# HG changeset patch # User fahadausaf # Date 1414873521 0 # Node ID d205c05e13d6a3ef4a87f779e53573cb30f22a58 # Parent 4cad306c68e7a1039be7c6c43be080b974aea81e Handout 2 diff -r 4cad306c68e7 -r d205c05e13d6 Fahad/Eclipse/ScalaProjects/src/CodeSamples/PatternMatching.sc --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/Fahad/Eclipse/ScalaProjects/src/CodeSamples/PatternMatching.sc Sat Nov 01 20:25:21 2014 +0000 @@ -0,0 +1,46 @@ +package CodeSamples + +object PatternMatching { + def matchTest(x: Any): Any = x match { + case 1 => "one" + case "two" => 2 + case y: Int => "scala.Int" + case _ => "many" + } //> matchTest: (x: Any)Any + + matchTest("Two") //> res0: Any = many + matchTest("Test") //> res1: Any = many + matchTest(1) //> res2: Any = one + matchTest(2) //> res3: Any = scala.Int + + def matchTest2(x: Any) { + x match { + case 1 => "one" + case "two" => 2 + case y: Int => "scala.Int" + case _ => "many" + } + } //> matchTest2: (x: Any)Unit + + //Matching Using case Classes + case class Person(name: String, age: Int) + + def caseClassTest(): Unit = { + val alice = new Person("Alice", 25) + val bob = new Person("Bob", 32) + val charlie = new Person("Charlie", 32) + + for (person <- List(alice, bob, charlie)) { + person match { + case Person("Alice", 25) => println("Hi Alice!") + case Person("Bob", 32) => println("Hi Bob!") + case Person(name, age) => + println("Age: " + age + " year, name: " + name + "?") + } + } + } //> caseClassTest: ()Unit + + caseClassTest() //> Hi Alice! + //| Hi Bob! + //| Age: 32 year, name: Charlie? +} \ No newline at end of file diff -r 4cad306c68e7 -r d205c05e13d6 Fahad/Eclipse/ScalaProjects/src/Handouts/Handout2.sc --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/Fahad/Eclipse/ScalaProjects/src/Handouts/Handout2.sc Sat Nov 01 20:25:21 2014 +0000 @@ -0,0 +1,118 @@ +package Handouts + +import io.Source +import scala.util.matching.Regex +import scala.util._ + +object Handout2 { + abstract class Rexp + case object NULL extends Rexp + case object EMPTY extends Rexp + case class CHAR(c: Char) extends Rexp + case class ALT(r1: Rexp, r2: Rexp) extends Rexp + case class SEQ(r1: Rexp, r2: Rexp) extends Rexp + case class STAR(r: Rexp) extends Rexp + case class NTIMES(r: Rexp, n: Int) extends Rexp + + def OPT(r: Rexp) = ALT(r, EMPTY) //> OPT: (r: Handouts.Handout2.Rexp)Handouts.Handout2.ALT + + /* + def NTIMES(r: Rexp, n: Int): Rexp = n match { + case 0 => EMPTY + case 1 => r + case n => SEQ(r, NTIMES(r, n - 1)) + } + */ + + def nullable(r: Rexp): Boolean = r match { + case NULL => false + case EMPTY => true + case CHAR(_) => false + case ALT(r1, r2) => nullable(r1) || nullable(r2) + case SEQ(r1, r2) => nullable(r1) && nullable(r2) + case STAR(_) => true + case NTIMES(r, i) => if (i == 0) true else nullable(r) + } //> nullable: (r: Handouts.Handout2.Rexp)Boolean + + def der(c: Char, r: Rexp): Rexp = r match { + case NULL => NULL + case EMPTY => NULL + case CHAR(d) => if (c == d) EMPTY else NULL + case ALT(r1, r2) => ALT(der(c, r1), der(c, r2)) + case SEQ(r1, r2) => + if (nullable(r1)) ALT(SEQ(der(c, r1), r2), der(c, r2)) + else SEQ(der(c, r1), r2) + case STAR(r) => SEQ(der(c, r), STAR(r)) + case NTIMES(r, i) => + if (i == 0) NULL else SEQ(der(c, r), NTIMES(r, i - 1)) + } //> der: (c: Char, r: Handouts.Handout2.Rexp)Handouts.Handout2.Rexp + + def _ders(s: List[Char], r: Rexp): Rexp = s match { + case Nil => r + case c :: s => ders(s, der(c, r)) + } //> _ders: (s: List[Char], r: Handouts.Handout2.Rexp)Handouts.Handout2.Rexp + + def ders(s: List[Char], r: Rexp): Rexp = s match { + case Nil => r + case c :: s => ders(s, simp(der(c, r))) + } //> ders: (s: List[Char], r: Handouts.Handout2.Rexp)Handouts.Handout2.Rexp + + def matches(r: Rexp, s: String): Boolean = + nullable(ders(s.toList, r)) //> matches: (r: Handouts.Handout2.Rexp, s: String)Boolean + + def simp(r: Rexp): Rexp = r match { + case ALT(r1, r2) => { + val r1s = simp(r1) + val r2s = simp(r2) + (r1s, r2s) match { + case (NULL, _) => r2s + case (_, NULL) => r1s + case _ => if (r1s == r2s) r1s else ALT(r1s, r2s) + } + } + case SEQ(r1, r2) => { + val r1s = simp(r1) + val r2s = simp(r2) + (r1s, r2s) match { + case (NULL, _) => NULL + case (_, NULL) => NULL + case (EMPTY, _) => r2s + case (_, EMPTY) => r1s + case _ => SEQ(r1s, r2s) + } + } + case NTIMES(r, n) => NTIMES(simp(r), n) + case r => r + } //> simp: (r: Handouts.Handout2.Rexp)Handouts.Handout2.Rexp + + /************************************************************************************************************************************/ + // der test + // r = {(a.b) + b}* + val r = STAR(ALT(SEQ(CHAR('a'), CHAR('b')), CHAR('b'))) + //> r : Handouts.Handout2.STAR = STAR(ALT(SEQ(CHAR(a),CHAR(b)),CHAR(b))) + + // => [{(_.b) + null} . {(a.b)+b}*] + der('a', r) //> res0: Handouts.Handout2.Rexp = SEQ(ALT(SEQ(EMPTY,CHAR(b)),NULL),STAR(ALT(SE + //| Q(CHAR(a),CHAR(b)),CHAR(b)))) + // => [{(null.b) + _} . {(a.b)+b}*] + der('b', r) //> res1: Handouts.Handout2.Rexp = SEQ(ALT(SEQ(NULL,CHAR(b)),EMPTY),STAR(ALT(SE + //| Q(CHAR(a),CHAR(b)),CHAR(b)))) + // => [{(null.b) + _} . {(a.b)+b}*] + der('c', r) //> res2: Handouts.Handout2.Rexp = SEQ(ALT(SEQ(NULL,CHAR(b)),NULL),STAR(ALT(SEQ + //| (CHAR(a),CHAR(b)),CHAR(b)))) + + val r2 = ALT(SEQ(CHAR('a'), CHAR('b')), CHAR('b')) + //> r2 : Handouts.Handout2.ALT = ALT(SEQ(CHAR(a),CHAR(b)),CHAR(b)) + der('a', r2) //> res3: Handouts.Handout2.Rexp = ALT(SEQ(EMPTY,CHAR(b)),NULL) + + val r3 = SEQ(CHAR('a'), CHAR('b')) //> r3 : Handouts.Handout2.SEQ = SEQ(CHAR(a),CHAR(b)) + der('a', r3) //> res4: Handouts.Handout2.Rexp = SEQ(EMPTY,CHAR(b)) + + val r4 = CHAR('a') //> r4 : Handouts.Handout2.CHAR = CHAR(a) + der('a', r4) //> res5: Handouts.Handout2.Rexp = EMPTY + + nullable(r) //> res6: Boolean = true + nullable(r2) //> res7: Boolean = false + nullable(r3) //> res8: Boolean = false + nullable(r4) //> res9: Boolean = false +} \ No newline at end of file