From 6919fac18f074d7faf7d9eca107442cefb6a9ce2 Mon Sep 17 00:00:00 2001
From: Danila Fedorin <danila.fedorin@gmail.com>
Date: Mon, 24 Jul 2017 14:37:56 -0700
Subject: [PATCH] Add promotion implementation.

---
 src/org/nwapw/abacus/number/NaiveNumber.java | 5 +++++
 src/org/nwapw/abacus/number/Number.java      | 2 ++
 2 files changed, 7 insertions(+)

diff --git a/src/org/nwapw/abacus/number/NaiveNumber.java b/src/org/nwapw/abacus/number/NaiveNumber.java
index 0ac9418..484f773 100644
--- a/src/org/nwapw/abacus/number/NaiveNumber.java
+++ b/src/org/nwapw/abacus/number/NaiveNumber.java
@@ -48,5 +48,10 @@ public class NaiveNumber implements Number {
         return new NaiveNumber(1);
     }
 
+    @Override
+    public Number promoteTo(Class<? extends Number> toClass) {
+        if(toClass == this.getClass()) return this;
+        return null;
+    }
 }
 
diff --git a/src/org/nwapw/abacus/number/Number.java b/src/org/nwapw/abacus/number/Number.java
index c2e7540..4541287 100755
--- a/src/org/nwapw/abacus/number/Number.java
+++ b/src/org/nwapw/abacus/number/Number.java
@@ -12,4 +12,6 @@ public interface Number {
     Number zero();
     Number one();
 
+    Number promoteTo(Class<? extends Number> toClass);
+
 }