From e4419c2e8d5469787f997fbf0e74f9ef8383c140 Mon Sep 17 00:00:00 2001
From: qunyanm <unknown>
Date: Fri, 17 Apr 2015 13:17:41 -0700
Subject: HashCode for Set/MultiSet/Map should be independent of the order of
 the elements.

---
 Binaries/DafnyRuntime.cs | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

(limited to 'Binaries')

diff --git a/Binaries/DafnyRuntime.cs b/Binaries/DafnyRuntime.cs
index 2a553c81..fd680a0b 100644
--- a/Binaries/DafnyRuntime.cs
+++ b/Binaries/DafnyRuntime.cs
@@ -75,9 +75,9 @@ namespace Dafny
       return other is Set<T> && Equals((Set<T>)other);
     }
     public override int GetHashCode() {
-      var hashCode = 0;
+      var hashCode = 1;
       foreach (var t in dict.Keys) {
-        hashCode = (hashCode << 3) | (hashCode >> 29) ^ t.GetHashCode();
+        hashCode = hashCode * (t.GetHashCode()+3);
       }
       return hashCode;
     }
@@ -232,10 +232,11 @@ namespace Dafny
       return other is MultiSet<T> && Equals((MultiSet<T>)other);
     }
     public override int GetHashCode() {
-      var hashCode = 0;
+      var hashCode = 1;
       foreach (var kv in dict) {
-        hashCode = (hashCode << 3) | (hashCode >> 29) ^ kv.Key.GetHashCode();
-        hashCode = (hashCode << 3) | (hashCode >> 29) ^ kv.Value.GetHashCode();
+        var key = kv.Key.GetHashCode();
+        key = (key << 3) | (key >> 29) ^ kv.Value.GetHashCode();
+        hashCode = hashCode * (key + 3);
       }
       return hashCode;
     }
@@ -401,10 +402,11 @@ namespace Dafny
       return other is Map<U, V> && Equals((Map<U, V>)other);
     }
     public override int GetHashCode() {
-      var hashCode = 0;
+      var hashCode = 1;
       foreach (var kv in dict) {
-        hashCode = (hashCode << 3) | (hashCode >> 29) ^ kv.Key.GetHashCode();
-        hashCode = (hashCode << 3) | (hashCode >> 29) ^ kv.Value.GetHashCode();
+        var key = kv.Key.GetHashCode();
+        key = (key << 3) | (key >> 29) ^ kv.Value.GetHashCode();
+        hashCode = hashCode * (key + 3);
       }
       return hashCode;
     }
-- 
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