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@2591e0c9
// In file functional-objects/ex2/Rational.scala class Rational(n: Int, d: Int) { override def toString = 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 = n + "/" + d }
class Rational(n: Int, d: Int) { // This won't compile require(d != 0) override def toString = 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 = 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 = 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 = 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 = 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 = 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 <console>:10: 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) 2 * r ^
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
|
For more information about Programming in Scala, Third Edition (the "Stairway Book"), please visit: http://www.artima.com/shop/programming_in_scala_3ed and: |
Copyright © 2007-2016 Artima, Inc. All rights reserved. Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License. |