--- a/Main/jungle-main/util/DefaultEither.cs	Fri Jan 20 07:43:43 2017 +0900
+++ b/Main/jungle-main/util/DefaultEither.cs	Sat Jan 28 19:12:18 2017 +0900
@@ -3,7 +3,17 @@
 	private A theA;
 	private B theB;
 
-	private DefaultEither(A _theA, B _theB){
+	public void SetB (B b) {
+		this.theB = b;
+	}
+
+	public void SetA (A a) {
+		this.theA = a;
+	}
+
+	public delegate B Func (B b);
+
+	public DefaultEither(A _theA, B _theB){
 		theA = _theA;
 		theB = _theB;
 	}
@@ -41,4 +51,12 @@
 		return theB != null;
 	}
 
+	public Either<A, B> fmap(System.Func<B, B> f, Either<A,B> e) {
+		if (e.isA ()) {
+			return e;
+		}
+		this.SetB (f (e.b()));
+		return this;
+	}
+
 }