From fa1f988bcff3459415fbe3908f369fdb40a7c798 Mon Sep 17 00:00:00 2001
From: Paul Phillips <paulp@improving.org>
Date: Mon, 14 Feb 2011 15:19:48 -0800
Subject: [PATCH] Fleshed out Rational even more.  Added an ExampleSpec for
 running tests on package example.

---
 src/main/scala/example/Rational.scala | 16 +++++++++++++++-
 src/test/scala/ExampleSpec.scala      | 13 +++++++++++++
 src/test/scala/TemplateSpec.scala     |  2 +-
 3 files changed, 29 insertions(+), 2 deletions(-)
 create mode 100644 src/test/scala/ExampleSpec.scala

diff --git a/src/main/scala/example/Rational.scala b/src/main/scala/example/Rational.scala
index a0e626c21..44434dd3b 100644
--- a/src/main/scala/example/Rational.scala
+++ b/src/main/scala/example/Rational.scala
@@ -29,14 +29,28 @@ class Rational(n: Int, d: Int) {
   // an implicit conversion.  (See the example package object.)
   def +(that: Int): Rational = this + new Rational(that)
   
-  // toString overrides a method in AnyRef so "override" is required.
+  // toString, equals, and hashCode all override methods in AnyRef
+  // so "override" is required.
   override def toString = n + "/" + d + (
     // The result of the if/else is a String:
     if (numerator == n) ""                          // the empty string if it is irreducible
     else " (" + numerator + "/" + denominator + ")" // the reduced form otherwise
   )
+  
+  // To preserve symmetry we will be equal only to other Rationals.
+  override def equals(other: Any) = other match {
+    case x: Rational  => this.numerator == x.numerator && this.denominator == x.denominator
+    case _            => false
+  }
+  // As with java, equals and hashCode should always be overridden together.
+  override def hashCode = numerator.## + denominator.##  
 }
 
 // The Rational companion object.
 object Rational {
+  // A factory method on the companion object allows construction
+  // without explicit calls to new.  Here, d is given a default argument
+  // of 1.  This is an alternative mechanism to the auxiliary constructor.
+  // used in the class.
+  def apply(n: Int, d: Int = 1): Rational = new Rational(n, d)
 }
\ No newline at end of file
diff --git a/src/test/scala/ExampleSpec.scala b/src/test/scala/ExampleSpec.scala
new file mode 100644
index 000000000..01ad8a1f1
--- /dev/null
+++ b/src/test/scala/ExampleSpec.scala
@@ -0,0 +1,13 @@
+package example
+
+import org.specs._
+
+class ExampleSpec extends Specification {
+  "An example project" should {
+    "implement rational numbers" >> {
+      Rational(5) mustEqual Rational(5, 1)
+      Rational(1, 10) mustEqual Rational(2, 20)
+      (Rational(1, 3) + Rational(5, 15)) mustEqual Rational(4, 6)
+    }
+  }
+}
diff --git a/src/test/scala/TemplateSpec.scala b/src/test/scala/TemplateSpec.scala
index a68dc1c44..7952ab21f 100644
--- a/src/test/scala/TemplateSpec.scala
+++ b/src/test/scala/TemplateSpec.scala
@@ -2,7 +2,7 @@ package template
 
 import org.specs._
 
-class SendSpec extends Specification {
+class TemplateSpec extends Specification {
   "A template project" should {
     "not violate universal realities" >> {
       1 mustEqual 1