{document}
@@ -52,7 +59,7 @@
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{frame}[c,fragile]
- \frametitle{My Scala Version}
+ \frametitle{Scala 2.13.1}
\begin{lstlisting}[language={},numbers=none,
basicstyle=\ttfamily\small,xleftmargin=-2mm]
@@ -112,7 +119,7 @@
\frametitle{Discussion Forum}
\large
- ``Since we cant use \code{var}s I was wondering if we could use a stack?''
+ ``Since we can't use \code{var}s I was wondering if we could use a stack?''
\bigskip\bigskip\bigskip\bigskip
\small
@@ -375,25 +382,226 @@
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[t]
+\begin{frame}[c,fragile]
+ %\frametitle{Option Type}
+
+ Find something below 4 in a list. What do you think Scala answers?\bigskip\bigskip
+
+ \begin{onlyenv}<1>
+ \begin{lstlisting}[language=Scala, numbers=none, xleftmargin=-1mm]
+ List(7,2,3,4,5,6).find(_ < 4)
+
+ List(5,6,7,8,9).find(_ < 4)
+ \end{lstlisting}
+ \end{onlyenv}
+ \begin{onlyenv}<2>
+ \begin{lstlisting}[language=Scala, numbers=none, xleftmargin=-1mm]
+ List(7,2,3,4,5,6).find(_ < 4)
+ res: Option[Int] = Some(2)
+
+ List(5,6,7,8,9).find(_ < 4)
+ res: Option[Int] = None
+ \end{lstlisting}
+ \end{onlyenv}
+
+ \end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c]
+\frametitle{Option Type}
+
+\begin{itemize}
+\item if the value is present, you use\bigskip
+\begin{center}\pcode{Some(value)}\end{center}\bigskip\bigskip
+
+\item if no value is present, you use\bigskip
+\begin{center}\pcode{None}\end{center}\bigskip\bigskip
+\end{itemize}
+
+\small e.g.~\code{Option[Int]}, then \code{Some(42)} and \code{None}\\
+good for error handling
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c,fragile]
\frametitle{Option Type}
+\small
+\begin{onlyenv}<1>
+\begin{lstlisting}[language=Scala, numbers=none, xleftmargin=-1mm]
+Integer.parseInt("1234")
+// vs.
+
+def get_me_an_int(s: String) : Option[Int] =
+ Try(Some(Integer.parseInt(s))).getOrElse(None)
+\end{lstlisting}
+\end{onlyenv}\bigskip\bigskip\bigskip
+
+in the Scala code it is clear from the type I have to deal
+with the \pcode{None}-case; no JavaDoc needed
\end{frame}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
-\begin{frame}[t]
+\begin{frame}[c,fragile]
\frametitle{Higher-Order Functions}
+In Scala, functions can take other functions as arguments and can return
+a function as a result.\bigskip\bigskip
+
+\begin{lstlisting}[language=Scala, numbers=none, xleftmargin=1mm]
+List(7,2,3,4,5,6).find(_ < 4)
+\end{lstlisting}
+
+\UParrow{1}{10}{11}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c,fragile]
+\frametitle{Higher-Order Functions (2)}
+
+
+\begin{lstlisting}[language=Scala, numbers=none, xleftmargin=1mm]
+def even(x: Int) : Boolean = x % 2 == 0
+
+List(1, 2, 3, 4, 5).filter(even)
+ res : List[Int] = List(2, 4)
+
+List(1, 2, 3, 4, 5).count(even)
+ res : Int = 2
+
+List(1, 2, 3, 4, 5).find(even)
+ res: Option[Int] = Some(2)
+\end{lstlisting}
\end{frame}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c,fragile]
+\frametitle{map (lower case)}
+
+ applies a function to each element of a list (and more)
+
+\begin{center}
+\begin{tikzpicture}[scale=0.9]
+
+ \node (A0) at (1.2,0) {\texttt{List(\,}};
+ \node (A1) at (2.0,0) {\texttt{1\makebox[0mm]{ ,}}};
+ \node (A2) at (2.9,0) {\texttt{2\makebox[0mm]{ ,}}};
+ \node (A3) at (3.8,0) {\texttt{3\makebox[0mm]{ ,}}};
+ \node (A4) at (4.7,0) {\texttt{4\makebox[0mm]{ ,}}};
+ \node (A5) at (5.6,0) {\texttt{5\makebox[0mm]{ ,}}};
+ \node (A6) at (6.5,0) {\texttt{6\makebox[0mm]{ ,}}};
+ \node (A7) at (7.4,0) {\texttt{7\makebox[0mm]{ ,}}};
+ \node (A8) at (8.3,0) {\texttt{8)}};
+
+ \node (B0) at (1.2,-3) {\texttt{List(\,}};
+ \node (B1) at (2.0,-3) {\texttt{1\makebox[0mm]{ ,}}};
+ \node (B2) at (3.0,-3) {\texttt{4\makebox[0mm]{ ,}}};
+ \node (B3) at (4.1,-3) {\texttt{9\makebox[0mm]{ ,}}};
+ \node (B4) at (5.2,-3) {\texttt{16\makebox[0mm]{ ,}}};
+ \node (B5) at (6.3,-3) {\texttt{25\makebox[0mm]{ ,}}};
+ \node (B6) at (7.4,-3) {\texttt{36\makebox[0mm]{ ,}}};
+ \node (B7) at (8.4,-3) {\texttt{49\makebox[0mm]{ ,}}};
+ \node (B8) at (9.4,-3) {\texttt{64\makebox[0mm]{ )}}};
+
+ \draw [->,line width=1mm] (A1.south) -- (B1.north);
+ \draw [->,line width=1mm] (A2.south) -- (B2.north);
+ \draw [->,line width=1mm] (A3.south) -- (B3.north);
+ \draw [->,line width=1mm] (A4.south) -- (B4.north);
+ \draw [->,line width=1mm] (A5.south) -- (B5.north);
+ \draw [->,line width=1mm] (A6.south) -- (B6.north);
+ \draw [->,line width=1mm] (A7.south) -- (B7.north);
+ \draw [->,line width=1mm] (A8.south) -- (B8.north);
+
+ \node [red] (Q0) at (-0.5,-0.3) {\large\texttt{n}};
+ \node (Q1) at (-0.5,-0.4) {};
+ \node (Q2) at (-0.5,-2.5) {};
+ \node [red] (Q3) at (-0.5,-2.65) {\large\texttt{n\,*\,n}};
+ \draw [->,red,line width=1mm] (Q1.south) -- (Q2.north);
+
+ \node [red] at (-1.5,-1.5) {\Large{}\it\textbf{map}};
+ \end{tikzpicture}
+\end{center}\bigskip
+
+\begin{lstlisting}[language=Scala, numbers=none, xleftmargin=1mm]
+List(1,2,3,4,5,6,7,8).map(n => n * n)
+\end{lstlisting}
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c,fragile]
+\frametitle{For-Comprehensions are maps}
+
+\begin{lstlisting}[language=Scala, numbers=none, xleftmargin=1mm]
+for (n <- List(1,2,3,4,5,6,7,8))
+ yield n * n
+
+
+// is just syntactic sugar for
+
+
+List(1,2,3,4,5,6,7,8).map(n => n * n)
+\end{lstlisting}
+
+\end{frame}
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c,fragile]
+\frametitle{Map (upper case)}
+
+a type, representing a key-value association datastructure\bigskip\bigskip
+
+\begin{lstlisting}[language=Scala, numbers=none, xleftmargin=-2mm]
+val ascii =
+ ('a' to 'z').map(c => (c, c.toInt))
+
+val ascii_Map = ascii.toMap
+
+ascii_Map.get('a') // -> 97
+\end{lstlisting}
+\end{frame}
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c,fragile]
+\frametitle{Recursion}
+
+
+
+\begin{lstlisting}[language=Scala, numbers=none, xleftmargin=-2mm]
+def fib(n: Int) : Int = {
+ if (n == 0 || n == 1) 1
+ else fib(n - 1) + fib(n - 2)
+}
+\end{lstlisting}
+\end{frame}
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[c,fragile]
+\frametitle{Recursion}
+
+\small
+\begin{lstlisting}[language=Scala, numbers=none, xleftmargin=-4mm]
+def my_flatten(xs: List[Option[Int]]): List[Int] =
+ xs match {
+ case Nil => Nil
+ case None :: rest => my_flatten(rest)
+ case Some(v) :: rest => v :: my_flatten(rest)
+ }
+\end{lstlisting}
+\end{frame}
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\begin{frame}[c]
@@ -414,6 +622,36 @@
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[t]
+
+ \begin{center}
+ \includegraphics[scale=0.3]{../pics/blow.png}
+ \end{center}
+
+ \begin{textblock}{14}(2,11.4)
+ \large\bf{}Mind-Blowing Programming Languages:\\
+ Overloading in any language is great but it makes a difference\; \code{10/3}
+ \;or\; \code{10.0/3}
+ \end{textblock}
+ \end{frame}
+ %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{frame}[t]
+
+ \begin{center}
+ \includegraphics[scale=0.3]{../pics/blow.png}
+ \end{center}
+
+ \begin{textblock}{14}(2,11.4)
+ \large\bf{}Mind-Blowing Programming Languages:\\
+ \centering PHP
+ \end{textblock}
+ \end{frame}
+ %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+
+
\end{document}
%%% Local Variables: