88 lines
2.1 KiB
Scala
88 lines
2.1 KiB
Scala
package ca.rekahsoft.rdm
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/**
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* (C) Copyright Collin Doering @!@YEAR@!@
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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/**
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* File: rdm.scala
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* Author: Collin J. Doering
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* Date: Jun 20, 2013
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*/
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def and(x: Boolean, y: => Boolean): Boolean = if (x) y else false
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def or(x: Boolean, y: => Boolean): Boolean = if (x) true else y
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def factorial(n: Int): Int = {
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def fact(x: Int, acc: Int): Int = if (x <= 1) acc else fact(x - 1, x * acc)
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fact(n,1)
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}
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// An implementation of a list (covariant)
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trait List[+T] {
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def isEmpty: Boolean
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def head: T
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def tail: List[T]
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}
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class Cons[T](val head: T, var tail: List[T]) extends List[T]{
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def isEmpty = false
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}
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object Nil extends List[Nothing] {
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def isEmpty: Boolean = true
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def head: Nothing = throw new Error("Nil.head")
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def tail: Nothing = throw new Error("Nil.head")
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}
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// An implementation of Natural numbers
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abstract class Nat {
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def isZero: Boolean
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def pred: Nat
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def + (x: Nat): Nat
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def - (x: Nat): Nat
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}
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class Succ(n: Nat) extends Nat {
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def isZero = false
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def pred = n
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def succ: Nat = new Succ(this)
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def + (x: Nat) = new Succ(n + x)
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def - (x: Nat) = if (x.isZero) this else n - x.pred
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}
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object Zero extends Nat {
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def isZero = true
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def pred = throw new Error("Zero.pred")
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def succ: Nat = new Succ(this)
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def + (x: Nat) = x
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def - (x: Nat) = if (x.isZero) this else throw new Error("negative number")
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}
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/* Note: the above use of var is shortform:
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* class Test[T](var x: T)
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* is transformed to:
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* class Test[T](x: T) {
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* var x = x
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* }
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*/
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// Implement a BST
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trait BTree[T] {
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}
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