5 // Ben Maurer (bmaurer@ximian.com)
7 // Copyright (C) 2004 Novell, Inc (http://www.novell.com)
9 // Permission is hereby granted, free of charge, to any person obtaining
10 // a copy of this software and associated documentation files (the
11 // "Software"), to deal in the Software without restriction, including
12 // without limitation the rights to use, copy, modify, merge, publish,
13 // distribute, sublicense, and/or sell copies of the Software, and to
14 // permit persons to whom the Software is furnished to do so, subject to
15 // the following conditions:
17 // The above copyright notice and this permission notice shall be
18 // included in all copies or substantial portions of the Software.
20 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
21 // EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
22 // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
23 // NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
24 // LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
25 // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
26 // WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
31 using System.Runtime.InteropServices;
33 namespace System.Collections.Generic {
35 public abstract class Comparer<T> : IComparer<T>, System.Collections.IKeyComparer,
36 System.Collections.IComparer, System.Collections.IHashCodeProvider {
38 public Comparer () {} /* workaround 60438 by not having a protected ctor */
39 public abstract int Compare (T x, T y);
40 public abstract bool Equals (T x, T y);
41 public virtual int GetHashCode (T obj)
44 throw new ArgumentNullException ();
45 return obj.GetHashCode ();
48 static DefaultComparer <T> _default;
49 public static Comparer<T> Default
52 throw new NotImplementedException ("Waiting on bug#60437");
53 //if (_default != null)
55 //return _default = new DefaultComparer<T> ();
59 int System.Collections.IComparer.Compare (object x, object y)
61 return this.Compare ((T)x, (T)y);
64 bool System.Collections.IKeyComparer.Equals (object x, object y)
66 return this.Equals ((T) x, (T) y);
69 int System.Collections.IHashCodeProvider.GetHashCode (object obj)
71 return this.GetHashCode ((T)obj);
74 class DefaultComparer<T> : Comparer<T> {
76 public override int Compare (T x, T y)
78 // `null' is less than any other ref type
80 return y == null ? 0 : -1;
84 if (x is IComparable<T>)
85 return ((IComparable<T>) x).CompareTo (y);
86 else if (x is IComparable)
87 return ((IComparable) x).CompareTo (y);
89 throw new ArgumentException ("does not implement right interface");
92 public override bool Equals (T x, T y)
94 return System.Object.Equals (x, y);