Sample run of chapter's interpreter examples
scala> val oneHalf = new Rational(1, 2) oneHalf: Rational = 1/2 scala> val twoThirds = new Rational(2, 3) twoThirds: Rational = 2/3 scala> (oneHalf / 7) + (1 - twoThirds) 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 res0: Rational = Rational@6121a7dd
// In file functional-objects/ex2/Rational.scala class Rational(n: Int, d: Int) { override def toString = s"n/d" }
scala> val x = new Rational(1, 3) x: Rational = 1/3 scala> val y = new Rational(5, 7) y: Rational = 5/7
scala> new Rational(5, 0) 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 = new Rational(n * that.d + that.n * d, d * that.d) }
<console>:11: error: value d is not a member of Rational new Rational(n * that.d + that.n * d, d * that.d) ^ <console>:11: error: value d is not a member of Rational new Rational(n * that.d + that.n * d, d * that.d) ^
// 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 = new Rational( numer * that.denom + that.numer * denom, denom * that.denom ) }
scala> val oneHalf = new Rational(1, 2) oneHalf: Rational = 1/2 scala> val twoThirds = new Rational(2, 3) twoThirds: Rational = 2/3 scala> oneHalf add twoThirds res2: Rational = 7/6
scala> val r = new Rational(1, 2) r: Rational = 1/2 scala> r.numer res3: Int = 1 scala> r.denom res4: Int = 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)) 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 = new Rational( numer * that.denom + that.numer * denom, denom * that.denom ) }
scala> val y = new Rational(3) y: Rational = 3/1
scala> new Rational(66, 42) res5: Rational = 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 = new 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) a else gcd(b, a % b) }
scala> new Rational(66, 42) res6: Rational = 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 = new Rational( numer * that.denom + that.numer * denom, denom * that.denom ) def * (that: Rational): Rational = new Rational(numer * that.numer, denom * that.denom) override def toString = s"numer/denom" private def gcd(a: Int, b: Int): Int = if (b == 0) a else gcd(b, a % b) }
scala> val x = new Rational(1, 2) x: Rational = 1/2 scala> val y = new Rational(2, 3) y: Rational = 2/3 scala> x + y res7: Rational = 7/6
scala> x.+(y) res8: Rational = 7/6
scala> x + x * y res9: Rational = 5/6 scala> (x + x) * y res10: Rational = 2/3 scala> x + (x * y) res11: Rational = 5/6
// In file functional-objects/ex10/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 = new Rational( numer * that.denom + that.numer * denom, denom * that.denom ) def + (i: Int): Rational = new Rational(numer + i * denom, denom) def - (that: Rational): Rational = new Rational( numer * that.denom - that.numer * denom, denom * that.denom ) def - (i: Int): Rational = new Rational(numer - i * denom, denom) def * (that: Rational): Rational = new Rational(numer * that.numer, denom * that.denom) def * (i: Int): Rational = new Rational(numer * i, denom) def / (that: Rational): Rational = new Rational(numer * that.denom, denom * that.numer) def / (i: Int): Rational = new Rational(numer, denom * i) override def toString = s"numer/denom" private def gcd(a: Int, b: Int): Int = if (b == 0) a else gcd(b, a % b) }
scala> val x = new Rational(2, 3) x: Rational = 2/3 scala> x * x res12: Rational = 4/9 scala> x * 2 res13: Rational = 4/3
scala> 2 * r ^ error: overloaded method value * with alternatives: (x: Double)Double <and> (x: Float)Float <and> (x: Long)Long <and> (x: Int)Int <and> (x: Char)Int <and> (x: Short)Int <and> (x: Byte)Int cannot be applied to (Rational)
scala> implicit def intToRational(x: Int) = new Rational(x)
scala> val r = new Rational(2,3) r: Rational = 2/3 scala> 2 * r res15: Rational = 4/3
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