Sample run of chapter's interpreter examples
scala> val oneHalf = Rational(1, 2) val oneHalf: Rational = 1/2 scala> val twoThirds = Rational(2, 3) val twoThirds: Rational = 2/3 scala> (oneHalf / 7) + (1 - twoThirds) val res0: Rational = 17/42
class Rational(n: Int, d: Int)
// In file functional-objects/ex1/Rational.scala class Rational(n: Int, d: Int): println("Created " + n + "/" + d)
scala> new Rational(1, 2) Created 1/2 val res0: Rational = Rational@6121a7dd
scala> Rational(1, 2) Created 1/2 val res1: Rational = Rational@5dc7841c
// In file functional-objects/ex2/Rational.scala class Rational(n: Int, d: Int): override def toString = s"n/d"
scala> val x = Rational(1, 3) x: Rational = 1/3 scala> val y = Rational(5, 7) y: Rational = 5/7
scala> Rational(5, 0) // 5/0 val res1: Rational = 5/0
// In file functional-objects/ex4/Rational.scala class Rational(n: Int, d: Int): require(d != 0) override def toString = s"n/d"
class Rational(n: Int, d: Int): // This won't compile require(d != 0) override def toString = s"n/d" def add(that: Rational): Rational = Rational(n * that.d + that.n * d, d * that.d)
5 | Rational(n * that.d + that.n * d, d * that.d) | ^^^^^^ |value n in class Rational cannot be accessed as a member | of (that : Rational) from class Rational. 5 | Rational(n * that.d + that.n * d, d * that.d) | ^^^^^^ |value d in class Rational cannot be accessed as a member | of (that : Rational) from class Rational. 5 | Rational(n * that.d + that.n * d, d * that.d) | ^^^^^^ |value d in class Rational cannot be accessed as a member | of (that : Rational) from class Rational.
// In file functional-objects/ex5/Rational.scala class Rational(n: Int, d: Int): require(d != 0) val numer: Int = n val denom: Int = d override def toString = s"numer/denom" def add(that: Rational): Rational = Rational( numer * that.denom + that.numer * denom, denom * that.denom )
val oneHalf = Rational(1, 2) // 1/2 val twoThirds = Rational(2, 3) // 2/3 oneHalf.add(twoThirds) // 7/6
val r = Rational(1, 2) // 1/2 r.numer // 1 r.denom // 2
// In file functional-objects/ex6/Rational.scala def lessThan(that: Rational) = this.numer * that.denom < that.numer * this.denom
// In file functional-objects/ex6/Rational.scala def max(that: Rational) = if this.lessThan(that) then that else this
// In file functional-objects/ex7/Rational.scala class Rational(n: Int, d: Int): require(d != 0) val numer: Int = n val denom: Int = d def this(n: Int) = this(n, 1) // auxiliary constructor override def toString = s"numer/denom" def add(that: Rational): Rational = Rational( numer * that.denom + that.numer * denom, denom * that.denom )
val y = Rational(3) // 3/1
Rational(66, 42) // 66/42
// In file functional-objects/ex8/Rational.scala class Rational(n: Int, d: Int): require(d != 0) private val g = gcd(n.abs, d.abs) val numer = n / g val denom = d / g def this(n: Int) = this(n, 1) def add(that: Rational): Rational = Rational( numer * that.denom + that.numer * denom, denom * that.denom ) override def toString = s"numer/denom" private def gcd(a: Int, b: Int): Int = if b == 0 then a else gcd(b, a % b)
Rational(66, 42) // 11/7
x + y
x.add(y)
x add y
// In file functional-objects/ex9/Rational.scala class Rational(n: Int, d: Int): require(d != 0) private val g = gcd(n.abs, d.abs) val numer = n / g val denom = d / g def this(n: Int) = this(n, 1) def + (that: Rational): Rational = Rational( numer * that.denom + that.numer * denom, denom * that.denom ) def * (that: Rational): Rational = Rational(numer * that.numer, denom * that.denom) override def toString = s"numer/denom" private def gcd(a: Int, b: Int): Int = if b == 0 then a else gcd(b, a % b)
val x = Rational(1, 2) // 1/2 val y = Rational(2, 3) // 2/3 x + y // 7/6
x.+(y) // 7/6
x + x * y // 5/6 (x + x) * y // 2/3 x + (x * y) // 5/6
// In file givens/rational-compare.scala class Rational(n: Int, d: Int): require(d != 0) private val g = gcd(n.abs, d.abs) val numer = n / g val denom = d / g def this(n: Int) = this(n, 1) def + (that: Rational): Rational = Rational( numer * that.denom + that.numer * denom, denom * that.denom ) def + (i: Int): Rational = Rational(numer + i * denom, denom) def - (that: Rational): Rational = Rational( numer * that.denom - that.numer * denom, denom * that.denom ) def - (i: Int): Rational = Rational(numer - i * denom, denom) def * (that: Rational): Rational = Rational(numer * that.numer, denom * that.denom) def * (i: Int): Rational = Rational(numer * i, denom) def / (that: Rational): Rational = Rational(numer * that.denom, denom * that.numer) def / (i: Int): Rational = Rational(numer, denom * i) override def toString = s"numer/denom" private def gcd(a: Int, b: Int): Int = if b == 0 then a else gcd(b, a % b)
val r = Rational(2, 3) // 2/3 r * r // 4/9 r * 2 // 4/3
scala> 2 * r 1 |2 * r |^^^ |None of the overloaded alternatives of method * in | class Int with types | (x: Double): Double | (x: Float): Float | (x: Long): Long | (x: Int): Int | (x: Char): Int | (x: Short): Int | (x: Byte): Int |match arguments ((r : Rational))
extension (x: Int) def + (y: Rational) = Rational(x) + y def - (y: Rational) = Rational(x) - y def * (y: Rational) = Rational(x) * y def / (y: Rational) = Rational(x) / y
val r = Rational(2,3) // 2/3 2 * r // 4/3
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