Merge pull request #85 from mperry/option-traverse

mperry · mperry · commit ef3d99b8f24d · 2015-01-16T20:38:07.000+10:00
Add traverse family of methods to Option
diff --git a/core/src/main/java/fj/data/Option.java b/core/src/main/java/fj/data/Option.java
@@ -17,6 +17,8 @@
 import fj.Unit;
 import fj.Show;
 import fj.function.Effect1;
+import fj.Equal;
+import fj.Ord;
 
 import static fj.Function.*;
 import static fj.P.p;
@@ -415,6 +417,47 @@ public final <B> Option<B> sequence(final Option<B> o) {
     return bind(c);
   }
 
+  public <L, B> Either<L, Option<B>> traverseEither(F<A, Either<L, B>> f) {
+    return map(a -> f.f(a).right().map(b -> some(b))).orSome(Either.right(none()));
+  }
+
+  public <B> IO<Option<B>> traverseIO(F<A, IO<B>> f) {
+    return map(a -> IOFunctions.map(f.f(a), b -> some(b))).orSome(IOFunctions.lazy(u -> none()));
+  }
+
+  public <B> List<Option<B>> traverseList(F<A, List<B>> f) {
+    return map(a -> f.f(a).map(b -> some(b))).orSome(List.list());
+  }
+
+  public <B> Option<Option<B>> traverseOption(F<A, Option<B>> f) {
+    return map(f);
+  }
+
+  public <B> Stream<Option<B>> traverseStream(F<A, Stream<B>> f) {
+    return map(a -> f.f(a).map(b -> some(b))).orSome(Stream.nil());
+  }
+
+  public <B> P1<Option<B>> traverseP1(F<A, P1<B>> f) {
+    return map(a -> f.f(a).map(b -> some(b))).orSome(P.p(none()));
+  }
+
+  public <B> Seq<Option<B>> traverseSeq(F<A, Seq<B>> f) {
+    return map(a -> f.f(a).map(b -> some(b))).orSome(Seq.empty());
+  }
+
+  public <B> Set<Option<B>> traverseSet(Ord<B> ord, F<A, Set<B>> f) {
+    Ord<Option<B>> optOrd = Ord.optionOrd(ord);
+    return map(a -> f.f(a).map(optOrd, b -> some(b))).orSome(Set.empty(optOrd));
+  }
+
+  public <B> F2<Ord<B>, F<A, Set<B>>, Set<Option<B>>> traverseSet() {
+    return (o, f) -> traverseSet(o, f);
+  }
+
+  public <E, B> Validation<E, Option<B>> traverseValidation(F<A, Validation<E, B>> f) {
+    return map(a -> f.f(a).map(b -> some(b))).orSome(Validation.success(none()));
+  }
+
   /**
    * Performs function application within an optional value (applicative functor pattern).
    *
diff --git a/core/src/test/java/fj/data/OptionTest.java b/core/src/test/java/fj/data/OptionTest.java
@@ -0,0 +1,30 @@
+package fj.data;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import static fj.data.Option.some;
+import static org.junit.Assert.assertTrue;
+
+/**
+ * Created by MarkPerry on 15/01/2015.
+ */
+public class OptionTest {
+
+    @Test
+    public void equals() {
+        int max = 4;
+        assertTrue(some(1).equals(some(1)));
+        assertTrue(some(List.range(1, max)).equals(some(List.range(1, max))));
+    }
+
+    @Test
+    public void traverseList() {
+        int max = 3;
+        List<Option<Integer>> actual = some(max).traverseList(a -> List.range(1, a + 1));
+        List<Option<Integer>> expected = List.range(1, max + 1).map(i -> some(i));
+        System.out.println(String.format("actual: %s, expected: %s", actual.toString(), expected.toString()));
+        assertTrue(actual.equals(expected));
+    }
+
+}
