Scala : week2: implement filter

2 files changed, 16 insertions, 1 deletions

diff --git a/Scala/funsets/src/main/scala/funsets/FunSets.scala b/Scala/funsets/src/main/scala/funsets/FunSets.scala
index 1fd2d31..8b7778d 100644
--- a/Scala/funsets/src/main/scala/funsets/FunSets.scala
+++ b/Scala/funsets/src/main/scala/funsets/FunSets.scala
@@ -43,7 +43,7 @@ object FunSets {
   /**
    * Returns the subset of `s` for which `p` holds.
    */
-  def filter(s: Set, p: Int => Boolean): Set = ???
+  def filter(s: Set, p: Int => Boolean): Set = (x => s(x) & p(x))
 
   /**
    * The bounds for `forall` and `exists` are +/- 1000.
diff --git a/Scala/funsets/src/test/scala/funsets/FunSetSuite.scala b/Scala/funsets/src/test/scala/funsets/FunSetSuite.scala
index 88dac91..7c3fd53 100644
--- a/Scala/funsets/src/test/scala/funsets/FunSetSuite.scala
+++ b/Scala/funsets/src/test/scala/funsets/FunSetSuite.scala
@@ -162,4 +162,19 @@ class FunSetSuite extends FunSuite {
       assert(!contains(s, 3), "Diff none")
     }
   }
+
+  test("filter") {
+    new TestSets {
+      val s = filter(s1, (x => x == 1))
+      assert(!contains(s, 0), "Filter none")
+      assert(contains(s, 1), "Filter 1")
+      assert(!contains(s, 2), "Filter none")
+      assert(!contains(s, 3), "Filter none")
+      val v = filter(s1, (x => x == 0))
+      assert(!contains(v, 0), "Filter none")
+      assert(!contains(v, 1), "Filter none")
+      assert(!contains(v, 2), "Filter none")
+      assert(!contains(v, 3), "Filter none")
+    }
+  }
 }