Scala : add funset

4 files changed, 248 insertions, 0 deletions

diff --git a/Scala/funsets/src/main/scala/common/package.scala b/Scala/funsets/src/main/scala/common/package.scala
new file mode 100644
index 0000000..f1c74c3
--- /dev/null
+++ b/Scala/funsets/src/main/scala/common/package.scala
@@ -0,0 +1,40 @@
+import java.io.File
+
+package object common {
+
+  /** An alias for the `Nothing` type.
+   *  Denotes that the type should be filled in.
+   */
+  type ??? = Nothing
+
+  /** An alias for the `Any` type.
+   *  Denotes that the type should be filled in.
+   */
+  type *** = Any
+
+  
+  /**
+   * Get a child of a file. For example,
+   * 
+   *   subFile(homeDir, "b", "c")
+   * 
+   * corresponds to ~/b/c
+   */
+  def subFile(file: File, children: String*) = {
+    children.foldLeft(file)((file, child) => new File(file, child))
+  }
+
+  /**
+   * Get a resource from the `src/main/resources` directory. Eclipse does not copy
+   * resources to the output directory, then the class loader cannot find them.
+   */
+  def resourceAsStreamFromSrc(resourcePath: List[String]): Option[java.io.InputStream] = {
+    val classesDir = new File(getClass.getResource(".").toURI)
+    val projectDir = classesDir.getParentFile.getParentFile.getParentFile.getParentFile
+    val resourceFile = subFile(projectDir, ("src" :: "main" :: "resources" :: resourcePath): _*)
+    if (resourceFile.exists)
+      Some(new java.io.FileInputStream(resourceFile))
+    else
+      None
+  }
+}
diff --git a/Scala/funsets/src/main/scala/funsets/FunSets.scala b/Scala/funsets/src/main/scala/funsets/FunSets.scala
new file mode 100644
index 0000000..594a49d
--- /dev/null
+++ b/Scala/funsets/src/main/scala/funsets/FunSets.scala
@@ -0,0 +1,90 @@
+package funsets
+
+import common._
+
+/**
+ * 2. Purely Functional Sets.
+ */
+object FunSets {
+  /**
+   * We represent a set by its characteristic function, i.e.
+   * its `contains` predicate.
+   */
+  type Set = Int => Boolean
+
+  /**
+   * Indicates whether a set contains a given element.
+   */
+  def contains(s: Set, elem: Int): Boolean = s(elem)
+
+  /**
+   * Returns the set of the one given element.
+   */
+  def singletonSet(elem: Int): Set = ???
+
+  /**
+   * Returns the union of the two given sets,
+   * the sets of all elements that are in either `s` or `t`.
+   */
+  def union(s: Set, t: Set): Set = ???
+
+  /**
+   * Returns the intersection of the two given sets,
+   * the set of all elements that are both in `s` and `t`.
+   */
+  def intersect(s: Set, t: Set): Set = ???
+
+  /**
+   * Returns the difference of the two given sets,
+   * the set of all elements of `s` that are not in `t`.
+   */
+  def diff(s: Set, t: Set): Set = ???
+
+  /**
+   * Returns the subset of `s` for which `p` holds.
+   */
+  def filter(s: Set, p: Int => Boolean): Set = ???
+
+  /**
+   * The bounds for `forall` and `exists` are +/- 1000.
+   */
+  val bound = 1000
+
+  /**
+   * Returns whether all bounded integers within `s` satisfy `p`.
+   */
+  def forall(s: Set, p: Int => Boolean): Boolean = {
+    def iter(a: Int): Boolean = {
+      if (???) ???
+      else if (???) ???
+      else iter(???)
+    }
+    iter(???)
+  }
+
+  /**
+   * Returns whether there exists a bounded integer within `s`
+   * that satisfies `p`.
+   */
+  def exists(s: Set, p: Int => Boolean): Boolean = ???
+
+  /**
+   * Returns a set transformed by applying `f` to each element of `s`.
+   */
+  def map(s: Set, f: Int => Int): Set = ???
+
+  /**
+   * Displays the contents of a set
+   */
+  def toString(s: Set): String = {
+    val xs = for (i <- -bound to bound if contains(s, i)) yield i
+    xs.mkString("{", ",", "}")
+  }
+
+  /**
+   * Prints the contents of a set on the console.
+   */
+  def printSet(s: Set) {
+    println(toString(s))
+  }
+}
diff --git a/Scala/funsets/src/main/scala/funsets/Main.scala b/Scala/funsets/src/main/scala/funsets/Main.scala
new file mode 100644
index 0000000..6126909
--- /dev/null
+++ b/Scala/funsets/src/main/scala/funsets/Main.scala
@@ -0,0 +1,6 @@
+package funsets
+
+object Main extends App {
+  import FunSets._
+  println(contains(singletonSet(1), 1))
+}
diff --git a/Scala/funsets/src/test/scala/funsets/FunSetSuite.scala b/Scala/funsets/src/test/scala/funsets/FunSetSuite.scala
new file mode 100644
index 0000000..e75ba8c
--- /dev/null
+++ b/Scala/funsets/src/test/scala/funsets/FunSetSuite.scala
@@ -0,0 +1,112 @@
+package funsets
+
+import org.scalatest.FunSuite
+
+import org.junit.runner.RunWith
+import org.scalatest.junit.JUnitRunner
+
+/**
+ * This class is a test suite for the methods in object FunSets. To run
+ * the test suite, you can either:
+ *  - run the "test" command in the SBT console
+ *  - right-click the file in eclipse and chose "Run As" - "JUnit Test"
+ */
+@RunWith(classOf[JUnitRunner])
+class FunSetSuite extends FunSuite {
+
+
+  /**
+   * Link to the scaladoc - very clear and detailed tutorial of FunSuite
+   *
+   * http://doc.scalatest.org/1.9.1/index.html#org.scalatest.FunSuite
+   *
+   * Operators
+   *  - test
+   *  - ignore
+   *  - pending
+   */
+
+  /**
+   * Tests are written using the "test" operator and the "assert" method.
+   */
+  test("string take") {
+    val message = "hello, world"
+    assert(message.take(5) == "hello")
+  }
+
+  /**
+   * For ScalaTest tests, there exists a special equality operator "===" that
+   * can be used inside "assert". If the assertion fails, the two values will
+   * be printed in the error message. Otherwise, when using "==", the test
+   * error message will only say "assertion failed", without showing the values.
+   *
+   * Try it out! Change the values so that the assertion fails, and look at the
+   * error message.
+   */
+  test("adding ints") {
+    assert(1 + 2 === 3)
+  }
+
+  
+  import FunSets._
+
+  test("contains is implemented") {
+    assert(contains(x => true, 100))
+  }
+  
+  /**
+   * When writing tests, one would often like to re-use certain values for multiple
+   * tests. For instance, we would like to create an Int-set and have multiple test
+   * about it.
+   * 
+   * Instead of copy-pasting the code for creating the set into every test, we can
+   * store it in the test class using a val:
+   * 
+   *   val s1 = singletonSet(1)
+   * 
+   * However, what happens if the method "singletonSet" has a bug and crashes? Then
+   * the test methods are not even executed, because creating an instance of the
+   * test class fails!
+   * 
+   * Therefore, we put the shared values into a separate trait (traits are like
+   * abstract classes), and create an instance inside each test method.
+   * 
+   */
+
+  trait TestSets {
+    val s1 = singletonSet(1)
+    val s2 = singletonSet(2)
+    val s3 = singletonSet(3)
+  }
+
+  /**
+   * This test is currently disabled (by using "ignore") because the method
+   * "singletonSet" is not yet implemented and the test would fail.
+   * 
+   * Once you finish your implementation of "singletonSet", exchange the
+   * function "ignore" by "test".
+   */
+  ignore("singletonSet(1) contains 1") {
+    
+    /**
+     * We create a new instance of the "TestSets" trait, this gives us access
+     * to the values "s1" to "s3". 
+     */
+    new TestSets {
+      /**
+       * The string argument of "assert" is a message that is printed in case
+       * the test fails. This helps identifying which assertion failed.
+       */
+      assert(contains(s1, 1), "Singleton")
+    }
+  }
+
+  ignore("union contains all elements") {
+    new TestSets {
+      val s = union(s1, s2)
+      assert(contains(s, 1), "Union 1")
+      assert(contains(s, 2), "Union 2")
+      assert(!contains(s, 3), "Union 3")
+    }
+  }
+}