1 package greeter |
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2 |
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3 |
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4 object Chapter6 { |
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5 println("Classes and Objects") //> Classes and Objects |
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6 |
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7 class Rational(n: Int, d: Int) { |
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8 private def gcd(x: Int, y: Int): Int = { |
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9 if (x == 0) y |
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10 else if (x < 0) gcd(-x, y) |
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11 else if (y < 0) -gcd(x, -y) |
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12 else gcd(y % x, x) |
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13 } |
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14 private val g = gcd(n, d) |
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15 |
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16 val numer: Int = n / g |
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17 val denom: Int = d / g |
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18 def +(that: Rational) = new Rational(numer * that.denom + that.numer * denom, denom * that.denom) |
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19 def -(that: Rational) = new Rational(numer * that.denom - that.numer * denom, denom * that.denom) |
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20 def *(that: Rational) = new Rational(numer * that.numer, denom * that.denom) |
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21 def /(that: Rational) = new Rational(numer * that.denom, denom * that.numer) |
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22 |
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23 //Inheritance and Overriding |
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24 override def toString = "" + numer + "/" + denom |
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25 //Parameterless Methods |
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26 def square = new Rational(numer * numer, denom * denom) |
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27 } |
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28 //Inheritance and Overriding |
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29 var i = 1 //> i : Int = 1 |
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30 var x = new Rational(0, 1) //> x : greeter.Chapter6.Rational = 0/1 |
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31 while (i <= 10) { |
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32 x += new Rational(1, i) |
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33 i += 1 |
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34 } |
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35 println("" + x.numer + "/" + x.denom) //> 7381/2520 |
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36 //Parameterless Methods |
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37 val r = new Rational(3, 4) //> r : greeter.Chapter6.Rational = 3/4 |
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38 println(r.square) //> 9/16 |
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39 |
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40 //Abstract Classes |
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41 abstract class IntSet { |
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42 def incl(x: Int): IntSet |
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43 def contains(x: Int): Boolean |
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44 } |
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45 |
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46 //Triats |
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47 trait IntSett { |
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48 def incl(x: Int): IntSet |
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49 def contains(x: Int): Boolean |
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50 } |
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51 |
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52 //Implementing abstract class |
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53 class EmptySet extends IntSet { |
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54 def contains(x: Int): Boolean = false |
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55 def incl(x: Int): IntSet = new NonEmptySet(x, new EmptySet, new EmptySet) |
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56 } |
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57 |
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58 class NonEmptySet(elem: Int, left: IntSet, right: IntSet) extends IntSet { |
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59 def contains(x: Int): Boolean = |
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60 if (x < elem) left contains x |
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61 else if (x > elem) right contains x |
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62 else true |
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63 def incl(x: Int): IntSet = |
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64 if (x < elem) new NonEmptySet(elem, left incl x, right) |
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65 else if (x > elem) new NonEmptySet(elem, left, right incl x) |
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66 else this |
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67 } |
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68 |
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69 } |
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