From 8df468e04aacaa4b79724ca235db51c690982229 Mon Sep 17 00:00:00 2001
From: Arthur Drobot <drobotarthur@gmail.com>
Date: Fri, 4 Aug 2017 10:33:55 -0700
Subject: [PATCH] Check arguments in factorial function.

---
 src/main/java/org/nwapw/abacus/plugin/StandardPlugin.java | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/main/java/org/nwapw/abacus/plugin/StandardPlugin.java b/src/main/java/org/nwapw/abacus/plugin/StandardPlugin.java
index 8165588..2e98b87 100755
--- a/src/main/java/org/nwapw/abacus/plugin/StandardPlugin.java
+++ b/src/main/java/org/nwapw/abacus/plugin/StandardPlugin.java
@@ -97,7 +97,9 @@ public class StandardPlugin extends Plugin {
         //private HashMap<Class<? extends NumberInterface>, ArrayList<NumberInterface>> storedList = new HashMap<Class<? extends NumberInterface>, ArrayList<NumberInterface>>();
         @Override
         protected boolean matchesParams(NumberInterface[] params) {
-            return params.length == 1;
+            return params.length == 1
+                    && params[0].fractionalPart().compareTo(NaiveNumber.ZERO.promoteTo(params[0].getClass())) == 0
+                    && params[0].signum() >= 0;
         }
 
         @Override