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 virtual bool Equals (T x, T y)
42 return Compare (x, y) == 0;
44 public virtual int GetHashCode (T obj)
47 throw new ArgumentNullException ();
48 return obj.GetHashCode ();
51 static DefaultComparer <T> _default;
53 [MonoTODO ("This is going to make a really slow comparer. We need to speed this up if T : ICompareable<T> create a class with a where clause of T : ICompareable <T>")]
54 public static Comparer<T> Default {
58 return _default = new DefaultComparer<T> ();
62 int System.Collections.IComparer.Compare (object x, object y)
66 return y == null ? 0 : -1;
71 return Compare ((T) x, (T) y);
73 throw new ArgumentException ();
76 bool System.Collections.IKeyComparer.Equals (object x, object y)
81 if (x == null || y == null)
85 return Equals ((T) x, (T) y);
87 throw new ArgumentException ();
90 int System.Collections.IHashCodeProvider.GetHashCode (object obj)
93 throw new ArgumentNullException ();
95 return GetHashCode ((T) obj);
97 throw new ArgumentException ();
100 class DefaultComparer<T> : Comparer<T> {
102 public override int Compare (T x, T y)
104 // `null' is less than any other ref type
106 return y == null ? 0 : -1;
110 if (x is IComparable<T>)
111 return ((IComparable<T>) x).CompareTo (y);
112 else if (x is IComparable)
113 return ((IComparable) x).CompareTo (y);
115 throw new ArgumentException ("does not implement right interface");
118 public override bool Equals (T x, T y)
120 return Object.Equals (x, y);