From fc242f52e835be85cc6030b6cae5619d18df7670 Mon Sep 17 00:00:00 2001
From: Jaron Kent-Dobias <jaron@kent-dobias.com>
Date: Mon, 30 Jul 2018 06:32:51 -0400
Subject: various changes

---
 lib/ising.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

(limited to 'lib/ising.h')

diff --git a/lib/ising.h b/lib/ising.h
index 473a18a..aaa0c52 100644
--- a/lib/ising.h
+++ b/lib/ising.h
@@ -53,6 +53,18 @@ class ising_t {
         return a;
       }
     }
+
+    inline int operator-(const ising_t &s) const {
+      if (x == s.x) {
+        return 0;
+      } else {
+        if (x) {
+          return -2;
+        } else {
+          return 2;
+        }
+      }
+    }
 };
 
 inline int& operator+=(int& M, const ising_t &s) {
-- 
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